高運動性モデルラットSPORTS の海馬におけるノルエピネフリン動態と自発運動量

Reduced physical exercise activity contributes to the development of several metabolic disorders including obesity, type ２ diabetes and hypertension. Especially in the developed countries, many people choose not to be active physically, possibly because of a reduced motivation to participate in exercise activities. Thus, augmentation of exercise motivation and subsequent increase in the physical activity would reduce an incidence of these metabolic disorders. In order to clarify the psychological mechanisms responsible for an increased exercise activity, we have generated and established a line of SPORTS （Spontaneously-Running-Tokushima-Shikoku） rat for high levels of voluntary wheel running. Male SPORTS rats run voluntarily in the running wheel almost six times longer than control Wistar rats. Here we examined the relation of the running activity of SPORTS rat with the hippocampal norepinephrine （NE） system including the levels of NE, adrenergic receptors, and degradation enzymes for monoamines. In the hippocampus of SPORTS rats, the level of NE in extracellular fluid was augmented, whereas the level in the homogenate of the whole tissue was decreased even for sedentary conditions. The level of striatal dopamine has not altered in both groups. The protein expression and the activity levels of monoamine oxidase A （MAOA）, a critical enzyme for the degaradation of NE, were decreased in the hippocampus of SPORTS rats to increase extracellular NE level. Thus, inhibition of oxidase activity in normal Wistar rats markedly increased wheel running activity. Our results indicate that the hippocampal NE determines the neural basis of the psychological regulation of exercise behavior in SPORTS rats. Modulation of NE transmission in the hippocampus will be a good method for enhancing the exercise behavior both in clinical patients and in healthy humans.

四国医学雑誌 : http://www.tokushima-u.ac.jp/med/research/shikoku_acta_medica.html