[Histonet] damage to dura; also cresyl violet

John Kiernan jkiernan <@t> uwo.ca
Mon Sep 3 11:16:22 CDT 2007

The simplistic answer is that your control drilling injures the dura and (subtly) the underlying cortex.  If PFC means prefrontal cortex, then damaging it causes behavioral changes!  
Is "a standard dremmel" the kind of drill sold in hardware and craft stores and advertized on TV? If so, it's too heavy for making  hole in a rat's skull. For rat neurosrgery you need an old-fashioned low speed dental drill with an angled handpiece that can be held between the thumb and the index and middle fingers, and a near-spherical burr about 1.5mm across. You also need an operating microscope with lighting that doesn't cast shadows, so that you can see where you are drilling. You see the dura after going through the inner table of the skull. Try not to scrape the dura, especially if it contains a blood vessel near the point of your intended stereotaxic needle penetration. 
Cresyl violet is not ordinarily used to detect "infiltration of immune cells". Is is a cationic dye of the oxazine series (or a mixture of similar compounds) used for fairly selective staining of cytoplasmic rRNA (Nissl substance of neurons) and the DNA of glial nuclei and nuclei of small neurons. (In nuclei of larger neurons, the DNA is rather thinly spread out and therefore only faintly stained for the most part.) In non-nervous tissue, cell nuclei, cartilage matrix, mast cell granules etc are stained, but cresyl violet is used principally for cytoarchitectonic studies of grey matter. For examining "immune cells" you need a stain that shows the different types of leukocyte. Giemsa is good. Lillie's azure-eosin is more trouble but can give excellent results. Both methods also show neurons well.

John Kiernan
Anatomy, UWO
London, Canada
----- Original Message -----
From: Caroline Bass <cbass <@t> bidmc.harvard.edu>
Date: Friday, August 31, 2007 0:54
Subject: [Histonet] damage to dura
To: Histonet <histonet <@t> lists.utsouthwestern.edu>

> Hey guys,
> i have a question I thought may be good for the group.  I 
> am doing  
> stereotax surgeries on rats, basically making lesions in 
> the  
> prefrontal cortex.  There are two potential sham controls, 
> one where  
> a vehicle is injected the other where the holes are drilled 
> but  
> nothing is injected.  So here's the problem.  In the 
> no injection  
> sham (i.e. only holes are drilled) the animals display an 
> alteration  
> of the behavior we're interested in.  The tissue looks 
> good, and  
> there is no sign of infiltration of immune cells in the PFC by 
> cresyl  
> violet.  However, the dura does have some damage where the 
> drill  
> pierced the skull.  We use a standard dremmel.
> Are there any suggestions for what could be going on?  Is 
> there an  
> immune response we should specifically look for, or is 
> there  
> something else about the dura that could be affecting our 
> system?   
> Does anyone know of how dura damage can alter nearby brain areas?
> Any and all advice is appreciated.
> Caroline
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