Eliminated Sections

I have been eliminating sections of  Boys without Fathers  to reduce its emphasis on evolution and increase its emphasis on humans.  This has occurred, so far, in two stages. 

SECOND STAGE   

The second stage was implemented on 03-10-11. 

03-09-11 

As recorded in the
02-15-11 blog, below, I found myself wondering if the amphioxus and the lamprey might be unnecessary distractions, so I started working on an abbreviated version under the original title.     

Now I've begun to wonder if the entire evolutionary perspective might be an unnecessary distraction.  So I've begun to explore the possibility of focusing mainly on humans and referring to nonhuman data only when necessary.   

So I've saved the current draft as
Evolution - Boys without Fathers  ,
and I'll start working on an abbreviated version under the original title
.     

begin Second Stage of eliminated sections 

Since both the nervous system and the endocrine system become increasingly complex during the course of evolution, this paper is organized in an evolutionary sequence. 

The male dominance hierarchy makes its first evolutionary appearance among the lampreys [5], and is more clearly seen among the sharks [6].  Although it is fully evident among the teleost fish [7], I was unable to find any real evidence for it among the lungfish [8], but this may be because lungfish are fairly uncommon and perhaps not very well studied. 
The male dominance hierarchy is once again clearly observed among the salamanders [9].   However, since we humans are mammals, we'll begin our discussion with the monotremes [10].   



START HERE



Monotremes
The description in the reference is graphic and well written, so I'm going to quote it extensively. 
    "By early spring, courtship and rivalry among platypuses is well underway and males become very aggressive. They will fight for dominance and the right to mate with the females living within their range. They have no teeth and their claws are blunt, but the sharp spurs on the ankles are deadly. Normally, they are kept folded away to avoid snagging, but during battle they are raised. Fights occur in the water, where the animals are most agile, and combatants swim in tight circles, each attempting to spike the other and inject a debilitating dose of venom. The venom is toxic enough to kill a dog and cause agonizing pain and prolonged paralysis in humans [11]."   


 a marsupial, the sugar glider.  


There's a complex four-way interaction between cortisol, testosterone,
serotonin and arginine vasopressin. 

There's overwhelming experimental evidence that cortisol directly inhibits the testicular receptor for luteinizing hormone, and this, in turn, reduces the level of circulating testosterone [9]. 

On the other hand, it's still not clear why elevated cortisol, and the resulting lowered testosterone, are accompanied by an
increase in serotonin activity, as indicated by an elevated 5-HIAA/5-HT ratio.  There are at least twelve 5-HT receptors.  Two, 5-HT1AR and 5-HT3R, are known to be inhibited by testosterone.  Therefore, at these receptors, a lower testosterone level results in an elevated 5-HIAA/5-HT ratio.  However, 5-HT2AR is activated by testosterone, and, therefore, at this receptor, a lower testosterone level results in a lowered 5-HIAA/5-HT ratio.  To obscure the situation even more, the action of testosterone at many of the remaining 5-HT receptors has not yet been determined [10] ,  




The hypothalamus contains receptors for both serotonin [?] and arginine vasopressin [?]. 


, and an increase in arginine vasopressin at these receptors increases aggression [11].  However, the number of receptors present depends on the testosterone level, so that increased testosterone levels increase the number of arginine vasopressin receptors and, therefore, the response to arginine vasopressin and aggression [11]. 

The  hypothalamus also contains serotonin receptors, and at least some of these receptors appear to be 
5-HT(1B/2C)
[?].  


Serotonin at these receptors reduces the sensitivity of whatever arginine vasopressin receptors are present [12].  The
response of these receptors to testosterone is not yet known. However, testosterone may reduce the sensitivity of these receptors, i.e., the 5-HIAA/5-HT ratio, and thereby help maintain the ability of arginine vasopressin to initiate aggression. 

Therefore, testosterone may increase aggression by two mechanisms: increasing the number of arginine vasopressin receptors and interfering with what seems to be the generalized inhibitory effect of serotonin.  This reduction in the generalized inhibitory effect of serotonin also results in what is known in humans as "impulsivity".   

