Effects of postnatal exercise on apoptotic neuronal cell death and cell proliferation in the maternal‐separated rat pups

We investigated the effects of postnatal treadmill exercise on the short‐term memory capability and spatial learning ability, on the 5‐hydroxytryptamine (5‐HT, serotonin) synthesis and triptophan hydroxylase (TPH) expression in the dorsal raphe nuclei, and on the apoptosis and cell proliferation in the hippocampal dentate gyrus following maternal separation in rat pups. The rat pups in the maternal separation group showed significantly deceased retention time in the step‐down avoidance task and significantly increased error rate in the radial‐arm maze task compared to the rat pups in the maternal care group. 5‐HT synthesis and TPH expression in the dorsal raphe nuclei and cell proliferation in the hippocampal dentate gyrus were significantly decreased in the maternal‐separated rat pups, and postnatal treadmill exercise increased 5‐HT synthesis, TPH expression, and cell proliferation. Apoptotic neuronal cell death in the hippocampal dentate gyrus, on the other hands, was significantly increased in the maternal‐separated rat pups, and postnatal treadmill exercise suppressed the maternal separation‐induced apoptosis. The present results demonstrated that postnatal treadmill exercise alleviated maternal separation‐induced decrease of short‐term memory capability and spatial learning ability by suppressing apoptotic neuronal cell death and by enhancing cell proliferation. This study was supported by the Brain Korea 21 Project in 2006.