title: Light stimulates the rapid formation of inositol trisphosphate in squid retinas.
abstract: To test the hypothesis that inositol trisphosphate (InsP3) mediates adaptation and excitation in invertebrate photoreceptors, we measured its formation on a rapid time scale in squid retinas. For squid, excitation and adaption occurs within 0.1 and 1-2 s respectively. We could detect an elevation in InsP3 within 200 ms of a bright flash. This increase is about 240% over dark basal levels and is maintained for at least 2 min after a flash. The increase probably occurs in the photoreceptors, which are the only neurons in squid retinas. Analysis by h.p.l.c. indicates that the light-regulated isomer is Ins(1,4,5)P3, which is formed by the hydrolysis of phosphatidylinositol bisphosphate (PtdInsP2).
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D049832:Decapodiformes; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000096:biosynthesis* / Q000302:isolation & purification; D008027:Light; D012160:Retina / Q000378:metabolism*; D013403:Sugar Phosphates / Q000096:biosynthesis*
chemical_list: D007295:Inositol Phosphates; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate