Kv4 (A‐type) potassium currents in the mouse medial nucleus of the trapezoid body

Abstract

Principal neurones of the mouse medial nucleus of the trapezoid body (MNTB) possess multiple voltage-gated potassium currents, including a transient outward current (or A-current), which is characterized here. The A-current exhibited rapid voltage-dependent inactivation and was half inactivated at resting membrane potentials. Following a hyperpolarizing pre-pulse to remove inactivation, the peak transient current was 1.07 nA at -17 mV. The pharmacological characteristics of this A-current were consistent with Kv4 subunits in expression studies; the A-current was resistant to block by tetraethylammonium and dendrotoxin-I but sensitive to millimolar concentrations of 4-aminopyridine and 5 microM hanatoxin. Immunohistochemistry confirmed that Kv4.3 sub-units are present in the MNTB. In a single-compartment model of an MNTB neurone, the A-current served to accelerate the decay of the initial action potentials in a stimulus train and suggested that removal of A-current steady-state inactivation could raise firing threshold for non-calyceal synaptic inputs. This A-type current was not observed in the rat.

Physiological Characterization of Vestibular Efferent Brainstem Neurons Using a Transgenic Mouse Model

“…This ion current is mediated via the Kv4 channel family, which includes three pore-forming α-subunits: Kv4.1, Kv4.2 and Kv4.3; of which Kv4.2 and Kv4.3 are specific for the brainstem [21], [33], [61]. In order to investigate if Kv4 subunits are expressed in VE neurons and, in that case which subtype, immunolabeling against ChAT, identifying the VE and LOC neurons, was combined with Kv4.2 and Kv4.3 antibodies in wild type animals.…”

“…However, this protocol failed to produce any specific Kv4.3 staining in the mouse. In accordance with another study of Kv4-immunolabeling in mice [33], the tissue preparation was switched from trans-cardial perfusion to a protocol using shock-freezing of the brain tissue. Presumably, this method better preserved antigenicity or opened up the cell membrane for better antibody-targeting of intracellular epitopes.…”

“…The A current, carried by the Kv4 channels [4], is a rapidly activating and inactivating K + current [32]. I A is characteristically active at the resting membrane potential, usually demonstrated as a ‘window-current’ in the −70 to −50 mV range [33], [63], [70]. The large transient outward currents, with instantaneous activation and rapid inactivation upon depolarization, being active at resting membrane voltages in VE neurons, are highly compatible with I A .…”

A simple modification of the Hodgkin and Huxley equations explains type 3 excitability in squid giant axons

“…Several groups have recently used the GHK normalization procedure described in this study and in an earlier report (Clay 2000) to obtain K C channel activation curves (DeFazio & Moenter 2002;Boland et al 2003;Van Hoorick et al 2003;Persson et al 2005;Nakamura & Takahashi 2007;Johnston et al 2008). A far larger number of reports have used normalization with (VKE K ).…”

The impact of synaptic conductance on action potential waveform: Evoking realistic action potentials with a simulated synaptic conductance

“…Brain slices were prepared as described previously (Postlethwaite et al, 2007;Johnston et al, 2008a). Briefly, CBA/Ca mice or Lister Hooded rats aged P10-P19 were decapitated in accordance with the UK animals (Scientific Procedures) Act 1986 and the brain was removed in a slush of iced artificial CSF (aCSF) of composition (in mM) 250 sucrose, 2.5 KCl, 10 glucose, 1.25 NaH 2 PO 4 , 0.5 ascorbic acid, 26 NaHCO 3 , 4 MgCl 2 , 0.1 CaCl 2 , gassed with 95% O 2 /5% CO 2 (pH 7.4).…”