Electrophysiological evidence that morphine can exert an antinociceptive effect in a neuropathic state: a study in the ventrobasal thalamus of rats after moderate ligation of one sciatic nerve.

This study was performed in rats with a mononeuropathy induced by loose ligatures around the common sciatic nerve 2 weeks before the recording session, and exhibiting clear alterations of several pain-related behaviours. Morphine injected intravenously (0.6 and 1 mg/kg) strongly depressed the ventrobasal thalamic neuronal responses to pinch applied to the lesioned or the non-lesioned hindpaw. The effect, comparable on the both sides, was dose-related and reversed by naloxone (0.1 mg/kg i.v.).