DEVELOPMENT OF CAT-301 IMMUNOREACTIVITY IN AUDITORY BRAIN-STEM NUCLEIOF THE GERBIL

The developing brainstem auditory system has been studied in detail by using anatomical and physiological techniques. However, it is not kno wn whether immature auditory neurons exhibit different molecular chara cteristics than those of physiologically mature neurons. To address th is issue, we examined the distribution of Cat-301 immunoreactivity in the developing auditory brainstem of gerbils. Cat-301 is a monoclonal antibody that recognizes a 680-kD chondroitin sulfate proteoglycan sim ilar to aggrecan, a high-molecular-weight chondroitin sulfate proteogl ycan found in cartilage. In the central nervous system, Cat-301 immuno reactivity is localized to the extrasynaptic surface of neurons. It ha s been hypothesized by Hockfield and co-workers (Hockfield et al. [199 0a] Cold Spring Harbor Symp. Quart. Biol. 55:504-514) that the Cat-301 proteoglycan is a molecular marker indicating that a neuron has acqui red mature neuronal properties. In the current study, Cat-301 staining is first seen at 7 days after birth in the anterior ventral cochlear nucleus (AVCN), the posterior VCN (PVCN), and the medial nucleus of th e trapezoid body (MNTB) shortly before the onset of sound-evoked activ ity. By 21 days after birth, neurons in the AVCN, the PVCN, and the la teral and medial superior olive have attained adult-like distributions of Cat-301 staining concomitant with the physiological maturation of these neurons. Neurons in MNTB attain adult-like distributions of Cat- 301 immunoreactivity at 1 year. The maturation of Cat-301 immunoreacti vity parallels the physiological maturation of gerbil auditory neurons , and the Cat-301 proteoglycan may play a role in the formation and/or stabilization of auditory synapses. (C) 1997 Wiley-Liss, Inc.