Function of the supraoptic nucleus of the hypothalamus in the cardiovascular and neuroendocrine responses observed in rats submitted to acute restraint stress in rats

Abstract

The supraoptic nucleus of the hypothalamus (SON) has been implicated in the central cardiovascular control. Furthermore, The SON has neural connections with several limbic structures involved with both autonomic and behavioral controls during defensive situations. It was shown that exposure of animals to acute restraint stress (ER) causes neuronal activation of the SON, suggesting that the SON may be involved in physiological responses to stress. The ER is an unavoidable stressor that causes mean arterial pressure increase and an intense tachycardiac response, with concomitant increase in the plasma concentrations of corticosterone and adrenocorticotrophin. Moreover, the stressful situations cause a reduction in temperature of the tail skin in rats that is due to skin vasoconstriction.It is an indicative of autonomic activity, together with cardiovascular changes. Besides the physiological adjustments, animals subjected to an aversive stimulus also develop emotional disorders such as anxiety. Among the neurotransmitters involved in the modulation of cardiovascular and neuroendocrine systems in the SON during several pathophysiological situations, we highlight the glutamatergic and nitrergic systems. Thus, the hypothesis of the present project is that there is an interaction between glutamatergic and nitrergic systems present in the SON involved in the mediation of autonomic, hormonal and behavioral changes caused by the exposure of rats to ER. To achieve this purpose we will study this interaction of neurotransmissions on cardiovascular, temperature, hormonal and behavioral effects induced by exposure to ER, by local PVN inhibition of glutamatergic receptors or nitrergic system made before exposing animals to the stress.