Morphine-Induced Straub Tail Reaction and Spinal Catecholamine Metabolite Content: Antagonism of Naloxone to Morphine-Induced Effects in Mice

The effects of morphine on the 3-methoxytyramine (3-MT) and normetanephrine (NM) level of various brain sites and two parts of spinal cord were investigated in mice with reference to our prior data on the effects of catecholaminergic agents on the morphine-induced Straub tail reaction (STR). Morphine (10 mg/kg) increased the 3-MT and NM content in the thoracic and lumbar regions of the spinal cord significantly, without affecting the 3-MT or NM content of the various brain sites. Naloxone (1 mg/kg) antagonized the morphine-induced increase in the 3-MT and NM in the thoracic and lumbar cord. These results suggest that morphine accelerates the release of spinal dopamine and norepinephrine. The morphine-induced STR might be due to the acceleration of catechol-aminergic neuronal activities in the spinal cord in mice.