Delta 9-tetrahydrocannabinol sensitization of the rat brain to direct cholinergic stimulation

In an attempt to define the nature of the involvement of delta 9-tetrahydrocannabinol (THC) with central cholinergic neurotransmission, the effects of THC on direct cholinergic stimulation of the rat brain were investigated. THC, in doses of 3 mg/kg and 6 mg/kg, administered intraperitoneally (i.p.), potentiated the effects of carbachol injection into the lateral septal nucleus, as manifested by enhancement of the drinking response elicited by the septal carbachol injection and by potentiation of the tendency of this carbachol injection to induce abnormal motor responses. Although atropine (10 mg/kg, i.p.) completely blocked the carbachol induced drinking, the atropine did not completely block the drinking response when THC was given with carbachol. The results indicate an apparent sensitization, by THC, of a limbic cholinergic system.