Suppressed serum prolactin in sinoaortic-denervated rats.

Abstract

We investigated the effect of arterial baroreceptor deafferentation on serum and pituitary prolactin (PRL) and on catecholamines in median eminence (ME) and anterior and posterior pituitaries. Male Wistar rats were sinoaortic denervated (SAD) or sham operated (SO). Three days after surgery serum prolactin, measured by radioimmunoassay, was suppressed in SAD rats (-54%, P less than 0.05), and dopamine (DA) and norepinephrine (NE) concentrations, measured by radioenzymatic or high-performance liquid chromatography electron capture methods, were significantly reduced in ME of SAD rats (NE, -54% P less than 0.005 and DA, -56% P less than 0.001). Simultaneously, anterior pituitary of SAD rats had significant increases in both catecholamines, whereas posterior pituitary showed no changes. Four hours after surgery serum PRL was also reduced (-40%, P less than 0.05) in SAD rats, but no changes in ME catecholamines were found. Mean arterial pressure (MAP) and heart rate were measured before and after injection of bromocriptine (0.5 mg/kg ip) in SAD and SO rats 3 days after surgery. Bromocriptine markedly suppressed serum PRL in both groups and reduced MAP from 144 +/- 10 to 84 +/- 5 and from 116 +/- 2 to 99 +/- 3 in SAD and SO rats, respectively; heart rate was reduced in SAD rats. We conclude that the SAD rat is a model of hypertension with suppressed serum PRL and that interruption of arterial baroreceptor nerves suppresses PRL secretion probably by modulating tuberoinfundibular turnover of catecholamines.