and the radioactivity in the cells was counted using a scintillation counter data were compared between the cells contacted or not contacted by a candidate agent and between cells having glyt 1 activity versus cells having glyt 2 activity depending on the assay being conducted positive control results are depicted in the bar graphs of fig1 a and 1b in which 3 h glycine uptake is shown for mock glyt 1a glyt 1b glyt 1c and glyt 2 transformed cells the results of the positive controls are presented as means u00b1 sem of a representative experiment performed in triplicate all cell cultures transformed with any of the glycine transporters evidenced a significant increase in glycine transport activity as compared to non transfected control cells this example illustrates the application of the method of example 2 and the identification thereby of certain agents that regulate selectively the glyt 1 or the glyt 2 transporter with respect to each other the agents recited below were tested for inhibition or enhancement of glycine transport in qt 6 cells that were transfected with prc cmv containing glyt 1c seq id no 3 or glyt 2 seq id no 4 and exhibited transient expression of glyt 1c or glyt 2 respectively in accordance with the procedures of examples 1 and 2 above str4 the data obtained with these compounds are as follows ______________________________________compound effect via glyt 1c effect via glyt 2 ______________________________________za pic sub 50 6 04 pic sub 50 5 51 zb pic.