The total number of neurons and calcium binding protein positive neurons during aging in the cochlear nucleus of CBA/CaJ mice: a quantitative study

The quantitative stereological method, the optical fractionator, was used f or determining the total number of neurons and the total number of neurons immunostained with parvalbumin, calbindin-D28k (calbindin), and calretinin in the dorsal and posteroventral cochlear nucleus (DCN and PVCN) in CBA/CaJ (CBA) mice during aging (1-39 months old). CBA mice have only a modest sen sorineural pathology late in life. An age-related decrease of the total num ber of neurons was demonstrated in the DCN (r = -0.54, P < 0.03), while the total number of neurons in the PVCN did not show any significant age-relat ed differences (r = 0.16, P = 0.57). In the DCN 5.5% of neurons were parval bumin positive in the very old (30 39 months) mice, vs. 2.2% in the 1 month old mice. In the DCN 3% of the neurons were calbindin immunopositive in th e 30-39 months mice compared to 1.9% in the I month old group. In the PVCN. 20% of the neurons in the very old mice were parvalbumin immunopositive. c ompared to 12% in the young mice. Calbindin did not show any significant ag e-related differences in the PVCN. The total number of calretinin immunopos itive neurons both in the DCN and PVCN did not show any significant change with increasing age. In conclusion. the total neuronal number in the DCN an d PVCN was age-related and region-specific. While the neuronal number in th e DCN and PVCN was decreased or unchanged, respectively, the calcium bindin g protein positive neuronal number showed a graded increase during aging in a region-specific and protein-specific manner. (C) 2001 Published by Elsev ier Science B.V.