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Rodent Models Used To Analyze Behavior

Stephanie Pace

Revue : BBC news on line

A UC Berkeley psychology researcher is experimenting with inbred mouse strains to forage for insight into how genes affect behavioral traits and emotionality. The research shows that prenatal and postnatal environments are also useful in determining adult behavior in mice.
?Why are some people highly responsive and highly reactive to stress? Why are some people calm and mellow?? said Darlene Francis, a professor in the School of Public Health and a researcher in the Helen Wills Neuroscience Institute.
Francis claims that it is more likely that the development of behavioral traits result more from environmental factors during development rather than from genetic differences between offspring.
?We?re using rat and mice models as mathematical approaches to research and as an alternative system to ask questions we can?t ask in people,? Francis said.
According to Francis, the mechanisms of gene regulation are similar among rats, mice and humans. Though there are critical variables in humans that are different from rat and mice models, the mechanism by which genes are regulated are the same, Francis said.
To investigate the biological basis of stress responses and differences in stress levels, Francis works with animal models to design experiments that cannot be duplicated in the real world.
?I think it?s fundamentally and inherently interesting why we are all so different. You know how you were raised and you know that what happens early in life are important on a fundamental level. So we are looking at a biological basis for these differences,? Francis said.
Francis ordered inbred mouse strains, each strain being genetically identical, from breeders. She then extracted embryos from each of these strains and placed them in a uterine environment. Using this animal model, researchers can control genetics, so any observed differences are likely to be due to the environment.
Stress can contribute to illness, ranging from autoimmune disorders to mental illness. The emotional and cognitive responses to stressors directly affect the development of brain structures, which can upset learning. Francis proposes that high-stress conditions created by poor parenting can cause anxiety in adulthood.
?The quality of parenting is important. The early years and environment for a developing child is important in molding who you become as an adult. Animal models help us study and ask questions in the context of stress responses,? Francis said.
Applying principles of psychopathology and neuroscience, Francis hopes to discover some of the many mechanisms of how stress can influence health.
?Berkeley is really interested now in fostering interdisciplinary research,? Francis said. ?I am working with students from integrative biology, psychology, neuroscience and social welfare, and so I?m not being constrained to one department as a single way of thinking but am also able to work with different people with different perspectives to offer.?
By focusing on early life events in individual rats and mice whose developments were formed by varying levels of stress, Francis was able to establish correlations among increased stress reactivity, exposure to stress hormones and the susceptibility to stress-induced illness.
According to Francis, different kinds of maternal care may contribute to behavior. For example, maternal licking in rodents, a basic postnatal mechanism, has shown to affect stress hormone regulation and maze learning.
However, the most divisive question on the minds of most clinical researchers today is whether a mother?s influence is the primary force in her offspring?s behavior. For decades, researchers have struggled to address the effects of maternal factors in the development of offspring.
?People now are looking at kids who have suffered sexual trauma, violence and abuse and we know that this has a permanent effect on the brain and on your behavior. People are now finding the neurological and biological correlates in humans and finding that particular areas of the brain are more sensitized after these traumatic events or after a stressful early life. This really sets the tone for how you live your life,? Francis said.
The rat and mice mothers affected by environmental challenges, such as scarcity of food, social instability and low dominance status, were shown to be more timid and fearful in raising their pups. Thus, these infants grew to be more submissive and less playful as adults than their counterparts whose mothers had easy access to food and predictable social environments.
This concept of specialized rearing of offspring by the mother raises a controversial question of whether the mothers are to blame for their children?s stress responses and personalities. According to Francis, they are not.
She also cautions against drawing too close a connection between the animal and human social systems.
?For rat pups, the only available resources they have are their moms. On the other hand, humans live such a longer period of time and have so many other resources available, which enhance the quality of parenting. There are moms and dads and communities and grandparents and so the opportunity to get parenting right is much greater than in animal models. People are often rash in jumping from rats to humans,? Francis said.

Friday, 1 April, 2005, 15:58 GMT 16:58 UK

 

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