Species differences in the vasopressin-immunoreactive pathways in the bed nucleus of the stria terminalis and medial amygdaloid nucleus in prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus).

Vasopressin-immunoreactive (AVP-ir) cells in the bed nucleus of the stria terminalis (BST) and medial amygdaloid nucleus (MA) and their AVP-ir projections to the lateral septum were studied in monogamous prairie voles (Microtus ochrogaster) and promiscuous meadow voles (M. pennsylvanicus). A sexually dimorphic AVP-ir pathway was found in both species; males had more AVP-ir cells in the BST and MA, as well as denser AVP-ir fibers in the lateral septum, than did females. A significant species difference was also found. Overall, meadow voles had more AVP-ir cells in the BST and MA than did prairie voles. Male prairie voles, however, had a higher density of AVP-ir fibers in the lateral septum than male meadow voles. The species difference in the sexually dimorphic AVP-ir projections in the BST and MA is implicated in the rodents' different life strategy and behavior.