Interaction of central and superficial peripheral thermosensors in control of thermoregulatory behaviors of the rat

The interaction of localized central and superficial peripheral thermal stimulation was studied in rats using diathermic warming of different brain areas controlling postural extension, locomotion, and grooming and a thermal floor warmed from thermally neutral 26.5 to 33.5 or 40.5°C, which induced locomotion and grooming. When behaviors were elicited by both central and superficial stimuli, combined stimuli were additive (activity) or partially additive subject to a ceiling (grooming). When behaviors were elicited by only one (or predominantly one) of two stimuli, combinations of the stimuli evidenced inhibition (grooming), multiplicative summation (activity), or mixtures of facilitation at low intensities and inhibition at high intensities (extension). Behaviors not elicited in significant amounts by either stimulus did not increase when both were combined (extension). It was concluded that the varied influences on thermoregulatory behaviors exerted by superficial and central thermosensors acting separately and in combination can largely explain the differences in behavioral response patterns induced by various thermal stress conditions that distribute heat differently between the surface and core of the body.