UPTAKE AND RELEASE OF NIPECOTIC ACID BY RAT BRAIN SLICES

—Nipecotic acid, a potent inhibitor of GABA uptake, is taken up by slices of rat cerebral cortex by a sodium-dependent, ‘high affinity’ system (K_m 11 μM), and can be released from these slices by an increased potassium ion concentration in a calcium-dependent manner. Nipecotic acid and GABA appear to be taken up by the same osmotically-sensitive structures. GABA and substances which inhibit GABA uptake also inhibit the uptake of nipecotic acid. GABA can release preloaded nipecotic acid from brain slices, and nipecotic acid can release preloaded GABA. This indicates that GABA and nipecotic acid can be counter-transported using the same mobile carrier. Nipecotic acid appears to have a higher affinity than GABA for this carrier.