Male, Wistar rats were sprint trained using a high intensity, interval type, treadmill running protocol. Sprint training produced a significant decrease in plasma β-endorphin levels. Conversely, animals who performed a high intensity acute run displayed significant increases in the concentration of plasma β-endorphin which may be stress-related. Neither training nor acute running had any significant effect on the β-endorphin levels of the pituitrary, cortex, posterior or anterior hypothalamus.
Bibliographical noteFunding Information:
This study was supported in part by the Marquette University Biology Department and grants from NIDA 02234 (EAS) and NIH AM-22037 (R.H. Fitts). We gratefully acknowledge Mr. Michael Blake for technical assistance, Dr. Robert Fitts for his guidance and advice and Ms. Barbara DeNoyer for typing the manuscript.