2005 Volume 55 Issue 6 Pages 345-353
Partner preference and paced mating tests were accomplished in ovariectomized female rats following bilateral radiofrequency lesions in the medial amygdala. Open field behavior and passive avoidance learning were also examined to investigate the underlying behavioral mechanism. Partner preference was determined in a chamber located between castrated and sexually active males. Airborne olfactory cues were presented to the female through small holes on the partition. The lesion diminished preference for the odor of sexually active males over that of castrated males, even after injection with a high-dose of estrogen. On the other hand, in a paced mating test the lesioned females without estrogen treatment showed a significantly shorter latency for entering the male's compartment in a two-compartment apparatus, which allowed the females, but not the males, to cross the barrier through a narrow opening at the bottom. However, an administration of estrogen and progesterone reduced the effect. The lesion had no effect on emotionality or exploratory behavior in an open field test, but it impaired passive avoidance learning capability. We suggest that a male poses an inherent threat to a female. The seemingly incompatible results of partner preference and paced mating tests can be compromised if the male is inherently aversive to the female; this emotional response can be removed by the medial amygdala lesion.