 


Marsupials:

A study of social status among sugar gliders showed that dominant males have lower cortisol levels and higher testosterone levels than subordinates.  Furthermore, if a dominant male is transferred to another colony where he finds himself in a subordinate position, his cortisol level rises and his testosterone level falls [30].  This inverse relationship between cortisol and testosterone, with cortisol level being the cause and testosterone level being the effect, is thought to be consistent among all vertebrates and a central element of the male dominance hierarchy [?]. 

We now have the outlines of the endocrinology of the male dominance hierarchy.  The loser in a contest between two males experiences an increase in cortisol levels consistent with a fear reaction as a consequence of losing.  The increased cortisol reduces circulating testosterone.  This, in turn, both reduces the number of arginine vasopressin receptors and unleashes the inhibitory influence of serotonin.  As a result, the defeated male becomes submissive and nonaggressive. 

But what is the evolutionary advantage of this?  It forces the defeated male to seek a new, as yet unclaimed, territory for breeding, and this, in turn, promotes the dispersal and long term survival of the species. 


Rodents:

There are hundreds of studies linking testosterone to aggressiveness in rodents.  In particular, elevating the animal's testosterone level over an extended period of time increases aggressiveness not only in males [31, 32] but also in females [33, 34], and lowering the testosterone level has just the opposite effect [35].  What is most important here is the clear conclusion that, at least in rodents in a laboratory setting, there is a definite cause and effect relationship between testosterone and aggression. 

Surprisingly, I was not able to find one single experiment which combined testosterone injection with manipulation of serotonin levels.  Most of the serotonin articles dealt with primates or humans, but there were two that found a correlation between decreased serotonin and increased impulsivity in rodents [36, 37].  Unfortunately, neither of these measured testosterone or cortisol levels. 

Although there are no published reports on the effect that injected testosterone has on serotonin, arginine vasopressin and cortisol, what we have already learned allows us a reasonable guess.  In both males and females, as testosterone goes up, serotonin responsiveness goes down and arginine vasopressin responsiveness goes up.  The animal becomes more active and aggressive and therefore more likely to prevail in dominance encounters.  This lowers the level of cortisol, the stress and fear hormone.  In males, the lowered cortisol level promotes release of testosterone by the testes which then supplements the effects of the originally injected testosterone. 

This has consequences for the dominance hierarchy because the more aggressive animal becomes dominant and the less aggressive animal is relegated to the subordinate position.  In fact, in rodents in the laboratory, testosterone has such a major influence on the dominant/subordinate relationship that subordinate males become dominant if their testosterone level is raised and dominant males become subordinate if their testosterone levels are lowered [35]. 


Primates:

Although I cannot find a reference for it, it seems to be generally assumed that the endocrine systems of primates and humans is pretty much the same as the endocrine system of rodents and that the differences in behavior as one goes up the phylogenetic scale from rodents to primates to humans is due to changes in the nervous system and not to changes in the endocrine system.  Even the changes in the nervous system and its relationship to the endocrine system are more a matter of degree than the addition of any new structures.  The rodent cerebral cortex has representations for all the primary senses but only limited capacity for making associations between the various senses.  The primate cerebral cortex has evolved large association areas which allow for integrating the input from all the senses.  The major change which characterizes humans is the enlargement of the prefrontal cortex which helps us guide our behavior in response to the emotional needs mediated by our endocrine systems [38]. 

Unlike the literature on rodents, there were far fewer articles on primates, and almost all of them concerned animals living outside the laboratory in more-or-less "free range" conditions.  The one report which described the consequences of artificially elevating a primate's testosterone levels by testosterone injections confirmed that, as was the case with rodents, administration of testosterone resulted in increased aggression [39]. 

