Colchizine or not ??

[falvarez at desire.wright.edu]

>What are your experiences concerning usage of colchizine in
>immunocytochemical investigations ?  Is it worth the additional effort
>? 
>Do you get more or better stained perikarya ?

Yes, usually you get much better staining in the cell somas after 
colchicine, particularly when immunocytochemistry is directed against 
molecules that are rapidly transported to the neurites and therefore the 
somatic concentration is generally low. Neuropeptides are premier examples of 
the advantage to use colchicine for enhancing immunostining in the cell body 
and proximal dendrites. In my experience, to know whether or not it will be 
usefull for you, you need to consider the following:

1) Do you already get cell body staining without colchicine? In some cells, 
neuropeptide-IR can only be detected after colchicine, however most times 
increasing the sensitivity of the immunocytochemical techniques is enough. 
e.g. better antibodies, adequate fixation regime for that neuropeptide, 
sensitive detection methods (i.e. ABC), proper peroxidase 
histochemistry, intensification of reaction products (i.e silver 
intensification).

2) In some neurons colchicine has been shown to alter gene 
expression for particular neuropeptides. Therefore controls using "in situ" 
hybridization or other means of assesing gene expression may be necessary, 
depending on your results. e.g. Rethelyi et al., 
Neuroscience 42(2): 531-539 (1991)

3) Colchicine is quite toxic to the animals. They should be care for 
adequately during the 24 hour survival.

Personally, I try to avoid the use of colchicine, however some 
neuropeptide-immunoreactivities are hardly visible in some cell somas without 
it. In my case was somatostatin in the superficial laminae of the trigeminal 
subnucleus caudalis. In contrast, somatostain-immunoreactivity in hypothalamic 
cells was beautifull even without colchicine.

I hope my experience is of any help to you

Francisco J. Alvarez
Dept. of Anatomy
Wright State University
Dayton, OH