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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 7 of 7. This is the beginning of the thread.
Posted by SLS on February 5, 2005, at 5:27:35
NEW NEURONS BORN IN ADULT RAT CORTEX
Recent evidence suggesting that antidepressants may act by triggering the birth of new neurons in the adult hippocampus,* the brain's memory hub, has heightened interest in such adult neurogenesis and raised the question: Could new neurons also be sprouting up in the parts of the adult brain involved in the thinking and mood disturbances of depression and anxiety?
Now, scientists at the National Institute of Health's (NIH) National Institute of Mental Health (NIMH) have found newly born neurons that communicate via the chemical messenger GABA (gamma-aminobutyric acid) in adult rat cortex, seat of higher order "executive" functions, and in the striatum, site of habits, reward and motor skill learning. In the cortex, the new neurons appear to arise from previously unknown precursor cells native to the area, rather than from cells migrating in from another area. NIMH's Drs. Heather Cameron, Alexandre Dayer, and colleagues, report on their findings in the January 31, 2005 "Journal of Cell Biology".
Their discovery adds to the scientific debate over adult neurogenesis, which has potential implications for understanding a variety of brain disorders, possibly including Alzheimer's and schizophrenia. While most researchers agree that new neurons are generated in the adult hippocampus and olfactory bulb, the existence of adult neurogenesis in other brain regions remains controversial.
The NIMH team used many more markers than previous studies to track newborn neurons as they matured and to identify the type of neurotransmitters they secreted. The markers exploited antibody affinities for specific proteins to tag particular cell types with telltale color codes, visible on brain slices under fluorescence with a laser-powered microscope.
The researchers found that the cortex and striatum were giving birth to new, widely scattered small cells, called interneurons, that make and secrete GABA, a neurotransmitter that dampens neuronal activity. The new interneurons closely resembled those seen in the hippocampus and olfactory bulb and seemed to arise at similar rates. Interneurons are thought to play a role in regulating larger types of neurons that make long-distance connections between brain regions and predominate in these areas.
The NIMH team was surprised to find that the new cortex interneurons appeared to arise from a previously unknown class of local precursor cells rather than from cells that migrate into the area from the subventricular zone, where other neurons - including those seen in the striatum and olfactory bulb - originate during adulthood. However, during development, both the cortex and striatum precursors likely stem from common ancestor cells that somehow retain their ability to divide and generate new GABA interneurons, propose the researchers.
"Since antidepressants increase neurogenesis in the adult hippocampus, they might have similar effects in the cortex, the region probably responsible for mood dysregulation in depression," suggested Cameron. "But answers to such questions about regulation and possible functions of the new neurons must await results of future studies."
Posted by linkadge on February 5, 2005, at 11:58:43
In reply to Neurogenesis in rat cortex - not just hippocampus, posted by SLS on February 5, 2005, at 5:27:35
Posted by emme on February 5, 2005, at 12:35:41
In reply to Neurogenesis in rat cortex - not just hippocampus, posted by SLS on February 5, 2005, at 5:27:35
Posted by sabre on February 5, 2005, at 18:28:01
In reply to Neurogenesis in rat cortex - not just hippocampus, posted by SLS on February 5, 2005, at 5:27:35
Very interesting, Scott. Thanks.
It leads to more questions:
Do the new neurons replace those lost to stress and depression?
Do these interneurons increase your GABA requirements?
What happens to them when you go off ADs?
Should ADs be supplemented with GABA drugs especially after the new neurons grow?
Perhaps this is why Ads lose their effectivenes for some people...they might then need a change or addition of GABA drugs ..What an amazing field to work in.
sabre
Posted by Willyee on February 6, 2005, at 0:47:13
In reply to Neurogenesis in rat cortex - not just hippocampus, posted by SLS on February 5, 2005, at 5:27:35
See this is what i like,real scieance,not a commercial of a bouncing smily face like were depressed and a bunch of morons.
When the public stops eating these blow off explanations from p-docs,and they have to refer to more than the pamphlet the sales rep just left them,maybe then well see more actual scieance like this one and actualy get some where instead of just masking these problems.
Great article.
Posted by SLS on February 6, 2005, at 8:10:31
In reply to Re: Neurogenesis in rat cortex - not just hippocampus, posted by sabre on February 5, 2005, at 18:28:01
> Very interesting, Scott. Thanks.
>
> It leads to more questions:I bet. :-) I really don't know enough to answer them. :-(
GABA neurons serve to "calm down" the one that are stimulatory (like glutamate). Interestingly, some areas of the cortex seem to be hyperactive in depression - not underactive. It is quite possible that an increase in GABA neurons would help stabilize these areas. Because the investigators were still limited to the number of protein markers they used to identify neuronal activity, it might be that new neurons that use other transmitters sprout as well. I have no idea. I hope so.
The guessing game:
> Do the new neurons replace those lost to stress and depression?
My guess is yes, although the new synapses might not directly replace old ones.> Do these interneurons increase your GABA requirements?
My guess is no. I believe the body does a good job of maintaining its own supply. In addition, I don't think these neurons require very much to function.> What happens to them when you go off ADs?
I think that depends on the state of the system at the time of discontinuation. In fully-remitted patients, perhaps these new neurons are maintained by a re-regulation of neural circuits that interact with them as these circuits are trained by the medications.> Should ADs be supplemented with GABA drugs especially after the new neurons grow?
My guess is no. Allow them operate the way the genetic machinery has programmed them for.> Perhaps this is why Ads lose their effectivenes for some people...they might then need a change or addition of GABA drugs ..
My guess is possibly. :-) Not a bad idea. It would be nice to be able to support these neurons with the supplementation or stimulation of endogenous growth factors. Lithium and Depakote do this.> What an amazing field to work in.
Really. Unfortunately, I lost much of my passion for it after being pounded by depression for so many years. I don't care anymore how things work. I care only to know what works for me.
:-(
- Scott
Posted by sabre on February 9, 2005, at 1:43:34
In reply to Re: Neurogenesis in rat cortex - not just hippocampus » sabre, posted by SLS on February 6, 2005, at 8:10:31
Sorry, not to get back to you Scott. Our Internet connection slowed to a crawl for a day. Thanks for your great answers.
I didn't know that parts of the brain could be overactive in depression. So I suppose that it is possible for parts of the brain to be underactive in anxiety! Perhaps this sheds some light on why glutamine can help some people suffering from anxiety. I couldn't understand how glutamine could be when it is converted to an excitatory neurotransmitter like glutamate in the brain. It also seemed strange that it was then converted to an inhibitor like GABA.
"Really. Unfortunately, I lost much of my passion for it after being pounded by depression for so many years. I don't care anymore how things work. I care only to know what works for me."
Are you hopeful for the future?
sabre
This is the end of the thread.
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