Heterogeneity of hypothalamic rewarding sites possibly involved in temperature regulation

The effect of hypothalamic self-stimulation on colonic temperature and the effect of cold and warm environments on self-stimulation rate were assessed in 97 rats. In most of the rats, self-stimulation induced a rise in colonic temperature. However, in seven animals the reverse occurred. In the whole sample self-stimulation was significantly depressed by the warm environment. The cold environment facilitated self-stimulation at some placements and inhibited it at others. From the first six placements most facilitated by the cold environment five were also most inhibited by the warm environment. When allowed to self-stimulate in the cold environment high rate self-stimulators had a significantly lower colonic temperature than when they self-stimulated at 25 degrees C while low rate self-stimulators had the same or a higher colonic temperature. Body temperature changes induced by self-stimulation on the one hand, and the effects of the cold and warm environments on self-stimulation on the other appear to be independent one from another. The results suggest that among distinct types of hypothalamic rewarding loci a few might be specifically related to temperature regulation.