Pain sensitivity, mood and plasma endocrine levels in man following long-distance running: effects of naloxone.
The effects of intense exercise on pain perception, mood, and plasma endocrine levels in man were studied under naloxone and saline conditions. Twelve long-distance runners (mean weekly mileage = 41.5) were evaluated on thermal, ischemic, and cold pressor pain tests and on mood visual analogue scales (VAS). Blood was drawn for determination of plasma levels of beta-endorphin-like immunoreactivity (BEir), growth hormone (GH), adrenocorticotrophic hormone (ACTH), and prolactin (PRL). These procedures were undertaken before and after a 6.3 mile run at 85% of maximal aerobic capacity. Subjects participated on two occasions in a double-blind procedure counterbalanced for drug order: on one day they received 2 i.v. injections of naloxone (0.8 mg in 2 ml vehicle each) at 20 min intervals following the run; on the other day, 2 equal volume injections of normal saline (2 ml). Sensory decision theory analysis of the responses to thermal stimulation showed that discriminability, P(A), was significantly reduced post-run under the saline condition, a hypoalgesic effect; response bias, B, was unaffected. Ischemic pain reports were significantly reduced post-run on the saline day, also a hypoalgesic effect. Naloxone reversed the post-run ischemic but not thermal hypoalgesic effects. Joy, euphoria, cooperation, and conscientiousness VAS ratings were elevated post-run; naloxone attenuated the elevation of joy and euphoria ratings only. Plasma levels of BEir, ACTH, GH, and PRL were significantly increased post-run. The results show that long-distance running produces hypoalgesia and mood elevation in man. The effects of naloxone implicate endogenous opioid neural systems as mechanisms of some but not all of the run-induced alterations in mood and pain perception.
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D000339:Affect; D004723:Endorphins / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006728:Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D009270:Naloxone; D010146:Pain / Q000503:physiopathology*; D005082:Physical Exertion; D011388:Prolactin / Q000097:blood; D012420:Running; D012684:Sensory Thresholds; D001615:beta-Endorphin
D004723:Endorphins; D006728:Hormones; D009270:Naloxone; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D013006:Growth Hormone