Three interesting studies looked for behavioral correlates to the levels of testosterone and a serotonin metabolite (5-HIAA) in the cerebrospinal fluid of free-ranging monkeys.  The first showed that elevated testosterone correlated with increased aggression, reduced serotonin correlated with increased impulsivity, and the combination correlated with extreme, impulsive aggression [40].  The second showed that the impulsive monkeys with low serotonin were more likely to achieve social dominance, at which time their serotonin and impulsivity would return to normal [41].  The third showed that monkeys with low serotonin and high impulsivity that did not achieve social dominance had a very high mortality rate [42].  So evidently the low serotonin, high impulsivity monkeys either achieve social dominance through fighting or die trying.  Most studies on primate groups with stable social structures did not find a significant correlation between testosterone and dominance rank [43, 44]. 


Humans:

Unlike the situation in rodents and even primates, supplemental testosterone does not induce overt aggression in normal adult male humans [45], but may cause minor aggressive mood changes [46] and some covert aggression in response to provocation [47].  As discussed at the beginning of this paper, normal adult male humans have both lower testosterone levels and higher levels of serotonin activity than those deviant adults that society labels "personality disordered", or "criminal" or "impulsively aggressive".  However, it has been found that, in competitive situations between normal males, the testosterone level of the winners rises while the testosterone level of the losers falls [39].  Among healthy, normal adolescent boys not receiving supplemental testosterone, boys with higher testosterone levels do not show more overt aggression but are more impatient and irritable and more likely to respond to provocations or threats [49]. 

Although there are no scientific experiments which shed light on this, it is easy to speculate that the diminished influence of testosterone on the behavior of normal humans, as compared to rodents and primates, is due to the moderating influence of our greatly expanded prefrontal cortex. 


The Hypothesis
:

The outlines of my hypothesis are probably pretty clear by now.  Boys who have fathers grow up thoroughly subordinate to their dominant fathers, and this is reflected in their endocrine systems.  Domination by their fathers maintains their cortisol at high enough levels that their testosterone levels are held in check.  This prevents the inappropriate proliferation of their arginine vasopressin receptors, which reduces their aggressiveness, and permits the inhibitory effect of their serotonin systems, which reduces their impulsiveness. 

As boys with fathers grow into manhood, their inclination toward male impulsiveness and aggressiveness is guided by their fathers into socially acceptable channels, such as competition in sports or in business. 

By contrast, boys who grow up without a father or some other dominant father figure are in danger of having endocrine systems which have not been guided into socially acceptable channels.  They become the high testosterone, low serotonin deviants branded by society as "criminals" who are "personality disordered" and "impulsively aggressive". 


References:

