P31 - Simultaneous Recording for Renal and Splenic Nerve Activity Reveals Coordinated Activity during Hypertension

Introduction: : Hypertension is a major global condition that affects more than 1.3 billion people worldwide and a major cause of stroke. Chronic high blood pressure also produces tissue damage and inflammation in several critical organs such as the kidney, heart and brain. It is known that a neuroimmune response is initiated by the increase in blood pressure that stimulates the activation of T-cells in the spleen, which then migrate to the affected organs to ameliorate the cellular damage. This suggests the possibility of coordinated activity between these organs. We have recently reported the application of sensitive and flexible platinized graphene electrodes (sutrodes) to record spontaneous and evoked electrophysiological activity in the cervical vagus nerve (cVN), right renal nerve (RN) and splenic nerve (SN) terminal branches. We observed an increase in the splenic neural spike frequency evoked by hypertension, presumably mediated by an efferent pathway, but whether is coordinated with efferent activity of the renal nerve, is unknown. We hypothesized that the neural activity of the renal and splenic nerves is coordinated to reduce blood pressure.

Materials and

Methods: : Sixteen male rats were used in this study, divided into two experimental groups: normotensive Wistar-Kyoto (WKY, n = 8) and spontaneously hypertensive rats (SHR, n = 8). Simultaneous recordings of sympathetic nerve activity were performed in the cVN, RN, and terminal branches of the SN. Flexible and biocompatible platinized graphene fiber electrodes were fine surgically implanted onto each target nerve. Neural activity was recorded during baseline and pharmacologically induced modulation of arterial pressure to assess differential autonomic responses between the groups. The neural activity was recorded using Omniplex Data Acquisition System at 40KHz sampling rate high-pass filtered (4-pole Bessel) at 300 Hz and analyzed with the Offline Sorter and NeuroExplorer software (Plexon, Inc).

Results, Conclusions, and Discussions:: Results. The electrode system allowed stable, high-resolution recordings, enabling the exploration of sympathetic crosstalk between renal and splenic innervation under hypertensive and normotensive conditions. We observed several sequential changes in the neural activity of these organs, with a first decrease in spiking in the cVN, followed by a tonic increase in RN activity, in turn followed by a burst activation increase in the SN branches 1 and 3. Power spectral analysis and statistical evaluation will be presented. We also obtained evidence that this coordinated activity is mediated by neurons in the nodose ganglia. Conclusion/Disccusion. Our preliminary data indicates that the spleen and kidney function in repones to hypertension is coordinated in part at the level of the nodose ganglia. This information can assist in improving neuromodulation therapies for the treatment of drug resistant hypertension.

Acknowledgements and/or References (Optional):: Hugo M Libreros-Jimenez, Zuha Yousuf and Mario Romero-Ortega.
University of Arizona.