Naloxone does not affect tube restraint-induced target biting by male Swiss mice

Opioid peptides have been implicated in the mediation of intermale conflict. The effect of naloxone upon tube restraint-induced target biting was investigated since a high correlation between bite scores and intermale aggression has been claimed. No significant modification of target biting behaviour by naloxone was produced, in mice either naive or habituated to the apparatus (high and low baselines of responding respectively) suggesting no involvement of opioid peptides in this paradigm. The results are discussed in terms of controllability of the presumably stressful situation and the relation of restraint-induced biting to conspecific aggression.