Carrageenan-Induced Hyperalgesia Is Partially Alleviated by Endomorphin-1 Locally Delivered into Inflamed Paws In Rat.
- Author:
Seo Eun LEE
1
;
Hong Kee SHIN
Author Information
1. Department of Physiology, College of Medicine, Hanyang University, Seoul 133-791, Korea. selee63@hanyang.ac.kr
- Publication Type:Original Article
- Keywords:
Endomorphin-1;
mu-Opioid receptors;
Inflammation;
Hyperalgesia;
Pain
- MeSH:
Animals;
Carrageenan;
Humans;
Hyperalgesia*;
Inflammation;
Male;
Rats*;
Rats, Sprague-Dawley
- From:The Korean Journal of Physiology and Pharmacology
2003;7(6):369-373
- CountryRepublic of Korea
- Language:English
-
Abstract:
This study was performed to test whether endomorphin-1 has analgesic effect, when locally administrated into inflamed peripheral tissue. Carrageenan suspension (0.5%) was injected intraplantarly into the right paw of Sprague-Dawley male rats, and the rats were subjected to a series of mechanical stimuli with von Frei filaments before and after the injection. Carrageenan-injected rats showed typical inflammatory hyperalgesic signs and decrease of withdrawal threshold, peaked at 3 to 6 hours after the injection and lasted more than 3 days. Endomorphin-1 was intraplantarly injected with carrageenan, simultaneously or 3~4 hours after carrageenan. Simultaneous injection of endomorphin-1 with carrageenan significantly reduced hyperalgesia and thd analgesic effect was prolonged up to 8 hours. The delivery of endomorphin-1 (50 microgram) into the inflamed area after 3 to 4 hours of carrageenan injection significantly increased the threshold of hyperalgesic mechanical withdrawal response, but only partially. Intrathecal treatment of endomorphin-1 completely reversed carrageenan-induced hyperalgesia. This report is the first to show that peripherally delivered endomorphin-1 relieved inflammatory hyperalgesia. But a control through peripheral mu-opioid receptors appears to be not sufficient for complete pain treatment.
