Brain control mechanism of sexual orientation

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1. Aggression ad wing removal influence brain serotonin levels in male crickets:When pairs of adult male crickets were placed together, they fought, and dominant-subordinate relationship were formed. Immediately after 10 min of aggressive interaction, brain serotonin levels reduced in subordinates. Dominants emit aggressive song during aggressive interaction, and the emission of aggressive song is abolished by removal of the wings. When pairs of males with wings removed were placed together, the wingless males formed dominant-subordinate relationships. The wingless, dominant male repeatedly displayed aggression. Brain serotonin levels in the wingless males were reduced immediately after 0 min of aggressive interaction, and no significant differences in brain serotnin levels were detected between the dominants and subordinates. These data suggest that aggressive behavior by dominants rapidly reduce brain serotonin levels in subordinates and that aggressive song is responsible for the ch … More ange in brain serotonin levels.2. Removal of both antennae influences the courtship and aggressive behaviors, ad brain serotonin levels in male crickets :At 7 days after removal of both antennae, pairs of antennectomized male crickets were placed together ; 80% displayed aggressive behavior toward other antennectomized males, 20% displayed aggressive behavior. Only 45%courted intact females. No intact males courted antennectomized males, and 80% displayed aggressive behavior. All intact males courted females. The results for males with one antenna removed were essentially the same as for intact males. These findings demonstrate that removal of antennae from male crickets induces male-male courtship and that an antenna is necessary for the expression of male-male aggression. Moreover, serotonin levels in the central body of the male cricket brain were markedly reduced at 7 days after removal of antennae. Thus, serotonin in the central body of the male cricket brain may be involved in the behavioral changes. Less