Does motherhood dampen cocaine's effects?

October 15, 2012

Mother rats respond much differently to cocaine than female rats that have never given birth, according to new University of Michigan research that looks at both behavior and brain chemistry.

The findings may help lay the groundwork for more tailored human , based on scientific understanding of how gender, hormones and life experience impact drug use.

In an oral presentation at the Society for Neuroscience meeting, U-M researcher Jennifer Cummings, Ph.D., summarized findings from experiments with rats at the Molecular and Behavioral Neuroscience Institute, part of the U-M Medical School. She worked with Jill Becker, Ph.D., of the U-M Department of Psychology.

They identified clear differences in how intensely the "pleasure centers" in the mother rats' brains reacted to the drug, compared with non-mothers. Mother rats' brains released less of a chemical called dopamine, which helps cause the "high" from cocaine.

They also found an interaction with stress: mother rats that were exposed to periods of increased stress weren't willing to work as hard to get a dose of cocaine, compared with rats that had never given birth or mother rats that weren't exposed to the stress – even though the stressed mother rats showed an increased tendency to use cocaine when it was easy to get.

Taken together, the findings suggest that the experience of becoming a mother alters a female's overall response to cocaine – adding complexity to the issue of how best to treat addiction.

"While we have not yet identified a mechanism to explain these differences, they do suggest that the reward system and affected by cocaine is changed with maternal experience," says Cummings, a research investigator at MBNI and former postdoctoral fellow in Becker's laboratory. "The next step is to determine how factors such as hormone changes in pregnancy and early motherhood, and the experience of caring for offspring, might be differentially contributing to this response."

While rats and people are admittedly very different, research on rodents allows scientists like Cummings and Becker to study and drug-related behavior in detail, and pave the way for translating those findings to human drug treatment. With drug use and abuse among women on the rise, gender-specific understanding and treatment is becoming more important than ever, Cummings says.

In general, researchers already know that motherhood can give animals a better memory and ability to navigate compared with non-mothers – and that these effects last beyond the time that the mother is caring for her offspring.

The new research used a system that gave rats access to cocaine if they poked a dispenser with their noses a minimum number of times.

At first, when the number of pokes needed to get a dose was low, the mother rats took more drug than the non-mothers after exposure to a brief, stressful situation. But as the researchers ramped up the number of pokes needed to as high as 70, the stressed mothers became more likely to stop seeking doses.

The researchers also used a technique called microdialysis to measure the level of dopamine in the rats' brains, especially in an area called the nucleus accumbens which is considered the brain's "pleasure center."

In this measurement of neurological response, the mother rats' dopamine levels after receiving cocaine were much lower than those of non-mothers.

"Even though there was reduced dopamine release in the nucleus accumbens of rats that had been mothers, many of their behavioral responses to cocaine were the same or greater than non-mothers, indicating that there are downstream long term changes to the brains of the rats that had been mothers," says Becker.

The research focused on that had given birth to and reared one litter of pups, compared with those that were virgins. Future experiments, Cummings says, might look at the impact of those that gave birth but didn't rear their pups, and those that reared pups born to other rats but never gave birth themselves.

Only through this careful research can the impact of hormones be teased apart from the impact of the actual motherhood experience.

Explore further: Chronic stress during pregnancy prevents brain benefits of motherhood, study shows

More information: Citation: Program No. 418.07. 2012 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2012. Online.

Related Stories

Chronic stress during pregnancy prevents brain benefits of motherhood, study shows

October 14, 2012
A new study in animals shows that chronic stress during pregnancy prevents brain benefits of motherhood, a finding that researchers suggest could increase understanding of postpartum depression.

A mother's touch may protect against drug cravings later

December 6, 2011
An attentive, nurturing mother may be able to help her children better resist the temptations of drug use later in life, according to a study in rats conducted by Duke University and the University of Adelaide in Australia.

Recommended for you

The neural codes for body movements

July 21, 2017
A small patch of neurons in the brain can encode the movements of many body parts, according to researchers in the laboratory of Caltech's Richard Andersen, James G. Boswell Professor of Neuroscience, Tianqiao and Chrissy ...

Faulty support cells disrupt communication in brains of people with schizophrenia

July 20, 2017
New research has identified the culprit behind the wiring problems in the brains of people with schizophrenia. When researchers transplanted human brain cells generated from individuals diagnosed with childhood-onset schizophrenia ...

Scientists discover combined sensory map for heat, humidity in fly brain

July 20, 2017
Northwestern University neuroscientists now can visualize how fruit flies sense and process humidity and temperature together through a "sensory map" within their brains, according to new research.

Scientists reveal how patterns of brain activity direct specific body movements

July 20, 2017
New research by Columbia scientists offers fresh insight into how the brain tells the body to move, from simple behaviors like walking, to trained movements that may take years to master. The discovery in mice advances knowledge ...

Team traces masculinization in mice to estrogen receptor in inhibitory neurons

July 20, 2017
Researchers at Cold Spring Harbor Laboratory (CSHL) have opened a black box in the brain whose contents explain one of the remarkable yet mysterious facts of life.

Speech language therapy delivered through the Internet leads to similar improvements as in-person treatment

July 20, 2017
Telerehabilitation helps healthcare professionals reach more patients in need, but some worry it doesn't offer the same quality of care as in-person treatment. This isn't the case, according to recent research by Baycrest.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.