Motivational aspects of maternal anxiolysis in lactating rats

This study examines the role of maternal motivation on the reduced anxiety-like responses displayed by lactating rats in the plus maze test.

Maternal animals, both lactating and sensitized (ovariectomized females behaving maternal after a continuous exposure to pups), displayed anxiolytic-like responses in the plus maze test in contrast to ovariectomized non-maternal rats. However, the levels of experimental anxiety were lower in lactating than in sensitized females. Pups placed in the open arms of the maze further reduced the low levels of anxiety-like behavior of both sensitized and lactating rats. Low doses of haloperidol (0.05 and 0.1 mg/kg), a dopamine antagonist, which interfere with maternal motivation but has neither anxiolytic nor anxiogenic effect in the plus maze test, significantly increased the anxiety-like responses of lactating rats. The presence of the pups in the open arms of the maze overrode the behavioral effect of haloperidol on lactating dams' anxiety-related behavior.

These experiments show that maternity induces changes in the way the animals react to the environment, rendering them less anxious to aversive stimuli. The degree of experimental anxiolysis displayed by maternal animals varies according to their maternal motivation, which is modulated by the female's endocrine state, the pups and/or the dopaminergic system.