Aspartate: Possible Neurotransmitter in Cerebellar Climbing Fibers

Autoradiography demonstrated prominent retrograde labeling of olivocerebellar climbing fiber neurons after injection of tritiated D-aspartate into the rat cerebellar cortex or deep nuclei. Mossy fiber systems originating in the brainstem and spinal cord remained unlabeled. Potassium ion-induced depolarization of cerebellar slices resulted in calcium ion-dependent release of endogenous L-aspartate, L-glutamate, gamma-aminobutyric acid, and glycine. A 26 percent decrease in aspartate release was observed after 3-acetylpyridine-induced destruction of the inferior olive, supporting the hypothesis that aspartate is a neurotransmitter in climbing fibers.