RESTORATION OF SEXUAL BEHAVIOR AND DOPAMINERGIC NEUROTRANSMISSION BY LONG TERM EXOGENOUS TESTOSTERONE REPLACEMENT IN AGED MALE RATS

AbstractPurpose: We investigated the effects of long-term testosterone replacement on copulatory behaviour and dopaminergic neurotransmission in the medial preoptic area of aged male rats.Materials and Methods: The rats were divided into 3 groups depending on testerone replacement. Those in the long-term replacement group were castrated at the age of 12 months and received testosterone replacement thereafter for 12 months. In the short-term replacement group, rats were castrated at the age of 22 months and high or low dose testosterone replacement was done for 2 months. The control group consisted of aged rats 24 months old and young rats 12 weeks old, neither of which had been castrated or received testosterone replacement. We observed sexual behavior in rats of these groups. After a behavioral test, we measured the tissue concentration of dopamine in the MPOA and the change rate of the extracellular dopamine level induced by infusion of N-methyl-D-aspartic acid (NMDA) in the MPOA and compared the long-t...