RESUMO
The question whether or not there will be an enhanced autonomic response in terms of heart rate in female rat, during sexual encounter with male rat was investigated. The heart rate recorded from partially restrained estrous female rat before and after the snout contact by the normal male rat showed a significant rise. There was no such rise in response to the snout contact by neonatally gonadectomised male rat of the same age as that of normal male. Treatment of testosterone propionate given to the gonadectomised male twelve hours prior to the experiment did not bring about significant rise in the heart rate of the estrous female. It is apparent that the perturbation in the structure of sexually dimorphic medial preoptic area (MPOA) in the male rat as a result of neonatal gonadectomy obliterates certain essential cues such as pheromone(s), visual and ultrasound communications which normally elicit a rise in the heart rate of the estrous female during sexual encounter.