Heterologous expression of Kir channels offers a tool to modulate excitability of neurons which provide insight into Kir channel functions in general. Inwardly-rectifying K+ channels (Kir channels) are potential candidate proteins to hyperpolarize neuronal cell membranes. However, heterologous expression of inwardly-rectifying K+ channels has previously proven to be difficult. This was mainly due to a high toxicity of the respective Kir channel expression. We investigated the putative role of a predominantly glial-expressed, weakly rectifying Kir channel (Kir4.1 channel subunit; KCNJ10) in modulating electrophysiological properties of a motoneuron-like cell culture (NSC-34). Transfection procedures using an EGFP-tagged Kir4.1 protein in this study proved to have no toxic effects on NSC-34 cells. Using whole cell-voltage clamp, a substantial increase of inward rectifying K+ currents as well as hyperpolarization of the cell membrane was observed in Kir4.1-transfected cells. Na+ inward currents, observed in NSC-34 controls, were absent in Kir4.1/EGFP motoneuronal cells. The Kir4.1-transfection did not influence the NaV1.6 sodium channel expression. This study demonstrates the general feasibility of a heterologous expression of a weakly inward-rectifying K+ channel (Kir4.1 subunit) and shows that in vitro overexpression of Kir4.1 shifts electrophysiological properties of neuronal cells to a more gliallike phenotype and may therefore be a candidate tool to dampen excitability of neurons in experimental paradigms., J. Zschüntzsch, ... [et al.]., and Obsahuje seznam literatury
Electrophysiological investigations in mice, particularly with altered myelination, require reference data of the nerve conduction velocity (CV). CVs of different fibre groups were determined in the hindlimb of anaesthetized adult mice. Differentiation between afferent and efferent fibres was performed by recording at dorsal roots and stimulating at ventral roots, respectively. Correspondingly, recording or stimulation was performed at peripheral hindlimb nerves. Stimulation was performed with graded strength to differentiate between fibre groups. CVs of the same fibre groups were different in different nerves of the hindlimb. CVs for motor fibres were for the tibial nerve (Tib) 38.5±4.0 m/s (Aγ: 16.7±3.0 m/s), the sural nerve (Sur) 39.3±3.1 m/s (12.0±0.8 m/s) and the common peroneal nerve (Per) 46.7±4.7 m/s (22.2±4.4 m/s). CVs for group I afferents were 47.4±3.1 m/s (Tib), 43.8±3.8 m/s (Sur), 55.2±6.1 m/s (Per) and 42.9±4.3 m/s for the posterior biceps (PB). CVs of higher threshold afferents, presumably muscle and cutaneous, cover a broad range and do not really exhibit nerve specific differences. Ranges are for group II 22-38 m/s, for group III 9-19 m/s, and for group IV 0.8-0.9 m/s. Incontrovertible evidence was found for the presence of motor fibres in the sural nerve. The results are useful as references for further electrophysiological investigations particularly in genetically modified mice with myelination changes., H. Steffens, P. Dibaj, E. D. Schomburg., and Obsahuje seznam literatury