Methyltestosterone induces male sensitivity to both primer and releaser pheromones in the urine of ovulated female masu salmon

We investigated the optimum term of 17 alpha -methyltestosterone (MT) -treatment for behavioral test and changes of plasma sex steroids levels in MT-treated immature male masu salmon, Oncorhynchus masou parr. Behavioral responses of MT-treated fish to the urine of ovulated or immature females were observed in an experimental trough. After 5 min of behavioral tests, plasma sex steroids levels were measured by RIAs. MT-treated fish showed specific behavioral responses to the ovulated female urine. MT-treated fish without exposure to the urine showed no clear changes in plasma 17,20 beta -dihydroxy-4-pregnene-3-one (DHP). However, plasma DHP in MT-treated fish increased when they were exposed to the urine.