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- Title
Two types of calcium currents of the mouse bipolar cells recorded in the retinal slice preparation.
- Authors
de la Villa, Pedro; Vaquero, Cecilia F.; Kaneko, Akimichi
- Abstract
In the vertebrate retina, the bipolar cell makes reciprocal synapses with amacrine cells at the axon terminal. It has been postulated that amacrine cells may control the transmitter release from bipolar cells by modulating their calcium currents (I[sub Ca]). To clarify this possibility calcium currents were studied in bipolar cells of the mouse retina using a slice preparation. I[sub Ca] was identified by voltage clamp protocols, ionic substitution and pharmacological tools. Depolarization to –30 mV from a holding voltage of –80 mV induced an inward current consisting of an initial transient and a long-lasting sustained component. The transient component was inactivated by holding the membrane at more positive voltages. Addition of 100 μm nifedipine suppressed the sustained component, leaving the transient component almost intact. The sustained component was enhanced when external solution contained 0.1 μm Bay K 8644 or when the external Ca[sup 2+] was substituted by equimolar Ba[sup 2+]. Omega-conotoxin (10 μm ω-ctxn GVIA) did not alter either component. We concluded that the transient component is a low-voltage activated T-type I[sub Ca], while the sustained component is a high-voltage activated L-type I[sub Ca]. T-type I[sub Ca] was recorded in all cells tested, while L-type I[sub Ca] was found only in cells that retained axon terminals ramifying in the inner plexiform layer. Thus, it is highly likely that L-type I[sub Ca] is generated at the axon terminal and contributes to the transmitter release from the bipolar cell. The present results confirm that in addition to the T-type I[sub Ca] that had been previously described, bipolar cells of the mammalian retina also contain L-type I[sub Ca] similar to the one that has been reported in bipolar cells of the goldfish. The use of retinal slice preparation allowed us to record this current that was not seen previously in the dissociated mouse bipolar cells.
- Subjects
CALCIUM; RETINAL (Visual pigment); SYNAPSES
- Publication
European Journal of Neuroscience, 1998, Vol 10, Issue 1
- ISSN
0953-816X
- Publication type
Article
- DOI
10.1046/j.1460-9568.1998.00051.x