孤束核および最後野のニューロン活動に対する血糖値上昇の影響

glucose

北海道歯学会

北海道歯学雑誌

To investigate the responsiveness of brainstem neurons to circulate glucose, we have to know about the quantitative estimation of temporal changes in blood glucose levels and the concurrently measured brainstem neuronal excitability during the elevation. In the present study, we used male Sprague-Dawley rats (250-500 g) and measured c-Fos expression in the nucleus tractus solitarius (NTS) and the area postrema (AP) in the animals with 24 h food deprivation and an intraperitoneal (i.p.) injection of saline containing 1.1 M glucose or saline (10 ml/kg in each).　Blood glucose concentration peaked at 15 minutes after i.p. injection of glucose and then gradually decreased for 90? 120 minutes toward normal levels. At 2 hours after injection of a glucose solution or saline, animals were anesthetized and fixed with 4% paraformaldehyde, and coronal sections (35 μm thick) were obtained from the brainstem. Expression of c-Fos protein in the brain sections were detected by using the immunostaining method. Significant increases in the number of c-Fos immunoreactive (Fos-ir) neurons were found in the NTS of animals injected with glucose as compared with animals injected with saline. The number of Fos-ir neurons likely to be increased in the area postrema, but a statistical significance was absent. This data suggested the increases in the neuronal excitability of glucose responsive neurons in the NTS or the increases in the excitability of NTS neurons responded to appetite-related peptides released during the elevation of blood glucose levels. We also found that changes in the excitability of area postrema neurons during the elevation of blood glucose level were not parallel with the NTS.