Stress-Induced Renin and Corticosterone Secretion Is Mediated by Catecholaminergic Nerve Terminals in the Hypothalamic Paraventricular Nucleus

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Abstract
Cell bodies in the hypothalamic paraventricular nucleus (PVN) mediate stress-induced increases in renin and corticosterone secretion. Since the PVN has an extensive catecholaminergic innervation, we wanted to determine the role of catecholamines in the neuroendocrine response to stress. The stressor was a conditioned emotional (fear) response paradigm (CER). The catecholamine neurotoxin, 6-hydroxydopamine (6-OHDA), was injected into the PVN 14 days before the rats were subjected to the CER procedure. Damage to noradrenergic nerve terminals was verified immunocytochemically, using an antibody against dopamine β-hydroxylase. Injection of 6-OHDA into the PVN prevented the stress-induced increase in plasma renin activity (PRA), plasma renin concentration (PRC) and plasma corticosterone concentration, suggesting that intact catecholaminergic innervation of neurons in the PVN is necessary for the stress-induced increase in renin and corticosterone secretion. To determine if β-adrenoceptors in the PVN mediate the effect of stress on renin and corticosterone secretion, the β-adrenoceptor antagonist sotalol was injected into the PVN through chronically implanted bilateral cannulae. The injection was performed on the 4th day of the CER paradigm, just before the rats were placed into the CER chamber. Sotalol prevented the stress-induced increase in corticosterone concentration, but did not diminish the stress-induced increase in PRA and PRC. These results suggest that the stress-induced increase in corticosterone concentration is influenced by β-adrenoceptors in the PVN. The stress-induced increase in PRA and PRC is mediated by different receptors whose ligands might be catecholamines acting at non-β-receptors or other neuroactive substances colocalized in catecholaminergic nerve terminals.

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