Effects of testosterone, estradiol, and temperature on neurons in preoptic tissue slices.

Thermosensitive preoptic neurons have been implicated in the regulation of body temperature. Testosterone- and estrogen-sensitive preoptic neurons have been implicated in reproductive behavioral and endocrine responses. In this study, rat preoptic tissue slices were used to examine the specificity of these neurons by determining their individual firing rate responses to both temperature and reproductive steroids. Of the 180 neurons classified according to thermosensitivity, 37% were warm sensitive, 8% were cold sensitive, and 55% were temperature insensitive. Ninety-three neurons were tested for their responses to perfusion media containing either testosterone or estradiol (30 pg/ml). Of the cells tested with both steroids, testosterone or estradiol affected half of the thermosensitive neurons and one-third of the temperature-insensitive neurons. This indicates that the population of temperature-insensitive neurons does not contain the majority of the steroid-sensitive neurons. There was much specificity, however, between the two types of steroid-sensitive neurons; testosterone and estradiol rarely affected the same neuron. Although these findings do not indicate a strong specificity between thermosensitive and steroid-sensitive neurons, they do support previous studies suggesting interactions between thermoregulatory and reproductive systems.