THE SIGNIFICANCE OF THE ROSTRAL RAPHE NUCLEI FOR THERMOREGULATORY EFFECTOR MECHANISMS

1. The nucleus raphe dorsalis (DR) and surrounding brain areas were el ectrolytically lesioned in fully awake, unrestrained rats. 2. Raphe le sions caused a delay in the onset of response to cold stress, resultin g in a larger drop of hypothalamic temperature, whereas in steady stat e both oxygen consumption and hypothalamic temperature were unchanged compared to intact animals. 3. Lesions which damaged the periventricul ar grey only had no effect. 4. The response to heat stress was unchang ed after all lesions. 5. Concerning thermoafferent pathways, mainly wa rm responsive neurons have been described in the raphe nuclei. A damag e of the thermoafferent system should therefore cause a disturbance of heat defence. This is not the case. We conclude that the DR has an ex citatory influence on thermoregulatory effector mechanisms.