ABSTRACT
Objective To explore the effect of DR on the expression of inhibitory neurotransmitter ,γ-aminobutyric acid ( GABA) and brain derived neurotrophic factor ( BDNF) in the primary visual cortex of young cats .Methods Totally 6 cats were wsed in this study . Nissl staining was used for cortical layer identification and cell counting . Immunohistochemical techniques were utilized to label GABA-and BDNF-positive neurons .Sections were observed under an Olympus light microscope and photographed with a digital camera .The cell density and absorbance of immunoreactivity were measured with Image-Pro Express 6.0 softwares .Results Our results showed that the mean density of Nissl-stained neurons in the primary visual cortex ( V1) of the DR group showed no significant difference from that of the control group . However , the mean density of GABA-immunoreactive neurons in each cortical layer of V 1 in DR cats was significantly higher than that in control cats .The mean immunoreactive intensity of GABA-positive neurons , as indicated by the average absorbance , increased significantly in DR cats relative to control ones . Accompanied with the elevation of GABA expression, DR enhanced BDNF expression in V1, as indicated by an increased mean density of BDNF-positive neurons and BDNF-immunoreactive average absorbance in DR cats relative to controls .Conclusion These results indicate that dietary restriction leads to a concurrent expression upregulation of GABA and BDNF , which may likely compensate for brain functional degradation during senescence and thus delay aging process .
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.