The action of phosphodiesterase inhibitors on the hypersensitivity of frog photoreceptor.
The increase in sensitivity of frog photoreceptors after illumination, "hypersensitivity", was studied by recording fast-PIII responses of the isolated bull frog retina superfused with physiological saline containing 5 mM sodium aspartate. The hypersensitivity is mot marked after illumination which bleaches only 0.01% of the rhodopsin initially present. The wavelength of light, which is optimum to induce the hypersensitivity, is about 500 nm. Several kinds of phosphodiesterase inhibitors, isobutylmethylxanthine (IBMX), papaverine, theophylline and caffeine act to induce the hypersensitivity, as does lowered extracellular concentrations of calcium ion, [Ca2+]out. Such action of phosphodiesterase inhibitor can be antagonized by an increase in [Ca2+]out. The relation between effects of Ca2+ and cyclic nucleotides on photoreceptor is discussed.
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D066298:In Vitro Techniques; D008027:Light; D010208:Papaverine / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010786:Photoreceptor Cells / Q000187:drug effects* / Q000528:radiation effects; D011892:Rana catesbeiana; D013806:Theophylline / Q000494:pharmacology
D010726:Phosphodiesterase Inhibitors; D002110:Caffeine; D013806:Theophylline; D010208:Papaverine; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine