Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mothers Turn Fearless When Peptide Level Drops

03.08.2004


Everyone knows not to get between a mother and her offspring. What makes these females unafraid when it comes to protecting their young may be low levels of a peptide, or small piece of protein, released in the brain that normally activates fear and anxiety, according to new research published in the August issue of Behavioral Neuroscience.


A female mouse gathers, grooms and nurses her 3-day-old pups in the research lab of assistant professor of zoology Stephen Gammie. Gammie has studied the link between maternal aggression in mice and levels of a peptide hormone that controls behavior, particularly an animal’s response to fear and anxiety. Photo by: Michael Forster Rothbart


View from below as a female mouse gathers her 8-day-old pups in the research lab of assistant professor of zoology Stephen Gammie. Gammie has studied the link between maternal aggression in mice and levels of a peptide hormone that controls behavior, particularly an animal’s response to fear and anxiety.Photo by: Michael Forster Rothbart



"We see this fierce protection of offspring is so many animals," says Stephen Gammie, a University of Wisconsin-Madison assistant professor of zoology and lead author of the recent paper. "There are stories of cats rescuing their kittens from burning buildings and birds swooping down at people when their chicks are on the ground."

In terms of biology, it makes sense that mothers would lay down their own lives to protect their offspring, especially if it means the parents’ genes will be passed down to the next generation, says Gammie.


But he adds that despite all the observations and the theories explaining why mothers display this behavior - commonly known as maternal aggression - very little research has investigated the biological mechanisms that turn on this trait in new mothers.

"We’ve known for a long time that fear and anxiety decrease with lactation," explains Gammie. "Maybe it’s this decrease that allows mothers to attack during a situation that normally would evoke a fear response."

Testing this hypothesis, the Wisconsin professor and his colleagues studied the link between maternal aggression in mice and levels of corticotropin-releasing hormone (CRH), a peptide that acts on the brain to control behavior.

About six days after a group of mice gave birth, the new mothers received injections containing either one of three doses of CRH or a saline solution with no amount of the peptide. Following each injection, which was given once a day for four consecutive days, the researchers returned the mother mice to their pups. Twenty-eight minutes later, the researchers removed the pups and introduced a male intruder.

Under normal conditions, female rodents will fiercely attack the males, says Gammie, noting that the males sometimes eat pups and that "the best defense for the mom is the offense."

For the study, only the mice that received either no dose or a low dose of the peptide displayed the expected behavior. As the levels of CRH increased, the number of attacks and the duration of them dramatically decreased.

The results show, for example, that while the mice with the lowest levels of CRH attacked more than 20 times for the duration of about 45 seconds, the mice with moderate levels of the peptide attacked about six times over about eight seconds. Mice with the highest levels of CRH didn’t attack at all.

"When we put the male in the cage, some moms would just sit there. They weren’t protective at all. If anything they were skittish. They showed a fear response," says Gammie.

The researchers note that altering the levels of the peptide appeared to affect only maternal aggression; normal maternal behaviors, such as nursing, were observed in all mothers both before and after the encounters with male mice.

Based on the results, Gammie says, "Low CRH levels appear to be a necessary part of maternal aggression. If you don’t keep them low, you won’t see this fiercely protective behavior."

He adds that this finding - some of the first evidence suggesting a biological mechanism that enables parents, regardless of the potential danger, to defend their offspring - may also begin to explain why mothers occasionally neglect or harm their offspring.

"Postpartum depression in some individuals has been linked to higher levels of CRH release and an overly active stress response," explains Gammie. "If CRH needs to be low to see maternal protection of offspring, as our work suggests, then it explains why moms with high postpartum depression and high CRH not only may neglect, but also may abuse, their children."

| newswise
Further information:
http://www.wisc.edu

More articles from Life Sciences:

nachricht Stiffness matters
22.02.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Separate brain systems cooperate during learning, study finds
22.02.2018 | Brown University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Stiffness matters

22.02.2018 | Life Sciences

Magnetic field traces gas and dust swirling around supermassive black hole

22.02.2018 | Physics and Astronomy

First evidence of surprising ocean warming around Galápagos corals

22.02.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>