Additive effects of endogenous cannabinoid anandamide and ethanol on alpha7-nicotinic acetylcholine receptor-mediated responses in Xenopus Oocytes.
The interaction between the effects of the endogenous cannabinoid receptor agonist anandamide and ethanol on the function of homomeric alpha(7)-nicotinic acetylcholine (nACh) receptors expressed in Xenopus oocytes were investigated using the two-electrode voltage-clamp technique. Anandamide and ethanol reversibly inhibited currents evoked with 100 microM acetylcholine in a concentration-dependent manner. Coapplication of anandamide and ethanol caused a significantly greater inhibition of alpha(7)-nACh receptor function than anandamide or ethanol alone. The IC(50) value of 238 +/- 34 nM for anandamide inhibition decreased significantly to 104 +/- 23 nM in the presence of 30 mM ethanol. The inhibition of alpha(7)-mediated currents by coapplication of anandamide and ethanol was not altered by phenylmethylsulfonyl fluoride, an inhibitor of anandamide hydrolyzing enzyme, or N-(4-hydroxyphenyl)-arachidonylamide, an anandamide transport inhibitor. Analysis of oocytes by matrix-assisted laser desorption/ionization technique indicated that ethanol treatment did not alter the lipid profile of oocytes, and there is negligible, if any, anandamide present in these cells. Results of studies with chimeric alpha(7)-nACh-5-HT(3) receptors comprised of the amino-terminal domain of the alpha(7)-nACh receptor and the transmembrane and carboxyl-terminal domains of 5-HT(3) receptors suggest that although ethanol inhibition of the alpha(7)-nACh receptor is likely to involve the N-terminal region of the receptor, the site of action for anandamide is located in the transmembrane and carboxyl-terminal domains of the receptors. These data indicate that endocannabinoids and ethanol potentiate each other's inhibitory effects on alpha(7)-nACh receptor function through distinct regions of the receptor.
Oz
Murat
M
National Institute on Drug Abuse/Intramural Research Program, Cellular Neurobiology Branch, Baltimore, MD 21224, USA. moz@intra.nida.nih.gov
Jackson
Shelley N
SN
Woods
Amina S
AS
Morales
Marisela
M
Zhang
Li
L
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D018118:Chloride Channels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D063388:Endocannabinoids; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D009865:Oocytes; D053284:Polyunsaturated Alkamides; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000502:physiology; D014982:Xenopus laevis; D064569:alpha7 Nicotinic Acetylcholine Receptor
D001095:Arachidonic Acids; D018118:Chloride Channels; D063388:Endocannabinoids; D018733:Nicotinic Antagonists; D053284:Polyunsaturated Alkamides; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D000431:Ethanol; D000109:Acetylcholine; D002118:Calcium; C078814:anandamide