SLC6A5 and Hypertension: Interestingly, the glycine transporters Slc6a9 (GlyT1), which acts at both pre- and postsynaptically at excitatory synapses to modulate the glutamatergic action on NMDA receptors, and Slc6a5 (GlyT2), which acts presynaptically at inhibitory synapses, are both upregulated in the NTS around the onset of hypertension (91, 130, 131).