 1.   See:  Human Cortisol, etc(Adults) 
   
 2.   See:  Human Cortisol, etc.  (Juveniles)  

 3.  S
ee:  Family Structure   

 4.  See: 
Dominance Hierarchies in General 

 5.  See: 
Lamprey Dominance Hierarchy   

 6.  See: 
Shark Dominance Hierarchy   

 7.  See: 
Teleost Dominance Hierarchies   

 8.  See: 
Lungfish   

 9.  See: 
Salamander Dominance Hierarchies   

10.  See: 
Monotremes  

11.  See:
  Monotreme Dominance Hierarchies 



 9.  See: 
Rodent Glucocorticoid-Testosterone Interaction   

10.  See: 
Rodent Glucocorticoid-Serotonin Interaction 
                
Testosterone Serotonin Interaction   
                
Rodent Hormone-Nerve Interaction 
             
  
11. 
See:  Human Cortisol, etc.   

12.  See: 
Vasopressin, Serotonin & Aggression    



30.  See: 
Monotremes & Marsupials    
 

31.  See: 
Vasopressin, Serotonin & Aggression     
 

32. 
See:  Vasopressin, Serotonin & Aggression   
 

33. 
See:  Vasopressin, Serotonin & Aggression        
 
34. 
See:  Vasopressin, Serotonin & Aggression      
 
35. 
See:  Vasopressin, Serotonin & Aggression      
 

36. 
See:  Vasopressin, Serotonin & Aggression      
 

37. 
See:  Vasopressin, Serotonin & Aggression      
 

38. 
See:   Human Neuroanatomy    

39.  See:  Primate Dominance Hierarchies     
 

40. 
See:  Primate Dominance Hierarchies     
  
41. 
See:  Primate Dominance Hierarchies       
 

42. 
See:  Primate Dominance Hierarchies        
 

43. 
See:  Primate Dominance Hierarchies        
 

44. 
See:  Primate Dominance Hierarchies        
 

45.  See: 
Testosterone Serotonin Interaction     
 

46. 
See:  Testosterone Serotonin Interaction    

47.  See:  Testosterone Serotonin Interaction
  
 
48. 
See:  Testosterone Serotonin Interaction   
 

49. 
See:  Testosterone Serotonin Interaction  


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FIRST STAGE
   

The first stage was initiated on 02-02-11 with the explanatory blog being updated on 02-15-11. 

02-15-11 

While revising the sections on the amphioxus and lamprey, I found myself wondering if they are an unnecessary distraction.  I find them interesting, but the average reader might find my basic thesis more accessible if I started with the mammals. 

So I've saved the current draft as 
Long Version - Boys Without Fathers ,
and I'll start working on an abbreviated version under the original title
.     



This page contains the early sections of  Boys without Fathers  that I eliminated. 


Eliminated Sections

begin First Stage of eliminated sections 


If the neurons which bear these receptors are GABAergic [14], then an increase in 5-HT input to these receptors will cause an increase in GABA output.  Since GABA is inhibitory, an increase in 5-HT input will cause an overall inhibitory output.  However, since testosterone desensitizes 5-HT1R and 5-HT3R, it reduces the excitatory effect of 5-HT and, consequently, reduces the output of GABA.  This, in turn, causes an overall excitatory result. 



, starting with the cephalocordate, amphioxus, and concluding with we humans. 

Perhaps I should skip the amphioxus and lamprey and jump immediately to the sharks.


Much of the next section may be deleted. 

[This means that, as we work our way up the evolutionary ladder, we will discuss the consequences of new physiological advancements as we come to them, even though these consequences have not yet been identified in the first organism in which they appear.  In particular, rats, mice and hamsters are the most frequent laboratory subjects, but the specific physiological structure or relationship discussed in a report of an experiment using one of these rodents may have originally evolved in a more primitive predecessor.  In order to highlight the behavioral consequences of the physiological structure or relationship under consideration, its consequences will be discussed at the evolutionary level where it first appears even though the understanding of these consequences was achieved through experiments with animals (usually rodents) that are more evolutionarily advanced.  I'm going to refer to this as the "reverse engineering of evolution", and you'll find the first example of this in the 'Amphioxus' section, below. ]


Amphioxus:

The amphioxus is a small (2 inch) fish-like creature that lives in shallow, somewhat warmer, coastal waters over a wide range.  Its only well developed sensory modality is touch, but, though it has no real eyes or ears, it is aware of both light and sound.  It may also have very rudimentary senses of taste and smell, but this is uncertain.  Although it is denied membership among the vertebrates because it does not have an articulated backbone, i.e.
'there are no true vertebrae', it is widely regarded as similar to the archetypal vertebrate form. [5]. 

What concerns us here is its endocrine system.  It should be noted first that arginine vasopressin is found only in mammals.  Its analogue in nonmammals is the very similar arginine vasotocin.  With this proviso, there is evidence in the amphioxus for three of the four bioactive compounds
mentioned above in relation to the male dominance hierarchy: testosterone, arginine vasotocin and serotonin.   However, only two of them: the sex hormone testosterone and the neurotransmitter serotonin; are expected to mediate the same aspects of behavior in amphioxus that they mediate in humans. 

In humans, the hypothalamus produces gonadotropin releasing hormone which is conveyed to the pituitary gland through the hypophysial portal circulation.  In response, the anterior pituitary releases luteinizing hormone into the blood.  In males, the luteinizing hormone causes the testes to produce testosterone, and in females it causes the ovaries to produce estrogen.  The testosterone or estrogen are then released back into the blood [6]. 

