[NO involvement in mediation of spinal neuron sensitization in morphine-withdrawal rats]

The effects of nitric oxide (NO) on the activation of spinal cord neurons were studied using immunocytochemistry, intrathecal injection and antisense oligonucleotides (AS-ONs) techniques in morphine-withdrawal rats. Acute administration of naloxone and chronic administration of morphine changed neither the expression of Fos-LI and NADPH-d positive neurons nor the expression of Fos/NADPH-d double-labeled neurons in the spinal cord of rats. Fos-LI, NADPH-d positive and Fos/NADPH-d double-labeled neurons were increased significantly in number in morphine-withdrawal rats and they were observed in all the laminae of the spinal cord. Intrathecal injection of L-NA, nNOS antisense oligonucleotides significantly inhibited the expression of Fos-LI in the spinal cord and decreased the scores for morphine-withdrawal symptoms in morphine-withdrawal rats, but not in nNOS-S group. The results suggest that NO mediates the spinal neurons sensitization in morphine-withdrawal rats.