Membrane Properties of Complex Spike Firing Neurons of the Mouse Dorsal Cochlear Nucleus in Vitro

Abstract

Intracellular recordings were made from complex spike firing neurons of the mouse dorsal cochlear nucleus (DCN) in vitro. The whole cochlear nucleus was dissected out and maintained submerged inrapidly flowing artificial cerebrospinal fluid (CSF). Recordings were made with current clamp techniques in the presence or absence of ion channel blocking drugs tetrodotoxin (TTX, 1 ?M), tetraethylammonium (TEA, 20 mM), 4-aminopyridine (4-AP, 5 mM) or verapamil (50, 100, 150, 250 ?M). The cells showed both spontaneous firing and responses to injections of depolarising current consisting of a mixture of a tall single action potential and complexes of 2 to 3 smaller wider action potentials superimposed on a plateau depolarisation. The membrane properties were: resting membrane potential -68.8±8.5 mV, cell resistance 54.1±26.5 M?, time constant 9.6±5.4 ms and capacitance 0.25±0.5 nF; the first three variables had bimodel distributions. The current/voltage (17V) relationship at membrane below resting was non-linear. Previously published histological evidence from the mouse DCN has shown that both cartwheel cells and Purkinje-like neurons are present. Both DCN cartwheel cells and cerebellar Purkinje cells are known to fire both tall single action potentials and complexes of smaller wider action potentials. It is therefore possible that the recordings shown here were made from these neuron types. © 2011 by Walter de Gruyter GmbH & Co. All rights reserved.