Differential expression of somatostatin receptors in the rat eye: SSTR4 is intensely expressed in the iris/ciliary body

Distribution of somatostatin receptors (SSTR1–5) was determined in the rat eye. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses revealed that SSTR4 and SSTR2 are major subtypes expressed predominantly in the iris/ciliary body and retina, respectively, and that SSTR1, SSTR3 and SSTR5 are minor subtypes expressed preferentially in the posterior eye segments including the retina. In situ hybridization showed predominant SSTR4 expression in the posterior iris epithelium and ciliary body, suggesting functional roles of somatostatin in the autonomic nervous system in the anterior segments of the eye. The differential expression of SSTR1–5 may be related to distinct roles of somatostatin in the physiology of different ocular tissues.