Simple behavioral measures of central alpha-adrenoceptor blocking activity of drugs

Behavior of mice exposed to open field was investigated after treatment with various alpha-adrenoceptor antagonists. In addition, the interaction with clonidine and exploratory response in rats were tested. Preferential alpha-2 antagonists were found to change characteristically the open-field behavior in mice: they consistently increased grooming and decreased rearing activity. Yohimbine, rauwolscine and piperoxane produced bell-shaped effects on grooming which were compatible with their alpha-1 antagonistic activity at higher doses. Similarly, these drugs antagonized the clonidine-induced hypoactivity at lower dose-ranges and decreased the exploration in rats after higher doses. Selective alpha-1 antagonists showed only depressant effects on various behavioral measures. The results of this study indicate that the selectivity of alpha-1 or alpha-2 receptor blockade in mice and rats can be reliably determined by using behavioral parameters.