The Role of Nucleus Tractus Solitarii (NTS) Cardiovascular Neurons for Vestibule-Autonomic Modulation in Hypertensive Diabetic Rat

Cardiovascular autonomic neuropathy (CAN) is a common form of autonomic neuropathy, causing abnormalities in heart rate control and central and peripheral vascular dynamics in patients with diabetes as well as the streptozotocin (STZ)-induced diabetic animals. Reduce of baroreflex sensitivity (BRS), caused by diabetic cardiovascular impairments, have been attributed to damage to baroreceptor afferent and efferent components in autonomic function. The nucleus tractus solitarii (NTS) is the central nervous system (CNS) termination site of baroreceptor afferent neurons and is the source of subsequent sympathetic and parasympathetic pathways for baroreflex control. Our previous data have shown that diabetes-induced impairment of barosensitive NTS neurons was observed in the baseline condition as well as vasopressor administration in STZ-induced diabetic rats. These abnormalities would make it difficulty to cope with the gravitational stress which induces the stimulation of vestibular nuclei to provide the information for the control of blood, the vestibulosympathetic reflex (VSR), redistribution requires immediate autonomic nervous action to maintain blood pressure. The results indicated that the baroreflexes and VSR play a significant role in short-term cardiovascular control in adaptation to orthostatic stress, caused by the gravity. To evaluate roles of the NTS cardiovascular neuronal activity to vestibulo-autonomic modulation in maintaining arterial blood pressure during gravitational stress, we measured the NTS neural activity by implanting the multi-wire electrode into NTS cardiovascular neurons for direct monitoring of neuronal firing as well as BRS in STZ-induced hypertensive diabetic rats, an animal model closely related to human diabetes, relative to normatensive rats. Through the present study, the changes observed in NTS cardiovascular neuronal activity and BRS results from phenylephrine administration would first provide baseline information to understand the effects caused by the hypertensive diabetic condition. Moreover, this advanced study would further provide a new point of view to investigate how the changes of NTS cardiovascular neurons regulation act on vestibulo-autonomic modulation during off-vertical axis rotation (OVAR) in awake rats, which is a crucial step to later human study.

Project ID:PB9801-2600
External Project ID:NSC98-2320-B182-001-MY2