IMPACT OF HYPOTHALAMIC PARAVENTRICULAR NUCLEUS ON VISCERAL SENSORY NEURONS OF THE SOLITARY TRACT AND HEART RATE VARIABILITY DURING PSYCHO - EMOTIONAL STRESS IN RATS

We investigated the influence of single, low- and high-frequency tetanic stimulation of the paraventricular
nucleus (PVN) of hypothalamus on the activity of the vagosensitive neurons of the solitary tract nucleus (STN)
and on heart rate variability (HRV) in norm and at psychoemotional stress.
In rats under urethane anesthesia bipolar stimulating electrodes introduced in the anteromedial region of the
hypothalamus. Extracellular recording of neuronal activity was carried out from the medial region of NTS Analysis
of cardiac activity was carried out by method of mathematical analysis of heart rate variability (MA HRV). We
studied the most important indices: heart rate (HR), vegetative balance index (PSI) and the tension index of regulatory systems (TIRS). The data is processed using a Microsoft Excel spreadsheet, the level of statistical significance was determined by Student's t-test.
Significant reactivity of solitary neurons (62%) to descending paraventricular inputs was revealed. The tetanic
stimulation of PVN (100-Hz during 1-sec) resulted in pronounced tetanic depression with post-tetanic potentiation.
In the mathematical analysis of some functionally significant HRV parameters: the HR, the vegetative equilibrium
index (IWR), the intensity index of the regulatory systems before and immediately after immobilization a beneficial effect of the frequency stimulation of PVN was found.
Our results suggest that some decrease in the stress reaction is evidently due to the initiation of the neuroregulative inhibitory control of PVN supporting the realization of vago-vagal reflexes via STN neurons