| Abstract #258, Date 2/15/99, Session K1, Poster (J5) |
| Aging and the total number of calbindin D-28k and parvalbumin immunopositive neurons in the dorsal cochlear nucleus of CBA/CaJ mice |
| *E. Idrizbegovic (Dept. of Aud., Huddinge Univ. Hosp., Dept. of Physiol.& Pharm., Karolinska Instit.); J.F. Willott (Dept. of Psych., Northern Illinois Univ., DeKalb, IL); N. Bogdanovic (Dept. of Geriatric, Karolinska Instit.); B. Canlon (Dept. of Physiol. & Pharm., Karolinska Instit., Stockholm) |
Calcium-binding proteins (calbindin D-28k and parvalbumin) may play an important role in central auditory physiology, and have been shown to undergo age-related changes in some central nervous system structures. This study examines the total number of calbindin D-28k and parvalbumin immunopositive neurons in the dorsal cochlear nucleus (DCN) of adult (1year old), old (2 years), and very old (3 years) CBA/CaJ mice using the stereological method for counting neurons, the optical fractionator. CBA mice have little loss of sensitivity during the first 18 months of life, while between 18-24 months thresholds become elevated by 15-30 dB across most of the hearing range. In very old CBA mice ( > 30 months), hearing loss continues to progress. The DCN was completely sectioned using a Vibratome, and free floating sections were reacted with anti-calbindin D-28k and anti-parvalbumin. Staining patterns were characterised, and quantification was performed according to stereological principles. The total number of calbindin immunopositive neurons did not differ significantly among age groups, and showed mean ± SD for the 1-, 2- and 3- year- old mice to be 1743 ± 23, 1684 ± 223, 1730 ± 233, respectively. The mean ± SD of the total number of parvalbumin immunopositive neurons for the 1-, 2- and 3- year- old mice was 2200 ± 661, 2533 ± 189, 3599 ± 617, respectively, showing the tendency of parvalbumin immunopositive neurons to increase with age. There was a positive correlation between age and the number of parvalbumin immunopositive neurons, r = 0.83, p < 0.04. Our data indicate that the total number of parvalbumin immunopositive neurons increases in the DCN of aging CBA mice, while the number of calbindin immunopositive neurons does not change, even in very old mice. The selective age-related increase in the number of parvalbumin immunopositive neurons in the DCN might reflect altered calcium homeostasis and/or plasticity associated with diminished auditory function. |