Although the reproductive physiology of amphioxus is much more primitive than that of the mammals, it shows the same broad outlines.  However, instead of there being a
luteinizing hormone to act as an intermediary, the levels of testosterone and estrogen are controlled directly by the release of gonadotropin releasing hormone from the amphioxus analog of the hypothalamus.  Increased release of gonadotropin releasing hormone during the breeding season causes the level of the sex hormones to peak [7]. 

Serotonin is found in the amphioxus brain in a position approximately analogous to its position in the brain of mammals [8]  Because the amphioxus has at least three, and perhaps even four, different serotonin receptors [9], the interactions between the neurons bearing these receptors and the remainder of the nervous system are quite complex, and they are still under study. 

Much of the next section may be deleted. 

[Nevertheless, all that has been learned
so far is consistent with the "reverse engineering" hypothesis that the less well studied amphioxus serotonergic system is similar to the more thoroughly studied serotonergic systems of its more advanced descendents.]     

Throughout the vertebrates, serotonin inhibits behavioral responsiveness
[10]
.  This has not yet been experimentally confirmed in the amphioxus, but, as you will see in the next section, clear experimental evidence of the inhibitory action of serotonin has been obtained in the lamprey.  

The next section needs more research.

[Both testosterone and estrogen interfere with serotonin-induced behavioral inhibition by desensitizing serotonin receptors, and they thereby increase behavioral responsiveness [11-12].] 

NOTE:  Reference [12], above is "
Inhibition by steroids of [14C]-guanidinium flux through the voltage-gated sodium channel and the cation channel of the 5-HT3 receptor of N1E-115 neuroblastoma cells".  Not only are mouse neuroblastoma cells a long way from amphioxus muscle cells, but, more importantly, the 5-HT3R has not yet been identified in either the amphioxus or the lamprey.  I obviously need to do more work here.   

The adult amphioxus spends its life in large colonies buried just beneath the surface of the sand.  There is no indication of any arrangement by rank or gender.  As the levels of testosterone and estrogen peak during the breeding season, the sex hormones reduce serotonin-induced behavioral inhibition, and the animal becomes ready to spawn.  The exact trigger for spawning has not yet been discovered, but when they do spawn, they leave the sand and swim to the surface.  The males and females mingle together while releasing their sperm and eggs into the surrounding water.  They then return to the sand.  There is no indication of any competition among them or of any male dominance hierarchy [13]. 

This very simple mating ritual is paralleled by the primitive state of some of the bioactive compounds important in mammalian reproduction.  Arginine vasotocin is found
only in the amphioxus spinal cord, not in the brain as with humans [14], and there is almost no evidence for the presence of cortisol. 


Cyclostomes

The next evolutionary stage above the amphioxus which has still living members, and the most primitive of the true vertebrates, are the cyclostomes.  The two existent genera are the lamprey and the hagfish.  Since hagfish live in salt water, usually at considerable depth, while lampreys always spend at least some of their life cycle in fresh water, much more is known about the lamprey.  In addition, the lamprey and the hagfish parted company about 400 million years ago during the Devonian, when the lamprey swam inland to become our ancestor and the hagfish stayed in the sea.  So the hagfish will not be considered here. 

The brain of the lamprey is a quantum leap up from the brain of the amphioxus [15].  Unlike the amphioxus, which has neither eyes nor ears and only a very questionable ability to taste or smell, the lamprey has fully functional eyes and ears, and definite appreciation for both tastes and odors.  In order to handle all this extra input, the lamprey brain has expanded enormously. 



In addition to its much more complicated brain, the lamprey endocrine system has also advanced over that of the amphioxus. 

The major advancement at this evolutionary level, among the bioactive compounds we are considering, is that arginine vasotocin is now found in the same parts of the brain in which arginine vasopressin is found in mammals [16].  There is a complex three way interaction between testosterone, arginine vasotocin/vasopressin and serotonin. 

