Anandamide inhibits excitatory transmission to rat substantia gelatinosa neurones in a manner different from that of capsaicin.
Actions of anandamide (10 microM) were examined on monosynaptic glutamatergic transmission from the periphery to substantia gelatinosa (SG) neurones in adult rat spinal cord slices using the whole-cell patch-clamp technique. In 64% of neurones examined, Adelta-fibre-evoked excitatory postsynaptic currents (EPSCs) were depressed (in amplitude; by 32 +/- 4%, n=21) by anandamide. On the contrary, an inhibitory action on C-fibre-evoked EPSCs was observed in only 31% of neurones tested; this magnitude (17 +/- 3%, n=4) was less than that of Adelta-fibre EPSCs (P<0.05). A cannabinoid-receptor agonist, WIN 55,212-2 (5 microM), exhibited similar actions on the EPSCs. In a neurone with minimal effects of anandamide on C-fibre EPSCs, capsaicin (1 microM) largely depressed the EPSCs (n=3); Adelta-fibre EPSCs were little affected by capsaicin. It is concluded that unlike capsaicin, anandamide inhibits more effectively Adelta-fibre than C-fibre-mediated excitatory transmission in the SG, possibly through the activation of the cannabinoid receptor.
Luo
Ceng
C
Department of Physiology, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan.
Kumamoto
Eiichi
E
Furue
Hidemasa
H
Chen
Jun
J
Yoshimura
Megumu
M
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002211:Capsaicin / Q000494:pharmacology; D004558:Electric Stimulation; D063388:Endocannabinoids; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects* / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D009412:Nerve Fibers / Q000187:drug effects* / Q000378:metabolism; D009413:Nerve Fibers, Myelinated / Q000187:drug effects* / Q000378:metabolism; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects* / Q000378:metabolism; D010146:Pain / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D053284:Polyunsaturated Alkamides; D051381:Rats; D013376:Substantia Gelatinosa / Q000187:drug effects* / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
D001095:Arachidonic Acids; D002121:Calcium Channel Blockers; D063388:Endocannabinoids; D053284:Polyunsaturated Alkamides; D018698:Glutamic Acid; D002211:Capsaicin; C078814:anandamide