Molecular identity, synaptic localization, and physiology of calcium channels in retinal bipolar cells.
Bipolar cells convey information through the retina via graded changes in their membrane potential and modulate transmitter release through the influx of calcium via L-type calcium channels. However, the molecular identity of the alpha(1) subunit has not been confirmed. We report the presence of the newly cloned alpha(1F) subunit in mouse bipolar cell synaptic terminals. The alpha(1F) subunits are localized to hot spots, possibly corresponding to active zones. We also report the physiological properties of two calcium currents present in mouse bipolar cells, a low-voltage-activated L-type current and a low-voltage-activated T-type calcium current. The physiological properties of the T-type current suggest that it is completely inactivated under physiological conditions. The L-type current may be mediated by the alpha(1F) subunit, and influx of calcium through the alpha(1F) channel may control neurotransmitter release from the bipolar cell terminal.
Berntson
Amy
A
John Curtin School of Medical Research, Australian National University, Canberra, Australia. berntson@helix.mgh.harvard.edu
Taylor
W Rowland
WR
Morgans
Catherine W
CW
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology*; D020746:Calcium Channels, L-Type; D002614:Chelating Agents / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D046508:Culture Techniques; D005455:Fluorescent Antibody Technique / Q000379:methods; D007395:Interneurons / Q000378:metabolism / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D012160:Retina / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
C113330:CACNA1F protein, human; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D002614:Chelating Agents; D003035:Cobalt; D009543:Nifedipine