Synaptic regulation of L-type Ca(2+) channel activity and long-term depression during refinement of the retinocollicular pathway in developing rodent superior colliculus.
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.
Lo
F S
FS
Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
Mize
R R
RR
D000818:Animals; D000831:Animals, Newborn; D020746:Calcium Channels, L-Type / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials; D066298:In Vitro Techniques; D009473:Neuronal Plasticity / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D012160:Retina / Q000254:growth & development / Q000502:physiology*; D013477:Superior Colliculi / Q000254:growth & development / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D014795:Visual Pathways / Q000254:growth & development / Q000502:physiology*
D020746:Calcium Channels, L-Type; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate