CANNABINOMIMETIC BEHAVIORAL-EFFECTS OF AND ADENYLATE-CYCLASE INHIBITION BY 2 NEW ENDOGENOUS ANANDAMIDES

We have previously shown that the endogenous putative cannabinoid liga nd arachidonylethanolamide (anandamide, 20:4, n - 6) induces in vivo a nd in vitro effects typical of a cannabinoid agonist. We now report th at two other endogenous anandamides, docosatetraenylethanoiamide (anan damide, 22:4, n - 6) and homo-gamma-linolenylethanolamide (anandamide, 20:3, n - 6), have similar activities. The new anandamides bind to SV 40-transformed African green monkey kidney cells transfected with the rat brain cannabinoid receptor cDNA and display K-I values of 253.4 +/ - 41.1 and 244.8 +/- 38.7, respectively. The value found for arachidon ylethanolamide was 155.1 +/- 13.8 nM. In addition, the new anandamides inhibit prostaglandin E(1)-stimulated adenylate cyclase activity in C hinese hamster ovary-K-1 cells transfected with the cannabinoid recept or, as well as in N(18)TG(2) mouse neuroblastoma cells that express th e cannabinoid receptor naturally. The IC,, values for the inhibition o f adenylate cyclase in transfected Chinese hamster ovary-K-1 cells wer e 116.8 +/- 8.7 and 109.3 +/- 8.6 nM for docosatetraenylethanolamide a nd homo-gamma-linolenylethanolamide, respectively. These values were s imilar to that obtained with arachidonylethanolamide (100.5 +/- 7.7 nM ), but were significantly higher than the IC50 value observed with the plant cannabinoid Delta(9)-tetrahydrocannabinol (9.2 +/- 8.6 nM). The inhibitory effects of the anandamides on adenylate cyclase activity w ere blocked by pertussis toxin, indicating the involvement of pertussi s toxin-sensitive GTP-binding protein(s). In a tetrad of behavioral as says for cannabinoid-like effects, the two new anandamides exerted sim ilar behavioral effects to those observed with Delta(9)-tetrahydrocann abinol and arachidonylethanolamide: inhibition of motor activity in an open field, hypothermia, catalepsy on a ring, and analgesia on a hot plate.