1. A bioassay for cannabis, called the ring test, has been developed in which the percentage of the total time spent on a horizontal wire ring during which a mouse remains completely immobile is recorded.
2. The effect of cannabis on mobility is a dose-related, graded response.
3. Threshold doses of cannabis extract are 12·5 mg/kg when injected intravenously, and 100 mg/kg when injected intraperitoneally or subcutaneously.
4. The method provides a measure of the `cataleptic’ effect of cannabis. Chlorpromazine in doses of 1 mg/kg upwards also produces the effect but barbitone does not.
5. It is concluded that Δ1-tetrahydrocannabinol (Δ1-THC) is largely responsible for the effect of cannabis extract on mobility; the potency ratio of Δ1-THC to cannabis extract is between 10 and 20. Δ1-Tetrahydrocannabidivarol (Δ1-THD) also affects mobility but is less active than Δ1-THC. Cannabidiol has no effect when injected intraperitoneally in doses up to 100 mg/kg.
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