Long Frontal Brain Regions In Rats After Swimming C-fos Expression

Objective To observe the expression of c-fos in the rat front lobe subregions after long-term swimming and explore the possible mechanism of c-fos expression and its function during swimming exercise.Materials and Methods 110 male Sprague - Dawley rats were divided into control group (group A,n=10), endurance exercise group(group B, n=50) and interval exercise group(group C, n=50). The rats in groups B and C were trained by different types of swimming for 6 weeks. The rats in control group remained in their home cages throughout the training and experimentation. At 0, 30, 60, 120, 240 min after the last swimming exercise, 10 respectively of the rats in groups B and C were anesthetized. Five rats were decapitated, then the brains were removed and put into liquid nitrogen. The others were perfused transcardially with heparinized physiological saline followed by 4% paraforaldehyde in 0.1 mmol/L phosphate buffer, while the rats in control group were processed in the same manner as described above at the time of 0min group. Total RNA in the cortex of frontal lobe were isolated, then c-fos mRNA was analyzed by reverse transcription PCR.Frontal lobe of the postfixed brain(anterior to optic chiasma) were sectioned coronally with a freezing microtome into 30-μm-thick sections. Every fourth serial section was processed for Fos protein immunocytochemistry. Sections were first washed in 0.01 M potassium phosphatebuffered saline (KPBS, pH 7.4), followed by incubated for with 0.3% H2O2, 3% normal goat serum, polyclonal rabbit anti-Fos overnight, biotinylated goat anti-rabbit IgG and SABC, stained in DAB. Finally, sections were mounted onto slides, air dried, dehydrated and delipidated, coverslipped, examined by using standard light microscopy. Serial sections of a representative animal in each group were taken with a camera to show the location and distribution of the labeled neurons within the primary and secondary motor cortex and nucleus accumbens. The labeled cells were counted by software for image analysis.The data were analyzed by SPSS, and expressed(Mean±S.E.).Difference was considered statistically significant at P<0.05.Results RT-PCR The expression of c-fos mRNA increased significantly after 6 weeks swimming. The maximum of c-fos appeared at 60min in group B and at 120min in group C, but no difference was not found between group B and C. Immunocytochemistry The number of c-fos positive cells in frontal lobe increased after 6 weeks exercise. The number of c-fos positive cells in rat primary motor cortex(M1) were maximal at 30 min in groups B and C. In secondary motor cortex(M2), the number of c-fos positive cells peaked at 60 min in group C, but there was not obvious changes in group B. In nucleus accumbens(A), the maximum of c-fos positive cells presented at 60 min in group C, however, the expression increased continually until 240min in group B.Conclusion①After long-time swimming exercise, the expression of c-fos increased in primary and secondary motor cortex and nucleus accumbens in rat brain but the timecourse of expression was different among the brain frontal lobe subregions. The c-fos maybe involves in plasticity of motor cortex and modulation of exercise.②The expression of c-fos was different between two types exercises which possibly deponds on the intensity and endurance of exercise.