I have always been interested in understanding the biological underpinnings of behavior with special emphasis on sex differences in both brain and behavior. Since I was an undergraduate, I have engaged in research that focused on how males and females differ in terms of their brains and the resultant behavioral differences that arise from this dimorphism. As such I have been involved in research projects ranging from how perinatal alcohol exposure affects male and female offspring to how males and females differ in terms of preferred patterns of sexual behavior to sex differences in susceptibility to addiction.This theme of sex differences is ever present among the animal research that I conduct. Much of the research that I conduct involves students who take general themes of interest and tweak them so as to make their own projects which dovetail with my own research interests.
One of the first projects that I worked on here at Mercer involved investigating how perinatal exposure to the phytoestrogen, genistein, would alter the display of sexually dimorphic behaviors in adolescent and adult rats. Genistein is a naturally occurring estrogenic compound found in fairly high concentrations in soy, legumes, and alfalfa. Estrogen plays an important role in normal sexual differentiation; and given that many infant formulas and dietary supplements marketed to pregnant women contain these ingredients, many researchers have focused their attention on the potential adverse consequences of this compound might be. There is a plethora of research suggesting that genistein exposure results in abnormalities in the reproductive tract as well as increased chances of developing certain types of cancer. However, very little research exists on the potential effects that genistein exposure may have on sex-typical behavior. Rodents, like primates, display sex differences in juvenile play behavior with males engaging in more "rough and tumble" play than females.
Therefore, I chose to investigate whether genistein altered the nature of play behavior patterns displayed by both males and females exposed to genistein during critical periods of development.Also, I investigated whether the display of normal sexual behavior in these animals once they reached sexual maturity. Although I have only collected limited data to this point, there have been some interesting observations made early on. Specifically, females exposed to genistein tend to exhibit "male-like" patterns of play behavior as adolescents, while males tend to exhibit less consistent patterns of sexual behavior as adults compared to control animals
Aside from genistein research, I have also become keenly interested in an increasingly popular recreational drug, salvia. Salvinorin A (SA)is the primary psychoactive agent in salvia and is classified as a kappa-opioid agonist. However, recent research suggests that SA may directly interact with thedopamine system. Given dopamine's role in mediating the reinforcing properties of various drugs of abuse, SA may have abuse potential.Currently, there is very little published research investigating this possibility, and the research that does exist is somewhat equivocal with some researchers observing conditioned place preferences (CPP) for drug -paired chambers and others showing conditioned place aversions.
I am investigating, in collaboration with Dr. Katie Norhcutt and Juan Salvatierra (a former Mercer University student who majored in Psychology and Biology) whether several different doses (0.1, 10, or 50 micrograms/kg) of SA would support the development of CPP in the rat. We are also investigating whether repeated SA administration has any effect on psychomotor activation. Finally, we are examining whether there are differences in the activity of dopaminergic neurons by counting cells in the substantia nigra and ventral tegmental area that are double-labeled for tyrosine hydroxylase and c-fos.Thus far,we have observed a conditioned place preference in those animals receiving 10 micrograms/kg salvinorin a, that these same animals had a higher level of locomotion after repeated administration of SA, and thatthere were a significantly higher number oftyrosine hydroxylase/c-fos double-labeled cells in the substantia nigraof these animals. The other doses we tested did not support conditioned place preferences or aversions, resulted in no significant differences in locomotor activity, and no differences in cell counts in the brain areas examined. This suggests that, at least at some doses, SA may indeed represent a potential drug of abuse that directly affects the dopamine system and the motor responses that it generates (view poster).
Recently, Dr. Northcutt, Rebecca Gregory (former Mercer student who majored in Psychology and Women's Studies), and I conducted a project investigating the effects that adolescent exposure to fluoxetine (Prozac) has on adult female sexual behavior. Fluoxetine is the only antidepressant medication currently available that is approved for use in adolescents.While the short-term side effects of fluoxetine are well-researched, very few researchers have focused on the potential long-term side effects that might exist from use of the drug, This is especially interesting among adolescent users given that their nervous system is still undergoing development during this period of time, and therefore, they might be more vulnerable to these potential effects. There is some research to suggest that male rats exhibit long-term changes in the display of their sexual behavior as a result of exposure to fluoxetine during a period of life that is roughly equivalent to human adolescence. However, there is no published research on what effects if any this type of exposure would have on female rat sexual behavior. Therefore, we conducted a study to investigate this possibility.
Adolescent female rats were exposed to 0, 10, or 50 mg/kg fluoxetine and then were left undisturbed until they reached sexual maturity.They were then allowed to interact with adult male rats and their behavior was videorecorded and was scored for measures of receptivity and proceptivity.We also analyzed the medial preoptic area and ventromedial nucleus of the hypothalamus for differences in serotonin receptor distribution. Fluoxetine exposure had no effect on female rat's receptivity or proceptivity. However, fluoxetine-exposed animals did receive a significantly higher number of sexual contacts from the males.There was no difference in the serotonin receptor distribution in the brain areas examined (view poster).