Searching for "lamprey neurotransmitters"
PubMed = 480
Google = 851,000
Effects of iontophoretically applied drugs on spinal interneurons of the lamprey.
from the Abstract
1. Intracellular records were obtained from giant interneurones in the isolated spinal cord of the sea lamprey. The cells had a mean resting potential of about 75 mV and action potentials with overshoots of about 35 mV. Their input resistances, measured by passing polarizing currents through the recording pipette, were in the range 3-7 MOmega.
2. Iontophoretic ejection of gamma-aminobutyric acid (GABA) from a micropipette placed near the surface of a cell resulted in a slight hyperpolarization, accompanied by a marked reduction in input resistance. The reversal point for the potential change was about 5 mV greater than the resting membrane potential.
3. Iontophoretic application of L-glutamate to the cells produced a depolarization with a decrease in input resistance much smaller than that accompanying a GABA potential of similar amplitude. The action potential amplitude was reduced by L-glutamate application. The reversal potential could not be determined accurately but appeared to be near zero membrane potential.
4. Glutamate application produced, in addition, a burst of inhibitory synaptic potentials in the cell, presumably by depolarizing either inhibitory presynaptic nerve terminals or nearby inhibitory cell bodies.
5. Acetylcholine (ACh) produced no detectable change in membrane resistance or potential.
6. Application of the three drugs to first-order sensory cells in the spinal cord had no effect on their membrane properties."
172 Related citations:
15 Cited by's:
Free PMC Article
Click on the active link above.
Inhibitory conductance changes at synapses in the lamprey brainstem
"Although the conductance and kinetic behavior of inhibitory synaptic channels have been studied in a number of nerve and muscle cells, there has been little if any detailed study of such channels at synapses in the vertebrate central nervous system or of the relation of such channels to natural synaptic events. In the experiments reported here, current noise measurements were used to obtain such information at synapses on Müller cells in the lamprey brainstem. Application of glycine to the cells activated synaptic channels with large conductances and relaxation time constants (70 picosiemens and 33 milliseconds, respectively, at 3 degrees to 10 degrees C). Spontaneous inhibitory synaptic currents had a mean conductance of 107 nanosiemens and decayed with the same time constant. In addition, the glycine responses and the spontaneous currents had the same reversal potential and both were abolished by strychnine. These results support the idea that glycine is the natural inhibitory transmitter at these synapses and suggest that one quantum of transmitter activates about 1500 elementary conductance channels."
"glycine is the natural inhibitory transmitter at these synapses"
101 Related citations:
and 2 Cited by's.
Effects of bath-applied excitatory amino acids and their analogs on spinal interneurons of the lamprey.
"Depolarizations, conductance increases and time courses of the responses
to bath application of glutamate, aspartate, DL-homocysteate,
N-methyl-DL-aspartate (NMDLA), quisqualate and kainate were determined
in interneurons of the isolated spinal cord of the lamprey, one of the
most primitive vertebrates. Conductance increases produced by these
excitants in perfusate containing tetrodotoxin (0.5 microgram/ml),
4-aminopyridine (1 mM) and without Ca2+ were very small in comparison
with those produced by glycine or GABA. NMDLA-induced depolarizations
were associated with conductance decreases and rhythmic oscillations in
membrane potentials in this perfusate. Quisqualate was strongest among
these amino acids in producing depolarizations and conductance
increases. Responses induced by analogs were slower than those produced
by glutamate and aspartate. Phylogenetic distribution of
N-methyl-D-aspartate receptors on neurons and muscles is discussed."
201 Related citations:
Serotonin modulates the central pattern generator for locomotion in the isolated lamprey spinal cord.
"The central pattern generator for locomotion in the spinal cord of the lamprey
can be activated in vitro by the addition of D-glutamate to the bathing
saline. Serotonin has no effects when bath-applied alone, but it
modulates the D-glutamate-activated swimming pattern. Three major
effects are observed: a dose-dependent reduction in the frequency of
rhythmic ventral root burst discharge; enhancement of the intensity of
burst discharge, due in part to the recruitment of previously inactive
motoneurones; prolongation of the intersegmental phase lag. Motoneurone
activation appears to result from enhanced synaptic drive from the
central pattern generator; no direct effects of serotonin on the
motoneurones themselves (resting potential, input resistance or
threshold for action potential generation) were observed. Theoretical
and experimental studies suggest that the prolongation of the
intersegmental phase lag results at least in part from differential
effects of serotonin on segmental oscillators in different parts of the
spinal cord. Isolated caudal pieces of the cord were more strongly
affected by serotonin than isolated rostral pieces. We propose that
serotonin may be an endogenous modulator of the central pattern
generator for locomotion in the lamprey.
