抄録
We found that the resistance for stress in diabetic rat was reduced, compared with that in normal rat, when serotonin (5-HT) levels in the brain were used as a stress-index. It is likely that diabetes-induced hyperglycemia led to such an attenuated stress-resistance. Then, we studied whether the concentration of perfusing glucose in the brain influences the stress-resistance. We used both spontaneously diabetic WBN/Kob rats and normal Wistar rats. The extracellular 5-HT in the hippocampus,was measured using an in vivo microdialysis technique. After exposed to first 100 min-restraint stress, second 100 min-restraint following 100 min-freely moving was loaded to the rats. We compared the value B/A(=C) with the value B,/A,(=D). Here, A and B show the levels of 5-HT before and during the exposure to the first restraint, respectively. Similarly, A, and B, show the levels of 5-HT after the exposure to the first restraint and during the exposure to the second restraint, respectively. The value D/C represents the stress-resistance. In addition, similar experiments in normal rats were undertaken in conditions of various concentrations of perfusing glucose. The value D/C was 0.85±0.24 in normal rats and 0.35±0.26 in diabetic rats, respectively. When the glucose concentration was gradually raised to 1000 mg/dl in normal rats, the value D/C inversely decreased. At a 1000 mg/dl, the value fell to 0.46±0.26, showing that it may decrease in the hyperglycemic condition. These results suggested that diabetes-induced hyperglycemia is at least a factor responsible for the attenuated stress-resistance observed in diabetic patients. [J Physiol Sci. 2008;58 Suppl:S217]
