J Korean Pain Soc.
1999 Nov;12(2):171-176.
Effects of L-NAME on the Mechanical Hyperalgesia after the Development of Inflammation by Freund's Complete Adjuvant in Rat Paw
- Affiliations
-
- 1Department of Anesthesiology, College of Medicine, University of Ulsan, Seoul, Korea. ychoi@www.amc.seoul.kr
- 2Department of Physiology, Yonsei University College of Medicine, Seoul, Korea.
Abstract
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BACKGROUND: Effect of nitric oxide on the hyperalgesia induced by inflammation is controversial.
From our previous experiment, NOS inhibitor, L-NAME given during the induction period decrease
mechanical hyperalgesia occurred by Freund's complete adjuvant induced inflammation.
In addition, we attempted to analyze the effects of L-NAME on mechanical hyperalgesia after
the development of inflammation by Freund's complete adjuvant in rat paw.
METHODS
Male Sprague Dawley rats were divided into four groups; control (normal saline),
and three different doses of L-NAME (0.1 mg, 1 mg, 10 mg). Inflammation was induced in rats
by injecting 0.15 ml of Freund's complete adjuvant (FCA) intraplantarly. Rats showed typical
hyperalgesia within twelve hours after injection and maintained this for about one week.
Tests were done 2 days after injection of FCA. After the baseline test either L-NAME or saline
was injected under light halothane anesthesia. Effect of L-NAME on hyperalgesia was assessed
by measuring mechanical hyperalgesia at 15, 30, 60, 90, 120 minutes. Same experients were repeated
on normal rats.
RESULTS
When injected at the site of inflammation, L-NAME caused dose dependent decrease
in mechanical hyperalgesia. However, normal rats also showed increased mechanical threshold
after L- NAME injection.
CONCLUSIONS
Although L-NAME reduces FCA induced mechanical hyperalgesia, this result may
solely be due to inhibition of nitric oxide production and need to be further determined.