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 Phagocytes versus killer cells - A closer look into the tumour tissue
21.10.2019 | Universität Duisburg-Essen

nachricht How intestinal cells renew themselves – the role of Klumpfuss in cell differentiation
21.10.2019 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Solving the mystery of quantum light in thin layers

A very special kind of light is emitted by tungsten diselenide layers. The reason for this has been unclear. Now an explanation has been found at TU Wien (Vienna)

It is an exotic phenomenon that nobody was able to explain for years: when energy is supplied to a thin layer of the material tungsten diselenide, it begins to...

Im Focus: An ultrafast glimpse of the photochemistry of the atmosphere

Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay between radiation and matter. Light strikes particles...

Im Focus: Shaping nanoparticles for improved quantum information technology

Particles that are mere nanometers in size are at the forefront of scientific research today. They come in many different shapes: rods, spheres, cubes, vesicles, S-shaped worms and even donut-like rings. What makes them worthy of scientific study is that, being so tiny, they exhibit quantum mechanical properties not possible with larger objects.

Researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National...

Im Focus: Novel Material for Shipbuilding

A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.

The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...

Im Focus: Controlling superconducting regions within an exotic metal

Superconductivity has fascinated scientists for many years since it offers the potential to revolutionize current technologies. Materials only become superconductors - meaning that electrons can travel in them with no resistance - at very low temperatures. These days, this unique zero resistance superconductivity is commonly found in a number of technologies, such as magnetic resonance imaging (MRI).

Future technologies, however, will harness the total synchrony of electronic behavior in superconductors - a property called the phase. There is currently a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Symposium on Functional Materials for Electrolysis, Fuel Cells and Metal-Air Batteries

02.10.2019 | Event News

NEXUS 2020: Relationships Between Architecture and Mathematics

02.10.2019 | Event News

Optical Technologies: International Symposium „Future Optics“ in Hannover

19.09.2019 | Event News

 
Latest News

Fraunhofer LBF and BAM develop faster procedure for flame-retardant plastics

21.10.2019 | Materials Sciences

For EVs with higher range: Take greater advantage of the potential offered by lightweight construction materials

21.10.2019 | Materials Sciences

Benefit and risk: Meta-analysis draws a heterogeneous picture of drug-coated balloon angioplasty

21.10.2019 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>