Anandamide transport inhibitor AM404 and structurally related compounds inhibit synaptic transmission between rat hippocampal neurons in culture independent of cannabinoid CB1 receptors.
N-(hydroxyphenyl)-arachidonamide (AM404) is an inhibitor of endocannabinoid transport. We examined the effects of AM404 on glutamatergic synaptic transmission using network-driven increases in intracellular Ca2+ concentration ([Ca2+] spikes) as an assay. At a concentration of 1 microM AM404 inhibited [Ca2+]i spiking by 73+/-8%. The cannabinoid CB1 receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride (SR141716A), the vanilloid VR1 receptor antagonist capsazepine (CPZ), and treatment with pertussis toxin failed to block AM404-mediated inhibition. AM404 (3 microM) inhibited action-potential-evoked Ca2+ influx by 58+/-3% but failed to affect calcium influx evoked by depolarization with 30 mM K+, suggesting that the inhibition of electrically evoked [Ca2+]i increases and that [Ca2+]i spiking was due to inhibition of Na+ channels. Palmitoylethanolamide (PMEA), capsaicin (CAP) and (5Z,8Z,11Z,14Z)-N-(4-hydroxy-2-methylphenyl)-5,8,11,14-eicosatetraenamide (VDM11), compounds structurally similar to AM404, inhibited [Ca2+]i spiking by 34+/-10%, 42+/-18% and 67+/-12%, respectively. Thus, AM404 and related compounds inhibit depolarization-induced Ca2+ influx independent of cannabinoid receptors, suggesting caution when using these agents as pharmacological probes to study synaptic transmission.
Department of Pharmacology University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street, Minneapolis, MN 55455, USA.
Brooke G
BG
Kelley
Stanley A
SA
Thayer
D000818:Animals; D001095:Arachidonic Acids / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002186:Cannabinoids / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D063388:Endocannabinoids; D005260:Female; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D053284:Polyunsaturated Alkamides; D011247:Pregnancy; D051381:Rats; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists / Q000502:physiology*; D013329:Structure-Activity Relationship; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
D001095:Arachidonic Acids; D002186:Cannabinoids; D063388:Endocannabinoids; D053284:Polyunsaturated Alkamides; D043884:Receptor, Cannabinoid, CB1; C078814:anandamide; C107594:N-(4-hydroxyphenyl)arachidonylamide