Modulation of short term and long term memory by steroid sexual hormones.

Many studies have evidenced a functional interrelation between the nervous and endocrine systems in the modulation of mnemonic processes, and others have established the role played by certain hormones in these processes; however, few studies have dealt with the effects of sexual steroids on learning and memory. The aim of this work was to determine whether short-term and long-term memory is subject to hormonal modulation. Male Wistar rats, randomly assigned to 13 groups, 1 control and 12 experimental groups, were trained on a one-trial passive avoidance conditioning. The control group received saline solution, and each of the 12 experimental groups received a treatment consisted in one of following pharmacological doses of: 5, 10, 20, 30 mg of testosterone enanthate, 0.2, 0.4, 0.8, 1.2 mg estradiol valeriate, or 1, 2, 4, 6 mg norandrostenolone decanoate, respectively. All substances were applied 45 min before the training session. Retention of the learned response was tested 10 min (short-term memory) and 24 h (long-term memory) after the training session. Results indicate that under these experimental conditions the short-term memory is facilitated with testosterone enanthate at doses of 20 and 30 mg, the estradiol valeriate at doses of 0.4 mg and the nor-androstenolone decanoate at doses of 4 mg, whereas the long-term memory is facilitated with testosterone enanthate at doses of 30 mg, estradiol valeriate at doses of 1.2 mg and the nor-androstenolone decanoate at doses of 4 mg. The other studied doses were no effective.