Restraint stress affects hippocampal cell proliferation differently in rats and mice

Granule cell neurogenesis occurs in the dentate gyrus of the mammalian hippocampus throughout adult life, and incorporation of bromodeoxyuridine (BrdU) into DNA can serve as a marker of cell division associated with such neurogenesis. We examined the effects of a stressor (3 h of restraint) on hippocampal cell proliferation in Sprague-Dawley rats and C57BL/6J mice. Animals were killed immediately following restraint stress and their brains were prepared for immunohistochemical studies. Restraint stress caused similar significant increases in c-Fos immunoreactivity among cells in the hypothalamic paraventricular nucleus of both species, indicating that the stress experienced was similar. The restraint procedure also caused a significant decrease in BrdU labeling in the dentate gyrus of rats, as previously reported, but a significant increase in the same region in mice. Hippocampal cell proliferation appears to respond differently to restraint stress in these species.