CHRONIC DELTA-9-TETRAHYDROCANNABINOL IN RATS - EFFECT ON SOCIAL INTERACTIONS, MOUSE KILLING, MOTOR-ACTIVITY, CONSUMMATORY BEHAVIOR, AND BODY-TEMPERATURE

Behavioral and physiologic effects of daily administration of .DELTA.9-tetrahydrocannabinol (THC) were assessed over a 60-day period, investigating different dose levels (10, 20, 50 mg/kg), routes of administration (i.p., orally (p.o.)), drug vehicles [5-18% propylene glycol (PG)/1% Tween 80-saline; sesame oil] and rat strains (Sprague-Dawley, Wistar, Long-Evans, Fischer). All THC-treated rats showed compulsive motor routines (i.e., forepaw treading, rhythmic jaw movements, prolonged head grooming and biting of cage wires) after 3-4 wk. Whether maintained on a restricted feeding regimen or not, there was no evidence for increased aggressive behavior between cagemates in any of the treatment groups. Mouse killing was induced in 70-75% of all Sprague-Dawley (i.p., PG/Tween 80-saline vehicle) and Fischer rats (p.o., sesame oil vehicle), but not in the other THC-treated groups. Rearing activity was greatly decreased in all THC-treated groups throughout the treatment period. Food and water intake decreased by approximately 40% during the 1st 2-6 days of THC administration. Growth rate was reduced for the entire treatment period in THC-treated rats. THC decreased rectal temperature on the 1st day and also on the 2nd day in Fischer rats receiving the drug in sesame oil, but not thereafter. This pattern of effects shows that tolerance develops rapidly to THC''s effects on body temperature and consummatory behavior, but not to changes of certain motor activities.