[Change of dopamine, serotonin and opioid neuromediator systems in the brain of rats adapted to prolonged effect of ethanol]

AIM OF THE STUDY

To investigate the effect of in vivo short-term ethanol administration (i.p., 1.5 g/kg, 6 h) on binding characteristics of opioid receptor agonists in rat midbrain, as well as the contents of dopamine, serotonin and their precursors and metabolites in midbrain, striatum and hypothalamus of rats after long-term alcohol consumption. The methods of receptor binding assay and high performance liquid chromatography with electrochemical detection were used. The data obtained suggest that the response of neurotransmitter systems to short-term ethanol administration in different regions of rats brain is not identical. Our findings demonstrate that short-term ethanol administration may modulate dopaminergic transmission in the rat hypothalamus and striatum but this effect may be attenuated by down-regulation of OP, in the midbrain after long-term alcohol consumption. Serotonin system in hypothalamus becomes more sensitive to short-term ethanol administration after the long-term ethanol-containing liquid diet in comparison with control rats. Our results suggest that reinforcing properties of ethanol may be partially mediated by mechanisms involving the ethanol-induced disturbing of dopaminergic metabolism in the midbrain and hypothalamus and serotoninergic metabolism in hypothalamus.

[State of the opioid system in rats with different sensitivity to ethanol]

In this work we investigated the content of opioids in plasma blood and the changes caused by ethanol (1.5 g/kg, i.p.) in midbrain opioid receptors of rats with different sensitivity to ethanol, as determined according to the duration of ethanol-induced sleep (DEIS). A receptor binding technique with selective delta-DADLE and mu-DAGO radioligands were used. Ethanol even at low dose produced changes in the midbrain opioid receptors which appeared after 6 hours. The response of the receptors and the content of opioids in plasma blood of rats with different DEIS were not identical.