Calcium Extrusion from Mammalian Photoreceptor Terminals

• DOI: 10.1523/jneurosci.18-07-02467.1998
• Publication Date: 2018-04-05T22:30:39Z
• Authors: Catherine W. Morgans; Oussama El Far; Amy Berntson; Heinz Wässle; W. Rowland Taylor
• Keywords: Calcium in biology

Ribbon synapses of vertebrate photoreceptors constantly release glutamate in darkness. Transmitter is maintained by a steady influx calcium through voltage-dependent channels, implying the presence mechanism that able to extrude at an equal rate. The two predominant mechanisms intracellular extrusion are plasma membrane ATPase (PMCA) and Na + /Ca 2+ -exchanger. Immunohistochemical staining retina sections revealed strong immunoreactivity for PMCA rod cone terminals, whereas -exchanger was very weak. localized along sides photoreceptor terminals excluded from base where active zones located. amplitude calcium-activated chloride current used monitor concentration. An upper limit time required remove free obtained constants measured tail currents: one 50 msec second 190 msec. Calcium inhibited absence ATP or inhibitor orthovanadate, but unaffected replacement external with Li . data indicate PMCA, rather than -exchanger, synaptic terminals.