It may have a role in the generation of a family of related undulatory
movements (swimming, crawling, burrowing) by a single central pattern
I'm confused. This reference used D-glutamate to activate swimming patterns. The previous two references used L-glutamate.
""The motor pattern underlying locomotion in the lamprey
can be elicited in the spinal cord in vitro by applying excitatory
amino acids that activate NMDA receptors."
"... amino acid transmitter that
excites motoneurons ..."
222 Related citations:
5 Cited by's:
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and chromatographic studies of peptides with tachykinin-like
immunoreactivity in the central nervous system of the lamprey.
Efficiency of electrical transmission in reticulomotoneuronal synapses of lamprey spinal cord.
"Synaptic responses in motoneurons in the isolated spinal cord of the
lamprey during stimulation of the reticulospinal axons were examined.
Chemical transmission in the synapses was partially or completely
blocked by temperature reduction of the perfusing solution,
pentobarbitone application or substitution of Mn2+ ions for Ca2+ in the
Excitatory postsynaptic potentials (EPSPs) which were
indifferent to the influences mentioned above, had an amplitude of 6-12
mV and were capable of evoking action potentials (APs) in motoneurons
due to their high amplitude, the absence of a shunting effect at the
postsynaptic membrane and the fast rise-time of the wave front.
suggestion is made that the electrical transmission is involved in
functioning of the lamprey nervous system. Its stability and efficiency
are likely to ensure functional connection between the brain and spinal
cord under such unfavourable conditions when the chemical transmission
does not operate and when the ability for locomotion would be
prerequisite for the individual to survive."
106 Related citations:
Single sensory neurons activate excitatory amino acid receptors in the lamprey spinal cord.
"The effects of excitatory amino acid (EAA) antagonists were tested on
sensory afferent excitation in the lamprey spinal cord. Paired
intracellular recordings were made from mechanosensory neurons (dorsal
cells) and second order sensory neurons (giant interneurons).
Stimulation of individual dorsal cells evoked mono- and/or polysynaptic
excitatory postsynaptic potentials (EPSPs) in giant interneurons. These
EPSPs were depressed by the EAA antagonists cis-2,3-piperidine
dicarboxylate and kynurenic acid.
Small components of the synaptic
potentials were due to electrical coupling since they were not depressed
by EAA antagonists or by calcium-free solution. The
N-methyl-D-aspartate antagonist 2-amino-5-phosphonovalerate did not
depress short-latency EPSPs. Thus, mechanosensory neurons in the lamprey
spinal cord activate EAA receptors (kainate/quisqualate receptors) on
interneurons, via mixed chemical and electrical synapses."
Once again I find myself wondering about the possible relationship between "electrical synapses" and Lamprey Fast-Slow Twitch .
175 Related citations:
See paper for individual links.
Reticulospinal neurones activate excitatory amino acid receptors.
"Paired intracellular recordings were used to study the monosynaptic
excitatory postsynaptic potentials (EPSP) in lamprey motoneurones evoked
by stimulation of single reticulospinal Müller and Mauthner cells. The
chemical component of the synaptic potentials was depressed by both
application of the non-selective excitatory amino acid antagonists
kynurenic acid and cis-2,3-piperidine dicarboxylate. The
N-methyl-D-aspartate (NMDA) antagonists Mg2+ and
2-amino-5-phosphonovalerate caused a selective depression of a late
component of the EPSP. Thus, fast-conducting reticulospinal neurones
appear to release an excitatory amino acid acting at both NMDA and
I trust the "paired intracellular recordings", but I think that the "application of the non-selective excitatory amino acid antagonists" tested for neuromodulators rather than neurotransmitters.
Excitatory amino acid-evoked membrane currents and excitatory synaptic transmission in lamprey reticulospinal neurons.
"The characteristics of excitatory amino acid-evoked currents and of
excitatory synaptic events have been examined in lamprey Müller neurons
using voltage clamp and current clamp recording techniques. Application
of glutamate evoked depolarizations associated with a decrease in input
"The order of potency of the excitatory amino acid agonists was
quisqualate greater than kainate greater than glutamate greater than
aspartate, while N-methyl-D-aspartic acid (NMDA) was inactive."
