Vasomotor thresholds in the squirrel monkey: effects of central and peripheral temperature.

Six squirrel monkeys (Saimiri sciureus) participated in two ex,eriments examining how central (preoptic/anterior hypothalamic, Tpo) and peripheral (ambient, Ta, or mean skin, Tsk) temperatures influence peripheral vasomotion. In the first experiment, four monkeys with unilateral preoptic thermodes were exposed to a wide range of central (23 degrees C less than Tpo less than 44 degrees C) and peripheral (10 degrees C less than Ta less than 38 degrees C) temperatures. Results indicated that the skin of both tail and foot vasodilates at discrete but unique Ta thresholds (Tpo congruent to 39 degrees C) and that raising Tpo lowers these thresholds. In the second experiment, results from two monkeys implanted with bilateral thermodes surrounding the preoptic area replicated those of experiment 1. Subsequent tests with these two monkeys on the quantitative interaction between central and peripheral temperatures indicated that the dilation threshold is approximately a linear function of Tpo and Tsk. These effects are related to the interaction between central and peripheral inputs to the thermoregulatory system.