Lack of enzyme creates skewed response to fear

August 12th, 2011 - 5:14 pm ICT by IANS  

Washington, Aug 12 (IANS) Do you run away when you should stay or stay when you should run away? If so, an enzyme deficiency might be to blame, a US medical study suggests.

Mice lacking a certain enzyme due to genetic mutation develop a topsy-turvy response to fear. For instance, they may show defensive behaviour, biting or tail rattling, in the presence of plastic bottles.

However, in the presence of real danger, these mice are found less cautious or defensive than their siblings, the International Journal of Neuropharmacology reports.

“Our findings suggest that monoamine oxidase A (moA) deficiency leads to a general inability to appropriately assess contextual risk,” said senior study author Jean C. Shih, professor of pharmacology at the University of Southern Californa.

MoA is the main enzyme in the brain that breaks down neurotransmitters such as 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, according to the study.

This study, currently only conducted on mice, is among the first to clarify that perceived aggressiveness may have been 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, post-doctoral research associate at Southern California and study co-author.

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