Cannabimimetic activity of cannabinol in rats and pigeons

The present experiments examined the cannabimimetic potential of cannabinol on its own as well as its interaction with delta 9-tetrahydrocannabinol (delta 9-THC) in vivo. Thus, cannabinol, as evaluated by repeated test procedures using drug-discrimination methodology (Hiltunen and Järbe, 1986; Järbe, Swedberg and Mechoulam, 1981) was found to substitute for the stimulus effects induced by delta 9-THC in both rats (delta 9-THC cue = 3 mg/kg) and pigeons (delta 9-THC cue = 0.56 mg/kg), though, relatively larger doses were required in the latter species (ED50 for cannabinol being 8.4 mg/kg, and 14.1 mg/kg at the time of maximum effect in rats and pigeons, respectively). When administered together, cannabinol added to the cue effects of delta 9-THC as shown by an increase in the percentage of responding appropriate to the drug, the effect appearing more pronounced in rats than in pigeons; no apparent change in the duration of the effect was indicated by the results obtained. Unconditioned effects of drug, as defined by rectal temperature recordings and open-field activity (ambulation, rearing, latency, circling, grooming, defecation and urination), as well as assessment of vocalization in rats were in keeping with the suggestion that the pharmacological profile of cannabinol is similar, though not necessarily identical, to that of tetrahydrocannabinols, such as delta 9-THC.