[Responses of different hypothalamic structures to stimulation of the viscero-caudal region of the nucleus of a the solitary tract of the medulla oblongata]

Responses of single units of anterior, ventromedial, lateral and posterior hypothalamus to stimulation of the caudal viscero-receptive region of nucleus tractus solitarius were recorded in anesthetized and immobilized cats. The patterns of the responses were mainly excitatory in all structures under study. The highest degree of reactivity was found for units in the lateral and posterior hypothalamus. According to the latency of the evoked discharges three types of responses were revealed: short (6-12 msec), middle (13-22 msec) and long-latency (22-60 msec) responses. At relatively low frequencies of stimulation the reproducibility was rather poor. Possible projections from nucleus tractus solitarius to the hypothalamus are discussed.