Immunocytochemical and lesion studies support the hypothesis that the projection from the medial nucleus of the trapezoid body to the lateral superior olive is glycinergic.

Pre- and postembedding immunocytochemical techniques were used to study the distribution of glycine immunoreactivity in the superior olivary complex of guinea pigs following kainic acid (KA) lesions of the medial nucleus of the trapezoid body (MNTB). Destruction of the MNTB by injecting 50-100 nl of 10 mM KA virtually abolished labeled neurons in the MNTB at the site of the lesion. This resulted in a marked decrease in the number of labeled fibers projecting to the ipsilateral lateral superior olive (LSO) and in the number of labeled fibers and presynaptic terminals in the neuropil of the LSO. Smaller volumes (20 nl) of KA produced similar but more restricted changes that conformed to the topographic organization of the MNTB projection to the LSO. The results support the hypothesis that the MNTB to LSO pathway is glycinergic.