1. Cannabis extract prolonged sleeping time in mice in a thermally neutral environment (30-32° C) in which hypothermia does not occur. The prolongation was dose related, just detectable at 50 mg/kg, and 4-fold at 500 mg/kg.
2. Under these conditions, ether sleeping time was not prolonged.
3. Cannabis extract inhibited the aerobic metabolism of phenazone by a microsome-rich 9,000 gsupernatant of mouse liver homogenate capable of nicotinamide adenine dinucleotide phosphate (NADPH) generation.
4. Δ1-Tetrahydrocannabinol (Δ1-THC) prolonged pentobarbitone sleep and inhibited phenazone metabolism, but its action was limited, and could not account for the effect of the extract. The carotenes and water-soluble fractions of the extract were inactive on pentobarbitone sleep.
5. Cannabidiol was strongly active by both tests; in vivo 39·8 μM/kg (12·5 mg/kg) prolonged sleep by 190%, and in vitro 12·7 μM inhibited phenazone metabolism 20%. These actions were dose related, and could account for the effect of the extract.
6. The prolongation of pentobarbitone sleep by cannabis extract in a dose of 200 mg/kg, intraperitoneally, was maximal when given 30 min before the pentobarbitone, still present at 3 h, but undetectable at 24 hours. No phase of enhanced metabolism at 24 or 48 h after single cannabis injection was detected.
7. It is concluded that cannabis extract inhibits microsomal activity of mouse liver, chiefly by virtue of its cannabidiol content. It is probable that cannabis consumption by man could lead to altered disposal of many other drugs, used in medicine or otherwise.
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