D₂-like dopamine receptors promote interactions between calcium and chloride channels that diminish rod synaptic transfer in the salamander retina

Abstract

Activation of D 2 -like dopamine receptors in rods with quinpirole stimulates L-type calcium currents (I Ca

TMEM16B, A Novel Protein with Calcium-Dependent Chloride Channel Activity, Associates with a Presynaptic Protein Complex in Photoreceptor Terminals

“…Regardless of the reported differences of equilibrium potentials for Cl Ϫ in rod and cones (Thoreson et al, 2002;Thoreson and Bryson, 2004) and of ambiguities in the values for intracellular Cl Ϫ concentrations, the crucial role of Ca 2ϩ -dependent Cl Ϫ currents as regulators of synaptic transmission at the photoreceptor synapse was demonstrated by complete interruption of transmitter release after extracellular Cl Ϫ removal (Thoreson and Miller, 1996). In addition, Ca 2ϩ -dependent action potentials in photoreceptors were sensitive to Cl Ϫ channel blockers indicating that Ca 2ϩ -dependent Cl Ϫ channels contribute to the fine regulation of voltagedependent Ca 2ϩ influx (Maricq and Korenbrot, 1988).…”

Synaptic transmission at retinal ribbon synapses

“…Thoreson et al (2002) tested the hypothesis that D 2 receptor enhancement of I Ca might increase I Cl(Ca) , thereby stimulating an efflux of Cl − from rods that in turn provided a negative feedback inhibition of I Ca . For measurements of I Ca , I Cl(Ca) was blocked with niflumic acid and by the use of Ba 2+ as the charge carrier.…”

Imaging of Ca2+Dynamics Within the Presynaptic Terminals of Salamander Rod Photoreceptors

“…Glutamate release from photoreceptors is largely Ca 2ϩ dependent (Dacheux and Miller 1976;Dowling and Ripps 1973) and regulated by Ca 2ϩ influx through dihydropyridine-sensitive L-type channels (Schmitz and Witkovsky 1997), although a calcium-insensitive component of release has been reported (Schwartz 1986). Several studies of salamander rod Ca 2ϩ currents and intracellular free Ca 2ϩ dynamics have been reported previously (Bader et al 1982;Corey et al 1984;Copenhagen 1998,2003;Krizaj et al 1999;NachmanClewner et al 1999;Rabl and Thoreson 2002;Stella et al 2002;Thoreson and Stella 2000;Thoreson et al 2002Thoreson et al , 2003. All of these, however, describe data obtained from rod inner segments for the most part and cite the difficulty in isolating fully intact rods retaining axons and presynaptic terminals.…”