" It is concluded that both glutamate responses and excitatory synaptic transmission
in lamprey Müller neurons are mediated by non-NMDA-type receptors and
that these receptors are associated with ionic channels with a low
elementary conductance. The combined pharmacological and biophysical
characteristics of these responses are therefore different from those
previously reported in other preparations. Spontaneous (but not
stimulus-evoked) inhibitory synaptic events in Müller neurons were
blocked reversibly by 1 mM KYN but not by 100 microM APV, suggesting
that excitation of interneurons inhibitory to Müller cells was also
mediated by non-NMDA receptors."
I think the experimental substances were bath-applied and therefore neuromodulators and not neurotransmitters.
889 Related citations:
Possible target neurons of the reticulospinal cholecystokinin (CCK) projection to the lamprey spinal cord: immunohistochemistry combined with intracellular staining with lucifer yellow.
"A subpopulation of reticulospinal neurons in the posterior
rhombencephalic reticular nucleus in lamprey contains a cholecystokinin
studies of cholecystokininlike peptides and their relation to 5-HT,
CGRP, and bombesin immunoreactivities in the brainstem and spinal cord
"In the spinal cord, three separate systems reacted with CCK antisera."
Neurotransmitters: 5-HT, bombesin, cholecystokinin
The effect of an uptake inhibitor (dihydrokainate) on endogenous excitatory amino acids in the lamprey spinal cord as revealed by microdialysis.
of excitatory interneurons contributing to generation of locomotion in
lamprey: structure, pharmacology, and function.
Discussion of "excitatory interneurons", but nothing about specific neurotransmitters or receptors.
Further evidence for excitatory
amino acid transmission in lamprey reticulospinal neurons: selective
retrograde labeling with (3H)D-aspartate.
"The distribution of radiolabeled neurons in the brain stem of Lampetra
fluviatilis was studied following unilateral injections of
(3H)D-aspartate in the rostral spinal cord.
After survival periods of
1-3 days, labeled perikarya were present within and nearby the
posterior, middle, and anterior rhombencephalic reticular nuclei and in
the mesencephalic reticular nucleus.
The highest number of
(3H)D-aspartate labeled cell bodies were present in the posterior
rhombencephalic reticular nucleus. The labeled reticulospinal
neurons were distributed mainly ipsilateral to the injection site and
included the giant Müller cells as well as medium-sized and small
neurons. Contralateral labeling occurred in cell bodies scattered along
the lateral margin of the rhombencephalic reticular formation, the most
rostral of these contralaterally projecting neurons being the Mauthner
The (3H)D-aspartate labeling correlates with previous
electrophysiological studies showing that lamprey reticulospinal neurons utilize excitatory amino acid transmission."
106 Related citations:
"lamprey reticulospinal neurons utilize excitatory amino acid transmission."
Monosynaptic excitatory amino acid transmission from the posterior rhombencephalic reticular nucleus to spinal neurons involved in the control of l...
Presynaptic GABAA and GABAB Receptor-mediated Phasic Modulation in Axons of Spinal Motor Interneurons.
GABA/Glycine Inhibition for full Abstract, Related citations and Cited by's.
GABAergic input to axons of spinal interneurons and primary sensory
neurons in the lamprey spinal cord as shown by intracellular Lucifer
yellow and GABA immunohistochemistry.
Lamprey GABA for full Abstract, Related citations and Cited by's.
5-Hydroxytryptamine depresses reticulospinal excitatory postsynaptic potentials in motoneurons of the lamprey.
Both GABA and
somatostatin hyperpolarized the edge cells but through different ionic
mechanisms. GABA activated a chloride current while somatostatin
activated a current most likely carried by potassium which, however,
could not be blocked by any of the conventional potassium blockers."
Co-localized GABA and somatostatin use different ionic mechanisms to hyperpolarize target neurons in the lamprey spinal cord.
"gamma-Aminobutyric acid (GABA) and somatostatin are co-localized in
cells close to the central canal in the lamprey. These cells project to
the lateral margin of the spinal cord where they form a GABA and
somatostatin containing plexus. Stretch receptor neurons (edge cells)
are situated along the lateral margin of the spinal cord and their
dendrites extend into the GABA and somatostatin containing plexus. To
investigate whether GABA and/or somatostatin exert an affect on edge
cells, these putative transmitters were applied from extracellular
pipettes onto edge cells during intracellular recordings.
101 Related citations:
root and dorsal column mediated synaptic inputs to reticulospinal
neurons in lampreys: involvement of glutamatergic, glycinergic, and
"This study was aimed at characterizing the inputs from
dorsal roots and dorsal columns to reticulospinal neurons within the
posterior rhombencephalic reticular nucleus in the lamprey. The in vitro
isolated brainstem and spinal cord preparation was used.
