REGIONAL DISTRIBUTION AND DEVELOPMENTAL VARIATION OF THE GLYCINE TRANSPORTERS GLYT1 AND GLYT2 IN THE RAT CNS

The high-affinity glycine transporter in neurons and glial cells is th e primary means of inactivating synaptic glycine. Previous molecular c loning studies have indicated heterogeneity of glycine transporters in the CNS. Here the distribution of glycine transporter GLYT1 and GLYT2 transcripts and proteins in different regions and developmental stage s of the rat brain were analysed by Northern, Western and in situ hybr idization techniques. Sequence-specific riboprobes and two specific an tibodies raised against fusion proteins were used, containing either 7 6 or 193 amino acids of the C or N terminus of the GLTY1 and GLYT2 tra nsporters respectively. High levels of GLYT1 transcripts were found in the spinal cord, brainstem and cerebellum, and moderate levels in for ebrain regions such as the cortex or hippocampus. GLYT2 transcripts ar e restricted to the spinal cord, brainstem and cerebellum. The onset o f both GLYT1 and GLYT2 expression in the brainstem occurred in late fe tal life, and full expression of these proteins was observed before we aning. There was a stepwise increase in the levels of mRNA and protein for these two transporters, reaching a maximum by the second postnata l week, followed by a slight decrease until adult values were reached by the fourth postnatal week. These data reveal interesting parallelis m between the distribution of different glycine transporters and glyci ne receptor subunits, and suggest discrete roles for distinct glycine transporters.