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Microinjection of L-NAME into dorsal raphe nucleus inhibits nociceptive response in sigmoid pain model of rats

Yang Bin, Zhang Licai, Zeng Yinming

Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College. Xuzhou 221002,China

Abstract

By means of Fos immunocytochemistry, nicotinamide adenine dinucleotide phosphate - dia-phorase (NADPH-d) histochemistry and microinjection methods, the role of nitric oxide synthase (NOS) ofdorsal raphe (DR) neurons in the modulation of rats sigmoid pain was studied. The results showed: (1 )Rats exhibited aversive behavioral responses related to visceral pain after injecting formalin into the sigmoidwall. NOS neurons in DR were up-regulated, in addition, about 8% of NOS-labeled neurons were Fos posi-tive. By contrast, there was no Fos/NOS double-labeled neurons in the control group. (2) Formalin-in-duced sigmoid pain scores and the expression of Fos in the spinal cord at S1 segment were decreased aftermicroinjecting L-NAME into the DR. These findings suggest that NOS neurons are involved in the modula-tion of formalin-induced sigmoid pain and that NO may play an important role in the transmission of visceralnociceptive message in the midbrain.

Key words: Dorsal raphe;Sigmoid wall;Fos;Nitric oxide synthase

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Citing This Article：

Yang Bin, Zhang Licai, Zeng Yinming. Microinjection of L-NAME into dorsal raphe nucleus inhibits nociceptive response in sigmoid pain model of rats. Acta Physiol Sin 2003; 55 (5): (in Chinese with English abstract).