Microstimulation of dorsal roots and columns on both sides induced,
in identified reticulospinal neurons, synaptic responses which consisted
of large IPSPs mixed with excitation, particularly from stimulation on
the ipsilateral side.
When the spinal cord was selectively exposed to kynurenic acid or to
Ca2+ free Ringer's containing 2mM Mn2+, synaptic responses to
stimulation of dorsal roots and columns were not modified, whereas the
same responses were abolished when the brainstem was exposed selectively
to kynurenic acid, thus suggesting that the responses were carried by
long fibres ascending directly to the brainstem.
The excitatory and inhibitory synaptic responses are relayed by
interneurons located in the brainstem. The ascending excitatory inputs
to inhibitory interneurons and, most likely, also to excitatory
interneurons, use excitatory amino acid transmission.
Inhibitory responses were abolished by adding the glycinergic
antagonist strychnine (5 microM) to the physiological solution, thus
suggesting that inhibitory interneurons use glycine transmission. The
synaptic transmission was depressed by (-)-baclofen, a GABAB agonist,
probably acting at a presynaptic site.
Taken together, the present results suggest that dorsal root and
dorsal column stimulations give rise to disynaptic inhibition and
excitation of reticulospinal neurons mediated by excitatory and
inhibitory amino acid transmission via brainstem interneurons."
252 Related citations:
No forwarding link. See PubMed abstract.
5-HT innervation of reticulospinal neurons and other brainstem structures in lamprey.
"In order to determine if reticulospinal neurons involved in the control
of locomotion and responsive to exogenously applied 5-hydroxytryptamine
(5-HT) are innervated by fibers that contain serotonin, the
serotoninergic innervation of reticulospinal neurons, identified by
retrograde labeling with fluorescein-conjugated dextran-amine (FDA), was
investigated by immunohistochemistry in the lamprey brainstem.
widespread distribution of 5-HT immunoreactive (5-HT-ir) fibers was seen
within the basal plate of the brainstem, an area containing
reticulospinal somata and dendritic aborizations. Numerous 5-HT varicose
fibers were found in close relation to large reticulospinal cell
bodies, particularly in the middle and anterior rhombencephalic
reticular nuclei (MRRN and ARRN). Some of these reticulospinal somata
were surrounded by a very dense pericellular 5-HT innervation. 5-HT-ir
fibers were also seen in other brain structures that are known to
influence reticulospinal neurons such as the rhombencephalic alar plate
containing sensory relay interneurons, cranial nerves (III-X),
cerebellum, and tectum.
These findings suggest that, as in the spinal
cord, motor behavior controlled by reticulospinal neurons may be subject
to a serotoninergic modulation."
149 Related citations:
Neural networks that co-ordinate locomotion and body orientation in lamprey.
Trigeminal inputs to reticulospinal neurones in lampreys are mediated by excitatory and inhibitory amino acids.
(RS) neurones integrate sensory inputs from several modalities to
generate appropriate motor commands for maintaining body orientation and
initiation of locomotion in lampreys. As in other vertebrates,
trigeminal afferents convey sensory inputs from the head region.
vitro brainstem/spinal cord preparation of the lamprey was used for
characterizing trigeminal inputs to RS neurones as well as the
transmitter systems involved. The trigeminal nerve on each side was
electrically stimulated and synaptic responses, which consisted of mixed
excitation and inhibition, were recorded intracellularly in the middle
and posterior rhombencephalic reticular nuclei.
The EPSPs were mediated
by activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic
acid (AMPA)/kainate receptors. An increase in the late phase of the
excitatory response occurred when Mg2+ ions were removed from the
Ringer's solution. This effect was antagonized by
2-amino-5-phosphonopentanoate (2-AP5) or reversed by restoring Mg2+ ions
to the perfusate suggesting the activation of N-methyl-D-aspartate
IPSPs were mediated by glycine. These findings are
similar to those reported for other types of sensory inputs conveyed to
RS neurones, where excitatory and inhibitory amino acid transmission is also involved."
This reference starts out by describing electrical stimulation of a
nerve and electrically monitoring the response, but then discusses
receptors which were apparently activated by bath-applied ligands.
These would have been neuromodulators rather than neurotransmitters.
102 Related citations:
See PubMed abstract page.
Rostrocaudal distribution of 5-HT innervation in the lamprey spinal cord and differential effects of 5-HT on fictive locomotion.
