Temperature sensitivity of the preoptic and anterior hypothalamic neurons in organ culture.

Single unit activities were recorded from the preoptic and anterior hypothalamic (POAH) explants obtained from newborn mice brain to study neural temperature sensitivities in the period of 10-34 days culture. The firing rate of recorded units was less than 13 impulses per sec at 35 degrees C. Fifteen warm sensitive, 2 cold sensitive and 37 thermally insensitive units were obtained. The temperature sensitivities of the cultured POAH neurons were similar to those of in vitro neurons, i.e. the discharge frequencies changed smoothly in proportion to 1-5 degrees C changes in local temperature. The thermal responses of warm sensitive units increased after 18 days and decreased over 30 days in vitro. Two warm sensitive neurons were identified and observed under the optical microscope. The cold sensitive units were unable to be recorded until about 20 days in vitro. It became evident that the neural temperature sensitivities of POAH neurons were maintained in an absence of the extrahypothalamic afferents.