However, the mutant males and females displayed clear differences in aggression and sexual activity compared to their normal counterparts.
Normally, nursing females are aggressive toward other lab mice that intrude or invade their nest. The nursing mutant females, however, were less aggressive when confronted by an intruder: there were fewer attacks, the first attack was delayed, and the total time spent attacking the invader was much less, when compared to the behavior of the females' normal counterparts in the same test situation.
The researchers studied four behaviors in the male mutant mice, and found two of these to be affected in the mutant mice. A first assay tested if male mutants emit 70 kilohertz ultrasounds when first exposed to a female. Removing the VNO reduces this behavior, but in the mutant mice it was unaltered. Second, male aggression against other males was also unchanged in the mutants.
A third test focused on male-male sexual behavior. Socially inexperienced mice are often observed to exhibit sexual behaviors toward other males until they become more experienced and learn to distinguish males from females. Socially inexperienced mutant mice, surprisingly, made fewer sexual advances toward males, suggesting that the mutants are better at distinguishing between sexes without prior experience, or that their sexual drive overall is reduced.
The fourth behavioral test analyzed sexual behavior of males toward females, which is also dependent on a functioning VNO. Compared to their normal counterparts, the mutant males tended to mount females fewer times, and the more they were exposed to females, the less they mounted.
Normally, male and female mice that spend time together engage sexual behavior with each other. This gain of sexual activity through experience does not occur in
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Contact: Joseph Bonner
bonnerj@mail.rockefeller.edu
212-327-8998
Rockefeller University
4-Sep-2002