High-intensity extended swimming exercise reduces pain-related behavior in mice: involvement of endogenous opioids and the serotonergic system.
The present study examined the hyponociceptive effect of swimming exercise in a chemical behavioral model of nociception and the mechanisms involved in this effect. Male mice were submitted to swimming sessions (30 min/d for 5 days). Twenty-four hours after the last session, we noticed that swimming exercise decreased the number of abdominal constriction responses caused by acetic acid compared with the nonexercised group. The hyponociception caused by exercise in the acetic acid test was significantly attenuated by intraperitoneal (i.p.) pretreatment of mice with naloxone (a nonselective opioid receptor antagonist, 1 mg/kg), ρ-chlorophenylalanine methyl ester (PCPA, an inhibitor of serotonin synthesis, 100 mg/kg once a day for 4 consecutive days), and by bilateral adrenalectomy. Collectively, the present results provide experimental evidences indicating for the first time that high-intensity extended swimming exercise reduces pain-related behavior in mice. The mechanisms involve an interaction with opioid and serotonin systems. Furthermore, endogenous opioids released by adrenal glands probably are involved in this effect.


CONCLUSIONS
Our results indicate that high-intensity extended exercise endogenously controls acute pain by activation of opioidergic and serotonergic pathways. Furthermore, these results support the use of exercise as a nonpharmacological approach for the management of acute pain.
Mazzardo-Martins
Leidiane
L
Departamento de Ciências Fisiológicas, Centro de Ciências Biológicas, Universidade, Federal de Santa Catarina, Campus Universitário, Trindade, Florianópolis, SC, Brazil.
Martins
Daniel F
DF
Marcon
Rodrigo
R
Dos Santos
Ubirajara D
UD
Speckhann
Breno
B
Gadotti
Vinícius M
VM
Sigwalt
André Roberto
AR
Guglielmo
Luiz Guilherme A
LG
Santos
Adair Roberto Soares
AR
D019342:Acetic Acid / Q000633:toxicity; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D010134:Fenclonine / Q000031:analogs & derivatives / Q000494:pharmacology; D007509:Irritants / Q000633:toxicity; D008297:Male; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D018847:Opioid Peptides / Q000378:metabolism*; D010146:Pain / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D013550:Swimming / Q000502:physiology*
D007509:Irritants; D009292:Narcotic Antagonists; D018847:Opioid Peptides; C020261:4-chlorophenylalanine methyl ester; D012701:Serotonin; D009270:Naloxone; D019342:Acetic Acid; D010134:Fenclonine