Role of medial preoptic area beta adrenoceptors in the regulation of sleep-wakefulness.

The role of the medial preoptic area (mPOA) beta adrenergic receptors in the regulation of sleep-wakefulness (S-W) was investigated in this study. S-W was assessed on the basis of polygraphic recording of EEG, EMG and EOG in free moving rats. Intracerebral microinjection of beta agonist, isoproterenol, into the mPOA produced arousal. The study was also conducted on another set of rats in which noradrenergic (NE) innervation to the mPOA was destroyed by injecting 6-hydroxydopamine into the ventral noradrenergic bundle, in the brain stem. Local application of isoproterenol, into the mPOA, in these animals, did not produce any significant change in S-W. Thus, the increase in awake period obtained on isoproterenol administration was the result of its action on the presynaptic NE terminals. Possible involvement of other responses in the isoproterenol induced increase in wakefulness, is discussed.