Effect of botulinum toxin on NMJ?

[Jody K. Hirsh]

In article <49a041$c02 at sun4.bham.ac.uk>, g0udm at g3iub.bham.ac.uk says...
>
>Hi All,
>
>I am a 1st year Medical Student, and I have been set an essay on the 
>effects of the botulinum toxins. I have been able to gather some info 
>from books, but what I am really lacking is info on what actually 
happens 
>at the neuromuscular junction, and how this affects the muscle itself. I 
>know that the toxin disables ACh release at the synapse, but I am not 
>clear on how this affects the NMJ - is there Wallerian degeneration of 
>the nerve fibre or something? Or is the effect felt in a different way? 
>The other thing I would like to know (I know this is not strictly 
>neuroscience, but I couldn't find any other newsgroups that seemed 
>relevant) is what effects there are on the muscle itself. We have been 
>asked to outline 'morphological and physiological changes in the muscle 
>which occur if recovery takes place'. Can anyone give me any clues on 
this?
>
>I would be very grateful for any replies!
>
>Thanks in advance, James
>
>
>
>
If the muscle fiber does not receive stimulation, it undergoes a kind of 
de-differentiation.  ACh receptors start to appear all over the surface, 
they are no longer clustered at the endplate region. They are also a 
different type, with one of the subunits being an embryonal form. Also, 
If a muscle does not receive stimulation, it will atrophy. There was a 
Scientific American article about the nmj about 12 years ago. Sorry I 
don't have anything more useful in front of me. Try looking in a 
neurophysiology text. A recent literature search probably would not help, 
you would need to go back a decade or two. 


-- 
Jody K. Hirsh
Northwestern University, Chicago, IL.   USA
jkh141 at nwu.edu