Receptor-dependent formation of endogenous cannabinoids in cortical neurons

We investigated the transduction mechanisms mediating formation of the endo genous cannabinoid (endocannabinoid) lipids, anandamide (arachidonylethanol amide) and 2-arachidonylglycerol, in primary cultures of rat cortical neuro ns. Unstimulated neurons contained 0.3 +/- 0.1 pmol of anandamide and 16.5 +/- 3.3 pmol of 2-arachidonylglycerol per mg of protein, as determined by g as chromatography/mass spectrometry. Ca2+ entry into the neurons via activa ted glutamate N-methyl-D-aspartate (NMDA) receptors increased 2-arachidonyl glycerol levels approximately three times, but had no effect on anandamide levels. By contrast, anandamide formation was stimulated five times by simu ltaneous activation of NMDA and acetylcholine receptors. Alone, acetylcholi ne receptor activation had no effect on anandamide or 2-arachidonylglycerol levels. The formation of fatty acid ethanolamides that do not activate can nabinoid receptors, including palmitylethanolamide and oleylethanolamide, w as stimulated by coactivation of NMDA and acetylcholine receptors. Pharmaco logical experiments suggest that the cholinergic contribution to anandamide formation was mediated by alpha7 nicotinic receptors (antagonized by methy llycaconitine), whereas the contribution to palmitylethanolamide and oleyle thanolamide formation was mediated by muscarinic receptors (antagonized by atropine). These findings indicate that cortical neurons produce anandamide and 2-arachidonylglycerol in a receptor-dependent manner, and that brain n eurons may generate different endocannabinoid lipids depending on their com plement of neuro transmitter receptors. (C) 2001 Elsevier Science B.V. All rights reserved.