ARACHIDONYLETHANOLAMIDE (ANANDAMIDE) BINDS WITH LOW-AFFINITY TO DIHYDROPYRIDINE BINDING-SITES IN BRAIN MEMBRANES

The purpose of this study was to explore the hypothesis that the dihyd ropyridine (DHP) binding site of the L-type calcium channel is a high affinity binding site for the cannabimimetic arachidonylethanolamide ( AEA). Binding affinities were determined from competition isotherms us ing the DHP analog [H-3]PN-200. AEA competed for [H-3]PN-200 binding w ith a K-1 of 40 +/- 4 mu M. Inclusion of phenylmethylsulfonyl fluoride to inhibit an amidohydrolase that converts AEA to arachidonic acid ha d little effect on the K-1 of AEA (48 +/- 6 mu M). Arachidonic acid ha d a slightly higher K-1 (120 +/- 11 mu M) and other N-acylethanolamide s examined (linolenylethanolamide, dihomo-gamma-linolenylethanolamide, docosatetraenylethanolamide, and palmitoylethanolamide) had no effect on [H-3]PN-200 binding at concentrations as high as 10 mu M. Our conc lusions are that AEA binds to the DHP binding site with relatively low affinity and its conversion to arachidonic acid is not required for b inding.