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The present work was designed to investigate the age related structural changes in cingulate cortex of rabbits that would help in treatment of emotional and cognitive age related disorders.
A total number of 15 Balady male rabbits were used. They were divided into three age groups; each group consisted of five rabbits:
group I: Young rabbits aging from 3-6 weeks, weighting 300-550 mg.
group II: Adult rabbits aging from 6-12 months, weighting 1.5: 2 kg
group III: Senile rabbits aging from 30-36 months, weighting 2.5- 3 kg
The heads were cut by a razor blade and put in Bouin’s solution for 2 days. Elevation of the soft membranous bone overlying the cerebral hemispheres was performed. The brains were dissected carefully and immersed in Bouin’s solution for 10 days till hardening occurred. The brains were hemi-sectioned by a midline incision passing through the corpus callosum. The sections were stained with haematoxylin and eosin and toluidine blue. Other sections were impregnated with silver according to the method of Glees.
The total width of cingulate cortex layers and the width of each layer were measured in the five specimens of the young and old group compared to the 5 specimens of the adult group. The means and standard deviations of all measurements were recorded and the results were tabulated and analyzed using image analyzer in Anatomy department – Ain Shams University.
The mean total width of the cingulate cortex layers and the mean width of each layer showed significant reduction from the young group to the adult group. Further reduction was evident in the old group.
Histological examination of the anterior cingulate cortex (area 24 a) of all groups revealed its laminar organization with five layers. The molecular layer (zonal layer) was the most superficial layer then external granular layer, pyramidal layer, ganglionic layer and finally the multiform layer.
Histological examination of the anterior cingulate cortex (area 24 a) of the young group showed some immature pyramidal neurones with long apical dendrites but poorly developed transverse basal processes. In addition the nerve fibers of all layers seemed with reduced affinity to silver stain as compared to the control group.
Histological examination of the anterior cingulate cortex (area 24 a) of the adult group exhibited its five layers. The superficial molecular layer contained small neurons whose dendrites run tangentially within the layer, the external granular layer formed of few pyramidal and non-pyramidal neurones. As well the pyramidal layer appeared with dispersed pyramidal cells of various sizes, oligodendrocytes, microglia and bundles of nerve fibers those pass through the neurons. Then the ganglionic layer which consisted of large pyramidal neurones with triangular soma and oval nuclei. Long apical dendrites and well developed transverse basal dendrites emerged from the pyramidal neurones. Finally the multiform layer appeared with neurones of different sizes and shapes; pyramidal neurons, spindle shaped neurons and ovoid neurons. Also other cells like oligodendrocytes and microglia were noticed.
Histological examination of the anterior cingulate cortex (area 24 a) of the old group revealed patchy disturbance in the arrangement of the different layers. Some neurones were degenerated with dark nuclei and fragmented dendrites, other pyramidal neurons appeared pale with fragmented peripheral nuclei. There were some degenerated nerve bundles with interrupted nerve fibers. Multiple aggregations of nerve fibers that lack the affinity to the toluidine stain were apparent in this group. Similar to the young group the nerve fibers of all layers revealed reduced affinity to the silver stain as compared to the adult group.
All results were discussed.