ABSTRACT
To explore the effect of sodium nitrite-induced hypoxia on the hippocampus and the dentate gyrus in adult rats. Adult male albino rats, weighing 180-200 gm were divided into two groups and treated as follows: Group I: served as control and received normal saline, Group II: served as hypoxic rats and received sodium nitrite [75 mg/kg] subcutaneously. One hour after sodium nitrite injection, rats were decapitated. The brains were removed and placed overnight in fixative containing 10% formalin. These were paraffin- embedded for hematoxylin and eosin staining and cut at 5 micro in the coronal plane. Sections passing through bregma level -2.8 to -3.3 mm were used to count the neurons in the CA1, CA2, CA3, and CA4 subsectors and the dentate gyrus. Round, clear and medium or large neurons with distinct nucleus were counted. Cells with darkly stained shrunken nuclei and cells with fragmented nuclei were excluded from the count. Cytological examination of hypoxic brains depicted degeneration in hippocampus and dentate gyrus. Cell density was comparatively lesser in all the sub regions of hippocampus i.e. CA1-CA4 and Dg in the hypoxic brains. The degeneration was evident by presence of pyknotic nuclei, darkly stained cells, cells with condensed nuclei, as well as vacuolated spaces. The changes were more marked in CA3, CA4 and dentate gyrus. It is concluded that pyramidal neurons of the hippocampus and granular neurons of the dentate gyrus are very vulnerable to hypoxia and show regional differences in their vulnerability