PURPOSE. To detect mRNAs for somatostatin (somatotropin release-inhibiting factor [SRIF]) receptor subtypes 1 to 5 (sst1 through sst5) in rabbit retinas by reverse transcription–polymerase chain reaction (RT-PCR) and to investigate the distribution of sst1 by single- and double-label immunocytochemistry. METHODS. Semiquantitative RT-PCR using sst-specific primers from mouse sequences was performed. sst1 was localized using a polyclonal antiserum directed to human sst1 in cryostat sections of retinas from either normal or optic nerve–transected animals. Immunolabeled cell sizes and densities were measured in wholemounted retinas using computer-assisted image analysis. Doublelabel immunofluorescence was performed using the sst1 antiserum in conjunction with monoclonal antibodies directed to SRIF, tyrosine hydroxylase (TH), parvalbumin (PV), or g-aminobutyric acid (GABA). RESULTS. With RT-PCR it was found that all five sst mRNAs were expressed in the rabbit retina, with highest levels of sst1 mRNA. sst1 immunolabeling was localized to amacrine cells in the proximal inner nuclear layer (INL) of all retinal regions and to displaced amacrine cells in the ganglion cell layer (GCL) of the ventral retina. Some large sst1-immunoreactive (IR) somata were also present in the GCL. They were not observed after optic nerve transection. Double-label immunofluorescence showed sst1 expression by all TH-IR amacrine cells and by other amacrine cells that were neither PV-IR nor GABA-IR. In addition, sst1 was expressed by all SRIF-containing displaced amacrine cells. CONCLUSIONS. All five sst mRNAs are expressed in the rabbit retina. The localization of sst1 suggests that it may mediate SRIF actions onto amacrine (including dopaminergic) and sparse ganglion cells. sst1 expression in SRIF-IR cells suggests that this receptor may also act as an autoreceptor.
File in questo prodotto:
Non ci sono file associati a questo prodotto.