The hypothalamus contains receptors for arginine vasotocin/vasopressin, and an increase in arginine vasotocin/vasopressin at these receptors increases aggression [17].  However, the number of receptors present depends on the testosterone level, so that increased testosterone levels increase the number of arginine vasotocin/vasopressin receptors and, therefore, the response to arginine vasotocin/vasopressin [18]. 

In addition, the  hypothalamus also contains serotonin receptors, and serotonin at these receptors reduces the sensitivity of whatever arginine vasotocin/vasopressin receptors are present [19].  At the same time, however, as discussed in relation to the amphioxus, testosterone reduces the sensitivity of serotonin receptors and thereby helps maintain the ability of arginine vasotocin/vasopressin to initiate aggression. 

Therefore, testosterone increases aggression by two mechanisms: increasing the number of arginine vasotocin/vasopressin receptors and interfering with the generalized inhibitory effect of serotonin.  This reduction in the generalized inhibitory effect of serotonin also results in what is known in humans as "impulsivity". 

In addition to their potential modulation of the aggression promoting effects of arginine vasotocin/vasopressin outlined above, testosterone, estrogen and serotonin continue to play their roles in reproduction as they had in amphioxus, and serotonin has extended its presence and effects throughout the newly enlarged lamprey brain in a pattern consistent with that found in mammals [20].  Only cortisol does not appear to have achieved the level of importance that it has in mammals.  In fact, it is almost undetectable in lampreys.  This is because the adrenal gland, which is the source of cortisol, has only just begun to evolve [21]. 

There is still no evidence of intraspecies aggression or a male dominance hierarchy [22].  River lampreys build nests which are used year after year.  As many as thirty will gather together to spawn in a manner very reminiscent of the amphioxus [23]. 

5.  See:  Amphioxus

 6. 
See:  Hormones in General   Human Endocrinology in General      
                Human Reproductive Endocrinology

 7. 
See:  Amphioxus Pituitary     
 
 8. 
See:  Amphioxus Neurotransmitters.      

 9.  See: 
Amphioxus Serotonin System     Receptors Evolution Timeline  
               
Reverse Engineering Amphioxus Serotonin   

10. 
See:  Rodent Hormone-Nerve Interaction  
                
Teleost Dominance Hierarchies  

11.  See: 
Rodent Hormone-Nerve Interaction  

12. 
See:  Reverse Engineering Amphioxus Serotonin 
                 
Receptors Evolution Timeline    

13.  See: 
Amphioxus Gonads    
 
14.  See: 
Amphioxus Neuropeptides   
 

15.  See: 
Lamprey Nervous System   
 
16.  See: 
Lamprey Hormones     

17.  See: 
Human Cortisol, etc.      

18. 
See:  Human Cortisol, etc.   
 
19.  See: 
Vasopressin, Serotonin & Aggression     

20.  See: 
Lamprey Neurotransmitters   Lamprey Serotonin System    
 
21. 
See:  Lamprey Hormones   

22. 
See:  Lamprey Hormones    
 

23. 
See:  Lamprey   



4-19-11 

Most of the below is probably repetitious.  I copied it from the Endocrinology of Dominance section of Boys without Fathers just in case. 

Relocated Segment #2

This is the more recent of the two 'Relocated Segments'

There's a complex four-way interaction between cortisol, testosterone,
serotonin and arginine vasopressin. 

There's overwhelming experimental evidence that cortisol directly inhibits the testicular receptor for luteinizing hormone, and this, in turn, reduces the level of circulating testosterone [9]. 


