16.4 : 鎮静剤と睡眠薬: 概要

Sedatives belong to a class of drugs that calms the individual, while hypnotics induce and maintain sleep. Both categories work by slowing down the brain activity.

Sedative-hypnotic drugs suppress the CNS activity in a dose-dependent manner. Older medications like barbiturates follow a linear curve, making them potentially fatal. Newer drugs like benzodiazepines deviate from the linear curve, making them useful for short-term relief.

Sedative-hypnotic drugs primarily target GABA_A ligand-gated ion channels and melatonin GPCRs.

Neurotransmitter GABA binds and opens the GABA_A ion channel, allowing chloride ion influx, decreasing the resting potential and, in turn, inhibiting neuronal firing.

Barbiturates, benzodiazepines, and newer agents like zolpidem bind at different allosteric sites on the GABA_A channel, promoting GABA binding and neuronal suppression.

In addition, melatonin activates MT₁ and MT₂ GPCRs in the anterior hypothalamus, decreasing neuronal firing and promoting sleep. Melatonin analogs, such as ramelteon, are helpful for insomnia without any dependency risk.