Nipecotic acid: preferential accumulation in the cochlea by GABA uptake systems and selective retrograde transport to...

[3H]Nipecotic acid was shown to be preferentially accumulated by the same cochlear structures which selectively accumulate [3H]gamma-aminobutyric acid ([3H]-GABA), including the terminals of a subset of olivocochlear neurons. With both amino acids, olivocochlear fibers selectively transported label in a retrograde direction, from cochlea to brainstem. However, only [3H]nipecotic acid produced dense labeling, and labeling of cell bodies in the superior olive, presumably because it is metabolized very slowly. Nipecotic acid appears to provide a selective retrograde tracer, specific to neurons whose terminals exhibit preferential GABA uptake.