Complementary lowering of the behavioural and physiological thermoregulatory set-points by tetrodotoxin and saxitoxin in the cat.

1. Injections of tetrodotoxin or saxitoxin (25 ng in 0.10 ml.) into a lateral cerebral ventricle caused deep body temperature of cats to fall approximately the same amount (2 degrees C) whether the animals were resting in the cold (4 degrees C) or were responding to escape heat.2. Continuous exposure to heat either prevented the hypothermic response or enhanced the level of tachypnoea required to lower body temperature. Tetrodotoxin also caused hypothermia when an animal was lever pressing to obtain heat in the cold environment.3. These results provide evidence that agents which alter the set-point for physiological thermoregulatory activity produce a complementary shift in the behavioural set-point as well.