Adaptive Responses Induced by Low Dose Radiation in Dentate Gyrus of Rats

The purpose of this study is to investigate the mechanism of alternative responses to low dose irradiation for neuronal cell proliferation in the dentate gyrus of rats. To determine the effect of a single exposure to radiation, rats were irradiated with a single dose of 0.1, 1, 10 or 20 Gy. To determine the effect of the cumulative dose, the animals were irradiated daily with 0.01 Gy or 0.1 Gy from 1 to 4 days. The neuronal cell proliferation was evaluated using immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU), Ki-67 and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining. Four consecutive daily irradiations with a 0.01 Gy/fraction increased the number of BrdU-positive and Ki-67-positive cells in a dose dependent manner, but this did not affect the number of TUNEL-positive cells. However, there was not a dose dependent relationship for the 0.1 Gy/fraction irradiation with the number of BrdU, Ki-67 and TUNEL positive cells. Our data support the explanation that the adaptive response, induced by low-dose radiation, in the hippocampus of rats is more likely a reflection of the perturbations of cell cycle progression.

Low Dose Radiation Overcomes Diabetes-induced Suppression of Hippocampal Neuronal Cell Proliferation in Rats

We investigated the effect of low dose radiation on diabetes induced suppression of neurogenesis in the hippocampal dentate gyrus of rat. After 0.01 Gy, 0.1 Gy, 1 Gy and 10 Gy radiation was delivered, the dentate gyrus of hippocampus of streptozotocin (STZ)-induced diabetic rats were evaluated using immunohistochemistry for 5-bromo-2-deoxyuridine (BrdU), caspase-3, and terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL) staining. The number of BrdU positive cells in the non-diabetic rats, diabetic rats without radiation, diabetic rats with 0.01 Gy radiation, diabetic rats with 0.1 Gy radiation, diabetic rats with 1 Gy radiation and diabetic rats with 10 Gy radiation were 55.4+/-8.5/mm2, 33.3+/-6.4/mm2, 67.7+/-10.5/mm2, 66.6+/-10.0/mm2, 23.5+/-6.3/mm2 and 14.3+/-7.2/mm2, respectively. The number of caspase-3 positive cells was 132.6+/-37.4/mm2, 378.6+/-99.1/mm2, 15.0+/-2.8/mm2, 57.1+/-16.9/mm2, 191.8+/-44.8/mm2 and 450.4+/-58.3/mm2, respectively. The number of TUNEL-positive cells was 24.5+/-2.0/mm2, 21.7+/-4.0/mm2, 20.4+/-2.0/mm2, 18.96+/-2.1/mm2, 58.3+/-7.9/mm2, and 106.0+/-9.8/mm2, respectively. These results suggest low doses of radiation paradoxically improved diabetes induced neuronal cell suppression in the hippocampal dentate gyrus of rat.

The Effect of Low Dose Radiation on the Neuronal Cell Proliferation in Diabetic Rats / 대한방사선종양학회지

PURPOSE: To investigate the effect of low dose radiation on neuronal cell proliferation in diabetic rats. MATERIALS AND METHODS: A group of rats (first group) were divided into three subgroups (nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy groups) to determine the effect of radiation on normal hippocampal neuronal cell proliferation. A further group of rats (second group) were divided into six subgroups (nondiabetic control, diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy groups) to determine the effect of radiation on hippocampal neuronal cell proliferation under diabetic conditions. Using immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU), the number of neuronal cells in the dentate gyrus of all the groups was counted. RESULTS: The number of BrdU-positive cells in the dentate Gyrus of the nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy subgroups of the first group were 45.96+/-3.42, 59.34+/-5.20 and 19.26+/-2.98/mm2, respectively. The number of BrdU-positive cells in the dentate gyrus of the diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy subgroups of the second group were 55.44+/-8.57, 33.33+/-6.46, 67.75+/-10.54, 66.63+/-10.05, 23.59+/-6.37 and 14.34+/-7.22/mm2, respectively. CONCLUSION: Low dose radiation enhances cell proliferation in the dentate gyrus of STZ-induced diabetic rats.

The Effect of Low Dose Radiation on the Neuronal Cell Proliferation in Diabetic Rats / 대한방사선종양학회지

PURPOSE: To investigate the effect of low dose radiation on neuronal cell proliferation in diabetic rats. MATERIALS AND METHODS: A group of rats (first group) were divided into three subgroups (nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy groups) to determine the effect of radiation on normal hippocampal neuronal cell proliferation. A further group of rats (second group) were divided into six subgroups (nondiabetic control, diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy groups) to determine the effect of radiation on hippocampal neuronal cell proliferation under diabetic conditions. Using immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU), the number of neuronal cells in the dentate gyrus of all the groups was counted. RESULTS: The number of BrdU-positive cells in the dentate Gyrus of the nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy subgroups of the first group were 45.96+/-3.42, 59.34+/-5.20 and 19.26+/-2.98/mm2, respectively. The number of BrdU-positive cells in the dentate gyrus of the diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy subgroups of the second group were 55.44+/-8.57, 33.33+/-6.46, 67.75+/-10.54, 66.63+/-10.05, 23.59+/-6.37 and 14.34+/-7.22/mm2, respectively. CONCLUSION: Low dose radiation enhances cell proliferation in the dentate gyrus of STZ-induced diabetic rats.

Acute Effect of Alcohol and Nicotine on 5-Hydroxytryptamine Synthesis and Tryptophan Hydroxylase Expression in Dorsal and Median Raphe of Rats

Alcohol abuse and cigarette smoking have been on the rise worldwide and it has been reported that alcohol and nicotine influence serotonergic neuronal activity in the dorsal raphe. Serotonin (5-hydroxytryptamine, 5-HT) has been implicated in the pathophysiology of various neuropsychiatric disorders. In the present study, the effects of alcohol and nicotine on the synthesis of 5-HT and the expression of tryptophan hydroxylase (TPH), the rate limiting enzyme of 5-HT synthesis, in the dorsal and median raphe of young rats were investigated via immunohistochemistry. The numbers of the 5-HT-positive and TPH-positive cells in raphe nuclei were reduced by alcohol and nicotine treatment, and these numbers were reduced more potently by co-administration of alcohol and nicotine. Based on the results, it can be suggested that the pathogenesis of alcohol- and nicotine-induced neuropsychological disorders involves alcohol- and nicotine-induced suppression of 5-HT synthesis and TPH expression in raphe, and that this may be of particular relevance in the consumption of alcohol and nicotine during adolescence.