Dear Kar Ling,
I entered ANATOMY MOUSE BOOK in Google, and the top item (of many) was
This is an atlas of drawings, covering the skeleton, vascular system and internal organs, by Margaret Cook, published originally in 1965=2E It does not include the nervous system. The sacrum is clearly shown to consist of 4 fused vertebrae. That answers one of your questions.
The forward to Cook's book (now free, even though it was published by Academic Press) is by one W.Lane-Petter, who was already the editor of a big book on the biology of animals used in research. I recall his visit to the Anatomy Department at Birmingham University (UK) when I was a student there in 1962. I had consulted his revered book for some information about hedgehogs, the species in which I was investigating possible cholinergic mechanisms in hypothalamic neurosecretion, under the supervision of the late Dr R.L.Holmes. All this has nothing to do with dorsal roots in mice, but it's an opportunity to acknowledge Bob Holmes for showing me that histochemistry was a worthwhile pastime. (Enzyme activities were the cutting edge in those days.) Thanks pm, Bob H!
The Google search for ANATOMY MOUSE BOOK brought up more than a million hits. Of those in the first fifty, many obviously were other references to Cook (1965).
Your email (quoted below) indicates that you can do the difficult dissection of spinal nerves quite quickly. I know an experienced anatomist who takes a week to dissect out a fixed mouse spinal cord.
The "biochemists' method" of ejecting the rat's spinal cord - removal of the head followed by injection of saline into the sacral hiatus - preserves some of the cauda equina, but it does not allow accurate identification of segmental levels. See
Meikle & Martin 1981: Stain Technology 5(4):235-237 (1981)
also Acta Morphologica Neerlando-Scandinavica 23: 357–368
Lumbar, sacral and caudal dorsal root ganglia are probably not all ejeccted in the biochemists' method for collecting rodents' spinal cords. Check the refs above.
You are in a position to provide and publish a new and detailed description of lubosacral neves in the mouse. Do it! Submit a paper to the Journal of Aatomy.
----- Original Message -----
From: Kar Ling
Date: Friday, August 10, 2007 16:03
Subject: [Histonet] mouse spinal cord atlas
> I have problems in defining ventral roots of lumbar spinal
> segments in mice. I try to look up some mouse anatomy
> book, but it only has bunch of spinal cord cross section.
> For gross anatomy of the spinal cord, I can only find rat
> ones. I wonder if there's such book with whole spinal cord
> My first questions is: Do mice has L1-L6 and S1-S4 as in rat?
> My way to dissect spinal cord is cutting the dorsal bones piece
> by pieces, and then carefully remove the ventral bones starting
> at the sides so that I can preserve DRG attached to both ventral
> and dorsal roots. (that took me an hour to expose sacral and
> lumber segments).
> If I count from conus medullaris, how can I be sure my counting
> is correct? should I count main nerves or emerging
> branches? Is there any hallmarks that can differentiate L6 from S1=3F
> According to what I see in mouse spinal cord, the last thick
> ventral spinal nerve coming out from the spinal cord appears to
> be several branches emerging from the cord then merging into
> one, but then split into 2 again. One of those nerves
> attach another dorsal root and DRG, yet I fail to preserve the
> other DRG if any. As for the 2 ventral nerves below this
> one are much thinner and also has few emerging branches from the
> cord. So, I am not sure about what I see is L6 or it's a
> merge of L6 & S1??
> If I count the afforementioned nerve as L6, I can locate 3 pairs
> of long dorsal and ventral roots (L6-L3) and 2 pairs of
> relatively short L2-L1 above. Yet, L1 roots are notably longer
> than Thoracic root along rib cage level. So, Is L1 always longer
> than T12??
> I read some histonet achieve suggesting saline injection to push
> the spinal cord out, can the DRG be preserved?
> Thank you.
> Karen Ling
> University of Southern California
> Program in Neuroscience
> 3641 Watt Way, HNB 209
> Los Angeles, CA 90089-2520