Pentobarbital sodium and attack behavior in male Siamese fighting fish

An experiment was undertaken to determine the effects of pentobarbital sodium on intraspecific attack behavior in male Siamese fighting fish in an attempt to extend earlier findings with chlordiazepoxide and secobarbital sodium. Pairs of fish fought while immersed in 20 microgram/ml or 40 microgram/ml pentobarbital sodium or plain water. The 40 microgram/ml group showed significantly less attack (e.g., biting, jaw locking) than either control or low dose groups without producing a change in general arousal. Quasisexual behavior, seen in an earlier chlordiazepoxide study, did not occur in the present study.