Interactions between temperature regulation and emotional arousal in the rabbit

Abstract

In our study we examined, in the rabbit, the interactions between temperature regulation and the state of increased vigilance and emotional arousal induced by a Classical Aversive Conditioning Procedure. A Delay Conditioning Procedure was used. The Conditioned Stimulus (CS) was a 1350 Hz, 85 dB tone, the Unconditioned Stimulus (UCS) a 1 mA, 0.5 s shock. Testing sessions were run at different ambient temperatures from 5 to 30 degrees C. At all ambient temperatures considered the CS induced desynchronisation of the EEG and stereotyped changes in all the autonomic variables studied. Hypothalamic temperature (Thy) first increased, then decreased below its initial value, whereas ear skin temperature (Ts) showed opposite changes. Respiratory frequency (RF) initially increased, then tended to revert to its original value. The average time course of this complex pattern was 300 s from the CS. The overall effect of the CS sequence in a session was a significant decrease in Thy and Ts and a significant increase in RF compared to control values at the beginning of the session. Both in the short (single trial) and long terms (whole session) the autonomic responses induced by the emotional stress (polypnoea and vasoconstriction) were not coherent from the point of view of thermoregulation. The hypothesis of an effect of emotional arousal in shifting set point temperatures can therefore be discarded in favour of a direct action of emotional stress on effector controllers for respiration and vasomotion.