The effect of intra-locus coeruleus injection of 17β-estradiol on inflammatory pain modulation in male rat
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- 作者：Roghaieh Khakpay ; Saeed Semnanian ; Mohammad Javan ; Mahyar Janahmadi
- 关键词：Locus coeruleus nucleus ; 17-β ; -Estradiol ; ICI 182 ; 780 ; APV ; Bicuculline ; CNQX ; Pain modulation ; Rat
- 刊名：Behavioural Brain Research
- 出版年：2010
- 出版时间：25 December 2010
- 年：2010
- 卷：214
- 期：2
- 页码：409-416
- 全文大小：514 K
文摘
Estradiol is a neuroactive steroid found in several brain areas such as locus coeruleus (LC). It modulates nociception by binding to its receptors and also by allosteric interaction with other membrane-bound receptors like glutamate and GABAA receptors. LC is involved in noradrenergic descending pain modulation. In order to study the effect of 17β-estradiol on both acute and persistent pain modulation and its mechanisms, formalin was injected into the male rat's hind paw. Formalin-induced responses including licking, flexing duration and paw jerking frequency were recorded for 60 min after injection of 50 μl of 2 % formalin. The results of the current study showed that intra-locus coeruleus injection of 17β-estradiol attenuated the second phase, but not the acute phase of formalin-induced pain (P < 0.05). AMPA receptor antagonists CNQX had no effect on pain-modulatory effect of 17β-estradiol. Estrogen and GABAA receptor antagonists (ICI 182,780 and bicuculline, respectively) could not reverse the antinociceptive effect of 17β-estradiol. However, NMDA receptor antagonist APV significantly antagonized the analgesic effect of 17β-estradiol on flexing behaviour (P < 0.05). It may be concluded that the analgesic effect of 17β-estradiol in formalin-induced inflammatory pain is mediated through interaction with membrane-bound receptors, probably the NMDA receptors.