Failure of papaverine to alter L-dopa-influenced GH and PRL secretion

Papaverine, 150 mg BID for 2 weeks, a dose which produced marked clinical impairment in Parkinsonian patients taking L-Dopa, failed to alter L-Dopa-stimulated GH secretion or L-Dopa inhibited PRL secretion in 6 normal volunteers. Failure to demonstrate an inhibitory effect of papaverine on dopaminergic hypothalamic-pituitary systems, despite its inhibition of striatal dopaminergic pathways, may imply qualitative or quantitative functional differences between hypothalamic and striatal dopaminergic systems.