Invertebrates endocannabinoid receptors

Elphick MR, Satou Y, Satoh N (2003) The invertebrate ancestry of endocannabinoid signalling an orthologue of vertebrate cannabinoid receptors in the urochordate Ciona intestinalis. Gene 302 95-101... 

In conclusion, there is now an emerging concept of TRP-type ion channels that are receptors for cannabinoids and/or endocannabinoids, and an interesting area for future research will be to investigate the occurrence of invertebrate TRP-type channels that are also activated by cannabinoid-related molecules. 

So far, the best-characterised example of endocannabinoid signalling in eukaryotes is CBl/CB2-mediated processes in vertebrates. Moreover, our phylogenetic analysis of the occurrence of CB1/CB2 receptors in invertebrates indicates that the ancestor of these receptors originated in a deuterostomian invertebrate, and in accordance with this view receptors of this type have so far not been found in protostomian invertebrates. The CiCBR gene that was recently identified in the invertebrate chordate Ciona intestinalis (Elphick et al. 2003) is an example of a receptor in a deuterostomian invertebrate that may resemble the putative ancestor of the vertebrate CBi and CB2 receptors. Therefore, analysis of CiCBR function in Ciona is now of particular interest. 

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