Neurosecretory and Non‐Neurosecretory Parvocellular Neurones of the Hypothalamic Paraventricular Nucleus Express Distinct Electrophysiological Properties

Abstract

Parvocellular neurones of the hypothalamic paraventricular nucleus (PVN) comprise neurosecretory and non-neurosecretory subpopulations. We labelled neurosecretory neurones with intravenous injection of the retrograde tracer, fluoro-gold, and recorded from fluoro-gold-positive and negative PVN parvocellular neurones in hypothalamic slices. Non-neurosecretory parvocellular neurones generated a low-threshold spike (LTS) and robust T-type Ca2+ current, whereas neurosecretory neurones showed no LTS and a small T-current. LTS neurones were located in non-neurosecretory regions of the PVN, and non-LTS neurones were located in neurosecretory regions of the PVN. These findings indicate that neurosecretory and non-neurosecretory subtypes of parvocellular PVN neurones express distinct membrane electrical properties.

Overactivity of Liver-Related Neurons in the Paraventricular Nucleus of the Hypothalamus: Electrophysiological Findings indb/dbMice

“…First, as described previously (Luther and Tasker, 2000;Stern, 2001;Luther et al, 2002), after a hyperpolarizing current step, a 10 mV depolarization compared with resting membrane potential was evoked by current injection. In the lean silent group, we were able to evoke firing in three of the eight recorded neurons with an average frequency of 8.6 Ϯ 0.7 Hz (range: 7.52-10.07 Hz), whereas the rest of the neurons remained silent.…”

“…Preautonomic PVN neurons regulate the sympathetic and parasympathetic tone through sympathetic neurons in the spinal cord and parasympathetic brainstem neurons, respectively (Rogers and Nelson, 1984;Yamashita et al, 1984;Lawrence and Pittman, 1985). Increased sympathetic activity was shown in the db/db mouse model (Rahmouni et al, 2003), which could contribute to elevated hepatic glucose production reported in db/db mice (Zhang et al, 2013). Because modulation of the synaptic balance and/or altering postsynaptic properties of liver-related PVN neurons is likely one of the underlying mechanisms of increased sympathetic activity, determining the cellular properties of liver-related PVN neurons is crucial to the understanding of the brain-liver circuit.…”

“…Activation of TRPV1 increases neurotransmission in autonomic brain areas and functional plasticity of TRPV1-dependent neurotransmitter release was observed in streptozotocin-treated hyperglycemic mice (Zsombok et al, 2011;Boychuk et al, 2013). Our previous study demonstrated that capsaicin increases mEPSC frequency in liver-related PVN neurons and this TRPV1-dependent regulation was diminished in the type 1 diabetic condition (Gao et al, 2012).…”

“…Traditionally, the hypothalamus, a key brain region in the regulation of homeostatic functions was valued for its neuroendocrine control systems; nevertheless, its role in governing the autonomic nervous system became well accepted (Sandoval et al, 2009;Kalsbeek et al, 2010;Seoane-Collazo et al, 2015;O'Hare and Zsombok, 2016;Ruud et al, 2017). In general, the autonomic nervous system modulates organ functions through opposing actions of the sympathetic and parasympathetic nervous systems.…”

“…These preganglionic neurons receive information from preautonomic neurons located in higher brain areas including the paraventricular nucleus of the hypothalamus (PVN). The PVN is considered a command component of the autonomic pathway that integrates signals from many different brain areas, including hypothalamic nuclei with well established roles in glucose and energy homeostasis (Yi et al, 2010;O'Hare and Zsombok, 2016). Excitation of PVN neurons with NMDA, a glutamate receptor agonist or removal of inhibition with a GABA A receptor antagonist elevated plasma glucose levels via the SNS (Kalsbeek et al, 2004).…”