AGE-RELATED CHANGES OF GABAergic NEURONS AND ASTROCYTES IN CAT PRIMARY AUDITORY CORTEX / 解剖学报

ABSTRACT

Objective A morphometric study was carried out on GABAergic neurons and astrocytes in primary auditory cortex of 4 young cats (1-3 years old, 20-2.5 kg) and 4 old cats (10-13-year-old, 3-3.5 kg), in order to explore the age-related changes and the probably physical effects underlying these changes. Methods The same regions of the primary auditory cortex (AI) were comparatively studied. Nissl staining and immunohistochemical methods were applied to explore the differences of GABAergic neurons and astrocytes(specifically labeled by GFAP as a mark as antibody) in the primary auditory cortex(Al) between young and old cats. Serial cross-sections from two age groups were stained with Nissl for layer structure observation and demonstration of neurons; Adjacent sections were stained with anti_GABA immunohistochemistry for localizing and characterizing GABAergic and with anti-GFAP for astrocytes in AI. Results The diameter, density and number of GABAergic neurons in Al of old cats declined significantly compared with the counterpart in young cats, especially in layers Ⅱ,Ⅲ of AI; but the change in GFAP-IR cells was reversed old cats showed clearly larger number and stronger staining of GFAP-IR cells than that in young cats. The GFAP-IR cell bodies and dendrites swelled obviously in old cats, especially in layer Ⅰ of AI and in white matter. Conclusion The result presented a direct morphological evidence for weakness of GABAergic intracortical inhibition, which is considered to be a possible mechanism for age-related acoustic function decline. The enhanced function of astrocytes may play an important role in decreasing the GABA content in AI of the old individuals.