丘脑中央下核内给予吗啡抑制福尔马林诱发的大鼠脊髓背角c-fos表达

Inhibition of formalin-evoked c-fos expression in the rat spinal dorsal horn by microinjection of morphine into the nucleus submedius

目的 研究丘脑中央下核 (Sm)内微量注射吗啡对大鼠福尔马林试验诱发的腰段脊髓背角c fos蛋白表达的抑制效应。方法 用免疫组化的方法观察c fos样免疫反应神经元在脊髓背角的表达与分布。结果 Sm内微量注射吗啡 (5 μg ,0 .5 μL)可以明显抑制大鼠后肢跖部皮下注射福尔马林诱发脊髓背角的c fos蛋白表达 ,c fos阳性神经元数为 (2 6 .5 8± 1.79)个 ,与注射生理盐水相比 [(6 2 .0 9± 14 .5 9)个 ],明显减少 (P <0 .0 0 1) ,并且这种抑制效应可被Sm内微量注射阿片受体拮抗剂纳洛酮 (1.0 μg ,0 .5 μL)所翻转 ,其c fos阳性神经元数为 (5 5 .5 0± 9.81)个 ,与单独注射吗啡相比差异显著 (P <0 .0 5 ) ,但与注射生理盐水相比 ,无显著差异 (P >0 .0 5 )。

Objective To identify the effect of microinjection of morphine into the nucleus submedius (Sm) on the formalin-induced c-fos protein expression of neurons in the spinal dorsal horn. Methods Immunohistochemical technique was employed in the c-fos protein expression. Results Microinjection of morphine (5 μg, 0.5 μL) into the Sm markedly depressed the c-fos protein expression of neurons in the spinal dorsal horn evoked by formalin injected subcutaneously. The number (26.58±1.79) of c-fos-like neurons after morphine administration lessened compared with that (62.09±14.59) of saline control (P<0.001), and this effect could be blocked by administration (55.50±9.81) of the opioid receptor antagonist naloxone (1.0μg, 0.5μL)) into the same site (P<0.05). Conclusion Opioid peptide and its receptors in the Sm may be involved in the descending antinociception.