Voltage-gated Potassium Channel (Kv) Subunits Expressed in the Rat Cochlear Nucleus

Zoltán Rusznák ¹, Gábor Bakondi ¹, Krisztina Pocsai ¹, Ágnes Pór ¹, Lívia Kosztka ¹, Balázs Pál ¹, Dénes Nagy ¹ and Géza Szcs ^1*

¹ Department of Physiology, Research Centre of Molecular Medicine, Medical and Health Science Centre, University of Debrecen, Debrecen, Hungary (ZR,GB,KP,LK,BP,DN,GS), and Department of Pathology, HBM Kenézy Gyula County Infirmary, Debrecen, Hungary (ÁP)

^* To whom correspondence should be addressed. E-mail: szg{at}phys.dote.hu.

Submitted on November 29, 2007
Accepted on 14 January 2008

	Abstract

Since the neuronal membrane properties and firing characteristics are crucially affected by the depolarization-activated K⁺ channel (Kv) subunits, data about the Kv distribution may provide useful information regarding the functionality of the neurones situated in the cochlear nucleus (CN). Using immunohistochemistry in free-floating slices, the distribution of 7 Kv subunits was described in the rat CN. Positive labelling was observed for Kv1.1-, 1.2-, 1.6-, 3.1-, 3.4-, 4.2-, and 4.3 subunits. Giant and octopus neurones showed particularly strong immunopositivity for Kv3.1; octopus neurones demonstrated intense Kv1.1- and 1.2-specific reactions, too. In the latter case, an age-dependent change of the expression pattern was also documented: although both young and older animals produced definite labelling for Kv1.2, the intensity of the reaction increased in older animals, and was accompanied with the translocation of the Kv1.2 subunits to the cell surface membrane. The granule cell layer exhibited strong Kv4.2-specific immunopositivity, and markedly Kv4.2 positive glomerular synapses were also seen. It was found that neither giant, nor pyramidal cells were uniform in terms of their Kv expression patterns. Our data provide new information about the Kv expression of the CN, and they also suggest potential functional heterogeneity of the giant and pyramidal cells.

Key Words: hearing, rhodamine, immunohistochemistry, confocal microscopy, age dependence, glomerular synapse

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