Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rats depleted of salt become sensitized to amphetamine, show unusual growth of brain cells

04.06.2002


Laboratory rats that have been repeatedly depleted of salt become sensitized to amphetamine, exhibiting an exaggerated hyperactive response to the drug and an unusual pattern of neuronal growth in a part of their brains, neuroscientists have found.



The researchers, headed by University of Washington psychologist Ilene Bernstein, discovered that nerve cells in the nucleus accumbens of sensitized rats have more branches and were 30 percent to 35 percent longer than normal. The nucleus accumbens, located in the forebrain, is involved in the reward and motivation system in rats and in humans. It is associated with regulating motivated behaviors of such natural drives as those for food and salt, and for artificial rewards provided by drugs.

The findings are published in the current issue of the Journal of Neuroscience.


"This number, 30 to 35 percent, is startling and implies an ability for neurons to make more connections," said Bernstein.

The research was triggered by several recent papers. One reported that rats sensitized to amphetamine showed this type of neuron growth. A second found that rats deprived of food seemed to be amphetamine sensitized. When an animal or person becomes sensitized their behavior changes. With amphetamine, animals and people become hyperactive. Rats that are salt sensitized drink and eat salt more rapidly and in greater quantities. Why they behave this way is unknown, Bernstein said.

"That research and ours seem to indicate that being hungry or sodium deprived enough can change an animal’s or a person’s response to a drug even if they have not been exposed to the drug previously," she said.

"We don’t know if this holds up in humans. But the same part of the brain and the response to drugs holds up across species. The same systems are involved in rats and humans when it comes to amphetamines and cocaine. This suggests evidence of a common natural substrate to natural and artificial rewards that is worth further investigation."

She added that the findings also point to questions that need to be explored. These include determining how long cross sensitization persists and whether physical challenges such as salt depletion alter people’s responses to drugs.

"There is differential response among people who are challenged or stressed based on their history. Some people may have a life-long susceptibility to these kinds of things. We also need to know why these drugs are so powerful and what systems they are taking advantage of that didn’t evolve naturally."

In the study, the researchers first gave a group of rats diuretics to deplete them of salt. Then they gave the animals a 3 percent saltwater solution, a mixture they ordinarily would not like or drink. This procedure was repeated two more times, with each treatment given a week apart.

Then the animals’ brains were examined under a microscope, revealing the 30 percent to 35 percent increase in neuron growth in the nucleus accumbens compared to the brains of normal rats. The ends of brain cells, or dendrites, are where neurons make connections with other neurons, implying an ability to make more connections, said Bernstein.

To check for cross sensitization to amphetamine, another group of rats was salt depleted twice. Then they were allowed to explore an open, dark plastic enclosure with the floor divided into a grid by white tape. A week after the second salt depletion, the rats and a control group of animals were injected with amphetamine and placed in the enclosure.

The psychostimulant effects of the drugs were measured by two behaviors – the number of taped lines each animal crossed over and how many times it reared up on its hind feet. The two groups didn’t differ in the number of lines each crossed, but the salt-depleted rats showed significantly more rearing behavior.

What was particularly striking about the findings is that they occurred relatively quickly, just two weeks after the first salt-depletion treatment, said Bernstein.


Other members of the research team included Mitchell Roitman, a UW graduate who is now a post-doctoral researcher at the University of North Carolina, and Theresa Jones, an assistant psychology professor at the University of Texas. The UW’s Royalty Research Fund supported the research.

For more information, contact Bernstein at (206) 543-4527 or ileneb@u.washington.edu


Joel Schwarz | EurekAlert

More articles from Life Sciences:

nachricht Fine organic particles in the atmosphere are more often solid glass beads than liquid oil droplets
21.04.2017 | Max-Planck-Institut für Chemie

nachricht Study overturns seminal research about the developing nervous system
21.04.2017 | University of California - Los Angeles Health Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>