Intracerebroventricular administration of riluzole prevents morphine-induced apoptosis in the lumbar region of the rat spinal cord.

Opiates are the most effective drugs for pain relief. However, the repeated use of opiates induces tolerance to their analgesic effects. It has been shown that this morphine-induced tolerance is associated with apoptosis in the central nervous system. The aim of this study is to evaluate the effects of intracerebroventricular (i.c.v.) administration of riluzole, an anti-glutamatergic drug, on morphine-induced apoptosis in the lumbar region of the rat spinal cord. Animals were given daily injections of morphine and vehicle, morphine and riluzole, or riluzole alone. Nociception was assessed using a hot plate apparatus, and apoptosis was assessed using the in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method. The levels of anti-apoptotic factors Bcl-2 and HSP 70 and the pro-apoptotic agent caspase-3 were evaluated using immunoblotting. The glutamate concentration in the lumbar spinal cord was measured with high performance liquid chromatography (HPLC). The results indicate that the i.c.v. administration of riluzole attenuated morphine tolerance and reduced the number of TUNEL positive cells. Immunoblotting revealed that the levels of the selected anti-apoptotic agents were greater in the treatment groups compared to the controls. Furthermore, the results demonstrated that the administration of riluzole can attenuate the morphine-induced elevation of glutamate in the lumbar spinal cord. In conclusion, i.c.v. administration of riluzole attenuated morphine-induced tolerance to analgesia and apoptosis in addition to preventing the morphine-induced increase of glutamate in the lumbar spinal cord of rats.