Dependence on 9-TetrahydrocannabinoI: Studies on Prec ipitated and Abru pt Withdrawal1

dose dependently pre-cipitated a behavioral withdrawal syndrome in rats continuously infused i.p. for only 4 days with relatively low-dose regimens of 9-tetrahydrocannabinol. The following dose regimens, ex-pressed as mg/kg/24 hr, were used for days 1 through 4: high-12.5, 25, 50 and 100; medium-2.5, 5, 10 and 20; and Iow-0.5, 1, 2 and 4. The major withdrawal signs of the syn-drome were scratching, rubbing face with paws, licking, wet-dog shakes, arched back and ptosis (at least 50 % closure of eyelids). At the highest dose regimen, other signs noted in fewer subjects were biting, tongue rolling, retropulsion, head shakes, extended limbs or high stepping, ataxia, myoclonic spasms and front paw treading. Dunng abrupt withdrawal (9 tetrahydrocannabinol was discontinued and vehicle substi-tuted) abstinence signs were also noted; however, except dur