Multiple actions of anandamide on neonatal rat cultured sensory neurones.
1. We have investigated the effects of the endocannabinoid anandamide (AEA) on neuronal excitability and vanilloid TRPV1 receptors in neonatal rat cultured dorsal root ganglion neurones. 2. Using whole-cell patch-clamp electrophysiology, we found that AEA inhibits high-voltage-activated Ca(2+) currents by 33+/-9% (five out of eight neurones) in the absence of the CB(1) receptor antagonist SR141716A (100 nM) and by 32+/-6% (seven out of 10 neurones) in the presence of SR141716A. 3. Fura-2 fluorescence Ca(2+) imaging revealed that AEA produced distinct effects on Ca(2+) transients produced by depolarisation evoked by 30 mM KCl. In a population of neurones of larger somal area (372+/-20 microM(2)), it significantly enhanced Ca(2+) transients (80.26+/-13.12% at 1 microM), an effect that persists after pertussis toxin pretreatment. In a population of neurones of smaller somal area (279+/-18 microM(2)), AEA significantly inhibits Ca(2+) transients (30.75+/-3.54% at 1 microM), an effect that is abolished by PTX pretreatment. 4. Extracellular application of 100 nM AEA failed to evoke TRPV1 receptor inward currents in seven out of eight neurones that responded to capsaicin (1 microM), with a mean inward current of -0.94+/-0.21 nA. In contrast, intracellular application of 100 nM AEA elicited robust inward currents in approximately 62% of neurones, the mean population response was -0.85+/-0.21 nA. When AEA was applied to the intracellular environment with capsazepine (1 microM), the mean population inward current was -0.01+/-0.01 nA. Under control conditions, mean population current fluctuations of -0.09+/-0.05 nA were observed.
Evans
Rhian M
RM
Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland.
Scott
Roderick H
RH
Ross
Ruth A
RA
D000818:Animals; D000831:Animals, Newborn; D001095:Arachidonic Acids / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D004357:Drug Synergism; D063388:Endocannabinoids; D016257:Fura-2 / Q000737:chemistry; D005727:Ganglia, Spinal / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects*; D037342:Pertussis Toxin / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D011189:Potassium Chloride / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D043884:Receptor, Cannabinoid, CB1 / Q000187:drug effects / Q000502:physiology; D011955:Receptors, Drug / Q000037:antagonists & inhibitors / Q000187:drug effects; D000077285:Rimonabant; D050916:TRPV Cation Channels
D001095:Arachidonic Acids; D015220:Calcium Channels; D063388:Endocannabinoids; D010880:Piperidines; D053284:Polyunsaturated Alkamides; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D011955:Receptors, Drug; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D011189:Potassium Chloride; D037342:Pertussis Toxin; C071423:capsazepine; D000077285:Rimonabant; D002211:Capsaicin; D016257:Fura-2; C078814:anandamide