Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Stress impairs thinking via mania-linked enzyme


An errant enzyme linked to bipolar disorder, in the brain’s prefrontal cortex, impairs cognition under stress, an animal study shows. The disturbed thinking, impaired judgment, impulsivity, and distractibility seen in mania, a destructive phase of bipolar disorder, may be traceable to overactivity of protein kinase C (PKC), suggests the study, funded by the National Institutes of Health’s (NIH) National Institute of Mental Health (NIMH) and National Institute on Aging (NIA), and the Stanley Foundation. It explains how even mild stress can worsen cognitive symptoms, as occurs in bipolar disoder, which affects two million Americans.

Abnormalities in the cascade of events that trigger PKC have also been implicated in schizophrenia. Amy Arnsten, Ph.D. and Shari Birnbaum, Ph.D. of Yale University, and Husseini Manji, M.D., of NIMH, and colleagues, report on their discovery in the October 29, 2004 issue of Science.

"Either direct or indirect activation of PKC dramatically impaired the cognitive functions of the prefrontal cortex, a higher brain region that allows us to appropriately guide our behavior, thoughts and emotions," explained Arnsten. "PKC activation led to a reduction in memory-related cell firing, the code cells use to hold information in mind from moment-to-moment. Exposure to mild stress activated PKC and resulted in prefrontal dysfunction, while inhibiting PKC protected cognitive function."

"In the future, drugs that inhibit PKC could become the preferred emergency room treatments for mania," added Manji, currently Director of NIMH’s Mood and Anxiety Disorders Program, who heads a search for a fast-acting anti-manic agent. "All current treatments – lithium, valproate, carbamazepine and antipsychotics – take days, if not weeks, to work. That’s because they’re likely acting far upstream of where a key problem is, namely in the PKC pathway. Since PKC inhibitors could act more directly, they might quench symptoms more quickly. Patients could carry PKC inhibitors and take them preventively, as soon as they sense a manic episode coming on."

Clinical trials of a PKC inhibitor, the anti-cancer drug tamoxifen, are currently underway in bipolar disorder patients. However, these may be more important for proof-of-concept than therapeutic utility, according to Manji, who says side effects will likely rule out tamoxifen itself as a practical treatment for mania. "While there are likely other pathways involved, PKC appears to be very important for bipolar disorder," he noted.

The fact that the current anti-manic drugs ultimately reduce PKC activity suggests that PKC may be a final common target of these treatments and may play a key role in bipolar disorder. Studies have also found signs of increased PKC activity in bipolar patients’ blood platelets and in the brain cells of deceased patients. Susceptibility to bipolar disorder may involve variants of genes that code for a key PKC precursor and for a stress-sensitive signaling protein that normally puts the brakes on PKC activity.

The new study shows how PKC triggers cognitive symptoms in response to stress. When the stress-sensitive messenger chemical norepinephrine binds to receptors on cell membranes in the prefrontal cortex, it activates PKC through a cascade of events. The enzyme then travels out to the cell membrane, opening ion channels that heighten the cell’s excitability, and stoking protein machinery that propels neurotransmitters into the synapse. PKC also moves into the cell’s nucleus, where it turns-on genes.

To tease out PKCs role, the researchers selectively targeted the prefrontal cortex in rats and monkeys performing working memory tasks with PKC activators, inhibitors, norepinephrine-like and stress inducing drugs – alone and in combination. They also found that by blocking PKC, the anti-manic drugs lithium and carbamazepine protected monkeys’ prefrontal cortex functioning from impairment by a norepinephrnine-like drug.

The researchers traced impairment to a reduction in memory-related firing of single cells in the prefrontal cortex, which was reversible by a PKC inhibitor.

Genetic and biochemical studies indicate that PKC may also be overactive in the brains of patients with schizophrenia. Antipsychotics, which are used to treat bipolar disorder as well as schizophrenia, block receptors in the brain that activate PKC.

Jules Asher | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Biologists unravel another mystery of what makes DNA go 'loopy'
16.03.2018 | Emory Health Sciences

nachricht Scientists map the portal to the cell's nucleus
16.03.2018 | Rockefeller 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: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>