A postsynaptic GABA transporter in rat spinal motor neurones

The plasma membrane uptake system for γ-amino butyric acid (GABA) is conventionally assumed to be presynaptic, so that after release GABA could be taken up and incorporated into synaptic vesicles for re-use. Using in situ hybridization histochemistry we find that rat spinal motor neurones express GAT-1, a transporter protein for GABA, but that they do not express glutamic acid decarboxylase, the synthetic enzyme for GABA. We conclude that the uptake system is located postsynaptically in these cells. Our observation may explain previous reports where GABA has been detected immunocytochemically in motor neurones.