Relationship Between Hypothalamic Temperature and Thermoregulatory Effectors in Unanesthetized Cat

Abstract

One mm. diamete thermistors were implanted under anesthesia in the hypothalamic region of cats, and leads were brought out through the scalp. The animals showed no ill effects and were maintained until the electrical connections broke. Hypothalamic temp. in the cats when unanesthetized and exposed to ambient temps. of 0[degree] = 30[degree]C, showed small irregular variations of as much as 0.5[degree]C about a relatively constant mean which was independent of environmental temp. and was on the avg. 0.1[degree]C below the avg. rectal temp. Anesthesia suppressed the small fluctuations and hypothalamic temp. slowly rose or fell with environmental temp. In 5 of 7 cats, panting and heat polypnea correlated with rises in hypothalamic temp.; in the 2 remaining cats, this correlation was lacking. In nearly all expts. on all 5 cats, there was no correlation between vasomotor tone, as indicated by ear temp., and hypothalamic temp.