The Neurochemical Mechanism Responsible For Regulation Of Cardiovascular Responses Induced By Swing Rotation In The PVN

The pareventricular nucleus of the hypothalamus (PVN) integrates neuroendocrineand autonomic activity to maintain physiological homeostasis and regulate thecardiovascular responses. Though several studies have shown that the PVN isinvolved in the regulation of cardiovascular responses induced by stressors, butneurochemical mediators in the PVN responsible for generation of the stress responsehave not been fully elucidated; moreover, most of these studies are performed in theanaesthetic state. Anesthesia is well known for its profound effect on cardiovascularand autonomic function, and reverses the responses. Therefore, in this study, Toinvestigate the neurochemical mechanisms responsible for regulation of swingrotation-induced cardiovascular responses, the changes in extracellular concentrationsof aspartate (Asp), glutamate (Glu), Glutamine (Gln), glycine (Gly), alanine (Ala),and tautine (Tau) were measured in PVN region in free-moving conscious rats, byusing microdialysis and high performance liquid chromatography (HPLC) techniques.Blood pressure (BP) and heart rate(HR) were also measured.The results were as follows:1. Swing rotation elicited significant increases in BP and HR from baseline levels of10.4±2.3mmHg and 367.3±2.4 beats/min to the maximums of 113.4±3.5mmHgand 418.3±11.4 beats/min, respectively. The concentration of Asp, Gly, and Ala inPVN were increased by swing rotation from basal level of 100% to 199.49±20.64%(P＜0.001), 185.68±24.63% (P＜0.01), and 143.92±8.94% (P＜0.01),respectively; There were no significant changes on the concentration of Glu, Gln,Tau in the PVN. (P＞0.05).2. MK-801, an NMDA receptor antagonist, was directly perfused in the PVN for20min, and swing rotation was added. The swing rotation increased the BP andHR from 99.9±0.5mmHg and 357.3±9.1 beats/min to 104.5±1.0mmHg and387.2±8.5 beats/min (P＜0.01); MK-801 attenuated the swing rotation-inducedincreases of BP and HR. 3. An antagonist of non-NMDA receptor, CNQX, was directly perfused in the PVNfor 20min, and swing rotation was added. The swing rotation increased the BP andHR from in 104.9±2.3mmHg and 375.2±5.7 beats/rain to 113.2±1.3mmHg and421.1±5.4 beats/min. (P＜0.001); CNQX did not affect the cardiovascularresponses induced by swing rotation..Conclusion:1. Asp,Gly and Ala in PVN may be involved in the central regulation ofcardiovascular responses induced by swing rotation.2. Asp and Gly in the PVN may act via NMDA receptors to mediate thecardiovascular responses induced by swing rotation.