Changes in GABA-immunoreactivity and GABA-transaminase activity in rat amygdaloid complex in aging

The distribution of gamma-aminobutyric acid (GABA), gamma-aminobutyric acid-transaminase (GABA-T) and glial fibrillary acid protein (GFAP) in the amygdaloid complex of young adult (3-month old) and aged (26-month old) Wistar rats was compared by using histo- and immunohistochemical techniques. The study revealed a heterogeneous distribution of GABA-immunoreactive and GABA-T positive nerve cells, fibers and terminals in various amygdaloid nuclei of young adult rats. A significant reduction in the density of GABA-immunoreactive neurons was demonstrated in the amygdala of aged rats. Reduced density and staining of GABA- and GABA-T-positive fibers and terminals were also seen in aged rat amygdala. Heavily GABA- and GABA-T-stained aberrant fibers and coarse puncta were clustered around blood vessels as well as under the pial and ependymal surfaces. GFAP-immunostaining demonstrated numerous hypertrophic astrocytes in these areas.