Inhibitory influence of catecholamines on prolactin release in the turkey (Meleagris gallopavo)

The involvement of catecholamines (CAs) in the control of prolactin (PRL) secretion was investigated in female turkeys. The birds were treate with dl-α-methyltyrosine methyl ester HCl (α-MT; 10, 100, or 200 mg/kg), diethyldithiocarbamate (DDC; 200 or 400 mg/kg), or phentolamine (5, 10, and 20 mg/kg), all antiadrenergic drugs. Reduction in central CAs by α-MT or DDC, or blockade of adrenergic receptors by phentolamine resulted in elevated serum PRL levels in a dose-dependent manner. Prior administration of the adrenergic stimulant clonidine (15, 150, or 1500 μg/kg) attenuated the elevated PRL response to phentolamine (20 mg/kg). These results are consistent with the view that the release of PRL in the turkey may be under the inhibitory influence of an adrenergic system.