Neurotransmitter: 5 -HT
fictive locomotion = CPG 1996 161<349
of pharmacologically distinct metabotropic glutamate receptors
depresses reticulospinal-evoked monosynaptic EPSPs in the lamprey spinal
"These results provide evidence for the colocalization of at least two
different subtypes of presynaptic mGluRs on a single reticulospinal axon
in the lamprey. These presynaptic mGluRs could serve as glutamatergic
autoreceptors limiting the extent of reticulospinal-mediated excitation
of spinal neurons."
Receptor: presynaptic mGluR
See: Central Pattern Generators for full Abstract and link to Free full text.
Organization of the lamprey striatum - transmitters and projections.
The purpose of the present study is to characterize the striatum of
the lamprey by immunohistochemical and tracing techniques. Cells
immunoreactive for GABA and substance P (SP), and positive for
acetylcholinesterase, are present in the lamprey striatum.
Immunoreactive (ir) fibers were detected by antisera raised against SP,
dopamine, enkephalin and serotonin.
These immunoreactive fibers were mainly located in the
periventricular neuropil that borders the striatum and in which
GABAergic striatal neurons distributed their dendritic arbors.
Putative connections between the striatum, the ventral part of the
lateral pallium, and the diencephalic motor centers involved in the
control of locomotion were studied by using fluorescein-coupled dextran
amines (FDA) as a tracer. The striatum projects to the ventral part of
the lateral pallium (lpv), where GABA-ir cells and SP-ir fibers were
The lpv in turn projects to the ventral thalamus, which has
descending connections to the reticulospinal cells involved in the
control of locomotion.
These results, together with previous findings of histaminergic and
neurotensin projections, suggest that the lamprey striatum and its
inputs with regard to neurotransmitters/modulators are very similar to
those of modem amniotes, including primates, and are thus conserved to a
Endogenous and exogenous dopamine presynaptically inhibits glutamatergic reticulospinal transmission via an action of D2-receptors on N-type Ca2+ channels.
"In this study, the effects of exogenously applied and endogenously released dopamine (DA), a powerful modulator of the lamprey
locomotor network, are examined on excitatory glutamatergic synaptic
transmission between reticulospinal axons and spinal neurons.
application of DA (1-50 micro m) reduced the amplitude of monosynaptic
reticulospinal-evoked glutamatergic excitatory postsynaptic potentials
(EPSPs). The effect of DA was blocked by the D2-receptor antagonist
eticlopride, and mimicked by the selective D2-receptor agonist 2,10,11
trihydroxy-N-propyl-noraporphine hydrobromide (TNPA). Bath application
of the DA reuptake blocker bupropion, which increases the extracellular
level of dopamine, also reduced the monosynaptic EPSP amplitude. This
effect was also blocked by the D2-receptor antagonist eticlopride.
investigate if the action of DA was exerted at the presynaptic level,
the reticulospinal axon action potentials were prolonged by
administering K+ channel antagonists while blocking l-type Ca2+
channels. A remaining Ca2+ component, mainly dependent on N and P/Q
channels, was depressed by DA. When DA (25-50 micro m) was applied in
the presence of omega-conotoxin GVIA, a toxin specific for N-type Ca2+
channels, it failed to affect the monosynaptic EPSP amplitude. DA did
not affect the response to extracellularly ejected d-glutamate, the
postsynaptic membrane potential, or the electrical component of the
DA thus acts at the presynaptic level to modulate reticulospinal
385 Related citations:
Development and organization of the descending serotonergic brainstem-spinal projections in the sea lamprey.
"The organization and development of the descending spinal
projections from serotonergic rhombencephalic neurons in the larval sea
lamprey were investigated by double labeling, tract-tracing methods and
immunocytochemistry against serotonin. The results showed that two
serotonergic populations of the isthmic and vagal reticular regions
present reticulospinal neurons from the beginning of the larval
Of the three serotonergic subpopulations recognized in
the isthmic reticular group, only two - the medial and ventral
subpopulations - project to the spinal cord, with most of the projecting
cells in the caudal part of the medial isthmic subpopulation.
Occasional cells projecting to the spinal cord were observed in the
The vagal reticular serotonergic
nucleus situated in the caudal rhombencephalon also presents cells with
The early development of the brainstem
serotonergic projections to the spinal cord appears to be a conserved
trait in all vertebrates studied. Although a serotonergic
hindbrain-spinal projection system appears to have been present before
the divergence of agnathans and gnathostomes, no serotonergic cells were
observed in the raphe region in lamprey. Moreover, proportionally more
rostral hindbrain serotonergic cells contribute to the spinal
serotonergic projections in the sea lamprey than in jawed vertebrates."
