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L-type calcium channel agonist induces correlated depolarizations in mice lacking the beta2 subunit nAChRs

Christine Torborg1, Chih-Tien Wang, Gianna Muir-Robinson

  • 1Neurobiology Section 0357, Division of Biological Sciences, UCSD, 9500 Gilman Drive, La Jolla, CA 92093-0357, USA.

Vision Research
|November 13, 2004
PubMed

Insights

Nicotinic acetylcholine receptors (nAChRs) are crucial for retinal waves. Pharmacological activation of L-type calcium channels in beta2-deficient mice did not restore normal retinal circuit development or eye-specific layers.

Area of Science:

  • Neuroscience
  • Developmental Biology
  • Retinal Circuitry

Background:

  • Retinal waves, driven by nicotinic acetylcholine receptors (nAChRs) with the beta2 subunit, are essential for refining retinal circuits and CNS projections.
  • Mice lacking beta2-containing nAChRs (beta2-/-) exhibit normal action potential firing but lack correlated retinal waves, leading to impaired circuit refinement.
  • Previous studies showed that L-type calcium channel agonist FPL-64176 could induce calcium transients resembling retinal waves in beta2-/- retinas.

Purpose of the Study:

  • To characterize the activity patterns induced by FPL-64176 in beta2-/- retina.
  • To determine if FPL-induced activity is sufficient to rescue developmental deficits in beta2-/- mice, specifically eye-specific layer formation.

Main Methods:

  • Whole-cell and multielectrode array recordings were used to analyze FPL-induced activity in beta2-/- retinal ganglion cells.
  • Electrophysiological recordings assessed spiking activity and nearest-neighbor correlations.
  • Intraocular injections of FPL were attempted in beta2-/- mice to evaluate rescue of eye-specific layer formation.

Main Results:

  • FPL-64176 induced strong depolarizations in previously non-spiking beta2-/- retinal ganglion cells.
  • The induced spiking activity showed highly variable effects on individual cells and significantly weaker nearest-neighbor correlations compared to wild-type (WT) mice.
  • Intraocular FPL injections did not rescue the formation of eye-specific layers in beta2-/- mice.

Conclusions:

  • Activity induced by FPL-64176 in beta2-/- retinas, while causing depolarization, does not replicate the correlated activity necessary for normal retinal development.
  • Pharmacological induction of L-type calcium channel activity is insufficient to drive eye-specific segregation in the absence of functional beta2-containing nAChRs.

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