Anterior and posterior hypothalamus: effects of independent temperature displacements on heat production in conscious goats.

Three goats were chronically implanted with thermodes to alter the temperatures of the anterior and posterior hypothalamus independently of each other. At an air temperature of +14 degrees C the anterior hypothalamus was cooled with different intensities, while the posterior hypothalamus was simultaneously either warmed (39 degrees C) or cooled (29 degrees C). In both conditions cooling anterior hypothalamus increased heat production. However, the increase was smaller, when the posterior hypothalamus was cooled. The inhibiting effect was most pronounced during the first parts of the periods and diminished with time. Nevertheless, in a separate series of experiments, the effects of posterior hypothalamic cooling were found to persist over periods of 3 h. At an air temperature of +3 degrees C the posterior hypothalamus temperature was altered between 28 and 42 degrees C, while anterior hypothalamus temperature was kept close to its control level. Shivering and heat production decreased with cooling and increased with warming of the posterior hypothalamus. The results suggest that those neurons which reside in the posterior hypothalamus and mediate shivering, are sensitive to temperature. Thermosensitivity of these allegedly integrative neurons affects shivering and heat production in a way inverse to the thermosensitivity of the temperature sensing neurons in the anterior hypothalamus.