Tonic activity of medial preoptic norepinephrine mechanism for body temperature maintenance in sleeping and awake rats.

The study was aimed at investigating the possible involvement of tonic activity of the adrenergic receptors in the medial preoptic area (mPOA) for maintenance of body temperature in rats. Differences in drug-induced changes in body temperatures during sleep and wakefulness--during the day and at night--were also investigated. Norepinephrine injected in the mPOA, produced a fall in body temperature, whereas phenoxybenzamine produced an increase. Saline and propranolol produced no alteration. Norepinephrine and phenoxybenzamine produced alterations in sleep-wakefulness also. These changes in sleep-wakefulness did not completely explain the thermal changes. The findings highlight the need for taking into account the basal activity and the time of application of drug in studies on thermo-regulation, using free moving animals.