Testosterone manipulations: effects on ranacide aggression and brain monoamines in the adult female rat

The effect of testosterone propionate on ranacide (frog-killing) behavior and brain norepinephrine (NE), dopamine (DA) and serotonin (5-HT) levels was determined in 40 female Wistar rats. Adult rats were screened for frog killing behavior on the basis of a single 30 min testing session. Aggressors were defined as animals which attacked or killed during this session while nonaggressors failed to do so. Using either aggressors or nonaggressors, testosterone and sesame oil equally increased aggresive behavior as measured in a second 30 min testing session. Biochemical analyses indicated that testosterone treated animals had significantly higher brain NE and NE/5-HT levels. Aggressors, testosterone or sesame treated had higher NE/5-HT ratios. Whole-brain levels of DA and 5-HT and the DA/5-HT ratios were unaffected. It is concluded that the elicitation of ranacide in the adult female rat is not androgen dependent nor is this behavior functionally related to the observed differences in brain noradrenergic/serotonergic levels. This study provides additional evidence that ranacide is a type of predatory aggression and yet presents data which may be at variance with the classic monoaminergic theory of aggressive behaviors.