Firing features and potassium channel content of murine spiral ganglion neurons vary with cochlear location.
Neurons from varied regions of the central nervous system can show widely divergent responses to electrical stimuli that are determined by cell-specific differences in ion channel composition. The well-ordered and highly characterized peripheral auditory system allows one to explore the significance of this diversity during the final stages of postnatal development. We examined the electrophysiological features of murine spiral ganglion neurons in vitro at a time when recordings could be made from the cell bodies before myelination. These cells carry information about sound stimuli from hair cell receptors in the basilar membrane and are arranged tonotopically. Spiral ganglion neuron responses to depolarizing current injection were assessed with whole-cell current clamp recordings from cells that were isolated separately from the apical and basal thirds of the mouse cochlea. These cells displayed systematic variation in their firing. Apex neurons (low frequency coding) showed longer latency, slowly adapting responses, whereas base neurons (high frequency coding) showed short latency, rapidly adapting responses to the same stimuli. This physiological diversity was mirrored by regional differences in ion channel content assessed immunohistochemically. Apex neurons had a preponderance of Kv4.2 subunits, whereas base neurons possessed greater levels of K(Ca), Kv1.1, and Kv3.1 subunits. Taken together, these results indicate that the distribution of a set of voltage-gated potassium channels may relate specifically to a particular range of coding frequencies. These studies also suggest that intrinsic properties of spiral ganglion neurons can contribute to the characteristic responses of the peripheral auditory system. Their potential role in development and adult function is discussed.
Adamson
Crista L
CL
W.M. Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey, 08854-8082, USA.
Reid
Michael A
MA
Mo
Zun-Li
ZL
Bowne-English
Janet
J
Davis
Robin L
RL
D000200:Action Potentials / Q000502:physiology*; D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D004558:Electric Stimulation; D006309:Hearing / Q000502:physiology*; D051662:Kv1.1 Potassium Channel; D051379:Mice; D008808:Mice, Inbred CBA / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D011930:Reaction Time / Q000502:physiology; D051672:Shal Potassium Channels; D051670:Shaw Potassium Channels; D015398:Signal Transduction / Q000502:physiology*; D013136:Spiral Ganglion / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*
C496947:Kcna1 protein, mouse; D009479:Neuropeptides; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D051672:Shal Potassium Channels; D051670:Shaw Potassium Channels; D051662:Kv1.1 Potassium Channel