EFFECTS OF CATECHOLAMINES ON THERMOREGULATION IN PIGEONS

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Abstract
In unanaesthetized pigeons, kept at room temperature (20–23°C) the effects on cloacal temperature were examined of catecholamines, phenoxybenzamine and propranolol, injected into the cerebral ventricles. Noradrenaline, adrenaline, dopamine and isoprenaline caused a fall in cloacal temperature. Phenoxybenzamine produced a long‐lasting small rise in cloacal temperature. This rise is attributed to removal of the hypothermic effect of noradrenaline released continuously from adrenergic neurones ending in the anterior hypothalamus. Propranolol produced a slight fall in cloacal temperature. The hypothermic effects of noradrenaline, adrenaline and dopamine were prevented by phenoxybenzamine but not by propranolol. They are therefore attributed to activation of α‐adrenoceptors. The hypothermic effect of isoprenaline was not prevented by either phenoxybenzamine or propranolol. The effect can therefore not be attributed to activation of either α or β‐adrenoceptors. Propranolol actually accentuated the isoprenaline‐induced hypothermia.