DIFFERENTIAL INTERACTIONS BETWEEN ETHANOL AND RO-15-4513 ON 2 ANXIETYTESTS IN RATS

The effects of low (2 g/kg) and high (4 g/kg) doses of ethanol and the ir interaction with the imidazobenzodiazepine Ro 15-4513 (a partial in verse agonist of the benzodiazepine receptor) were studied in two diff erent models of anxiety in rats: the ''elevated plus-maze'' test and t he early acquisition of two-way (shuttlebox) avoidance. In the elevate d plus-maze, ethanol (2 g/kg) increased the percentage of entries into the open arms (%EOA) and both ethanol doses increased the percentage of time spent into the open arms (%TOA), thus indicating an anxiolytic action which was reversed by Ro 15-4513 (5 mg/kg). By contrast, Ro 15 -4513 did not counteract the anxiolytic effect of the low dose of etha nol in the acquisition of shuttlebox avoidance. Thus, the treatment wi th 2 g/kg of ethanol (plus either vehicle or Ro 15-4513) significantly increased the total number of avoidances. Conversely, animals treated with 4 g/kg of ethanol showed impaired shuttlebox avoidance acquisiti on, and this effect was completely reversed by Ro 15-4513. Ro 15-4513 was without effect on its own in any of the anxiety-related parameters (i.e., %EOA, %TOA, and avoidance acquisition). The results indicate a different pattern of ethanol effects and Ethanol x Ro 15-4513 interac tions depending upon the task used.