Suppression by dopamine-agonists of the ethanol-induced stimulation of locomotor activity and brain dopamine synthesis
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Summary
Ethanol, 2.2 g/kg was given intraperitoneally to mice, grouped 3 by 3, alone or together with either of the dopamine-receptor stimulating agents apomorphine, 2.5 mg/kg, or ET 495, 5 mg/kg. Control animals received saline injections. Locomotor activity was then recorded every 5 min for 60 min, starting 5–7 min after the injection. Apomorphine and ET 495, which had no marked effect on the locomotor activity, both inhibited the locomotor stimulation induced by ethanol. Other animals received ethanol, 4 g/kg, alone or together with either apomorphine or ET 495, and at various time intervals thereafter, 3H-labelled tyrosine. Control animals received 3H-tyrosine alone. The net yield of 3H-dopamine and 3H-noradrenaline in the brain as well as the specific activity of 3H-tyrosine in plasma 10 min after the 3H-tyrosine injection were measured. Apomorphine and ET 495, 2.5 and 5 mg/kg, respectively, did not change the net yield of 3H-dopamine and 3H-noradrenaline. However, both of them inhibited the ethanol-induced increase in net yield of 3H-dopamine. This effect of apomorphine and ET 495 could not be ascribed to changes in the specific activity of 3H-tyrosine in the plasma. Apomorphine had no effect on the blood level of ethanol as measured 1 h after the administration of ethanol. The possibility that the inhibitory effects of the dopamine-agonists on the ethanol-induced stimulation of the dopamine synthesis and locomotor activity may be mediated by stimulation of presynaptic, inhibitory receptors is discussed.
Key words
Ethanol Apomorphine ET 495 Locomotor Activity Dopamine Receptors Dopamine SynthesisPreview
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References
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