Changes in brain temperature and thermoregulation produced by destruction of medial septal neurons in rats

Brain temperatures (Tbr) of male Wistar rats were recorded at every 15 min interval for 24 h, prior to the destruction of the medial septal (MS) neurons with N-methyl-D-aspartic acid, and on the 7th, 14th and 21st days after the destruction. The capacity of the rats to regulate their body temperature under severe cold and heat was assessed by recording their Tbr when they were exposed to 5+/-1 and 37+/-1 degrees C for 2 h, before lesion and on 8th, 9th, 15th, 16th, 22nd and 23rd days after the lesion. The Tbr was decreased and its circadian variation increased after the MS lesion. On exposure to an ambient temperature of 5+/-1 degrees C the Tbr was decreased on 9th and 16th days after the lesion, when compared with the sham lesion group on identical days, though the fall in temperature was not significant on the 23rd day. The change in Tbr (compared with the sham lesion group) was not significantly different on all days of exposure to 37+/-1 degrees C. The decrease in Tbr after the MS lesion is in contrast to the hyperthermia produced by lesion of the adjoining thermoregulatory areas. The present findings suggest that the MS lesions caused an alteration in the set point of body temperature, without drastic changes in thermoregulatory ability.