Different effects of calcium flux-blocking agents on light and potassium stimulated release of taurine from retina.

Conditions for the stimulation of taurine release by illumination or increased K+ concentrations were established. The effect of Mg2+, ruthenium red and verapamil on taurine release induced by both procedures was compared. All these agents antagonize Ca2+-dependent release of neurotransmitters. Illumination-induced release of taurine was not blocked by any of these agents while the K+-induced release was blocked by all of them. It is discussed whether illumination and potassium act through processes that increase Ca2+ influx through different mechanisms, or if illumination-induced release is a Ca2+-independent process.