Effects of formalin-induced pain on ACTH, beta-endorphin, corticosterone and interleukin-6 plasma levels in rats.
The behavioral and immunoendocrine effects of formalin-induced pain were studied in male rats following a subcutaneous injection of formalin (50 microliters; 0.1%, F01 groups, 10%, F10 groups) or sham injection (control groups). After treatment, animals were tested in a transparent open field for either 30 or 60 min and thereafter sacrificed by decapitation. Plasma was collected for adrenocorticotropic hormone (ACTH), corticosterone, beta-endorphin (beta-EP) and interleukin-6 (IL-6) determinations. Pain-evoked responses (licking, flexing, paw jerk), standard measures of activity (locomotion, rearing, olfactory exploration) and self-grooming were recorded. The higher formalin concentration induced stronger pain-evoked behavioral responses, paralleled by higher levels of ACTH, beta-EP and IL-6, but did not affect the other behavioral parameters. In contrast, the lower formalin concentration induced a marked increase in locomotion and rearing and a decrease in ACTH levels. In both formalin-injected groups, corticosterone did not differ from controls.
Aloisi
A M
AM
Istituto di Fisiologia Umana, Università degli Studi di Siena, Italia.
Albonetti
M E
ME
Muscettola
M
M
Facchinetti
F
F
Tanganelli
C
C
Carli
G
G
D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003345:Corticosterone / Q000097:blood*; D005557:Formaldehyde / Q000494:pharmacology*; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D010146:Pain / Q000139:chemically induced*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D001615:beta-Endorphin / Q000097:blood*
D015850:Interleukin-6; D005557:Formaldehyde; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone