Comparison of synaptosomal and glial uptake of pipecolic acid and GABA in rat brain.

The active uptake of [3H]pipecolic acid increased with incubation time and its uptake at 3 min was half of that at 20 min. On the other hand, a ratio (pellet/medium) of [3H]pipecolic acid uptake into glial cell-enriched fractions, was much less (0.4 - 0.6) than that of [14C]GABA (25.8 - 74.1). GABA, 10(-4) M, and pipecolic acid, 10(-4) M, produced a significant inhibitor of [3H]pipecolic acid uptake into P2 fractions. Pipecolic acid, 10(-4) M, significantly reduced the synaptosomal and glial uptake of [14C]GABA. GABA, 10(-4) M, affected neither spontaneous nor high K+-induced release of [3H]pipecolic acid from brain slices. It is suggested that pipecolic acid is involved in either synaptic transmission or in its modulation at GABA synapses in the central nervous system.