Comparative effects of progesterone and alphaxalone on aggressive, reproductive and locomotor behaviors.

Progesterone can reduce aggressive behaviors in rodents under various experimental conditions, but it could be argued that this effect is due to the well known anesthetic/sedative properties of some steroids. We have tested this hypothesis by comparing the effects of progesterone and the anesthetic progestin, alphaxalone, on the aggressive, reproductive and locomotor behaviors of hamsters. Locomotion is used as a sensitive index of sedative/soporific effects. Progesterone reduced aggressive behavior without depressing the general locomotor activity of the animals, and it also facilitated feminine sexual behaviors in both sexes. Alphaxalone induced mild sedation in hamsters but this did not decrease their aggressive display. Alphaxalone did not facilitate feminine sexual behavior in either sex. We proposed that the inhibitory effect of progesterone on hamster aggressiveness is unlikely to follow from the hormone's sedative properties.