Comparison of the dorsal raphe nucleus and the median raphe nucleus in thermoregulation of freely moving rats

Abstract

Brain serotonin (5-HT) is an important monoaminergic neurotransmitter in the regulation of physiological functions and behaviours, including thermoregulation. The two main sources of 5-HT innervation of the forebrain are the dorsal raphe nucleus (DRN) and the median raphe nucleus (MRN). The physiological function of both nuclei has not been clarified though it is suggested that they have the different roles in the animal behaviour and homeostasis. The present study was designed to compare the role of the DRN and the MRN in thermoregulation of freely moving rats by using microdialysis/biotelemetry techniques. We have already reported that perfusion of tetrodotoxin (TTX) into the MRN induced a decrease in body temperature (Tb) with an increase in increment of heat loss and no change in heat production of freely moving rats (JPS, 57 Suppl.: S185, 2007). Perfusion of TTX into the DRN also induced Tb decrease with the increment of heat loss and change in heat production responses similar to the MRN. These results suggested that the role of 5-HT projection from the DRN and the MRN in thermoregulation mainly is the heat loss system. In addition, it was suggested that there was no functional difference beween these two nuclei in thermoregulation. [J Physiol Sci. 2008;58 Suppl:S101]