Ann S. Clark - US grants

Dr. Clark has received a research planning grant to explore the use of anabolic steroids as a means to examine the relationship between brain and behavior. Until recently, the mechanism of steroid action was thought to require genomic activity. Steroids, such as testosterone, estrogen and corticosterone, are lipid soluble compounds that readily enter all cells. Within target tissues, such as the brain, uterus and prostate, the cells contain intracellular protein receptors that bind the hormone. The steroid-receptor complexes interact with the nuclear DNA and initiate RNA and protein synthesis. This increase and/or decrease in protein synthesis mediate the physiological and behavioral responses to the hormone. Recently, membrane binding of steroid hormones has been proposed as an alternative mechanism to explain some biological functions that occur too rapidly for genomic activation. Because the family of anabolic steroids have a different chemical structure and metabolic properties, these compounds may be ideal to investigate this alternative mechanism of steroid action. Dr. Clark will carry out a series of studies to determine the ability of anabolic steroids to bind to intracellular and membrane receptors. Anabolic steroids were initially developed for medicinal purposes and were used for the treatment of hypogonadal dysfunction in men, initiation of delayed puberty and growth production. Although these synthetic compounds were synthesized to have maximal effects on protein synthesis and muscle growth, they also have androgenic or masculinizing effects. Therefore, Dr. Clark will examine how these synthetic compounds modulate the biochemical and behavioral action of naturally occurring androgens and estrogens. Anabolic abuse by athletics is receiving international attention. Although little is known about the mechanisms of action, it is clear that these drugs have harmful side-effects, especially on muscle, liver and cardiovascular functions. The results from these types of studies will provide needed important about how these compounds are working.

The long-term objective of this project is to elucidate the neural and behavioral actions of anabolic-androgenic steroids (AAS). AAS are synthetic androgen-like compounds which are taken in massive quantities by athletes with the intention of enhancing their muscular appearance, strength, and/or athletic performance. Abuse of AAS has become a major substance abuse problem in this country. AAS have been shown to have profound adverse effects on the liver, cardiovascular and endocrine systems. AAS are also known to produce severe and deleterious changes in affect and behavior, however, at the present time, few systematic studies have evaluated AAS effects on the central nervous system or behavior. Although endogenous steroid hormones (e.g., testosterone) are known to regulate sexual behavior and aggression, there is paucity of data on the neuroendocrine effects of AAS. Nonetheless, case reports clearly indicate the need for this knowledge, as alterations in reproductive function and an increase in violent behavior have been associated with AAS use. The goal of the present proposal is to investigate the effects of AAS on the central nervous system focusing on three specific questions. First, how do AAS influence sexual behavior and neuroendocrine function in adult male and female rats? Second, what is the impact of AAS on the display of aggression in adult male rats? A focus of this research proposal is to examine the effects of AAS on sexual behavior, neuroendocrine function and aggression in both gonadectomized and gonadally intact animals. Studies of AAS action in the gonadectomized rat allow for the determination of AAS actions in the absence of gonadal secretions, while analyses of AAS effects in the gonadally intact animal more closely mimic the human condition and permit evaluation of the interactions between AAS and endogenous hormones. The third goal of the proposed research is to determine the neural steroid receptors and brain areas at which AAS act in the brain using several strategies. First, the ability of AAS to compete with brain androgen, estrogen and corticosteroid receptors will be assessed. In addition, the extent to which AAS occupy cell nuclear receptors will be explored. Finally, changes in steroid receptor number which occur within specific brain areas as a consequence of chronic AAS will be examined. In all studies, special attention will be given to analyzing the effects of specific classes of AAS which are commonly abused, and comparing the behavioral and biochemical responses to different doses, dosing regimens, and durations of exposure to these drugs. Taken together, the results from these experiments will lead to a better understanding of the impact of AAS on human health and behavior.

