Brain :: Information processing in the central nervous system

[Max]

Brain :: Information processing in the central nervous system

Research by Renee Theiss, Jason Kuo and C J Heckman, which has just been published in The Journal of Physiology, throws light on how information is processed in the Central Nervous System (CNS) to drive movement.
http://www.spiritindia.com/health-ca...cles-8355.html

[Wise Young]

Max, I moved this to Science and Tech. Wise.

[Wise Young]

The article by Theiss, et al. (2007)
http://jp.physoc.org/cgi/content/abs...24123v1?ck=nck

Persistent inward currents in rat ventral horn neurones
Renee D. Theiss1, Jason J. Kuo1, and C. J. Heckman1*

1 Northwestern University Feinberg School of Medicine

* To whom correspondence should be addressed. E-mail: c-heckman@northwestern.edu.

Throughout the mammalian spinal cord, interneurones have been shown to exhibit distinct firing patterns in response to a step of injected current. In this study of ventral horn interneurones in a thick slice preparation of the lumbar cord of 11 to 19 day old rats, four distinct firing patterns were observed and classified as repetitive-firing, repetitive/burst, initial-burst or single-spiking. The hypothesis that a persistent sodium current was the predominant determinant of cell firing behaviour was investigated. A slow voltage ramp was used to assess persistent inward currents (PICs). Cells with repetitive-firing patterns had significantly larger PICs than cells displaying repetitive/burst, initial-burst or single-spiking patterns. Repetitive-firing, repetitive/burst and initial-burst firing cells were reduced to a single spiking pattern with the application of riluzole, which also markedly reduced the persistent sodium current. Persistent sodium current was found to account for most of the PIC with only a small contribution from L-type calcium current. These results suggest that the persistent sodium current plays a major role in determining firing patterns in these cells.

Let me paraphrase the work. First, it is not really about spinal cord injury. The authors studied thick slice preparations of neonatal rat ventral spinal cords. By the way, this is quite a traumatic model (the spinal cord is sliced) and they recorded from neurons in the slices. They found four distinct firing patterns that appear to be governed by persistent inward currents (PICs) which are carried by sodium. When they gave riluzole, a drug that has been approved for treatment of ALS (amyotrophic lateral sclerosis), the PIC decreased and the complex firing pattern simplified to a single firing pattern.

It is a very long stretch for the authors (as they did in the press release) to suggest that these findings have anything to do with spinal cord injury. Unless one counted the preparation of the spinal cord for recording (i.e. slice) to be spinal cord injury, the results are relevant to neonatal rat spinal cords. Theissman did cite an earlier study by Kuo, et al.

J. J. Kuo, R. H. Lee, L. Zhang, C. J. Heckman (2006)
Essential role of the persistent sodium current in spike initiation during slowly rising inputs in mouse spinal neurones
The Journal of Physiology 574 (3), 819–834.
doi:10.1113/jphysiol.2006.107094

This previous study used cultured spinal neurons to test the hypothesis that persistent sodium current causes repetitive firing and that riluzole stops this firing. The real question that was not answered in either of these studies is the mechanism of the persistent sodium current. Because riluzole affects this current and riluzole is known to be a glutamate receptor blocker, one possibility is that this is an NMDA receptor mediate sodium current (one of the glutamate receptors that is believed to contribute to neuronal injury). By the way, many previous studies have shown dramatic and long-lasting effects of various neurotransmitters on motoneuronal and interneuronal firing patterns, such as serotonin. So, in general, I find the breathless pronouncements of the press release to be off-putting and disengenuous.

Wise.

[Max]

Max, I moved this to Science and Tech. Wise.

oK Somehow neither this article nor research appeared in Search You know I do check before posting.........

[Wise Young]

oK Somehow neither this article nor research appeared in Search You know I do check before posting.........

Max, yes and thanks. I know that this article had not been posted before and you do check. I moved it because this article is more related to Science and Technology than to Cure. The reason why I started the Science and Technology Forum is so that people can discuss science and technology that they think are interesting and relevant to them or spinal cord injury. The discussion on the Cure forum should be directed at therapies aimed to restoring function or eradicating the conditon.

Wise.

[Leif]

But isn’t the understanding of interneuron’s important for a SCI cure? I also understand that not too much is understood and mapped when it comes to interneurons.