Elizabeth Adkins-Regan - US grants

Great progress is being made on understanding exactly how sex steroids act on the nervous system to yield adaptive behavior and physiology that serves to promote reproductive success. Dr. Adkins-Regan is performing experiments on birds which investigates the spinal level neuroendocrine processes. This work will contribute to our understanding of the role of testosterone metabolites in androgenic actions on the nervous system. Dr. Adkins-Regan has data that show that these sex steroids change the dendritic arborizations of motor neurons. This finding has ramifications for neuronal plasticity in the adult. This work is important because there is increasing recognition that in addition to specific reproduction related effects on the nervous system such as the production of sexual dimorphism, sex hormones may have more general trophic effects on neural development. Neuroendocrinology is a tremendously fast moving field, and its study should yield many new findings regarding the physiology of human behavior.

The proposed project is an investigation of a potentially valuable animal model for the study of specific anosmia to androstenone, a steroid derivative of testosterone. Specific anosmia to androstenone occurs in approximately 40% of human adults tested, and age and sex differences in sensitivity have been reported. Investigation of responses to androstenone in the pig is of particular interest because previous work has indicated that androstenone plays a role in chemical communication in swine and that pigs' behavioral responses to the steroid vary with age and sex. Specific questions to be addressed by the study are whether the lack of behavioral response to androstenone in certain groups of pigs reflects an inability to detect the chemical, analogous to specific anosmia in humans, and if the developmental shift in sensitivity to androstenone during adolescence noted in humans also occurs in swine. Pigs' ability to detect androstenone will be determined using a discrete trials, "go, no-go" successive discrimination task. The animals will be trained to discriminate between an odor and a blank, opening a reward box in the presence of one, but not in the presence of the other. In order to investigate effects of age and sex on detection of androstenone, the study will include 6 groups of 8 pigs: mature females, intact and castrated mature males, prepubertal females, and intact and castrated prepubertal males. Measuring and comparing the ability of pigs of different ages and sexes to detect androstenone will indicate whether the sensitivity shift in humans and the dimorphic behavioral responses in swine are analogous, and whether further study of the pigs' psychophysical responses to the steroid can increase understanding of specific anosmia in particular, and of coding in olfaction in general.

Abstract Adkins-Regan 9514088 The goal of the proposed research is to analyze developmental processes leading to adult mate choice and mate preferences, especially preferences that are sexually dimorphic (different in males and females). The project will focus on a particularly robust and widespread aspect of mate choice, preference for opposite-sex partners (sexual partner preference), and a species well-suited to the goal, the zebra finches treated with estrogen during the first two weeks posthatch and housed in an all-female zebra finches treated with estrogen during the first two weeks posthatch and housed in an all-female environment from 40 days (independence from the parents)to 100 days (young adulthood) then prefer to pair with other females. In order to address important questions raised by this discovery, a series of experiments will be conducted in which annals are exposed to different hormonal or social environment manipulations during development and then tested for sexual partner preference--organizational effects of hormones produce early in development, and sexual imprinting--and will elucidate the manner in which hormonal and experiential influences interact during development. This work will advance our understanding of mate choice and of reproductive behavior development.

Dissertation Research: A Functional and Mechanistic Investigation of Yolk Androgens in the European Starling (Sturnus Vulgaris)

