Localization of chick retinal 24,000 dalton protein (visinin)-like immunoreactivity in the rat lower brain stem

The distribution of visinin, a 24,000 dalton peptide, in the lower brain stem of the rat was examined by means of an indirect immunofluorescent method. Visinin-immunoreactive structures were found to be unevenly distributed only in the neuronal elements. The following neuronal systems were strongly labeled by the antiserum; the Purkinje cell system, mammillotegmental system, habenulointerpeduncular system, the second layer of the superior colliculus, ventral tegmental area, substantia nigra pars lateralis, area medial to the medial geniculate body, parabrachial area, dorsal and ventral nuclei of the lateral lemniscus, pontine reticular formation just medial to the trigeminal principal nucleus, superior olivary nucleus, solitarii nucleus, external layer of the inferior colliculus and spinal trigeminal nucleus. The densities of the labeled fibers in these areas paralleled those of the labeled cells. In addition, highly dense visinin-immunoreactive fiber plexuses were seen in the zona compacta of the substantia nigra, lateral portion of the interpeduncular nucleus, ventral tegmental nucleus of Gudden and vestibular nucleus.