The Journal of Neuroscience, 2000, 20:RC58:1-6
RAPID COMMUNICATION
Synaptic Regulation of L-Type Ca2+ Channel Activity
and Long-Term Depression during Refinement of the Retinocollicular
Pathway in Developing Rodent Superior Colliculus
Fu-Sun
Lo1 and
R.
Ranney
Mize1, 2
1 Department of Cell Biology and Anatomy and
2 Department of Ophthalmology and Neuroscience Center of
Excellence, Louisiana State University Health Sciences Center, New
Orleans, Louisiana 70112
The retinocollicular pathway undergoes activity-dependent
refinement during postnatal development, which results in the precise retinotopic order seen in adults. This process is NMDA- and nitric oxide-dependent. Recent studies have shown that L-type
Ca2+ channels may also play a role in synaptic
plasticity, but such channel activity has not previously been reported
in the developing superior colliculus (SC). Here we report the presence
of a postsynaptic plateau potential mediated by L-type
Ca2+ channels using whole-cell current clamp of the
SC in an isolated brainstem preparation of rats. Seventy percent of SC
neurons showed these potentials as early as postnatal day 0 (P0)-P2.
The potential was blocked by nitrendipine and/or APV and facilitated by
bicuculline, showing that the channel is activated by NMDA
receptor-mediated EPSPs and deactivated by GABAA
receptor-mediated IPSPs. Blockade of L-type Ca2+
channels also diminished long-term depression, which we could induce in
the retinocollicular pathway in neonatal animals. The incidence of
plateau potentials decreased to 39% of neurons by P10-P14, suggesting
that L-type calcium channels may contribute to retinocollicular pathway
refinement in the developing SC.
Key words:
voltage-gated Ca2+ channels; brain
development; retinotectal pathway; sensory systems; synaptic
plasticity; NMDA; GABA
Copyright © 2000 Society for Neuroscience 0270-6474/00/$05.00/0
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