WIN 55,212-2 is more potent in CHO-CB2 cells than in CHO-CB1 cells by a factor of 6O. WIN 55,212-2 has no effect on arachidonic acid release in CHO-CB2 or control CHO cells. WIN 55,212-2 fails to stimulate any increase in intracellular Ca up to 10 μM. In primary cultures of rat cerebral cortex neurons, WIN 55,212-2 (0.01--100 nM) increases extracellular glutamate levels, displaying a bell-shaped concentration-response curve. The facilitatory effect of WIN 55,212-2 (1 nM) is fully counteracted by SR141716A (10 nM), by the replacement of the normal Krebs Ringer-bicarbonate buffer with a low Ca medium (0.2 mM) and by the IP(3) receptor antagonist xestospongin C (1 μM). WIN 55,212-2 evokes CGRP release from TG neurons in vitro (EC50=26 μM) in a concentration- and calcium-dependent manner. WIN 55,212-2-2 neither inhibits capsaicin-evokes CGRP release nor does it inhibit forskolin-, isoproteranol- or prostaglandin E2-stimulated cAMP accumulation. WIN 55,212-2 significantly inhibits (EC50=1.7 μM) 50 mm K-evoked CGRP release by approximately 70%. WIN 55,212-2 inhibition of 50 mm K-evoked CGRP release is not reversed by antagonists of cannabinoid type 1 (CB1) receptor, but is mimicks in magnitude and potency (EC50=2.7 μM) by its cannabinoid-inactive enantiomer WIN 55,212-2-3.