Initiation of maternal behavior in the rat: possible involvement of limbic norepinephrine

The dorsal norepinephrine (NE) fiber system was manipulated in pregnant female rats. Brainstem lesions of the dorsal bundle, depleting NE in cortex and hippocampus, resulted in deficits in maternal-behavior onset in primiparous rats. Similarly, fornix-bundle transections, depleting only hippocampal NE, were associated with an absence of pup care. Hypothalamic NE levels, as well as dopamine and serotonin concentrations in cortex, hippocampus and hypothalamus, were not significantly affected by these manipulations. The data are discussed in terms of behavioral specificity, possible hormonal involvement and interactions with diencephalic mechanisms controlling the onset of maternal behavior in the female rat.