Presynaptic N-type and P/Q-type Ca2+ channels mediating synaptic transmission at the calyx of Held of mice.
At the nerve terminal, both N- and P/Q-type Ca2+ channels mediate synaptic transmission, with their relative contribution varying between synapses and with postnatal age. To clarify functional significance of different presynaptic Ca2+ channel subtypes, we recorded N-type and P/Q-type Ca2+ currents directly from calyces of Held nerve terminals in alpha1A-subunit-deficient mice and wild-type (WT) mice, respectively. The most prominent feature of P/Q-type Ca2+ currents was activity-dependent facilitation, which was absent for N-type Ca2+ currents. EPSCs mediated by P/Q-type Ca2+ currents showed less depression during high-frequency stimulation compared with those mediated by N-type Ca2+ currents. In addition, the maximal inhibition by the GABAB receptor agonist baclofen was greater for EPSCs mediated by N-type channels than for those mediated by P/Q-type channels. These results suggest that the developmental switch of presynaptic Ca2+ channels from N- to P/Q-type may serve to increase synaptic efficacy at high frequencies of activity, securing high-fidelity synaptic transmission.
Ishikawa
Taro
T
Department of Neurophysiology, University of Tokyo Graduate School of Medicine, Tokyo 113-0033, Japan.
Kaneko
Masahiro
M
Shin
Hee-Sup
HS
Takahashi
Tomoyuki
T
D000818:Animals; D000831:Animals, Newborn; D001418:Baclofen / Q000494:pharmacology; D001933:Brain Stem / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D020865:Calcium Channels, P-Type / Q000235:genetics / Q000378:metabolism*; D020907:Calcium Channels, Q-Type / Q000235:genetics / Q000378:metabolism*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D018755:GABA Agonists / Q000494:pharmacology; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009473:Neuronal Plasticity; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
D001418:Baclofen; D002118:Calcium; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D018755:GABA Agonists; D020866:omega-Conotoxin GVIA