There appear to be critical behavioral and neural differences between a parent and a non-parent, or a good parent versus a bad parent. Because of the vast diversity in paternal responses across mammalian species, paternal responsiveness will be the focus of this project which will determine the underlying brain and hormonal mechanisms of parental nurturing responses. Specifically, Peromysus californicus, a monogamous, bi-parental species that exhibits full paternal care toward their offspring will be compared to Peromyscus maniculatus, a species that typically does not exhibit paternal care. These studies will compare the neuronal activation of brain circuits following pup-exposure and will examine the number of newly proliferated cells in the brain. Since vasopressin and oxytocin are neuropeptides known to be involved in affiliation processes, vasopressin and oxytocin distributions in the brain will be measured and the levels of these neuropeptides in circulation will be assessed to determine the plasticity of the nurturing response, even in mammals that are not predisposed toward paternal affiliative responses. Information related specifically to the characterization of the paternal response or, more generally, to enhanced social motivation will have implications for understanding complex social responses (e.g., nurturing and affiliative responses) in various species. During the course of these studies, a high priority will be placed on the recruitment and training of undergraduate students in all phases of the project. Further, the PI will serve as a mentor for a post-doctoral assistant interested in a subsequent career establishing an engaging undergraduate neuroscience research program.
. Kelly G. Lambert, Randolph-Macon College, Ashland VA 23005 USA National Science Foundation (RUI) awarded from 2008-2012 NSF# 0723341 In this series of experiments a comparative species approach was used to investigate brain areas associated with paternal responsiveness. Specifically, two closely related species--Peromyscus californicus, known for its paternal responses and Peromyscus maniculatus, known for its lack of paternal responsiveness—were used in this project. Males from both species with varying degrees of paternal experience (i.e., biological fathers, foster fathers, and control males with no experience with offspring) were exposed to pups to assess approach and avoidance responses. California mice consistently approached and nurtured the pups, regardless of paternal status (but more so with previous paternal experience), whereas the maniculatus mice exhibited little evidence of paternal responsiveness, even if they were biological fathers. When relevant brain areas were explored, it became apparent that the brains of the nonpaternal maniculatus mice exhibited activation of the fear and anxiety circuits whereas activation in areas such as the preoptic area of the hypothalamus, typically involved in maternal responses, were more active in the paternal California mice. Further, increased plasticity in brain areas involved with learning and memory were observed in paternal California mice trained in a spatial learning task. In a final assessment, males of both species and varying paternal responsiveness were exposed to a pup in a small enclosure so that their persistence to contact the pup (when the maternal mouse was not present) could be assessed. Interestingly, even in these conditions, the California paternal mice exhibited much more interest in the enclosed pup than the nonpaternal maniculatus mice that spent more time trying to escape from the cage, sleeping, or self-grooming. Finally, in one study in this series, two neuropeptides involved in social bonding—oxytocin and vasopressin—were found to be more prevalent in the California mice than the maniculatus mice. Thus, the present series of experiments revealed key variables contributing to a mammal’s shift in interest from self to other; specifically, decreased social fear and enhanced social awareness, with accompanying reshaping of certain brain structures involved in learning, comprise the cornerstones of mammalian nurturing and social affiliative responses.
