Prolonged hypothermia after phenobarbital-induced anesthesia in adrenalectomized rats.

Adrenalectomized rats are hypersensitive to the hypothermic as well as hypnotic effects of phenobarbital. The exaggerated hypnotic response is more pronounced in the chronic (10 day) than the acute (1 day) adrenalectomized rat and is reversed by glucocorticoid replacement. The prolonged hypothermia to a hypnotic dose of phenobarbital occurs in adrenalectomized but not adrenodemedullated rats. This hypersensitivity is characterized by an impaired ability to regain normal body temperatures for as long as 24 hours after regaining the righting reflex. The prolonged hypothermia is prevented by prior treatment with glucocorticoids but not mineralocorticoids. There appears to be no gross alteration in disposition of phenobarbital following adrenalectomy suggesting that the prolonged duration of hypothermia is not a consequence of accumulation of the drug.