Downregulation of M Current Is Coupled to Membrane Excitability in Sympathetic Neurons Before the Onset of Hypertension

Abstract

Neurohumoral activation is an early hallmark of cardiovascular disease and contributes to the etiology of the pathophysiology. Stellectomy has reemerged as a positive therapeutic intervention to modify the progression of dysautonomia, although the biophysical properties underpinning abnormal activity of this ganglia are not fully understood in the initial stages of the disease. We investigated whether stellate ganglia neurons from prehypertensive SHRs (spontaneously hypertensive rats) are hyperactive and describe their electrophysiological phenotype guided by singlecell RNA sequencing, molecular biology, and perforated patch clamp to uncover the mechanism of abnormal excitability. We demonstrate the contribution of a plethora of ion channels, in particular inhibition of M current to stellate ganglia neuronal firing, and confirm the conservation of expression of key ion channel transcripts in human stellate ganglia. We show that hyperexcitability was curbed by M-current activators, nonselective sodium current blockers, or inhibition of Na v 1.1-1.3, Na v 1.6, or I NaP . We conclude that reduced activity of M current contributes significantly to abnormal firing of stellate neurons, which, in part, contributes to the hyperexcitability from rats that have a predisposition to hypertension. Targeting these channels could provide a therapeutic opportunity to minimize the consequences of excessive sympathetic activation.

Post-Ganglionic Sympathetic Neurons can Directly Sense Raised Extracellular Na+ via SCN7a/Nax

“…Animal experiments were approved and regulated under British Home Office Project Licenses (PPL 30/3131 and P707EB251). Rats were used as the chosen model in this study based upon the breadth of cardiovascular research on this model organism (as reviewed in Herring et al, 2019), and our preexisting single-cell RNA-sequencing dataset from the rat stellate ganglia (Davis et al, 2020). Rats were purchased from Envigo, United Kingdom Animals were housed in the local animal facility in open top conventional cages at 20-24 °C with 55% Relative Humidity on a 12-h day-night cycle.…”

What gets on the nerves of cardiac patients? Pathophysiological changes in cardiac innervation

“…Postganglionic sympathetic neurons become hyperactive in cardiovascular disease, and that increased activity corresponds with increased cell body size, enhanced synaptic transmission within stellate ganglia, and increased NA release to cardiac myocytes in animals and humans alike (Ajijola et al 2012;Han et al 2012). Downregulation of the M current, changes in neuronal cyclic nucleotide signalling, and decreased nitric oxide synthase (nNOS) in cardiovascular disease also drive excess NA release by increasing intracellular Ca 2+ and intrinsic neuronal excitability (Bardsley & Paterson, 2020;Davis et al 2020).…”

“…Downregulation of the M current, changes in neuronal cyclic nucleotide signalling, and decreased nitric oxide synthase (nNOS) in cardiovascular disease also drive excess NA release by increasing intracellular Ca 2+ and intrinsic neuronal excitability (Bardsley & Paterson, 2020; Davis et al . 2020).…”

From Mice to Mainframes: Experimental Models for Investigation of the Intracardiac Nervous System

“…As more refined methodologies develop, researchers are now utilising molecular analyses to better characterise differences in intracardiac neuron populations. For instance, a recent study provided the first report of single cell RNA sequencing and functional analysis of stellate ganglia neurons, validated against human stellate ganglia neurons, in an effort to better characterise neurons innervating the heart [77].…”