Rosemary Strasser - US grants

DESCRIPTION (applicant's abstract): Because early hormonal exposure, whether endogenous or exogenous, may have long-lasting effects on the behavior of an organism, such as maturation, reproduction, and cognition, it is important to understand these changes. The presence of maternal hormones in vertebrate eggs suggest a hormonal link between the mother and the offspring which may allow the mother to differentially influence offspring fitness. The present proposal is designed to specifically investigate the role of maternal androgens in the organization of the developing brain and the effects on behavior using the house sparrow, Passer domesticus, as our working model. Our hypothesis is that maternal hormones deposited in variable amounts in the avian egg influence brain differentiation during development leading to differences in behavior among siblings and broods of birds. Using radioimmunoassays to measure androgen levels, and immunocytochemistry in in situ hybridization to detect androgen receptors, this study will examine the ontogeny of behavioral differences relating to individual fitness. This study is unique in that it will examine individual variation at multiple levels. In addition to neuronal differences, I will also be examining hormone levels, physiology (weight, plumage) and behavior (aggression, courtship, reproduction & cognition) to determine if variable amounts of maternal hormones provide a selective advantage to specific individuals.

DESCRIPTION (provided by applicant): Vertebrate mothers deposit variable amounts of maternal steroid hormones in their eggs. Early exposure to steroids, whether endogenous or exogenous, may have long-lasting effects on the development and survival of an organism. In avian species, the concentration of these steroids, mostly androgens, found in the egg yolks vary within and among clutches. The possibility of organizational actions of these naturally occurring doses of maternal androgens, analogous to that regulating development of sexually dimorphic traits and behavior, remains largely unexplored. Because the offspring develop outside the mother, birds provide an excellent model system in which to manipulate and examine maternal hormonal effects without potential feedback effects derived from maternal endocrine physiology. The avian model of early hormone effects thus represents a very promising alternative system to the well-established mammalian model. It is the specific goal of the following proposed study to provide information regarding long-term maternal hormone effects on offspring development including potential transgenerational effects. Using an experimental design, exposure to testosterone and anti-androgens during development will be manipulated in order to examine the effects on morphology, physiology, and behavior of juvenile and adult offspring. New information will be obtained regarding 1) the effects of prenatal testosterone and anti-androgen treatment on offspring growth and development; 2) the organizational effects of testosterone and antiandrogens on offspring reproduction and parental behavior; and 3) the plasticity of maternal hormonal effects on subsequent generations. Results from these studies will contribute to our knowledge of how early hormone exposure (or absence) influence and organize the brain for later occurring activational events. With the growing popularity of hormonal treatments in various clinical populations and the prevalence of environmental anti-androgens, it is critical to not only understand how early hormonal histories influences an individual's current physiology and behavior but also how it might influence the phenotype of their future offspring via transgenerational maternal effects.