Limbic system fos expression associated with paternal behavior

Axon-sparing lesions of the medial nucleus of the amygdala (MeA) decrease male parental behavior in the highly social prairie vole. To assess further the role of the amygdala in paternal behavior, male and female prairie voles were exposed to a pup or a non-social olfactory stimulus for 3 hours, and cells expressing Fos peptide were labelled using immunocytochemistry. Compared to controls, males exposed to a pup showed an increase in Fos expression in the MeA, as well as in several areas with connections to it: the accessory olfactory bulb, lateral septum, medial preoptic area, medial bed nucleus of the stria terminalis, nucleus reuniens and paraventricular nucleus of the thalamus. There was no increase in Fos immunoreactivity in the paraventricular nucleus of the hypothalamus or piriform cortex. The same pattern of Fos expression was found in female voles, with the exception of the thalamic paraventricular nucleus, where there was an increase in the pup-exposed group that was not statistically significant (P = 0.11). In addition, the magnitude of induction in females was markedly less than that in males in the medial preoptic area. These results provide further evidence that the MeA is involved in paternal behavior, and suggest certain other areas previously implicated in maternal behavior may also be involved in the control of paternal behavior in this species.