Long-term effects of androgen treatment on fear reactions in ewes.

We have previously demonstrated that testosterone treatment reduces fear reactions of ewes subjected to daily injections of testosterone propionate (10 mg/day) for 56 days. The long-term effects of this treatment were studied in the same ewes and using the same battery of fear-eliciting tests (isolation from conspecifics, surprise, and presence of a human) 4 and 8 months after the injections were terminated. Twenty-six behavioral items related to fear were recorded. A number of differences in the behavior of treated vs control animals indicate that the former are still less fearful, especially in the surprise and human tests. Overall fearfulness scores of treated and control ewes (the higher the score, the more fearful the animals) were 7.3 +/- 1.7 vs 9.7 +/- 1.9, (P < 0.05) for the surprise test, and 7.0 +/- 1.4 vs 10.0 +/- 2.0 (P < 0.01) for the human test at 4 months, and 6.8 +/- 1.4 vs 8.2 +/- 1.1 (P < 0.05) for the human test at 8 months. Thus, not only does testosterone treatment reduce fear reactions in ewes but it also has a long lasting effect on such reactions.