Abstract 412: Electrophysiological Properties of Kidney-related Neurons in the Rostral Ventrolateral Medulla
Presympathetic neurons in the rostral ventrolateral medulla (RVLM) play an important integrative role in the neuronal network mediating cardiovascular regulation. In this study, we employed a retrograde, transsynaptic pseudorabies viral label (PRV-152), a PRV construct which expresses enhanced green fluorescent protein (EGFP), to identify kidney-related neurons in the RVLM. Whole-cell, patch-clamp recordings were made from 86 kidney-related neurons in the RVLM in transverse brainstem slices from 4-7-week-old rats. Under control conditions, we identified two populations of PRV-labeled RVLM neurons based on their electrophysiological properties. The resting membrane potential of large kidney-related neurons was -48 ± 2 mV and the input resistance was 205 ± 28 MΩ. The resting membrane potential of small kidney-related neurons was -51 ± 2 mV and the input resistance was 430 ± 36 MΩ. Spontaneous firing was observed in 2 out of 15 large cells with frequency of firing 0.008 and 0.05 Hz and 7 out of 16 small cells with average of firing 0.4 ± 0.2 Hz. Both spontaneous and miniature inhibitory and excitatory postsynaptic currents (i.e., sEPSCs, sIPSCs and mEPSCs, mIPSCs) were observed in small and large neurons. Tonic inhibitory and excitatory currents were identified in large kidney-related neurons of the RVLM. Application of the type A γ-aminobutyric acid (GABAA) receptor-linked Cl- channel blocker, bicuculline methiodide (30 μM), blocked sIPSCs and revealed a robust tonic inhibitory current with an average amplitude of 145.3 ± 30 pA. The cocktail of potent N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA)/kainate ionotropic glutamate receptor antagonist, AP-5 (50 μM) and CNQX (10 μM), blocked sEPSCs and revealed a two-component tonic excitatory current mediated by NMDA and AMPA/kainate ionotropic glutamate receptors with overall amplitude of 65.2 ± 11.3 pA. These data demonstrate the synaptic complexity involved in the regulation of kidney-related RVLM neurons.
- © 2012 by American Heart Association, Inc.