[Noradrenaline role in regulation of dopamine-producing neurons in rat arcuate nucleus].

Among most important functions of the neuroendocrine system is the regulation of reproduction, including the inhibitory control of prolactin secretion by dopamine (DA) synthesized in the arcuate nucleus (AN). Besides DA, noradrenaline (NA) contributes to this regulation though, in contrast DA, its concrete functional role remains to be uncertain. In the previous studies, it has been suggested that NA inhibits compensatory synthesis of DA in DA-producing neurons of AN under the failure of the dopaminergic system though no evidence were obtained. Therefore, the goal of this study was to specify the role of NA in the regulation of DA-producing neurons in AN. Two pharmacological models were used to this aim: a) switching off dopaminergic and noradrenergic neurons and their afferents in An or b) switching of only dopaminergic neurons and afferents that allowed us to recognize NA role in the complex catecholaminergic regulation of prolactin secretion. According to our data, the maintaining of the noradrenergic innervation of AN under the neurotoxin-induced failure of dopaminergic neurons resulted in the decrease of the expression of tyrosine hydroxylase (TH), the first enzyme ofDA synthesis, thereby enhancing DA deficit. This is considered as direct evidence of noradrenergic inhibitory control of TH expression in the neurons of AN.