Morphine-induced running analgesia in two strains of mice following septal lesions or modification of brain amines.

Groups of two inbred strains of mice (C 57 B1/6J and DBA/2J) with septal and control lesions were tested for morphine-induced analgesia and running activity (running fit). As previously observed the effects of morphine on the running fit and analgesia were strain-dependent and a negative strain correlation was evident between the two measures in C 57 and DBA operated control mice which are characterized by different brain levels and turnover of cholinergic and adrenergic mediators. Septal lesions, which cause a reduction in the levels of acetylcholine in the brain areas which receive a cholinergikc input from the septum, anatogonized morphine analgesia in both strains while the running fit syndrome was unaffected. Pharmacological manipulation of brain catecholamines did not interfer with morphine-induced analgesia. The effacts of different pharmacological agents with interfere with noradrenaline synthesis and catecholamine oxidation were assessed in the two strains which are characterized by presence (C 57) or absence (DBA) of increased motor activity following the injection of morphine. The results argue against an exclusive association of morphine-induced motor activity with noradrenergic mechanism.