Journal of neuroendocrinology
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J. Neuroendocrinol. · Apr 1993
Alpha 2 and beta adrenoceptors in the mediobasal hypothalamus and alpha 2 adrenoceptors in the preoptic-anterior hypothalamus stimulate prolactin secretion in the conscious male rat.
Plasma prolactin concentrations were measured in unanaesthetized male rats before and after stereotaxic microinjection of adrenergic agents into the mediobasal and preoptic-anterior hypothalamus. In the mediobasal hypothalamus injection of the alpha 2 agonist clonidine produced a dose-dependent increase in prolactin secretion over the dose range 0.1 to 10 nmoles, the stimulation due to 1 nmole being blocked by idazoxan (alpha 2 antagonist). Stimulation of prolactin release was also caused by isoprenaline (beta agonist) and was significantly reduced by the beta antagonist propranolol. ⋯ We conclude that the activation of alpha 2 and beta 2 adrenoceptors in the mediobasal hypothalamus and of alpha 2 adrenoceptors in the preoptic-anterior hypothalamus, on or near prolactin-regulating neurons, results in increased prolactin secretion. An alpha 1 inhibitory action in the mediobasal hypothalamus has however not been ruled out. Adrenergic inputs in the preoptic-anterior hypothalamus appear to exert a predominant facilitatory effect on prolactin secretion.