Muscarinic stimulation of inositolphosphate (IP) release in the albino rat retina changes during development. Little is known, however, about the developmental profile of receptor-stimulated IP release in pigmented rat retina. Carbachol-stimulated IP release was studied in the whole retina from Long-Evans rats of different ages (day 5, 10, 15, 20, adult) following in vitro incorporation of (3)H-myo-inositol. The pigmented retina is light-sensitive, making it necessary to dark adapt the animals and perform retinal dissections under low illumination in order to prevent light-induced IP release. Retinae from postnatal day 10 rats showed the highest amount of carbachol-stimulated IP release. This response to carbachol decreased with age until postnatal day 20 when it reached adult levels. The pigmented rat retina showed a sharp fall in the degree of carbachol (100 micro M)-stimulated IP release at the time of eye-opening (409% above basal in retina from 10 day old animals, as compared to 190% above basal in 15 day old retina). Basal release of IP was not altered in the retina during development. Retinal weight and protein per retina also increased four fold from day 5 to adult; however, the in vitro incorporation of (3)H-myo-inositol into phosphoinositides (calculated as per mg protein) did not change during development. Thus, in animals prior to eye opening, a much higher proportion of phosphoinositides appears to be hydrolyzed upon muscarinic receptor stimulation.