Identification and characterization of the leech CNS cannabinoid receptor: coupling to nitric oxide release

Brain Res. 1997 Apr 11;753(2):219-24. doi: 10.1016/s0006-8993(96)01484-9.


The present study demonstrates that stereoselective binding sites for anandamide, a naturally occurring cannabinoid substance, can be found in leech (Theromyzon tessulatum and Hirudo medicinalis) central nervous system. The anandamide binding site is monophasic and of high affinity exhibiting a Kd of approximately 32 nM with a Bmax of 550 fmol/mg protein in both animals. These sites are highly select as demonstrated by the inability of other types of signaling molecules to displace [3H]anandamide. Furthermore, this binding site is coupled to nitric oxide release. A deduced amino acid sequence (153 residues) analysis from a 480 pb amplified RT-PCR fragment cDNA exhibits a 49.3% and 47.2% sequence identity with human and rat cannabinoid receptors (CB1R), respectively. Thus, the leech cannabinoid receptor may be a G-protein coupled receptor with seven transmembrane domains as in CB1R. Moreover, this sequence exhibits highly conserved regions, particularly in the putative transmembrane domains 1 and 2. The presence of a cannabinoid receptor in these organisms indicates that this signaling system has been conserved during evolution.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arachidonic Acids / metabolism
  • Base Sequence
  • Cannabinoids / metabolism
  • Central Nervous System / metabolism*
  • Endocannabinoids
  • Humans
  • Leeches / metabolism*
  • Molecular Sequence Data
  • Nitric Oxide / metabolism*
  • Polyunsaturated Alkamides
  • Rats
  • Receptors, Cannabinoid
  • Receptors, Drug / genetics
  • Receptors, Drug / metabolism*


  • Arachidonic Acids
  • Cannabinoids
  • Endocannabinoids
  • Polyunsaturated Alkamides
  • Receptors, Cannabinoid
  • Receptors, Drug
  • Nitric Oxide
  • anandamide