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Aggression in female hamsters as a function of reproductive state and availability of serotonin
Abstract
A series of five experiments evaluated aggressive behaviors in female golden hamsters (Mesocricetus auratus) towards conspecific males. Aggression was measured across the estrous cycle, during induced estrus, and during pregnancy. The relationship of aspects of the male's copulatory pattern to receptivity termination was assessed and the effects of parachlorophenylalanine (PCPA), a serotonin depleter, on aggressive behavior in these various reproductive states was evaluated. Latency to aggression varied across days of the estrous cycle with the shortest latency occurring the evening after estrus. In addition, a significant interaction effect was obtained between day of cycle and day of the cycle on which observations started. Injections of PCPA (2 millimoles/kg daily for three days) had no effect on the aggression exhibited by the cycling females. Ovariectomized females injected with estrogen and progesterone to induce heat were presented with either a series of sexually rested males, or with males mated to the point of exhibiting the "long-intromission" patterns typical of nearly exhausted males followed by successive sexually rested males. The duration of receptivity was longer for females in the "long-intromission" condition; however, the amount of time females spent in lordosis was not different between conditions. Treatment with PCPA (2 millimoles/kg daily for three days) prior to testing for estrous behaviors yielded significantly shorter lordosis and total receptivity durations. Females treated with PCPA also received fewer mounts, intromissions, and ejaculations. Aggression exhibited during and at the end of receptivity was not affected by PCPA. Pregnant females were tested at Day 5 and Day 15 of gestation with injections of PCPA or vehicle prior to testing. PCPA significantly decreased aggression at Days 5 and 15. Pregnant females were found to be neither more nor less aggressive than cycling non-estrous females. It is concluded that aggression in the female hamster is modulated by variation in hormonal changes associated with the estrous cycle and with pregnancy. However, it would appear that changes in neurotransmitter activity also affect aggression in concert with and independent of hormones. Data from the present study suggest involvement of the neurotransmitter serotonin in female aggression exhibited in some but not all reproductive states.
Subject Area
Psychobiology
Recommended Citation
Dudley, Victoria, "Aggression in female hamsters as a function of reproductive state and availability of serotonin" (1988). ETD collection for University of Nebraska-Lincoln. AAI8911107.
https://digitalcommons.unl.edu/dissertations/AAI8911107