JIAXU, C., and Y. WEIYI. Influence of acute and chronic treadmill exercise on rat brain POMC gene expression. Med. Sci. Sports Exerc., Vol. 32, No. 5, pp. 954–957, 2000.
Methods: In situ hybridization using biotin-labeled POMC cRNA probes and integrated image pattern analysis were used to observe the effect of chronic (total 7 wk) and acute treadmill exercise (an initial speed of 15 m·min−1 gradually increased to 35 m·min−1 with 0°, 20–25 min·d−1 duration) on the changes of POMC mRNA expression in different areas of the rat brain.
Results: Acute exercise performed after 7 wk of training resulted in a decrease in the expression of POMC mRNA in both the frontal cortex and hippocampal CA1 of the experimental rats. Three hours postexercise, the POMC mRNA indicator had not yet returned to normal expression levels in the frontal cortex, but hippocampal CA1 levels showed increases above normal levels 30 min postexercise. Expression levels in the hypothalamus were shown to be increased immediately after acute exercise and remained high even during remeasurement 3 h postexercise.
Conclusion: Changes in POMC gene expression in response to chronic and high-intensity acute exercise vary depending on the brain region examined.
There are many reports about ACTH and β-endorphin responses to exercise (4), and it also has been argued that exercise training may influence the physiological stress response to nonexercise challenges (i.e., there may be a cross-stressor adaptation) (15). For example, it has been shown that ACTH responses to nonexercise stressors such as immobilization (17) and foot shock (18) are augmented after treadmill exercise training. In order for these responses and adaptations to be better understood, it important to consider the precursor molecule proopiomelanocortin (POMC). POMC gives rise to β-endorphin, ACTH, α-melanocyte-stimulating hormone (α-MSH), and corticotropin-like intermediate lobe peptide (CLIP). POMC has emerged as a potential neuroregulator of energy balance (7,11). Moreover, POMC has been shown to play a role in the feedback component of the response of the hypothalamic-pituitary-adreno-cortical (HPAC) axis to acute and chronic stressors such as foot shock, prolonged swimming or restraint (14). Exercise is a complex, and the influence of POMC mRNA expression in brain areas other than the hypothalamus and pituitary has not, yet, been reported. Hence, the purpose of this investigation was to examine the effects of acute and chronic treadmill exercise on POMC mRNA expression not only in the hypothalamus but also in the frontal cortex and hippocampus, brain areas that are involved in the stress process—including memory and the processing of emotions such as fear.