Referenced in: none

Automatically associated channels: Cav1.4 , Cav2.2

Title: L-type calcium channels mediate transmitter release in isolated, wide-field retinal amacrine cells.

Authors: Jozsef Vigh, Eric M Lasater

Journal, date & volume: Vis. Neurosci., 2004 Mar-Apr , 21, 129-34

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/15259564

Abstract
Transmitter release in neurons is triggered by intracellular Ca2+ increase via the opening of voltage-gated Ca2+ channels. Here we investigated the voltage-gated Ca2+ channels in wide-field amacrine cells (WFACs) isolated from the white-bass retina that are functionally coupled to transmitter release. We monitored transmitter release through the measurement of the membrane capacitance (Cm). We found that 500-ms long depolarizations of WFACs from -70 mV to 0 mV elicited about a 6% transient increase in the Cm or membrane surface area. This Cm jump could be eliminated either by intracellular perfusion with 10 mM BAPTA or by extracellular application of 4 mM cobalt. WFACs possess N-type and L-type voltage-gated Ca2+ channels. Depolarization-evoked Cm increases were unaffected by the specific N-type channel blocker omega-conotoxin GVIA, but they were markedly reduced by the L-type blocker diltiazem, suggesting a role for the L-type channel in synaptic transmission. Further supporting this notion, in WFACs the synaptic protein syntaxin always colocalized with the pore-forming subunit of the retinal specific L-type channels (Cav1.4 or alpha1F), but never with that of the N-type channels (Cav2.2 or alpha1B ).