Retrograde labelling of auditory brainstem neurons following tritiated glycine injection into the inferior colliculus of the chicken, Gallus domesticus.

We investigated retrograde labelling with tritiated glycine injected into the inferior colliculus of the chicken. Tracer deposits were placed in the central nucleus of the inferior colliculus at positions yielding unit activity with best frequencies between 0.4 and 4 kHz. Most neuron systems known to project to the inferior colliculus in birds were unlabelled, whereas strongly labelled cells were found in three nuclei, only on the ipsilateral side. The nucleus lemnisci lateralis pars ventralis contained numerous small glycine-transporting cells. The superior olivary nucleus contained few such cells of similar size in its peripheral region. The nucleus of the trapezoid body contained a group of larger labelled neurons. The observed specificity suggests that we labelled glycinergic neurons projecting to the inferior colliculus.