The research of relation between the effect of niacin in spatial learning ability and the expression of glut4 in prefrontal cortex, hippocampus and amigdala in sprague dawley rats

Both nicotinic asid and nicotinamide is called niacin. Nicotinic asid has a receptor in plasma membrane but nicotinamide has not. Niacin can alter the expression of glucose transporters. Glucose transporter 4 (GLUT4) is a transporter protein in plasma membrane so glucose can be transported into the cell and like periferic tissues, GLUT4 exists in hippocampus, amygdala and prefrontal cortex. Brain uses glucose for energy and amount of GLUT4 may affect spatial memory. The aim of this study is to investigate the relation with the effects of niacin to spatial memory and expression of GLUT4 and insulin receptor in hippocampus, prefrontal cortex and amygdala. İn this study we used 28 male Sprague Dawley rats. Rats were distribute 4 grups. They are control group, 30 mg/kg nicotinic asid administered group, 90 mg/kg nicotinic asid administered group and 270 mg/kg nicotinic asid administered group. We administered drinking water to control group and respectively administered 30 mg/kg/day nicotinic asid, 90 mg/kg/day nicotinic asid and 270 mg/kg/day nicotinic asid to other 3 groups into rats stomach with gavage during 21 days. Then Morris Water Maze test was done for 5 days. Just after the Morris Water Maze test ether was used in rats sacrification and blood was taken from rats ventricule then extracted bilateral hippocampus, prefrontal cortex and amygdala. During sacrification blood serum was taken for to measure serum insulin levels soon and was kept into -80 celcius refrigerator. During sacrification, glucose levels is measured with glucometer that taken blood from rats. Tissues were kept into -80 celcius refrigerator until to the homogenization. After the homogenization GLUT4, insulin reseptor and serum insulin levels were measured with ELİSA method. Comparing the groups in itself, between first day and last day weight of control group, there was statistically significant difference (p<0.05). First day of Morris Water Maze, there was no statistically significant difference between groups thigmotaksis results which reflects anxiety (p>0.05). Last day of Morris Water Maze, there was no statistically significant difference between groups thigmotaksis results which reflects anxiety (p>0.05). Last day of Morris Water Maze, time spent in the platform quadrant, there was no statistically significant difference between groups (p>0.05). On the fifth day of Morris Water Maze, 30 mg/kg nicotinic asid administered group went more distance than 270 mg/kg administered group and there was statistically significant difference between the groups (p<0.05). İn this study 30 mg/kg and 90 mg/kg nicotinic asid groups GLUT4 levels in hippocampus and 30mg/kg, 90 mg/kg ve 270 mg/kg nicotinic asid groups insulin receptor levels in amygdala were lower than control group and there was statistically significant difference (p<0.05). 30mg/kg, 90 mg/kg ve 270 mg/kg nicotinic asid groups GLUT4 ve insülin receptor levels were more lower than control group and there was statistically significant difference (p<0.05). There was no statistically significant difference between groups GLUT4 and insulin receptor levels in prefrontal cortex. (p>0.05). There was no statistically significant difference between groups insulin levels in blood serum (p>0.05). Blood glucose levels were more higher in the control group than nicotinic asid administered groups and there was statistically significant difference (p<0.05). Keywords: Nicotinic asid, niacin, glucose transporter 4, GLUT4, insulin receptor, hippocampus, prefrontal cortex, amygdala