Functional conections between right & left hypothalamus in thermcregulation.

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The present study explored the laterality of central nervous thermoregulatory control in anesthetized rats by measuring paw skin vasomotor activity and cold-induced shivering in hind leg muscles during unilateral POAH warming and electrical stimulation or during unilateral thermal stimulation of abdominal skin. Unilateral POAH warming produced vasodilation on both sides of the body, but vasodilation on the ipsilateral side always either occurred at a lower threshold hypothalamic temperature or was stronger than on the contralateral side. In a cold environment(5ﾟC), shivering was suppressed simultaneously in both hind legs when one side of the POAH was warmed, and shivering reappeared simultaneously on both sides when POAH warming stopped. These results suggest that different thermoregtilarory effectors are regulated in a different way by each side of the POAH. In the next series of experiments, the possibility of direct exchange of thermoregulatory control information between the left … More and right sides of the preoptic area and anterior hypothalamus(POAH)was tested by extracellularly recording single unit activity in the POAH of urethane-anaesthetized rats during local temperature changes and electrical stimulation of the contralateral POAH. Twenty-four of 123 neurons were facilitated and 20 inhibited by contralateral stimulation ; none were antidromically activated. Twenty-seven of the 82 of these neurons tested for thermosensitivity were warm-sensitive, and 20 were cold-sensitive : a neuron's thermosensitivity was not significantly correlated with its response to contralateral stimulation. The highest incidence of response to contralateral stimulation(60%)was found when stimulation and recording sites were both in the anterior half of the POAH. These responses were absent after midsagittal transection of the anterior commissure and its rostral area. These results indicate plentiful and predominantly polysynaptic connections between the right and left sides of the anterior POAH. Less