PROPRANOLOL BLOCKS THE STIMULATORY EFFECTS OF NALOXONE ON VENTILATIONAND OXYGEN-CONSUMPTION IN HAMSTERS

The purposes of these studies were: 1) to determine the effects of var ious doses of propranolol, a nonspecific beta-adrenergic antagonist, o n ventilation, oxygen consumption, and body temperature in hamsters, a nd 2) to test the hypothesis that in hamsters the stimulatory effects of naloxone, an opioid receptor antagonist, on ventilation and oxygen consumption occur, at least in parr, through the release of catecholam ines that act via beta-adrenergic receptors. Propranolol, a non specif ic beta adrenergic receptor antagonist, at a 20 mg/kg de pressed body temperature, oxygen consumption, tidal volume, and ventilation relativ e to saline. The lower dose of 10 mg/kg had only transitory effects on tidal volume at 60 min and ventilation at 30 min post-injection. Nalo xone (1 mg/kg) relative to saline stimulated ventilation and oxygen co nsumption. These effects were blocked by propranolol pretreatment. The results of these experiments demonstrate that in the hamster, 1) body temperature, oxygen consumption, and ventilation appear to be modulat ed by beta-adrenergic receptors, and 2) the stimulatory effects of nal oxone on oxygen consumption and ventilation may occur through the inte raction of endogenous opioids and beta-adrenergic receptor systems. (C ) 1997 Elsevier Science Inc.