Role of prelimbic cortex cholinergic neurotransmission in autonomic responses to acute restraint stress in rats

Abstract

Individuals are daily exposure to stressful situations. The maintenance of homeostasis during stress is mediated by the coordinated activation of autonomic and neuroendocrine systems. The autonomic nervous system provides the most immediate response during aversive situations. The autonomic adjustments during stress are characterized by increase in blood pressure and heart rate, reduction in visceral and cutaneous blood flow and changes on baroreflex activity. Although the importance of autonomic responses during threat situations, the mechanisms involved in these responses are poorly understood. The physiological and behavioral responses during stress are mediated by limbic structures in the central nervous system through action of several neurochemical mechanisms. The medial prefrontal cortex (MPFC) is a limbic structure divided in cingulate cortex 1 and 2 (Cg1 and Cg2), prelimbic cortex (PL), infralimbic cortex (IL) and dorsal penducular cortex (DP). It has been demonstrated that MPFC regions differently modulates the responses to stress. In this way, it has been proposed a inhibitory role of PL cortex, whereas IL cortex seems to play an facilitatory role in autonomic, neuroendocrine and behavioral responses to stress. Although above evidences to suggest an important role of MPFC in the integration of autonomic responses during threat situations, information regarding the local neurochemical mechanism involved in MPFC control of stress responses is unclear. It has been demonstrated that cholinergic inputs to the MPFC are activated by stressful stimuli. Moreover, MPFC cholinergic neurotransmission is involved in control of cardiovascular function. Based on above evidences, our proposal in the present study is to test the hypothesis that cholinergic neurotransmission in the PL cortex play an inhibitory role in autonomic response to acute restraint stress in rats. To test this hypothesis, our aim is to investigate the effect of bilateral IL cortex treatment with vehicle or hemicholinium (inhibitor of choline uptake) in blood pressure and heart rate increase and reduction of tail cutaneous temperature induced by acute restraint stress in rats. (AU)