Brain's 'switch' for long-term memory identified
http://www.indianexpress.com/news/brain-s--switch--for-longterm-memory-identified/1139531/
Scientists have identified calcium in the cell nucleus to be
a cellular "switch" responsible for the formation of long-term
memory.
Neurobiologists at Heidelberg
University in Germany used
the fruit fly Drosophila melanogaster as a model to investigate how the brain
learns.
The team led by Professor Dr Christoph Schuster and
Professor Dr Hilmar Bading wanted to know which signals in the brain were
responsible for building long-term memory and for forming the special proteins
involved.
The team from the Interdisciplinary
Center for Neurosciences
(IZN) measured nuclear calcium levels with a fluorescent protein in the
association and learning centres of the insect's brain to investigate any
changes that might occur during the learning process.
Their work on the fruit fly revealed brief surges in calcium
levels in the cell nuclei of certain neurons during learning. It was this
calcium signal that researchers identified as the trigger of a genetic
programme that controls the production of "memory proteins." If this
nuclear calcium switch is blocked, the flies are unable to form long-term
memory.
Schuster explained that insects and mammals separated
evolutionary paths approximately 600 million years ago. In spite of this
sizable gap, certain vitally important processes such as memory formation use
similar cellular mechanisms in humans, mice and flies, as the researchers'
experiments were able to prove.
"These commonalities indicate that the formation of long-term
memory is an ancient phenomenon already present in the shared ancestors of
insects and vertebrates. Both species probably use similar cellular mechanisms
for forming long-term memory, including the nuclear calcium switch,"
Schuster said.
The researchers assume that similar switches based on
nuclear calcium signals may have applications in other areas presumably
whenever organisms need to adapt to new conditions over the long term.
"Pain memory, for example, or certain protective and survival functions of
neurons use this nuclear calcium switch, too," said Bading.
"This cellular switch may no longer work as well in the
elderly, which Bading believes may explain the decline in memory typically
observed in old age. "Thus, the discoveries by the Heidelberg
neurobiologists open up new perspectives for the treatment of age- and
illness-related changes in brain functions," Bading said. The study was
published in the journal Science Signaling.
Estrogen helps women cope better with stress
http://www.indianexpress.com/news/estrogen-helps-women-cope-better-with-stress/1140029/
Women are better at coping with stress
than men due to the protective effect of female hormone estrogen, a new study
has claimed. Researchers from the University at Buffalo in US found that the enzyme
aromatase, which produces estradiol, an estrogen hormone, in the brain, is
responsible for female stress resilience.
"We have examined the molecular mechanism underlying
gender-specific effects of stress," said senior author Zhen Yan, a
professor in the Department of Physiology and Biophysics in the university.
"Previous studies have found that females are more resilient to chronic
stress and now our research has found the reason why," Yan said.
The research showed that in rats exposed to repeated
episodes of stress, females respond better than males because of the protective
effect of estrogen.
In the UB study, young female rats exposed to one week of
periodic physical restraint stress showed no impairment in their ability to
remember and recognise objects they had previously been shown. In contrast, young
males exposed to the same stress were impaired in their short-term memory.
An impairment in the ability to correctly remember a
familiar object signifies some disturbance in the signalling ability of the
glutamate receptor in the prefrontal cortex, the brain region that controls
working memory, attention, decision-making, emotion and other high-level
"executive" processes.
Last year, Yan and colleagues published in journal Neuron a
paper showing that repeated stress results in loss of the glutamate receptor in
the prefrontal cortex of young males. The new study shows that the glutamate
receptor in the prefrontal cortex of stressed females is intact.
The findings provide more support for a growing body of
research demonstrating that the glutamate receptor is the molecular target of
stress, which mediates the stress response, according to the study in the
journal Molecular Psychiatry.
The stressors used in the experiments mimic challenging and
stressful, but not dangerous, experiences that humans face, such as those
causing frustration and feelings of being under pressure, Yan said.
By manipulating the amount of estrogen produced in the
brain, the UB researchers were able to make the males respond to stress more
like females and the females respond more like males. "When estrogen
signalling in the brains of females was
blocked, stress exhibited detrimental effects on them. When
estrogen signalling was activated in males, the detrimental effects of stress
were blocked," Yan said. "We still found the protective effect of
estrogen in female rats whose ovaries were removed. It suggests that it might
be estrogen produced in the brain that protects against the detrimental effects
of stress," Yan said.