Elizabeth Adkins-Regan and Kevin Pilz

Female birds deposit steroid hormones, such as testosterone, in the yolks of their eggs. In captive-bred canaries, high levels of "yolk testosterone" in eggs cause elevated growth rates and begging behavior in the chicks that hatch from those eggs. There is currently no information regarding the behavioral effects of yolk hormones in other species of birds. Nor is there well-substantiated evidence that females deposit different levels of hormones in eggs under different ecological circumstances to maximize their reproductive success. This study intends to fills these gaps in our knowledge by studying two types of "yolk androgens", one being testosterone and the other being a related hormone called androstenedione, in wild-living European starlings (Sturnus vulgaris). The first goal of this research is to document the effects of yolk androgens on European starling chick growth and behavior. Eggs will be injected with hormone or with a control solution and the growth and begging behavior of the chicks will be monitored until the chicks are ready to leave the nest. The second goal of this research is to test the hypothesis that females who engage in the reproductive strategy of brood parasitism deposit high levels of yolk androgens in their eggs. A brood parasite female lays her eggs in the nests of other females to avoid raising the chicks herself; starlings sometimes brood parasitize other starlings. If yolk androgens cause chicks to compete more, by begging more and growing faster, then a female who lays brood parasitic eggs should deposit high levels of androgen in those eggs so that her chicks will be able to selfishly outcompete their unrelated nestmates. The third goal of this research is to examine whether female characteristics such as body size and age are related to the levels of yolk androgens that females deposit in eggs. This data will be used to determine if the small size and young age of brood parasitic females may explain why brood parasitic eggs have high levels of yolk androgens. This data will also be used to test the hypothesis that "high quality" females (larger, older females) should invest more yolk androgens in eggs than "low quality" females.

In summary, this research will investigate within a single species of wild songbird, 1) the effects of yolk androgens on chicks; 2) whether females allocate androgens to eggs in ways which benefit their reproductive success; and 3) whether female allocation of yolk androgens varies with female characteristics such as body size and age. This research will increase our knowledge of hormone effects on development in birds and provide understanding of non-genetic means by which females can adaptively manipulate offspring characteristics. The research may also be useful as a model of maternal hormone effects on developing offspring in mammalian species.

PI: Elizabeth Adkins-Regan

This project will explore the mechanisms of the lifetime pair bond that forms between male and female zebra finches. Biology seeks to explain not only general features of most organisms (fundamental processes of life) but also the diversity in organismal forms and lifestyles. There is great diversity in animal mating systems. This diversity includes interesting variation in whether males and females form long-term close social relationships in order to reproduce. Long-term monogamous relationships, including pairing for the life of the animals, are scattered throughout the animal world (including some human populations) but are most common in birds. This kind of mating system is poorly understood. The objective of this research is to explain the function (how such relationships lead to better reproduction) and the physiology responsible for the formation and maintenance of these relationships using a species, the zebra finch, that pairs for life. The research will answer questions such as: are the birds more reproductively successful if they continue with the same partner rather than choose a new partner? Are sex hormone actions required for birds to pair and to remain paired? Do pubertal sex hormones have any long-term effect on pairing? Are they responsible for the transition from attachment to the parents to attachment to the pairing partner? What is the role of the physiological stress response following separation of the pair in re-pairing following loss of the partner? Are physiological changes following separation part of the costs that normally prevent separation? The methods will include hormonal and social manipulations during juvenile development and adulthood, behavioral testing designed to measure pairing preference and status, and determination of reproductive success and hormone levels. By discovering what is responsible for pairing and remaining together, this research will answer important questions and will offer and test new hypotheses about the physiology of ecologically relevant behavior applicable to a broad array of socially monogamous animals. The research will also provide valuable training and an important start to a scientific career for a large number of undergraduate and graduate students of both genders and of diverse backgrounds and origins.

Exclusive male-female pairbonds (socially monogamous mating systems) are seen in only a few kinds of mammals and in some humans, but are a very common reproductive arrangement in birds. Yet almost nothing is known about the internal mechanisms (neurohormones, brain systems) for pairing in birds. Using a common laboratory species, the zebra finch, that forms long-lasting pair relationships, the project aims to discover these mechanisms as they operate at three different life stages to promote socially monogamous pairing: (1) early in life in nestlings when the strong tendency to form close affiliations with family members begins, (2) during juvenile life when the birds first become more interested in the opposite sex than in the parents, and (3) following adult loss of the mate (through death) when a new pair relationship with a new partner can occur. The project is aimed at determining the physiological mechanisms that promote these pair bonding behaviors. Experiments are designed to specifically test the potential involvement of neuropeptides, such as oxytocin, and the adrenal "stress" hormone, corticosterone, in facilitating pair bonding. The project will also investigate the role of corticosterone in the ability of the birds to remember and prefer their first partner even after a long period of separation. Overall, the project will solve a long-standing mystery "what makes birds like zebra finches form strong pair bonds?" It will suggest mechanisms that might apply to the thousands of other socially monogamous birds and more generally to other vertebrates. It will provide new information on mechanisms acting in birds that can be compared with mechanisms operating in socially monogamous mammals, and thus, has the potential to increase understanding of how brains and hormones produce close relationships in all animals, including humans. The project will provide training of students at all levels and will include specific activities to recruit and train women and underrepresented minorities for scientific research careers. The work will be disseminated to the public through general audience publications, a web site, and through outreach programs to middle school girls and local K-12 biology teachers.