"no serotonergic cells were observed in the raphe region in lamprey"
So the actions of serotonin in the lamprey are very different from the actions in humans described in
Boys without Fathers .
522 Related citations:
See the PubMed abstract page.
Forebrain dopamine depletion impairs motor behavior in lamprey.
"The structure of the basal ganglia appears to be conserved throughout
vertebrate evolution, with characteristic cellular and transmitter
components in each area, and the same types of afferent input. As
described in rodents and primates, depletion of the striatal dopamine
results in characteristic motor deficits. To explore if this role of the
basal ganglia in modulating motor function was present early in
vertebrate evolution, we investigated here the effects of striatal
dopamine depletion in the lamprey, a cyclostome, which diverged from the
main vertebrate line around 560 million years ago. The lamprey striatum
contains the same cellular elements as found in mammals, and receives
the same types of input, including a prominent dopamine innervation. We
show here that MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine; 100
mg/kg i.p.), a neurotoxin, depletes forebrain and striatal dopamine
levels in lamprey to 15% of control values, and has profound effects on
motor performance. Twenty-four and 48 h after MPTP injection, lampreys
demonstrated marked reductions in spontaneous swimming and the duration
of each swimming episode. Impairments in the ability to initiate
movements were shown by a decreased rate of initiation. Furthermore, the
initiation and maintenance of locomotion induced by olfactory mucosa
stimulation was severely impaired, as was the coordination of different
motor tasks. These deficits were ameliorated by the dopamine agonist
apomorphine. The motor deficits arising after striatal dopamine
depletion are thus qualitatively similar in cyclostomes and mammals. The
role of the dopamine innervation of the striatum thus appears to be
conserved throughout vertebrate evolution."
10 Cited by's:
Serotonin and GABA are colocalized in restricted groups of neurons in
the larval sea lamprey brain: insights into the early evolution of
neurotransmitter colocalization in vertebrates
"Colocalization of the classic neurotransmitters serotonin (5-HT) and
gamma-aminobutyric acid (GABA) (or the enzyme that synthesizes the
latter, glutamate decarboxylase) has been reported in a few neurons of
the rat raphe magnus-obscurus nuclei. However, there are no data on the
presence of neurochemically similar neurons in the brain of
Lampreys are the oldest extant vertebrates
and may provide important data on the phylogeny of neurochemical
systems. The colocalization of 5-HT and GABA in neurons of the sea
lamprey brain was studied using antibodies directed against 5-HT and
GABA and confocal microscopy. Colocalization of the neurotransmitters
was observed in the diencephalon and the isthmus.
In the diencephalon,
about 87% of the serotonergic cells of the rostral tier of the dorsal
thalamus (close to the zona limitans) exhibited GABA immunoreactivity.
In addition, occasional cells double-labelled for GABA and 5-HT were
observed in the hypothalamic tuberal nucleus and the pretectum.
three serotonergic isthmic subgroups already recognized in the sea
lamprey isthmus (dorsal, medial and ventral), such double-labelled cells
were only observed in the ventral subgroup (about 61% of the
serotonergic cells in the ventral subgroup exhibited GABA
immunoreactivity). An equivalence between these lamprey isthmic cells
and the serotonergic/GABAergic raphe cells of mammals is suggested.
Present findings suggest that serotonergic/GABAergic neurons are more
extensive in lampreys than in the rat and probably appeared before the
separation of agnathans and gnathostomes. Cotransmission by release of
5-HT and GABA by the here-described lamprey brain neurons is proposed."
107 Related citations:
Free PMC Article with many active links.
I also got the PDF from the library.
A parallel cholinergic brainstem pathway for enhancing locomotor drive
"The brainstem locomotor system is believed to be organized serially from the mesencephalic locomotor region (MLR) to reticulospinal neurons, which in turn project to locomotor neurons in the spinal cord. We identified brainstem muscarinoceptive neurons in lampreys (Petromyzon marinus) that received parallel inputs from the MLR and projected back to reticulospinal cells to amplify and extend the duration of locomotor output. These cells responded to muscarine with extended periods of excitation, received direct muscarinic excitation from the MLR and projected glutamatergic excitation to reticulospinal neurons. Targeted blockade of muscarine receptors over these neurons profoundly reduced MLR-induced excitation of reticulospinal neurons and markedly slowed MLR-evoked locomotion. The presence of these neurons forces us to rethink the organization of supraspinal locomotor control, to include a sustained feedforward loop that boosts locomotor output."
