[Chronic morphine intoxication and metabolism of neuroactive amino acids in the rat brain]

The influence of chronic morphine intoxication (for 7, 14 and 21-days) has been studied on the contents of neuroactive amino acids (GABA, glutamate, glutamine, alanine, aspartate, glycine, taurine) and on the activities of their metabolizing enzymes (GABA-transaminase, succinic semialdehyde dehydrogenase, succinic dehydrogenase, alanine- and aspartate-aminotransferase) in the rat brain regions: cortex, brain stem and cerebellum. We detected the significant decrease of glutamate level and the enhancement of GABA and aspartate levels in cortex after long-term morphine administration. In brain stem the increase in the contents of GABA, glutamine and taurine was noted together with the tendency in attenuation of this effect when intoxication was prolonged. The dose-dependent enhancement in the levels of glutamate, aspartate and glycine was observed after longer courses of morphine administration. In cerebellum the 21-day morphine administration led to attenuation of the morphine-induced increase in the contents of GABA, glutamate, alanine and glycine.