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Membrane Currents Influencing Action Potential Latency in Granule Neurons of the Rat Cochlear Nucleus
Author(s) -
Rusznák Zoltán,
Forsythe Ian D.,
Brew Helen M.,
Stanfield Peter R.
Publication year - 1997
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1997.tb01652.x
Subject(s) - depolarization , dorsal cochlear nucleus , hyperpolarization (physics) , neuroscience , cochlear nucleus , membrane potential , biophysics , nucleus , chemistry , electrophysiology , patch clamp , biology , organic chemistry , nuclear magnetic resonance spectroscopy
Granule cells are the most numerous neurons in the cochlear nucleus, but, because of their small size, little information on their membrane properties and ionic currents is available. We used an in vitro slice preparation of the rat ventral cochlear nucleus to make whole‐cell recordings from these cells. Under current clamp, some granule neurons fired spontaneous action potentials and all generated a train of action potentials on depolarization (threshold current, 10–35 pA). Hyperpolarization increased the latency to the first action potential evoked during a subsequent depolarization. We examined which voltage‐gated currents might underlie this latency shift. In addition to a fast inward Na + current, depolarization activated two outward potassium currents. A transient current was rapidly inactivated by membrane potentials positive to ‐60 mV, while a second, more slowly inactivating current was observed following the decay of the transient current. No hyperpolarization‐activated conductances were observed in these cells. Modelling of the currents suggests that removal of inactivation on hyperpolarization accounts for the increased action potential latency in granule cells. Such a mechanism could account for the ‘pauser’‐type firing patterns of the fusiform cells which receive a prominent projection from the granule cells in the dorsal cochlear nucleus.