The active component of cannabis preparations is delta-9-tetrahydrocannabinol (THC) . Marijuana is made from the flowering top and leaves of Cannabis sativa, and hashish, which is more concentrated, is derived from a dried exudate from the flowers. Around
50% of THC is absorbed into the blood when cannabis is smoked and a subjective effect is detectable within 10 min but disappears after around 2-4 h. Delta-9-tetrahydrocannabinol is metabolized in the liver.
It acts at two types of specific G protein receptor. CB1 is widely distributed within the CNS, and is found especially in immune cells derived from the brain. CB1 is antagonized by an endogenous compound, anandamide, whose metabolism is blocked by interleukin-1. There is also interaction with opiate, GABA, dopamine, glutamate and 5HT systems.
The duration of REM sleep is reduced by THC, which is a sedative, and it disproportionately reduces the number of rapid eye movements. It slightly increases the duration of stages 3 and 4 NREM sleep, but these effects become less marked with long-term THC use. Withdrawal leads to REM sleep rebound and a reduction in REM latency, as well as anxiety and anorexia.
Delta-9-tetrahydrocannabinol causes euphoria and is a mild anxiolytic which may help to induce sleep. In low doses it improves memory, but in higher doses psychomotor and cognitive skills and reaction times are impaired. It is frequently abused and dependency is common. Its effects are potentiated by alcohol and chronic use leads to increased duration of sleep and lassitude.
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