Propranolol induced changes in plasma catecholamine, corticosterone, T4, T3 and prolactin levels in the pigeon

Concentrations of plasma noradrenaline, adrenaline, corticosterone, thyroxine (T4), triiodothyronine (T3) and prolactin were measured in pigeons at 22 degrees C after intravenous injection of propranolol (1 mg/kg). An increase in catecholamines occurred in 5 or 15 min. T4, T3 and prolactin increased within 30 and 60 min after injection, however, after correction for the differences in plasma protein content, only the concentration of prolactin was significantly above the control values. It is concluded that the impairment of heat production produced by propranolol in birds is not primarily induced by inhibition of the secretion or release of these hormones.