Gambel’s White-Crowned Sparrow Provides a Medical Breakthrough

October 5, 2007 by  
Filed under Features

There may be new hope on the horizon for sufferers of age related degenerative brain diseases such as Parkinson’s and dementia. This is thanks to a little song bird species known as Gambel‘s white-crowned sparrow. Scientists have discovered that an extraordinary change takes place every year in the brains of these tiny song birds and it is hoped that understanding the mechanisms that control this change may assist researchers in the development of treatments for these diseases.

Scientists have noted that under certain conditions there is significant shrinkage in the size of the regions of the brain that control the singing behavior of the Gambel’s white-crowned sparrow. This drastic change is triggered by the withdrawal of the naturally occurring steroid hormone testosterone and the change is apparent within 12 hours. This scientific study is the first to report such a rapid regression of brain nuclei as a response to the withdrawal of a hormone and change in daylight conditions.

Once testosterone is removed from circulation, it takes just 12 hours for the volume of the song-control region, known as the HVC, to collapse. By the fourth day, thousands of HVC neurons have been destroyed. It is believed that this destruction is carried out by a cell suicide program known as apoptosis.

Natural seasonal changes were simulated and the effect on the brain of the sparrows monitored. It was noted that the song-control regions of the brain expands in the spring and summer. The purpose of this is to establish territories and attract mates for the Alaskan breeding season. Later in the summer, the same brain regions shrink as they prepare to migrate back to California. Similar research connected to seasonal changes has been carried out on the brains of reptiles, fish, amphibians and mammals such as mice, gerbils and even humans. But the degree of change in birds is far more significant than observed in other animals.

With the objective of gaining a better understanding of what happens the in song bird’s brain, the researchers were granted federal and state permits to capture 25 male birds. These were kept in captivity for 12 weeks and then exposed to 20 days of simulated long-day conditions which are comparable to what the sparrows would naturally experience during the breeding season in Alaska. In addition, the birds received testosterone implants.

With the approval of the UW’s Institutional Animal Care and Use Committee and the National Institute of Mental Health, at the end of the 20 days 6 of the birds were euthanized. The remaining 19 birds were castrated as well as having the implants removed to ensure that no testosterone would be circulating in their systems. The remainder of the birds were euthanized at pre-determined intervals.

The results of the research strongly indicate that regions of the brain that are sensitive to hormonal changes regress without testosterone. Conversely, an increase in hormones such as testosterone, could serve to protect neurons. These findings have led researchers to the conclusion that some form of hormone replacement therapy may provide protection against neurodegeneration, providing hope for people who suffer from age related degenerative brain diseases.

So next time you hear one of these little song birds calling, remember that the Gambel’s white-crowned sparrow could provide answers for scientists who are searching for ways to bring relief to thousands of people.

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