Effects of acute δ1-tetrahydrocannabinol treatment, of hypothermia and of ambient temperature on choline incorporation into mouse brain

Abstract

[Me- 14C]-choline was injected intravenously in mice after acute i.p. treatment with Δ 1-THC and the uptake of radioactive label by brain was measured in its aqueous and lipid extracts. The endo-genous plasma choline level of 4.96 μg/ml was not affected by Δ 1-THC treatment. At an ambient temperature of 22° only the higher dose of Δ 1-THC (15 mg/kg) influenced the appearance of label in the brain: incorporation into the lipid fraction fell by 52 per cent, and into the brain as a whole by 23 per cent. Phenobarbitone (300 mg/kg) showed similar effects. Both drugs, when administered to mice housed at 22°, caused a marked lowering of rectal temperature for the duration of the radioactive studies. At an ambient temperature of 33.5°, most or all of the hypothermie effects of Δ 1-THC (15 mg/kg) and phenobarbitone were abolished. At this temperature, Δ 1-THC (15 mg/kg) inhibited radioactive incorporation into the brain lipid fraction by 19 per cent. Phenobarbitone also had a smaller effect but also inhibited incorporation into the whole brain in both its aqueous and lipid fractions (by 19% and 23% respectively). At 33.5° the lower dose of Δ-THC (3.75 mg/kg) caused an increase in incorporation into the brain aqueous (26%) and lipid (25%) fractions. These different responses are discussed in relation to the effects of (a) hypothermia, which caused decreased radioactive incorporation into brain, (b) ambient temperature, which increased incorporation when high, and (c) the spontaneous motor activity of the mice.