Long-term pairing (selective affiliation) between males and females is rare in mammals, but is a very common reproductive arrangement in birds. Selective affiliation begins with parents and family early in development and switches to the opposite-sex pair partner as the individual reaches adulthood. Using a common laboratory species that forms lifelong close cooperative pair relationships, the zebra finch, this project investigates the development of such selective affiliative behavior and its neural and hormonal mechanisms. The goal of the research is to test the hypothesis that the brain nonapeptide arginine vasotocin (AVT, avian homolog of vasopressin) plays an important role in the organization of affiliative behavior at two critical periods in development in the zebra finch: 1) early in life prior to leaving the nest and 2) during the transition from juvenile to adult life. This research aims to establish a causal link between changes in the nervous system and changes in affiliative behavior by using an advanced technique that measures the expression of a hormone receptor gene and neural activity in the same neurons in the brain. The research will provide new information on the mechanisms of selective affiliation in birds, which can then be compared to the mechanisms operating in socially monogamous mammals. Thus, this study has the potential to increase understanding of how brains and hormones produce close relationships in all animals, including humans. This research project will contribute to the training of undergraduates, including women and underrepresented minorities, who will be working in the laboratory. Additionally, the results from this work will be promptly published in journals accessed by a broad audience of researchers and presented at national meetings. The results will be disseminated to the public through a website and outreach programs for middle school girls.

All recordings and data in digital form will be archived at Cornell University using the archiving services of the CU Library (including eCommons) or other services that are currently under development under the leadership of the Research Data Management Service Group (http://data.research.cornell.edu/).

Parental care is an important component of reproduction that is observed in a diverse range of animals and is especially common in birds. The neural and hormonal basis of avian parental care is not well understood, especially in the many birds where young are raised by both mothers and fathers working together. The hormone prolactin has a well-established role in maternal care in mammals, and so prolactin and its brain receptors are a promising candidate mechanism of parental care to investigate in birds. The goal of this research is to experimentally test for a causal role of prolactin in promoting the onset of parental behavior in a biparental songbird, the zebra finch. This research will provide new insight into the mechanisms of avian parental care, allowing the integration of this important group into the comparative framework that will provide the predictive power for understanding how these mechanisms may function and evolve in other animals, including humans. The project will contribute to the scientific training of undergraduates, including women and underrepresented minorities. Additionally, the results will be promptly published in journals accessed by a broad audience of researchers, presented at national meetings, and disseminated to the public through a website and outreach programs for middle school girls.

The researchers determined that circulating prolactin (PRL) is significantly higher in zebra finches (Taeniopygia guttata) during late incubation and early post-hatching care compared to other times in the breeding cycle. To test the hypothesis that PRL plays a causal role in promoting the onset of parental behavior, they will perform two experiments testing the effect of suppressing the normal peak in PRL during late stage incubation in breeding birds, and experimentally increasing PRL in paired, but non-breeding, birds given foster chicks. Parental behavior will be recorded in the nests with small video cameras. To confirm that the treatments have the predicted effect on PRL concentrations, plasma will be assayed before and after treatment using a validated ELISA. On the last day of treatment brains will be collected to determine the effect on central PRL-mediated cell signaling via the PRL receptor using immunohistochemistry. All recordings and data in digital form will be archived at Cornell University to allow public access using the archiving services of the CU Library.