Ultras1ructure of the Cat Inferior Olive

In order to identify cerebellar terminals in the cat inferior olive which contain gamma-aminobutyricacid (GABA), a technique was developed combining anterograde transport of wheatgerm agglutinine-conjugated horseradish peroxidase (WGA-HRP) with gold-immunocytochemistry. With this technique both the HRP reaction product and the immunogold labeling can be visualized in a single ultrathin section. Our results suggest that most, if not all of the WGAHRP labeled cerebellar terminals in the rostral medial accessory olive (MAO) and the rostral principal olive (PO) are GABAergic. In an additional experiment the GABAergic innervation of the rostral MAO was studied in combination with WGA-HRP anterograde tracing from the rostral mesencephalon. In this case the WGA-HRP labeled terminals were never found to be GABA-positive.