Catalase inhibition in the Arcuate nucleus blocks ethanol effects on the locomotor activity of rats

Previous studies have demonstrated that there is a bidirectional modulation of ethanol-induced locomotion produced by drugs that regulate brain catalase activity. In the present study we have assessed the effect in rats of intraperitoneal, intraventricular or intracraneal administration of the catalase inhibitor sodium azide in the locomotor changes observed after ethanol (1 g/kg) administration. Our results show that sodium azide prevents the effects of ethanol in rats locomotion not only when sodium azide was systemically administered but also when it was intraventricularly injected, then confirming that the interaction between catalase and ethanol takes place in Central Nervous System (CNS). Even more interestingly, the same results were observed when sodium azide administration was restricted to the hypothalamic Arcuate nucleus (ARC), a brain region which has one of the highest levels of expression of catalase. Therefore, the results of the present study not only confirm a role for brain catalase in the mediation of ethanol-induced locomotor changes in rodents but also point to the ARC as a major neuroanatomical location for this interaction. These results are in agreement with our reports showing that ethanol-induced locomotor changes are clearly dependent of the ARC integrity and, especially of the POMc-synthesising neurons of this nucleus. According to these data we propose a model in which ethanol oxidation via catalase could produce acetaldehyde into the ARC and to promote a release of beta-endorphins that would activate opioid receptors to produce locomotion and other ethanol-induced neurobehavioural changes. (C) 2004 Elsevier Ireland Ltd. All rights reserved.