AGE-RELATED-CHANGES IN CALBINDIN D-28K AND CALRETININ IMMUNOREACTIVITY IN THE INFERIOR COLLICULUS OF CBA CAJ AND C57BL/6 MICE/

This study examines calbindin D-28k and calretinin immunoreactivity in the inferior colliculus (IC) of young and old mice of two strains. Th e CBA/CaJ mouse maintains good hearing until very late in life, wherea s the C57B1/6 strain exhibits severe sensorineural hearing loss at an early age. Young and old mice of both strains were selected with match ing auditory brainstem response audiograms and gap detection threshold s. Brain sections were reacted with anti-calbindin D-28k (CB) and anti -calretinin (CR). Staining patterns were characterized and cell counts performed. CB immunoreactivity was high only in the nucleus of the co mmissure (NCO); counts revealed a 22.3% decrease in the number of CBcells in old CBA mice and a 25.1% decrease in old C57 mice. Calretinin immunoreactivity was high in the pericentral regions of the IC, but t he central nucleus was devoid of CR+ cells. The dorsal cortex, lateral nucleus, and NCO showed increases of 42.3, 49.0, and 61%, respectivel y, in the number of CR+ cells, but only in the old CBA mice. No signif icant change was observed in the old C57 mice. Whereas decreases in CB immunoreactivity are common with age, this study is the first to repo rt an age-related increase in CR immunoreactivity in the auditory syst em. The increase in CR+ cells is a possible compensatory adaptation to the decrease in CB+ cells. That the number of CR+ cells remains const ant with age in C57 mice suggests this compensation may depend upon st imulus-driven activity, but this requires further study. (C) 1997 Wile y-Liss, Inc.