106 Related citations:
11 Cited by's:
The dopamine D2 receptor gene in lamprey, its expression in the striatum and cellular effects of D2 receptor activation.
"All basal ganglia subnuclei have recently been identified in lampreys, the phylogenetically oldest group of vertebrates. Furthermore, the interconnectivity of these nuclei is similar to mammals and tyrosine hydroxylase-positive (dopaminergic) fibers have been detected within the input layer, the striatum. Striatal processing is critically dependent on the interplay with the dopamine system, and we explore here whether D2 receptors are expressed in the lamprey striatum and their potential role.
We have identified a cDNA encoding the dopamine D2 receptor from the lamprey brain and the deduced protein sequence showed close phylogenetic relationship with other vertebrate D2 receptors, and an almost 100% identity within the transmembrane domains containing the amino acids essential for dopamine binding. There was a strong and distinct expression of D2 receptor mRNA in a subpopulation of striatal neurons, and in the same region tyrosine hydroxylase-immunoreactive synaptic terminals were identified at the ultrastructural level. The synaptic incidence of tyrosine hydroxylase-immunoreactive boutons was highest in a region ventrolateral to the compact layer of striatal neurons, a region where most striatal dendrites arborise. Application of a D2 receptor agonist modulates striatal neurons by causing a reduced spike discharge and a diminished post-inhibitory rebound.
We conclude that the D2 receptor gene had already evolved in the earliest group of vertebrates, cyclostomes, when they diverged from the main vertebrate line of evolution (560 mya), and that it is expressed in striatum where it exerts similar cellular effects to that in other vertebrates. These results together with our previous published data (Stephenson-Jones et al. 2011, 2012) further emphasize the high degree of conservation of the basal ganglia, also with regard to the indirect loop, and its role as a basic mechanism for action selection in all vertebrates."
108 Related citations:
Free PMC Article
Dopamine differentially modulates the excitability of striatal neurons of the direct and indirect pathways in lamprey.
http://www.ncbi.nlm.nih.gov/pubmed/23637194 Free full text
"The functions of the basal ganglia are critically dependent on dopamine.
In mammals, dopamine differentially modulates the excitability of the
direct and indirect striatal projection neurons, and these populations
selectively express dopamine D1 and D2 receptors, respectively. Although
the detailed organization of the basal ganglia is conserved throughout
the vertebrate phylum, it was unknown whether the differential dopamine
modulation of the direct and indirect pathways is present in
non-mammalian species. We aim here to determine whether the receptor
expression and opposing dopaminergic modulation of the direct and
indirect pathways is present in one of the phylogenetically oldest
vertebrates, the river lamprey.
Using in situ hybridization and patch-clamp recordings, we show that D1
receptors are almost exclusively expressed in the striatal neurons
projecting directly to the homolog of the substantia nigra pars
reticulata. In addition, the majority of striatal neurons projecting to
the homolog of the globus pallidus interna/globus pallidus externa
express D1 or D2 receptors. As in mammals, application of dopamine
receptor agonists differentially modulates the excitability of these
neurons, increasing the excitability of the D1-expressing neurons and
decreasing the excitability of D2-expressing neurons. Our results
suggest that the segregated expression of the D1 and D2 receptors in the
direct and indirect striatal projection neurons has been conserved
across the vertebrate phylum. Because dopamine receptor agonists
differentially modulate these pathways, increasing the excitability of
the direct pathway and decreasing the excitability of the indirect
pathway, this organization may be conserved as a mechanism that biases
the networks toward action selection."
Forebrain dopamine neurons project down to a brainstem region controlling locomotion.
"The contribution of dopamine (DA) to locomotor control is traditionally attributed to ascending dopaminergic projections from the substantia
nigra pars compacta and the ventral tegmental area to the basal ganglia,
which in turn project down to the mesencephalic locomotor region (MLR),
a brainstem region controlling locomotion in vertebrates. However, a
dopaminergic innervation of the pedunculopontine nucleus, considered
part of the MLR, was recently identified in the monkey. The origin and
role of this dopaminergic input are unknown. We addressed these
questions in a basal vertebrate, the lamprey.
