Abstract
Brain serotonin (5-HT) is an important monoaminergic neurotransmitter and its system has been involved 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 median raphe nucleus (MRN). These raphe nuclei send serotonergic fibers to a variety of fore brain areas such as hypothalamus. We have recently reported that the perfusion of tetrodotoxin (TTX) into the MRN, by using a microdialysis technique, induced a decrease in body temperature (Tb) in freely moving rats (Neuroscience Letters, 306, 126-128, 2001). The present study was designed to determine the mechanism of decrease in Tb after perfusion of TTX into the MRN, by measuring tail skin temperature (Ttail) as an index of heat loss, and heart rate (HR) as indexes of heat production. Tb and HR of freely moving rats were continuous monitored by a telemetry device. Ttail was also continuous measured on the dorsal surface of the skin about 10cm from the tail base using alumel-chromel thermocouple wire. The thermocouple wire was covered with a plastic tube and a metal spring. TTX solution (5μM) was perfused for 60 min into the MRN. [J Physiol Sci. 2007;57 Suppl:S185]
