Hibernation “trigger” injected in brain induces hypothermia and hypophagia in the monkey

Abstract

In ovariectomized adult female macaque monkeys, cannulae were affixed bilaterally to the skull for intracerbroventricular injection. Baseline temperature, heart rate, food and water intakes were monitored in each animal after it had been acclimatized to a primate restraining chair. Lyophilized serum albumin fractions extracted from the blood of hibernating woodchucks or summer active, non-hibernating woodchucks were reconstitued in an artificial CSF. Following the intracerebroventricular injection of 3.0 to 4.0 mg of hibernating woodchuck albumin (HWA) in a volume of 300 to 400 μl, a decline in the temperature of the monkey occurred which varied in magnitude and duration. A marked inhibition of food intake, accompanied by a decline in prandial water intake, persisted for 24 to 36 hours. This hypophagia was due mainly to a reduction in the number of feeding episodes during the periods of observation. Although heart rate declined intermittently, respiratory rates remained unchanged. Summer active woodchuck albumin (SAWA) or bovine serum albumin (BSA) given in the identical range of doses, as well as artificial CSF, exerted little or no effect either on body temperature of the primate or on its food intake. These results demonstrate for the first time that a plasma “trigger” factor, obtained from a hibernating animal in torpor, exerts a direct physiological action on the brain of a mammal which is incapable of entering into hibernation. Vital metabolic, thermoregulatory and other control processes mediated by diencephalic and other systems in the CNS are directly suppressed by the “trigger” factor. The clinical implications of these findings are presented.