Calbindin-like immunoreactivity in the central auditory system of the mustached bat, Pteronotus parnelli

Abstract

With the aid of a polyclonal antibody specific for Calbindin D-28k, we studied the distribution of this calcium-binding protein in the central auditory system of the mustached bat, Pteronotus parnelli. Components of the cochlear nucleus (CN) that were calbindin-positive (cabp(+] included the root of the auditory nerve, multipolar and globular bushy cells in the anteroventral CN, multipolar and octopus cells in the posteroventral CN, and small and medium-size cells in the dorsal CN. Not stained were spherical bushy cells of the anteroventral CN and pyramidal/fusiform cells in the dorsal CN. In the superior olivary complex, labeled cells were found in the lateral and medial nuclei of the trapezoid body, the ventral and ventromedial periolivary nuclei, and the anterolateral periolivary nucleus. No cellular labeling was seen in the lateral superior olive. In the medial superior olive, only marginal cells were cabp(+). Labeled fibers could be seen surrounding the gosts of unlabeled cells in both the latter nuclei. Most cells in the intermediate nucleus and the columnar division of the ventral nucleus of the lateral lemniscus were cabp(+). However, the dorsal nucleus was cabp(-). A group of cabp(+) cells was also seen in the paralemniscal zone. The inferior colliculus had a relatively low density of cabp(+) cells. Labeled cells were more common in the caudal half of the central nucleus, and in the external nucleus and dorsal cortex. In the auditory thalamus, nearly every cell in the medial geniculate body was cabp(+), but those in the suprageniculate nucleus and in the posterior group did not stain. Small cells in the intermediate layer and giant cells in the deep layers of the superior colliculus were densely cabp(+). In the pons, cabp(+) cells and neuropil could be seen in the medial and lateral pontine nuclei (pontine gray). In conclusion, calbindin-like immunoreactivity was found in most of the brainstem auditory system, as well as in regions associated with acoustic orientation or control of vocalization. However, except for a minority of cells of the medial superior olive, it is conspicuously absent from the nuclei receiving binaural input below the level of the inferior colliculus.