Here we report a functional descending dopaminergic pathway from the
posterior tuberculum (PT; homologous to the substantia nigra pars
compacta and/or ventral tegmental area of mammals) to the MLR. By using
triple labeling, we found that dopaminergic cells from the PT not only
project an ascending pathway to the striatum, but send a descending
projection to the MLR. In an isolated brain
preparation, PT stimulation elicited excitatory synaptic inputs into
patch-clamped MLR cells, accompanied by activity in reticulospinal
cells. By using voltammetry coupled with electrophysiological
recordings, we demonstrate that PT stimulation evoked DA release in the
MLR, together with the activation of reticulospinal cells. In a
semi-intact preparation, stimulation of the PT elicited reticulospinal
activity together with locomotor movements. Microinjections of a D1
antagonist in the MLR decreased the locomotor output elicited by PT
stimulation, whereas injection of DA had an opposite effect. It appears
that this descending dopaminergic pathway has a modulatory role on MLR
cells that are known to receive glutamatergic projections and promotes
"It appears that this descending dopaminergic pathway has a modulatory role on MLR cells that are known to receive glutamatergic projections and promotes locomotor output."
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3 Cited by's:
Free PMC Article
2013 29<349 Free Article
Dopamine differentially modulates the excitability of striatal neurons of the direct and indirect pathways in lamprey.
111 Related citations:
Evolutionarily conserved organization of the dopaminergic system in lamprey: SNc/VTA afferent and efferent connectivity and D2 receptor expression.
"The dopaminergic system influences motor behavior, signals reward and novelty, and is an essential component of the basal ganglia in all vertebrates including the lamprey, one of the phylogenetically oldest vertebrates. The intrinsic organization and function of the lamprey basal ganglia is highly conserved. For instance, the direct and indirect pathways are modulated through dopamine D1 and D2 receptors in lamprey and in mammals. The nucleus of the tuberculum posterior, a homologue of the substantia nigra pars compacta (SNc)/ventral tegmental area (VTA) is present in lamprey, but only scarce data exist about its connectivity. Likewise, the D2 receptor is expressed in the striatum, but little is known about its localization in other brain areas. We used in situ hybridization and tracer injections, both in combination with tyrosine hydroxylase immunohistochemistry, to characterize the SNc/VTA efferent and afferent connectivity, and to relate its projection pattern with D2 receptor expression in particular. We show that most features of the dopaminergic system are highly conserved. As in mammals, the direct pallial (cortex in mammals) input and the basal ganglia connectivity with the SNc/VTA are present as part of the evaluation system, as well as input from the tectum as the evolutionary basis for salience/novelty detection. Moreover, the SNc/VTA receives sensory information from the olfactory bulbs, optic tectum, octavolateral area, and dorsal column nucleus, and it innervates, apart from the nigrostriatal pathway, several motor-related areas. This suggests that the dopaminergic system also contributes to the control of different motor centers at the brainstem level."
109 Related citations:
2 Cited by's.
Dopamine: a parallel pathway for the modulation of spinal locomotor networks.
"The spinal cord contains networks of neurons that can produce locomotor
patterns. To readily respond to environmental conditions, these networks
must be flexible yet at the same time robust. Neuromodulators play a
key role in contributing to network flexibility in a variety of
invertebrate and vertebrate networks. For example, neuromodulators
contribute to altering intrinsic properties and synaptic weights that,
in extreme cases, can lead to neurons switching between networks. Here
we focus on the role of dopamine in the control of stepping networks in
the spinal cord. We first review the role of dopamine in modulating
rhythmic activity in the stomatogastric ganglion (STG) and the leech,
since work from these preparations provides a foundation to understand
its role in vertebrate systems. We then move to a discussion of
dopamine's role in modulation of swimming in aquatic species such as the
larval xenopus, lamprey
and zebrafish. The control of terrestrial walking in vertebrates by
dopamine is less studied and we review current evidence in mammals with a
focus on rodent species. We discuss data suggesting that the source of
dopamine within the spinal cord is mainly from the A11 area of the
diencephalon, and then turn to a discussion of dopamine's role in
modulating walking patterns from both in vivo and in vitro preparations.
Similar to the descending serotonergic system, the dopaminergic system
may serve as a potential target to promote recovery of locomotor
function following spinal cord injury (SCI); evidence suggests that
dopaminergic agonists can promote recovery of function following SCI. We
discuss pharmacogenetic and optogenetic approaches that could be
deployed in SCI and their potential tractability. Throughout the review
we draw parallels with both noradrenergic and serotonergic modulatory
effects on spinal cord networks. In all likelihood, a complementary
monoaminergic enhancement strategy should be deployed following SCI.
5 Cited by's:
Serotonergic modulation of post-synaptic inhibition and locomotor alternating pattern in the spinal cord. Free PMC Article
CotA Lamprey Neurotransmitters
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