During development, gonadal steroids (androgens and estrogens) confer permanent sex-specific differences (sexual dimorphism) onto the organization and function of the brain. This sexual dimorphism in the brain, in turn, leads to production of behavior that is different in male and female animals. The estrogens and androgens act during a very specific and limited period in early development to induce these permanent sex-specific differences in brain structure and in behavior. The best studied brain structure which is both sexually dimorphic and is known to be critical in mediating sex-specific behavior is the hypothalamus. We know that much of the information transfer in neurons in the hypothalamus depends upon the presence of a class of proteins called GABA (gamma-aminobutyric acid) receptors. The goal of this work is to determine if androgens and estrogens act during this critical period in early development to alter the types of GABA receptors that are expressed in the hypothalamus and to determine if steroid-dependent changes in GABA receptor expression lead to changes in sex-specific behaviors in adult animals. The results from this study may help us to understand how development in the brain is regulated to produce sex-specific behaviors.

DESCRIPTION (provided by applicant): Anabolic-androgenic steroids (AAS) are synthetic derivatives of testosterone originally designed for therapeutic uses. Although AAS continue to be used clinically today, the medical benefits of low therapeutic doses of AAS stand in sharp contrast to the potential health risks associated with the excessive doses self-administered by a growing number of recreational users. While the stereotypical AAS user is an adult male, recent studies indicate that the most rapid increases in AAS abuse are in females. In spite of this fact, few studies have assessed AAS effects on behavior in females, and no studies have been performed to test if AAS act through the same signaling mechanisms in the male and female brain. Heightened aggression is the most commonly described psychological effect of AAS use. Signaling mediated by androgen and estrogen receptors (AR and ER) is essential for the expression of innate aggression in both sexes: however the roles of AR and ER in mediating AAS-induced aggression are not known. The first goal of this proposal is to determine the dose-response characteristics of the aggression-promoting effects of a cocktail of commonly abused AAS, how AAS may alter cues important in eliciting aggressive behavior, and the importance of AR and ER signaling in mediating AAS-evoked aggression by experiments using pharmacological inhibitors of AR and ER and using mutant mice that lack functional AR or ER (specifically ERalpha). Importantly, this study will be the first to compare and contrast these effects in male and female mice. Neural transmission mediated by forebrain gamma-aminobutyric acid type A (GABAA) receptors is required for the expression of innate aggression. We have shown that AAS treatment alters forebrain GABAA receptor expression and function, but does so differently in male and female mice. The second goal of this proposal is to determine the dose-response characteristics for AAS-dependent changes in GABAA receptors in forebrain regions critical for the expression of aggression, the importance of AR and ER signaling in mediating those changes, and to further establish how the effects of AAS on forebrain GABAA receptors differ between male and female mice. To date over 60 AAS have been synthesized that vary in their estrogenic and androgenic properties. Data from these experiments will have important implications for understanding the effects each of these abused AAS may have on untoward aggression and if they will act differently in men and women. These data will also provide important new information on the mechanisms by which AAS elicit changes in synaptic transmission that may contribute to AAS-induced aggression in both the male and female brain. Such data may be relevant towards understanding not only the effects of AAS, but of other abused drugs that act via GABAergic pathways.

[unreadable] DESCRIPTION (provided by applicant): Sexual dysfunction, including disorders of sexual desire, arousal, orgasm and sexual pain, affects approximately 40% of American women, often with significant consequences on quality of life. Despite the prevalence, the causes of female sexual dysfunction remain poorly understood, and treatments are accordingly limited. Animal models of female sexual function have focused on the mechanics of sexual interaction, e.g., the lordosis reflex, limiting the generalizability of such findings for the understanding of sexual dysfunction in women. The goal of the proposed research is to take advantage of the tractability afforded by animal models, but to extend our analysis to include an integrated assessment of female sexual arousal and nociception; facets of sexual functioning that are applicable to women. Studies in Aim 1 will test the role of the medial preoptic area (mPOA) in sexual arousal in anesthetized female rats. In addition, the effects of inhibitors of phosphodiesterase type 5 (PDE-5) on female sexual functioning will be tested. In Aim 2, the role of peripheral estrogen receptors in vaginal nociception will be tested. The results garnered from these studies will address gaps in knowledge of the physiology of female sexual function that may improve the ability to diagnose and to treat sexual dysfunction in women. [unreadable] [unreadable] [unreadable]