title: Hyperpolarization-activated current Ihin mouse trigeminal sensory neurons in a transgenic mouse model of familial hemiplegic migraine type-1.
abstract: Transgenic knock-in (KI) mice that express CaV2.1 channels containing an R192Q gain-of-function mutation in the α1Asubunit known to cause familial hemiplegic migraine type-1 in patients, exhibit key disease characteristics and provide a useful tool to investigate pathophysiological mechanisms of pain transduction. Previously, KI trigeminal sensory neurons were shown to exhibit constitutive hyperexcitability due to up-regulation of ATP-gated P2X3 receptors that trigger spike activity at a more negative threshold. This implies that intrinsic neuronal conductances may shape action potential generation in response to ATP, which could act as a mediator of migraine headache. Here we investigated whether the hyperpolarization-activated conductance Ih, mediated by hyperpolarization activated cyclic nucleotide-gated channels (HCN), contributes to sub-threshold behavior and firing in wild-type (WT) and KI trigeminal ganglia (TG) neurons. Whereas most WT and KI trigeminal neurons expressed Ihcurrent, blocked by the specific inhibitor ZD7288, it was smaller in KI neurons despite similar activation and deactivation kinetics. HCN1 and HCN2 were the most abundantly expressed subunits in TG, both in situ and in culture. In KI TG neurons, HCN2 subunits were predominantly present in the cytoplasm, not at the plasma membrane, likely accounting for the smaller Ihof such cells. ZD7288 hyperpolarized the membrane potential, thereby raising the firing threshold, and prolonging the spike trajectory to generate fewer spikes due to P2X3 receptor activation. The low amplitude of Ihin KI TG neurons suggests that down-regulation of Ihcurrent in sub-threshold behavior acts as a compensatory mechanism to limit sensory hyperexcitability, manifested under certain stressful stimuli.
authors.affiliation: Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy. Electronic address: feroli@sissa.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Eroli
authors.affiliation: Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy. Electronic address: vilotti@sissa.it.
authors.forename: Sandra
authors.initials: S
authors.lastname: Vilotti
authors.affiliation: Department of Neurology, Leiden University Medical Centre, Leiden, Netherlands; Department of Human Genetics, University Medical Centre, Leiden, Netherlands. Electronic address: A.M.J.M.van_den_Maagdenberg@lumc.nl.
authors.forename: Arn M J M
authors.initials: AMJM
authors.lastname: van den Maagdenberg
authors.affiliation: Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy. Electronic address: nistri@sissa.it.
authors.forename: Andrea
authors.initials: A
authors.lastname: Nistri
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002524:Cerebellar Ataxia / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D004195:Disease Models, Animal; D055879:Gene Knock-In Techniques / Q000379:methods; D008564:Membrane Potentials / Q000187:drug effects; D008822:Mice, Transgenic; D008881:Migraine Disorders / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D011743:Pyrimidines / Q000494:pharmacology; D058477:Receptors, Purinergic P2X3 / Q000235:genetics / Q000378:metabolism; D011984:Sensory Receptor Cells / Q000187:drug effects* / Q000378:metabolism; D012668:Trigeminal Ganglion / Q000187:drug effects* / Q000378:metabolism
chemical_list: D011743:Pyrimidines; D058477:Receptors, Purinergic P2X3; C082246:ICI D2788
keywords: CGRP; HCN; P2X3; ZD7288; excitability; trigeminal ganglion