TRPV4 and KCa functionally couple as osmosensors in the PVN

Feetham, Claire, Nunn, Nicholas, Lewis, Rebecca, Dart, Caroline ORCID: 0000-0002-3509-8349 and Barrett-Jolley, Richard ORCID: 0000-0003-0449-9972 (2015) TRPV4 and KCa functionally couple as osmosensors in the PVN. British Journal of Pharmacology, 172 (7). pp. 1753-1768.

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Abstract

BACKGROUND AND PURPOSE: Transient receptor potential vanilloid type 4 (TRPV4) and calcium-activated potassium channels (KCa ) mediate osmosensing in many tissues. Both TRPV4 and KCa channels are found in the paraventricular nucleus (PVN) of the hypothalamus, an area critical for sympathetic control of cardiovascular and renal function. Here, we have investigated whether TRPV4 channels functionally couple to KCa channels to mediate osmosensing in PVN parvocellular neurones and have characterized, pharmacologically, the subtype of KCa channel involved. EXPERIMENTAL APPROACH: We investigated osmosensing roles for TRPV4 and KCa channels in parvocellular PVN neurones using cell-attached and whole-cell electrophysiology in mouse brain slices and rat isolated PVN neurons. Intracellular Ca(2+) was recorded using Fura-2AM. The system was modelled in the NEURON simulation environment. KEY RESULTS: Hypotonic saline reduced action current frequency in hypothalamic slices; a response mimicked by TRPV4 channel agonists 4αPDD (1 μM) and GSK1016790A (100 nM), and blocked by inhibitors of either TRPV4 channels (RN1734 (5 μM) and HC067047 (300 nM) or the low-conductance calcium-activated potassium (SK) channel (UCL-1684 30 nM); iberiotoxin and TRAM-34 had no effect. Our model was compatible with coupling between TRPV4 and KCa channels, predicting the presence of positive and negative feedback loops. These predictions were verified using isolated PVN neurons. Both hypotonic challenge and 4αPDD increased intracellular Ca(2+) and UCL-1684 reduced the action of hypotonic challenge. CONCLUSIONS AND IMPLICATIONS: There was functional coupling between TRPV4 and SK channels in parvocellular neurones. This mechanism contributes to osmosensing in the PVN and may provide a novel pharmacological target for the cardiovascular or renal systems.

Item Type:	Article
Uncontrolled Keywords:	Paraventricular Hypothalamic Nucleus, Neurons, Animals, Mice, Rats, Wistar, Potassium Channels, Calcium-Activated, Membrane Potentials, Models, Biological, Female, Male, TRPV Cation Channels, In Vitro Techniques
Subjects:	?? Q1 ?? ?? QP ?? ?? RM ??
Depositing User:	Symplectic Admin
Date Deposited:	25 Mar 2015 10:26
Last Modified:	16 Dec 2022 12:11
DOI:	10.1111/bph.13023
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/2009013