Somatostatin-like immunoreactive material in the rabbit retina

Somatostatin-like immunoreactivity was detected by a specific radioimmunoassay in extracts of retinas of Dutch-belted rabbits at a mean concentration of 1.1 +/- 0.1 ng/retina, or 170 +/- 30 pg/mg protein. On both gel permeation chromatography and reversed phase high performance liquid chromatography, the majority of this material was indistinguishable from somatostatin-14; a smaller amount of immunoreactive material co-chromatographed with somatostatin-28. The somatostatin-like immunoreactivity was concentrated in a P2 (synaptosomal) fraction prepared by differential centrifugation. The concentration of somatostatin-like immunoreactivity was unaffected by the prior intravitreal injection of the selective neurotoxins 6-hydroxydopamine and 5, 7-dihydroxytryptamine. The rabbit retina, therefore, contains readily detectable amounts of material chemically similar to somatostatin-14 and somatostatin-28. This material is concentrated in neurosecretory elements of the retina, but is not contained in cells which accumulate dopamine or indoleamines. The rabbit retina is suitable for in vitro studies of the central nervous system function of the somatostatin family of peptides.