Effect of pheromones on the plasma level of prolactin during pregnancy and lactating periods in female rat

Introduction: Pheromones play a great role in the reproductive and social behavior of animals. The main sources of pheromones are urine and paracrine secretions. Through the neuroendocrine system, prolactin is a safe parameter to measure and compare the effects of pheromones on the sexual, maternal and also lactating behavior. Methods: Female rats were divided into 19 groups (n=8). To measure the plasma prolactin levels of rats, blood samples were collected and tested with prolactin RIA kits. Effects of sexual pheromones in the lactating period (3rd, 6th, 9th and 16th days after delivery), pregnancy priod (7th, 14th and 20th days) and lactating period (6th, 9th and 16th post-delivery days) on plasma prolactin level were surveyed. The effects of sexual pheromones on the plasma level of Prolactin were determined using a special cage without any sensory stimulation interferences, such as visual, auditory and tactile senses. Results: Data showed a significant decline in plasma levels of prolactin following sexual pheromones administration (p<0.05). Significant increase in the prolactin plasma level was observed as the female rats were kept with a castrated male rat (p<0.05). During pregnancy period, prolactin level did not show any significant change in the first week of pregnancy with or without present male rat, but it showed a significant increase during the second and third weeks of pregnancy in the presence of male rat (p<0.01). The presence of male rat during the third, sixth and ninth days after delivery causes a significant increase in prolactin level (p<0.01). The females exposed to alien pups showed a significant decline in prolactin level compared those exposed to their own pups (p<0.05), but both groups showed same level of prolactin on the ninth and sixteenth days of delivery. Conclusion: These findings suggest that male sexual pheromones change plasma levels of prolactin in the pregnancy and lactating period and subsequently affect mating reproductive activities of rats.