Effect of Piperoxane on Serum Prolactin: Possible Role of Epinephrine-Mediated Synapses in the Inhibition of Prolactin Secretion*

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Abstract
I.v. administration of 2.5 mg/kg piperoxane produced a rapid and significant increase in serum PRL [prolactin] concentrations in 4 non-human primates [Macaca arctoides]. This PRL increase was maximal 15 min after piperoxane infusion and significant when compared with baseline levels in the +15, +30, +45, +60 and +90 min samples. The i.v. administration of 5 mg/kg piperoxane also produced a rapid and significant increase, whereas saline, 0.5 mg/kg or 1.0 mg/kg, did not change serum PRL levels. The i.v. administration of 10 .mu.g/kg clonidine, but not saline, produced a rapid and significant reduction in serum PRL levels. PRL levels were significantly reduced +15, +30 and +60 min after the clonidine infusion. Pretreatment with a bolus of 10 .mu.g/kg clonidine at -15 min caused a significant attenuation of the piperoxane-induced elevation in serum PRL in 2 monkeys. .alpha.-Adrenergic receptors apparently are involved in the inhibition of PRL secretion. These data are compatible with noradrenergic or adrenergic mechanisms which remain to be defined.