Role of cholinergic inputs to the medial preoptic area in regulation of sleep-wakefulness and body temperature in freely moving rats

The medial preoptico-anterior hypothalamic area receives adrenergic as well as cholinergic inputs. Independent studies showed that both these inputs influence sleep, wakefulness and body temperature. The role of the adrenergic inputs was studied earlier. The role of cholinergic inputs is reported here. The cholinergic agonist, carbachol, and antagonist, scopolamine, were injected into this area during the day and the night in freely moving rats and the effects on sleep-wakefulness and body temperature studied. It was observed that carbachol induced wakefulness accompanied by a fall in body temperature while scopolamine induced an opposite effect, i.e. sleep accompanied by an increase in body temperature. This suggested that the cholinergic input into the medial preoptic area is spontaneously active in regulating sleep-wakefulness and body temperature and this regulation is mediated through muscarinic receptors present in this area. The results also suggest that, contrary to the action of adrenergic inputs (which have a dissociated effect on sleep-wakefulness and body temperature), the cholinergic input is unlikely to have a dissociated effect on those functions. (C) 1997 Elsevier Science B.V.