 9.  See: 
Rodent Glucocorticoid-Testosterone Interaction   


On the other hand, it's still not clear why elevated cortisol, and the resulting lowered testosterone, are accompanied by an
increase in serotonin activity, as indicated by an elevated 5-HIAA/5-HT ratio.  There are at least twelve 5-HT receptors.  Two, 5-HT1AR and 5-HT3R, are known to be inhibited by testosterone.  Therefore, at these receptors, a lower testosterone level results in an elevated 5-HIAA/5-HT ratio.  However, 5-HT2AR is activated by testosterone, and, therefore, at this receptor, a lower testosterone level results in a lowered 5-HIAA/5-HT ratio.  To obscure the situation even more, the action of testosterone at many of the remaining 5-HT receptors has not yet been determined [10] ,  


10.  See:  Rodent Glucocorticoid-Serotonin Interaction 
                
Testosterone Serotonin Interaction   
                
Rodent Hormone-Nerve Interaction 



The hypothalamus contains receptors for both serotonin [?] -
[19] and arginine vasopressin [?] - [16]

19.  See:  Vasopressin, Serotonin & Aggression     

16.  See:  Lamprey Hormones       

, and an increase in arginine vasopressin at these receptors increases aggression [11] -
[17].  However, the number of receptors present depends on the testosterone level, so that increased testosterone levels increase the number of arginine vasopressin receptors and, therefore, the response to arginine vasopressin and aggression [11] - [18]


17.  See: 
Human Cortisol, etc.      

18. 
See:  Human Cortisol, etc.   


 

The  hypothalamus also contains serotonin receptors
[19], and at least some of these receptors appear to be 5-HT(1B/2C) [?].  

19.  See:  Vasopressin, Serotonin & Aggression     


Serotonin at these receptors reduces the sensitivity of whatever arginine vasopressin receptors are present [12] -
[19].  The response of these receptors to testosterone is not yet known. However, testosterone may reduce the sensitivity of these receptors, i.e., the 5-HIAA/5-HT ratio, and thereby help maintain the ability of arginine vasopressin to initiate aggression.   

19.  See:  Vasopressin, Serotonin & Aggression     

Therefore, testosterone may increase aggression by two mechanisms: increasing the number of arginine vasopressin receptors and interfering with what seems to be the generalized inhibitory effect of serotonin.  This reduction in the generalized inhibitory effect of serotonin also results in what is known in humans as "impulsivity".   

 

Relocated Segment #1

This is the older of the two 'Relocated Segments'


This was originally a portion of the long version of  
Boys without Fathers  . 

There is a complex three way interaction between testosterone, arginine vasotocin/vasopressin and serotonin. 

The hypothalamus contains receptors for arginine vasotocin/vasopressin, and an increase in arginine vasotocin/vasopressin at these receptors increases aggression [20].  However, the number of receptors present depends on the testosterone level, so that increased testosterone levels increase the number of arginine vasotocin/vasopressin receptors and, therefore, the response to arginine vasotocin/vasopressin [21]. 

In addition, the  hypothalamus also contains serotonin receptors, and serotonin at these receptors reduces the sensitivity of whatever arginine vasotocin/vasopressin receptors are present [22].  At the same time, however, as discussed in relation to the amphioxus, testosterone reduces the sensitivity of serotonin receptors and thereby helps maintain the ability of arginine vasotocin/vasopressin to initiate aggression. 

Therefore, testosterone increases aggression by two mechanisms: increasing the number of arginine vasotocin/vasopressin receptors and interfering with the generalized inhibitory effect of serotonin.  This reduction in the generalized inhibitory effect of serotonin also results in what is known in humans as "impulsivity". 

In addition to their potential modulation of the aggression promoting effects of arginine vasotocin/vasopressin outlined above, testosterone, estrogen and serotonin continue to play their roles in reproduction as they had in amphioxus, and serotonin has extended its presence and effects throughout the newly enlarged lamprey brain in a pattern consistent with that found in mammals [23].  Only cortisol does not appear to have achieved the level of importance that it has in mammals.  In fact, it is almost undetectable in lampreys.  This is because the adrenal gland, which is the source of cortisol, has only just begun to evolve [24]. 

??? refs???

























CotA - Eliminated Sections
130611 - 1331 original



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