Comparison of the effect of prazosin with that of dihydrobenzperidol and nifidepine on thermoregulatory responses produced by pyrogen in rabbits.

1. Thermal responses to prazosin (0.75 mg/kg; i.v.), dihydrobenzperidol (0.75 mg/kg or 2.25 mg/kg; i.v.), nifidepine (0.05 mg/kg or 0.16 mg/kg; i.v.) administered in the form of bolus injection or infusion were investigated in febrile rabbits. 2. Pyrogen (Escherichia coli lipopolysaccharide, LPS, 1 mcg/kg; i.v.) produced a fever reaction resulting from stimulation of the metabolic rate and heat conservation responses. 3. Prazosin (PRA) and dihydrobenzperidol (DHBP) reduced the pyretic as well as metabolic activity of pyrogen. The former drug enhanced heat elimination from the ear. 4. Nifidepine (ADA) did not significantly affect postpyrogen thermoregulatory parameters. 5. It is suggested that alpha-adrenergic receptor blockade might be responsible for the antipyretic activity of PRA and DHBP.