Chronic pain induces a paradoxical increase in growth hormone secretion without affecting other hormones related to acute stress in the rat.
In several diseases chronic pain is associated with long-lasting pathophysiological responses which differ strongly from those observed in acute situations. When persisting, acute pain often results in physical and psychological stress which may in turn aggravate the initial pathological state. In the present work we examined the secretory patterns of pituitary hormones related to acute stress (growth hormone (GH), prolactin (PRL) and beta-endorphin (beta-END)) in rats during the phase of Freund adjuvant-induced arthritis (AIA, a model used for chronic pain studies) when chronic pain is maximum (14 and 21 days, postinoculation (PI)). Using radio-immunoassay hormones were measured in plasma samples taken every 30 min for 7 h in free-moving rats 14 and 21 days after Freund adjuvant or vehicle injection and in control animals. The total amount of GH secretion was higher at 14 and 21 days PI in AIA rats as compared to vehicle-treated and control animals, and the pulsatility of GH secretory pattern was not modified by AIA. PRL and beta-END secretion were not significantly different in arthritic rats as compared to controls. These results show that GH, PRL and beta-END responses induced by acute stress are not observed during the AIA phase when chronic pain is maximum. Thus, in our experimental conditions, beta-END and PRL do not seem to be good plasma markers of chronic pain.(ABSTRACT TRUNCATED AT 250 WORDS)
Calvino
Bernard
B
Unité de Recherches de Physiopharmacologie du Système Nerveux de l'INSERM (U 161), 75014 ParisFrance Unité de Recherches de Dynamique des Systèmes Neuro-Endocriniens de l'INSERM (U 159), 75014 ParisFrance.
Besson
Jean-Marie
JM
Mounier
Françoise
F
Kordon
Claude
C
Bluet-Pajot
Marie-Thérèse
MT
D000818:Animals; D001169:Arthritis, Experimental / Q000097:blood / Q000378:metabolism / Q000503:physiopathology; D002908:Chronic Disease; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D010146:Pain / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
D013006:Growth Hormone