Location and quantification of muscarinic receptor subtypes in rat pons: implications for REM sleep generation

jetting cholinomimetics into the pontine reticular formation produces a state that resembles natural rapid eye movement (REM) sleep. Evocation of this REM sleeplike state is anatomi-cally site dependent within the pons and is mediated by muscarinic receptors. The cellular and molecular mecha-nisms underlying cholinergic REM sleep generation and muscarinic receptor subtype involvement remain to be speci-fied. This study tested the hypothesis that muscarinic recep-tor subtypes are differentially distributed within the oral and caudal divisions of rat pontine reticular nucleus. In vitro receptor autoradiography was used to localize and quantify M1, M2, and M3 binding sites in the pontine reticular forma-tion and in pontine brain stem regions known to regulate REM sleep. Ml-M3 binding sites were present in some REM sleep-related nuclei, such as dorsal raphe and locus ceruleus