Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine
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The gamma-aminobutyric acid subtype A (GABAA) receptor is widely considered to be an important target for most clinically effective sedative-hypnotic compounds, including general anesthetics, benzodiazepines, barbiturates, and gaboxadol or THIP (4,5,6,7-tetrahydroisoxazolo (5,4-c)pyridin-3-ol). GABAA receptors are highly expressed in anatomical regions that are implicated in sleep processes, notably the thalamus. Furthermore, concentrations of these drugs that modify behavior in vivo also increase GABA-induced inhibitory conductances in vitro. ⋯ Particular emphasis is placed on subpopulations of GABAA receptors that are expressed in extrasynaptic regions of neurons, as these receptors are exquisitely sensitive to several classes of sedative-hypnotic compounds. Evidence to date suggests that extrasynaptic GABAA receptors can be broadly classified into two groups; those containing the delta subunit and the non-delta subunit-containing GABAA receptors. Finally, the probable contribution of extrasynaptic GABAA receptors in the modulation of sleep will be considered.