Beta-endorphin administration interferes with the acquisition and initial maintenance of ethanol preference in the rat
Attention has been focused on the possibility of an interaction between the endorphinergic system and ethanol intake. In the present study, the effects of subcutaneous (SC) administration of beta-endorphin (beta-E) (0.25, 1 and 5 micrograms/kg) and/or naloxone (NX) (1 or 2.5 mg/kg) on ethanol preference (EP) have been investigated in rats. Under our procedural conditions, rats developed ethanol preference (EP) by a forced ethanol drinking session (conditioning session). Preconditioning administration of beta-E (1 microgram/kg) reduced later EP. When beta-E was administered postconditioning, the opioid affects ethanol preference depending on the dose: both 0.25 micrograms/kg and 5 microgram/kg reduced EP, but the dose of 1 microgram/kg did not alter it. Administration of beta-E (1 and 5 micrograms/kg) before the first testing session attenuated EP. NX antagonized the effects of beta-E on EP in the three experimental procedures used, indicating that mu-opioid receptors might be involved in the beta-E-induced reductions on EP. Our results provide further evidences for a beta-endorphinergic system involvement on the mechanism leading to consumption of ethanol.
Keywords: Alcohol Drinking/ drug effects ; Animals ; Brain/drug effects ; Choice Behavior/ drug effects ; Conditioning ; Operant/drug effects ; Dose-Response Relationship ; Drug ; Male ; Rats ; Rats ; Inbred Strains ; Receptors ; Opioid/drug effects ; Retention (Psychology)/drug effects ; beta-Endorphin/ pharmacology
Author address: Department of Psychobiology, Cajal Institute, Madrid, Spain.
Record created on 2007-01-18, modified on 2016-08-08