Hypothalamic serotonergic activity correlates better with brain temperature than with sleep-wake cycle and muscle tone in rats

The activity of the serotonergic system varies in phase with the sleep-wake cycle, which is associated with changes in several physiological functions , including electroencephalographic activity, brain temperature, and locomo tion. The aim of the present study was to clarify which of these parameters correlates better with serotonergic activity in spontaneous conditions. Vo ltammetric recordings by telemetry of serotonergic metabolism in the medial preoptic area and polygraphic recordings of sleep-wake activity (by means of electroencephalographic delta band, brain cortical temperature and neck electromyographic activity recordings) were simultaneously performed in fre ely moving rats. Univariate analyses of variance revealed that each variabl e under investigation was statistically correlated with serotonergic metabo lism. When the variables were entered into the model simultaneously, both p artial correlation and step-wise multiple regression analyses indicated tha t the highest correlation exists between serotonergic metabolism and brain cortical temperature. The present data show that serotonergic activity in the medial preoptic are a is closely linked to physiological changes in brain temperature. (C) 1999 IBRO. Published by Elsevier Science Ltd.