Effects of Different Concentrations of Formalin on Paw Edema and Pain Behaviors in Rats.
10.3346/jkms.2002.17.1.81
- Author:
Il Ok LEE
1
;
You Seong JEONG
Author Information
1. Department of Anesthesia, College of Medicine, Korea University, Korea University Guro Hospital, Seoul, Korea. iloklee@hotmail.com
- Publication Type:Original Article
- Keywords:
Pain Measurement;
Nociceptors;
Formalin Concentration;
Inflammation;
Edema
- MeSH:
Animals;
*Behavior, Animal;
Edema/*chemically induced;
Extremities;
Formaldehyde/*adverse effects;
Male;
Pain/*chemically induced;
Rats;
Rats, Sprague-Dawley
- From:Journal of Korean Medical Science
2002;17(1):81-85
- CountryRepublic of Korea
- Language:English
-
Abstract:
The aim of this study was to determine whether formalin reliably provokes a paw edema and pain behavior. The paw of male Sprague-Dawley rats were injected with 100 microliter of formalin with 2.5% (F2.5), 5% (F5), and 10% (F10) concentrations. Following the formalin (n=8) or saline (control, n=6) injection, the flinching or licking of the paw was recorded for the phase 1 response (0-5 min after injection) and phase 2 response (20-60 min). The formalin-induced paw edema was assessed by measuring the diameters of the injected paws at 4 hr after injection. As for flinching, phase 1 and 2 of all three groups showed higher frequency than those of the control group (p<0.05). As for licking, phase 1 cumulative time of the F2.5 and F10 groups, and phase 2 cumulative time of the F2.5 and F5 groups showed a longer duration than those in the control group (p<0.05). The diameters of the paw in the F10 group were significantly larger than those in the control group (p<0.05). Flinching behavior was more reliably expressed the biphasic response than licking response at all formalin concentrations. Peak of the licking was reached at 2.5% and that of flinching was reached at 5%, whereas the paw edema peaked at 10% concentration. This suggests that there may be some dissociation of nociception from the edema formation.
