Coelenterata Receptors

Cross references:  Coelenterata       Receptors in General  
Parazoa Receptors   Ligand-gated Ion Channel   
G-Protein Coupled Receptors
    Receptors Evolution Timeline  
Coelenterata Hormones   Coelenterata Nerves   
Coelenterata Hormone-Nerve Interaction    Coelenterata Neuropeptides   
Coelenterata Neurotransmitters     Coelenterata Genomics        

A new
G protein-coupled receptor from a primitive metazoan
... (PubMed 2003)
Full length article. 
    "Biogenic amine receptors mediate wide-ranging hormonal and modulatory functions in vertebrates, but are largely unknown in primitive invertebrates. In a ... cnidarian ... we obtained a full-length cDNA encoding a polypeptide with typical
G-Protein Coupled Receptor (GPCR) characteristics and which displayed a significant degree of sequence similarity (up to 45%) to biogenic amine receptors, particularly dopamine and adrenergic receptors.

NMDA and GABA B receptors are involved in control ... Hydra (PubMed) 
Abstract only.  I got PDF from the library. 
    "Our results support the mounting evidence that hydra's nervous system, acting through specific neurotransmitter receptors, mediates nematocyst discharge and that at least glutamate and GABA are involved in controlling the discharge of stenoteles and desmonemes." 
    "... glutamate was found to increase the output of the ectodermal and endodermal pacemaker systems controlling body column and tentacle contractions while GABA inhibited them."