DIMETHYL-SULFOXIDE ELEVATES INTRACELLULAR CA-2+ AND MIMICS EFFECTS OF INCREASED LIGHT-INTENSITY IN A PHOTORECEPTOR

A 1% (v/v) solution of dimethyl sulfoxide (DMSO) added to the saline bath of isolated Balanus eburneus photoreceptors increased receptor potential amplitude by 40-50% and shortened time to peak amplitude and latency by 20-25%. The light-sensitive membrane current of voltage-clamped cells was increased systematically as DMSO concentration was increased from 1% to 10%. The null potential of the light sensitive current was unaffected by DMSO with short pulses of light, indicating that DMSO has no direct effect on ion selectivity of the light-sensitive channel. Absorbance changes of cell injected with the calcium indicator arsenazo III show that DMSO elevates intracellular Ca2+ (Cai). Current-voltage relations in darkness reveal that DMSO induces a small sustained inward current (≈5 nA) which has a null potential similar to the lightinduced current. DMSO may activate the light-sensitive conductance via the increase in Cai However, the altered kinetics and increased amplitude of the receptor current are opposite to the desensitizing effects normally observed with increased Cai. © 1990 Springer-Verlag.