Brian Trainor Assistant Professor Department of Psychology University of California One Shileds Ave. Young Hall Davis, CA. Office phone: 530-752-1672 Email: Brian
Brian Trainor, Behavioral Neuroendocrinology Lab
University of California, Davis, CA.
Research
Current Research Interests
Introduction
Hormones are typically thought to influence behavior by increasing or decreasing the probability of its expression. Context is also critical, as behaviors are expressed under specific environmental and social conditions. In some cases, the effects of hormones on behavior depend on the environment. We have shown that the effects of estrogens on aggressive behavior in male mice (Peromyscus) depend on the amount of light they are exposed to each day. When mice are housed in a summer like photoperiod (16 hours of light per day), estrogens decrease aggression. However, if these same mice are housed in a winter-like photoperiod (8 hours of light per day), estrogens increase aggression. How can a simple environmental cue radically change the effects of estrogens on behavior and what is the relevance for human health? These are the questions that are the focus of several ongoing projects in the lab.
Genomic and Nongenomic Effects of Estrogens
Estrogens can affect physiology and behavior through two general pathways. Estrogens can alter the activity of neural cells by genomic action. This occurs when estrogens bind to classical estrogen receptors (ER alpha or ER beta) in the cytoplasm, enter the nucleus, and change gene expression (which ultimately changes leads to changes in proteins). In general, this process occurs slowly over the course of several hours or even days. This is why it is often necessary to wait several days or weeks for effects of hormone manipulations to occur. Estrogens can also change the activity of neural cells through non-genomic action. This occurs much more rapidly and involves the activation of second messenger systems within the cell. There is still some uncertainty as to which receptors are involved, as studies have suggested that classical ERs, unique membrane ERs and the orphan receptor GPR30 may all be involved in mediating non-genomic actions of estrogens. Nongenomic effects of estrogens on behavior have become an exciting research topic in the past few years. We are also exploring how these processes may be related to breast cancer.
Estrogens and Aggression
In Peromyscus, it appears that photoperiod determines whether estrogens act via genomic or nongenomic pathways in the brain. In the bed nucleus of the stria terminalis, a brain nucleus that influences aggressive behavior, genes that are estrogen-dependent are upregulated in long days compared to short days. The increased estrogen-dependent gene expression in long days suggests that estrogens may decrease aggression by changing gene expression. In contrast, we demonstrated that an injection of estradiol increases aggressive behavior within 15 minutes when mice are housed in short days. The same estradiol injection has no effect on behavior when mice are housed in long days. Most researchers agree that 15 minutes is not enough time frame for changes in gene expression (and protein) to occur, so this suggests that the effects of estradiol on aggression in short days is occurring though nongenomic pathways. We will be testing this hypothesis by using an estrogen agonist that can not enter the nucleus (thereby preventing changes in gene expression).
Media coverage of research
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Training
Post-doc: Ohio
State University, Randy
Nelson
Post-doc: Harvard University,
Hans Hofmann
PhD: University of Wisconsin, Cathy
Marler
MS: University of Nebraska, Alex
Basolo
BS: University of Texas:
Mike Ryan