No abstract

We examined the effects of prolonged voluntary wheel-running on skeletal muscle functional and/or structural characteristics in rats. Male Sprague-Dawley rats (5 weeks old) were divided into five groups: (1) 15W-SC, sedentary controls housed in normal plastic cages until age 15 weeks; (2) 15W-VE, housed in a voluntary-exercise (running-wheel) device equipped with housing space until age 15 weeks; (3) 35W-SC, housed in normal plastic cages until age 35 weeks; (4) 35W-VE, housed in the voluntary-exercise device until age 35 weeks, and (5) 35W-MVE, housed in normal plastic cages until age 15 weeks, then in the voluntary-exercise device from age 16 weeks to 35 weeks ("middle age"). At the end of each rat's experimental period, the plantaris muscle was dissected from each hindlimb for analysis of the muscle's functional and/or structural characteristics. Total running distance was similar in 15W-VE and 35W-VE, both being significantly greater than in 35-MVE. The percentage of type IIb myosin heavy chain isoform was significantly lower in each VE group than in the corresponding SC group. This shift from type IIb was significantly greater for 35W-VE than for the other VE groups, which were similar to each other. The cross-sectional area of type IIx fibers was significantly greater in 35W-VE than in 35W-SC, but this was not true for 15W-VE versus 15W-SC or for 35W-MVE versus 35W-SC. No significant difference in citrate synthase activity was detected between any VE group and the corresponding SC group. These results suggest that a prolongation of voluntary wheel-running leads to some advantageous enhancements of functional and/or structural characteristics in rat plantaris.

No abstract

The purpose of this study was to investigate the effects of exercise on blood leptin concentrations and expression of leptin receptor subtype-b (Ob-Rb) mRNA in the arcuate nucleus of hypothalamus (ARC). Male Wistar rats (26 weeks old) underwent regular wheel exercise for 12 weeks. The expression of Ob-Rb mRNA in the ARC decreased at the end of the study period despite reductions of abdominal fat-pad weight and serum leptin concentration. Serum 1,5-anhydroglucitol levels were higher in exercising rats, suggesting lower serum insulin levels in exercising rats. Our results suggested that 12-week wheel exercise reduced the expression of Ob-Rb mRNA in the ARC probably through improvement in insulin resistance.

It was concluded that the functional recovery was mainly due to increased wet weight and cross-sectional area of type I SOL fibres, which probably reflected the functional reorganization and neuromodulation in the non-damaged contralateral sensorimotor cortex and ipsilateral sensorimotor cortex lateral to the lesion identified in a previous study.