Do you run when you should stay? Are you afraid of all the wrong things? An enzyme deficiency might be to blame, reveals new research in mice by scientists at the University of Southern California.
In a paper appearing in the October 2011 issue of the International Journal of Neuropharmacology, USC researchers show that mice lacking a certain enzyme due to genetic mutation are unable to properly assess threat. The mice exhibited defensive behaviors (such as biting or tail rattling) in the presence of neutral stimuli, such as plastic bottles.
Conversely, in the presence of true danger cues such as predator urine or an anesthetized rat, the mice with the enzyme mutation were less cautious and defensive than their littermates, even climbing on the unconscious rat.
Mice without the enzyme also took longer to leave an open chamber, indicating reduction in exploratory and escape tendencies.
"Taken together, our findings suggest that monoamine oxidase A deficiency leads to a general inability to appropriately assess contextual risk, as indicated by the inappropriateness of their defensive behaviors," said senior author Jean C. Shih, University Professor and Boyd and Elsie Welin Professor of pharmacology and pharmaceutical sciences in the USC School of Pharmacy.
Monoamine oxidase A is the main enzyme in the brain that breaks down serotonin, norepinephrine and dopamine, which have been shown to contribute to the "fight or flight" impulse by raising heart rates and increasing blood and oxygen flow. Previous research in Shih's lab and elsewhere has shown that deficiency in monoamine oxidase A causes aggression in mice and humans, but this study is among the first to clarify that what was perceived as aggressiveness may more accurately be described as an inability to properly adapt and respond to environmental cues.
"Mice without monoamine oxidase A exhibited a distinct inability to attune their response to the situation," said Sean Godar, a post-doctoral research associate at the USC School of Pharmacy and co-lead author of the study. "The paradoxical responses to neutral and fear-inducing stimuli are markedly reminiscent of deficits in facial affect processing in schizophrenia and autism."
The researchers found no significant differences in sensory ability between the mice with a monoamine oxidase A deficiency and their littermates — both groups found buried mini-chocolate cereal chips at about the same rate, on average, and were similarly able to traverse a ledge and recognize objects.
"When compared to the broader, multi-faceted behavioral repertoire of other mice, the behavior observed in mice without monoamine oxidase A may reflect a limited range of emotional responses and flexibility," said Marco Bortolato, co-lead author of the study and research assistant professor of pharmacology and pharmaceutical sciences at the USC School of Pharmacy.
The researchers suggest that the strange defensive behavior exhibited by the enzyme-deficient mice may actually reflect a limited range of adaptive responses and lack of emotional flexibility — the mice may only have one gear for fear.
The research was supported by a MERIT Award and a research grant from the National Institute of Mental Health, National Institutes of Health; the Boyd and Elise Welin Professorship, held by Shih; and a Zumberge Research Individual Grant, awarded to Bortolato.
Roberto Frau, Mona Dousti and Kevin Chen, all in Shih's laboratory at the USC School of Pharmacy, were also co-authors of the study.
Godar et al., "Maladaptive defensive behaviors in monoamine oxidase A-deficient mice." International Journal of Neuropharmacology: October 2011.
Suzanne Wu | EurekAlert!
Researchers release the brakes on the immune system
18.10.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn
Norovirus evades immune system by hiding out in rare gut cells
12.10.2017 | University of Pennsylvania School of Medicine
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
19.10.2017 | Materials Sciences
19.10.2017 | Materials Sciences
19.10.2017 | Physics and Astronomy