[Histonet] mouse spinal cord atlas

[Kar Ling]

Hi,

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 illustration.

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?

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