EMOTIONAL HYPOTHERMIA IN RABBITS

Abstract

Restraint of rabbits in normal posture by enclosure in a loosely-fitting wire mesh cage induces hypothermia, sometimes exceeding 2.5[degree]C, and even a strange environment may cause some hypothermia. The effect is due to paradoxical activation of heat loss mechanisms (polypnea, ear vasodilation). Cooling is usually later reversed, but several hrs. may elapse before normal temp. is restored, or restoration may not occur at all. Oxygen uptake is not depressed, but shivering is absent, while heat loss mechanisms are active. Cooling does not occur if the rabbit is exposed to cold (4[degree]C) before and during restraint. Pyrogen injns. interrupt cooling, but consequent fever is not shown by restrained rabbits even when injected after recovery of normal temp. The effect is attributed to "emotional" disturbance of thermoregulatory centers. It is recommended that rabbits used for thermal studies and pyrogen testing should not be restrained.