nystatin-a1 and 1-4-dihydropyridine

Dihydropyridine-sensitive calcium currents (I(Ca)) in photoreceptors are unusual in that they can be inhibited by reductions in extracellular chloride. The present study examined whether I(Ca) in retinal bipolar cells, which as in photoreceptors mediates sustained neurotransmission, is also inhibited by reductions in chloride. Nystatin-perforated patch, whole cell recordings were obtained from bipolar cells in a retinal slice preparation of larval tiger salamander. In the presence of Ba(2+), voltage steps above -40 mV evoked sustained inward currents, which were enhanced by the dihydropyridine, (-)BayK8644, and inhibited by nisoldipine. Similar to photoreceptors, replacing Cl(-) with gluconate or CH(3)SO(4) inhibited bipolar cell I(Ca) and produced a negative shift in the current/voltage relationship. Thus, sensitivity to Cl(-) may be a more general property of L-type Ca(2+) channel subtypes that mediate sustained neurotransmission.

Topics: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; Ambystoma; Animals; Barium; Calcium Channels, L-Type; Chlorides; Dihydropyridines; Gluconates; In Vitro Techniques; Larva; Membrane Potentials; Nisoldipine; Nystatin; Patch-Clamp Techniques; Photoreceptor Cells, Vertebrate; Retina