Does nutrients modulate food-intake behavior? Measurement of neurotransmitters using in vivo brain microdialysis in diabetic rat.

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In the present work, the following studies were undertaken : (Exp.1) Whether the abnormal behavior of food intake in diabetic animals just like human diabetic patients exists or not ; (Exp.2) Whether the abnormality of food-intake behavior will be responsible for the altered release of neurotransmitters in the diabetic brain or not, presumably permitting the frailty to stressors ; (Exp.3) Whether among many foods coffee and its main components are effective in stress-ralaxation or not. (Exp.1) WBN/Kob rat and KK/Ta mouse as spontaneously diabetic animal, and normal Wistar-rats and C57/BL mouse as thc control were used. In diabetic animals the spontaneous locomotor activity decreased. In both normal and diabetic animals, acute stress (100 min-restraint) elicited the decrease in food- and water-intake, and the circadian rhythm of food- and water-intake was disturbed especially in diabetic mice. (Exp.2) In this experiment the hippocampal levels of serotonin (5-HT) and dopamine (DA) of WBN … More /Kob rat, streptozotocin (STZ)-induced diabetic rat and normal Wistar rat were measured using in vivo brain microdialysis method. The 5-HT level in normal Wistar rat was the largest value, followed by that in STZ-rat and WBN/Kob rat in that order. The 5-HT level in WBN/Kob rat was about a half of that of the normal rat, and the DA level in WBN/Kob rat was about one-tenth of that of the normal rat. The experiment using several ion channel blockers suggested the dysfunction of ion channels in diabetic synapse. (Exp.3) Acute restraint stress led to prominent increase in the hippocampal levels of 5-HT.In normal rat, "peak 5-HT value during 2nd restraint/peak 5-HT value during 1st restraint" (stress-ralaxing index) in pretreatment of coffee, caffeine, chlorogenic acid and saline was about 37%, 34%, 130% and 85%, respectively. This suggests that the administration of coffee contributes to relaxation of restraint stress and further this effect of coffee could be due to the caffeine which is contained in the coffee. On the other hand, in WBN rat, the stress-ralaxing index in pretreatment of coffee, caffeine, and saline was about 45%, 51%, 68% and 85%, respectively, suggesting the frailty to stressors in diabetic animals. Less