The role of catecholamines in regulation of episodic GH [growth hormone] secretion was investigated in the male rat. Administration of .alpha.-methyl-p-tyrosine (.alpha.-MT; 250 mg/kg i.p.) suppressed GH bursts and elevated plasma PRL [prolactin]. I.v. administration of apomorphine (.03 and .1 mg/kg) had no effect on decreased GH levels, whereas, clonidine (150 .mu.g/kg) restored GH secretion. Apomorphine significantly reduced PRL levels in .alpha.-MT-treated rats, whereas, clonidine further increased PRL.