Responses of preoptic thermo sensitive neurons to mediobasal hypothalamic stimulation

HORI, T., T. KIYOHARA, T. OSAKA, M. SHIBATA AND T. NAKASHIMA. Responses of preoptic thermosensitiveneurons to mediobasal hypothalamic stimulation. BRAIN RES. BULL. 8(6) 677–683, 1982.—Single-unit responses of preoptic-anterior hypothalamic (PO/AH) thermosensitive neurons to electrical stimulation of the mediobasal hypothalamus (MBH: ventromedial and arcuate nuclei) have been studied in urethane-anesthetized male rats. About half of thermosensitive neurons (46.4% of 69 warm-units and 50% of 28 cold-units) were initially inhibited following MBH stimulation with latencies up to 51.2 msec, while only 29.7% of 91 thermally insensitive units showed the inhibitory response. Orthodromic excitation of spontaneous activity was observed in 17.6% of the units (13.0% of warm-units, 14.3% of cold-units and 21.9% of insensitive units) with the onset latencies between 1.0 and 41.3 msec. A small proportion of neurons (5.3%) were antidromically activated by MBH stimulation, and the estimated conduction velocities of these neurons ranged from 0.11 to 0.67 m/sec. The results suggest reciprocal connections between PO/AH thermosensitive neurons and MBH, which may play some roles in thermoregulation and, also, in functional interactions between thermoregulation and other vital functions controlled in the hypothalamus.