[Prolactin after baclofen in healthy subjects and prolactinoma patients]

Serum prolactin (PRL) levels in basal conditions (two samples) and 30, 60, 90, 120, 150 e 180 minutes after oral administration of baclofen (20 mg) were evaluated in 6 healthy subjects and in 10 patients with prolactinoma. The effect of baclofen (20 mg by mouth) on the PRL secretion cimetidine (400 mg i.v.) or domperidone (20 mg i.v.) induced were evaluated in 9 healthy women by administration of baclofen 60 minutes before cimetidine or domperidone. Baclofen was unable to significantly rise serum PRL levels in healthy subjects and in patients affected by prolactinoma and furthermore did not interfere with PRL rise domperidone induced. On the contrary baclofen decreased PRL rise cimetidine induced. It was concluded that: in basal condition, GABAb receptor don't play an obvious role in modulation of PRL secretion; when H2 istaminergic inhibition on PRL secretion is blocked (at an hypothalamic site), a GABA inhibition, b receptor mediated, on PRL secretion became more clear; the domperidone blockade of hypophysial dopaminergic receptors suggests that GABAb modulation of prolactin secretion don't obtain itself by dopaminergic pathways.