NA-DEPENDENT AND CL--DEPENDENT NEUROTRANSMITTER TRANSPORTERS IN BOVINE RETINA - IDENTIFICATION AND LOCALIZATION BY IN-SITU HYBRIDIZATION HISTOCHEMISTRY()

The physiological actions of biogenic amine and amino-acid neurotransm itters are terminated by their removal from the synaptic cleft by spec ific high-affinity transport proteins. The members of the Na+- and Cl- -dependent neurotransmitter transporter family expressed in bovine ret ina and responsible for the uptake of biogenic amine and amino-acid ne urotransmitters were identified using a reverse transcriptase-polymera se chain reaction-based approach. cDNA clones encoding bovine homologu es of glycine (GLYT-1), gamma-aminobutyric acid (GAT-1), creatine (Cre aT), and orphan (NTT4) transporters were identified using this strateg y. The expression pattern of mRNAs encoding these proteins in the reti na was determined by in situ hybridization histochemistry. GLYT-1, Cre aT, NTT4, and GAT-1 mRNAs were expressed in the retina by cells in the inner nuclear, inner plexiform, and ganglion cell layers. They were n ot expressed at detectable levels in the photoreceptor cells whose cel l bodies are in the outer nuclear layer and are the most abundant cell type in the retina. GLYT-1 mRNA was present exclusively in the proxim al inner nuclear layer. GAT-1 mRNA was localized to both the inner nuc lear and ganglion cell layers. CreaT mRNA was expressed in all cell ty pes in the retina, except photoreceptors, and NTT4 mRNA was expressed by a subpopulation of cells in the ganglion cell layer. Elucidation of the expression pattern of these neurotransmitter transporter mRNAs in the retina provides a basis for studies of the role of glycine, gamma -aminobutyric acid, and creatine transporters in retinal function.