Role of Different Types of Adrenoreceptors in Regulation of Functional Activity of Vasopressinergic Neurosecretory Cells of Rat Hypothalamus

Abstract

The goal of the present study was to find out by which adrenoreceptors noradrenaline affects synthesis and release of vasopressin from perikarya of neurosecretory cells in paraventricular and supraoptic nuclei of rat hypothalamus and what the character of this effect. In experiments in vitro with incubation of surviving hypothalamic slices in the medium containing noradrenaline or one of antagonists of adrenoreceptors (cirazoline—of α1-, UK14304—of α2-, cimaterol—of β-adrenoreceptors) it was shown that application of different adrenoreceptor agonists resulted in different changes of the functional state of vasopressinergic cells in the supraoptic and paraventricular nuclei. Comparison of the content of vasopressin mRNA (method of hybridization in situ) and of vasopressin-immunoreactive substance (immunohistochemical method) has allowed us to conclude about different ratios of intensities of vasopressin synthesis and release in these cells under effects of noradrenaline and adrenoreceptor agonists studied. The results obtained indicate that noradrenaline has no effect on intensity of synthesis of vasopressin, but can inhibit its release from perikarya. Meanwhile, noradrenaline via α 1-adrenoreceptors is able to inhibit synthesis of vasopressin and, possibly, its release; via α2-adrenoreceptors it also inhibits release of vasopressin, but does not affect its synthesis, whereas activation of β-adrenoreceptors stimulates vasopressin synthesis by neurons of supraoptic and paraventricular nuclei of rat hypothalamus. The diversity of responses of vasopressinergic system to action of noradrenaline, which has been reported by many authors, seems to be due to predominant involvement of particular types of adrenoreceptors.