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Microinjection of opioid antagonist into periaqueductal gray blocks formalin-induced alterations of substance P in spinal dorsal horn

Du Junhui, He Lianfang

Department of Neurobiology, Shanghai Medical University. Shanghai

Abstract

Using formalin injected into the rat^s hind paw as nociceptive stimulation, the effect of naloxone and #beta#-endorphin(#beta#-EP)antiserum microinjected into the periaqueductal gray (PAG) on the level of substance P like immunoreactivity (SPLI) of the spinal dorsal horn was observed. After formalin injection, a significant increase in SPLI was found as compared with the control(P<0.01). After naloxone or #beta#-EP antiserum microinjection, SPLI level in the dorsal horn was decreased (P<0.05). It is thus suggested that nociceptive stimulation induce the release of #beta#-EP in the PAG, which, in turn, modulate SP release in the spinal dorsal horn.

Key words: Naloxone;#beta#-endorphin;Periaqeductal gray;Substance P;Spinal dorsal horn;Immunohistochemistry;Image processing;Formalin test

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Citing This Article：

Du Junhui, He Lianfang. Microinjection of opioid antagonist into periaqueductal gray blocks formalin-induced alterations of substance P in spinal dorsal horn. Acta Physiol Sin 1994; 46 (4): (in Chinese with English abstract).