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Differential expression of voltage‐activated calcium channels in III and XII motoneurones during development in the rat
Author(s) -
Miles Gareth B.,
Lipski Janusz,
Lorier Amanda R.,
Laslo Peter,
Funk Gregory D.
Publication year - 2004
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.1460-9568.2004.03550.x
Subject(s) - chemistry , nifedipine , voltage dependent calcium channel , medicine , neuroscience , endocrinology , patch clamp , biophysics , calcium , electrophysiology , biology
To further our understanding of the role that voltage‐activated Ca 2+ channels play in the development, physiology and pathophysiology of motoneurones (MNs), we used whole‐cell patch‐clamp recording to compare voltage‐activated Ca 2+ currents in oculomotor (III) and hypoglossal (XII) MNs of neonatal [postnatal day (P)1–5] and juvenile (P14–19) rats. In contrast to III MNs that innervate extraocular muscles, XII MNs that innervate tongue muscles mature more rapidly, fire bursts of low frequency action potentials and are vulnerable to degeneration in amyotrophic lateral sclerosis. In neonates, low voltage‐activated (LVA) Ca 2+ current densities are similar in XII and III MNs but high voltage‐activated (HVA) Ca 2+ current densities are twofold higher in XII MNs. The HVA Ca 2+ channel antagonists (nimodipine and nifedipine for L‐type, ω‐agatoxin‐TK for P/Q‐type and ω‐conotoxin‐GVIA for N‐type) revealed that, while N‐ and P/Q‐type HVA Ca 2+ channels are present in both MN pools, a 3.5‐fold greater P/Q‐type Ca 2+ current in XII MNs accounts for their greater HVA Ca 2+ currents. Developmentally, LVA and HVA Ca 2+ current densities decrease in III MNs but remain unchanged in XII MNs. Thus, the differences between these MN pools increase developmentally so that, in juveniles, the LVA Ca 2+ current density is twofold greater and the HVA Ca 2+ current density is threefold greater in XII compared with III MNs. We propose that this differential expression of LVA and HVA Ca 2+ channels in XII and III MNs during development contributes to their distinct physiology and may also be a factor contributing to the greater susceptibility of XII MNs to degeneration as seen in amyotrophic lateral sclerosis.