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

Abstract

-Bihar Megyei Kené zy Gyula County Infirmary, Debrecen, Hungary (Á P) S U M M A R Y Because the neuronal membrane properties and firing characteristics are crucially affected by the depolarization-activated K 1 channel (Kv) subunits, data about the Kv distribution may provide useful information regarding the functionality of the neurons situated in the cochlear nucleus (CN). Using immunohistochemistry in free-floating slices, the distribution of seven Kv subunits was described in the rat CN. Positive labeling was observed for Kv1.1, 1.2, 1.6, 3.1, 3.4, 4.2, and 4.3 subunits. Giant and octopus neurons showed particularly strong immunopositivity for Kv3.1; octopus neurons showed intense Kv1.1-and 1.2-specific reactions also. In the latter case, an age-dependent change of the expression pattern was also documented; although both young and older animals produced definite labeling 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 also suggest potential functional heterogeneity of the giant and pyramidal cells. (J Histochem Cytochem 56:443-465, 2008) K E Y W O R D S hearing rhodamine immunohistochemistry confocal microscopy age dependence glomerular synapse THE MAMMALIAN cochlear nucleus (CN) is an assembly point of numerous types of neurons forming local networks that receive and process the primary acoustic information arriving from the cochlea (Brawer et al. 1974;Disterhoft et al. 1980;Webster and Trune 1982;Hackney et al. 1990). The nucleus is divided into three morphologically distinct parts (anteroventral, posteroventral, and dorsal divisions; aVCN, pVCN, and DCN, respectively), each contacted by the incoming and branching axons of the auditory nerve (Moore 1986). Because of the fact that these regions of the CN play different roles in the processing of the auditory information, the parallel secondary pathways emerging from the CN and targeting higher centers in the brain carry activity patterns, providing information about different features of the sound (Cant and Benson 2003; Malmierca 2003).To understand the function of the CN, it is essential to know how the various cell types contribute to its overall task. Thus far, numerous authors have provided valuable information about the morphological and functional properties of the individual CN neurons, revealing that the behavior and firing characteristics of the projection cells of the CN are markedly different. The bushy neurons (Brawer et al. 1974) of the VCN produce rapidly adapting (type II) response pattern [i.e., they fire a single action potential at the start of suprathreshold electrical stimulation (Manis and Marx 1991;Schwarz an...

Genetic perturbations suggest a role of the resting potential in regulating the expression of the ion channels of the KCNA and HCN families in octopus cells of the ventral cochlear nucleus

“…Octopus cells express Kv1.1, a subunit of ion channels that generate g KL , and HCN1, a subunit of ion channels that generate g h ( Koch et al, 2004; Oertel et al, 2008; Rusznak et al, 2008; Robbins and Tempel, 2012). We examined octopus cells in which Kv1.1 was eliminated to alter g KL and their wild type controls (Smart et al, 1998), and compared them with those in outbred ICR mice and in mice in which HCN1 was eliminated to alter g h (Bal and Oertel, 2000; Bal and Oertel, 2001; Nolan et al, 2003; Cao and Oertel, 2011).…”

“…Kv1.1 α subunits are present on the somatic and dendritic membranes of octopus cells as well as at perinodes of auditory nerve axons and octopus cell axons (Oertel et al, 2008; Rusznak et al, 2008; Robbins and Tempel, 2012). Immunohistochemical visualization of Kv1.1 (Oertel et al, 2008; Robbins and Tempel, 2012), Kv1.2 (Rusznak et al, 2008), Kv1.4 (Fonseca et al, 1998; Lujan et al, 2003), and Kv1.6 (Rusznak et al, 2008) subunits suggests that these subunits are expressed in octopus cells. The sensitivity of g KL to DTX K, a blocker that is specific for Kv1.1 containing channels (Robertson et al, 1996), confirms the role of Kv1.1 in g KL (Bal and Oertel, 2001).…”

“…HCN1 and Kv1.1 are colocalized in the somatic and dendritic octopus cell membrane (Oertel et al, 2008; Rusznak et al, 2008; Robbins and Tempel, 2012). In an earlier study we examined mice in which HCN1 was eliminated to alter g h (Cao and Oertel, 2011).…”

Posthearing Ca2+Currents and Their Roles in Shaping the Different Modes of Firing of Spiral Ganglion Neurons

“…Whereas the α-subunit of Ca v 2.1 was expressed robustly in pre-hearing mouse SGNs, it was undetected in adult chinchilla neurons (Lopez et al, 2003; Chen et al, 2011). To ensure accurate representation of the frequency map of the cochlea, the properties of type 1 SGNs vary depending on their apico-basal location (Rusznak et al, 2008; Rusznak and Szucs, 2009). Differences in the membrane properties of apical versus basal SGNs have been ascribed to differential expression of distinct K + channels, yielding two distinct cell-types, namely fast and slow adapting neurons (Adamson et al, 2002b; Beisel et al, 2005; Chen and Davis, 2006; Bakondi et al, 2009).…”

Protein phosphatase‐1M and Rho‐kinase affect exocytosis from cortical synaptosomes and influence neurotransmission at a glutamatergic giant synapse of the rat auditory system

“…Detailed description of the preparation and the major steps of the immunolabelling have been presented elsewhere (Pál et al. 2005; Rusznák et al. 2008) and detailed in Supporting information.…”