pAAV-CAG-GFP in Guinea pig (AAV Retrograde)
Addgene #37825-AAVrg

This is an image taken at 10X on a Zeiss AxioImager microscope. The tissue is paraformaldehyde-fixed, frozen-sectioned, then mounted onto a gelatin-coated slide and coverslipped with DPX mountant. This is direct EGFP fluorescence in pyramidal cells of layers V and VI of auditory cortex in a guinea pig. The fluorescence is the result of an injection of rgAAV-CAG-EGFP into the ipsilateral inferior colliculus of this animal.

Caption: This is an image taken at 10X on a Zeiss AxioImager microscope. The tissue is paraformaldehyde-fixed, frozen-sectioned, then mounted onto a gelatin-coated slide and coverslipped with DPX mountant. This is direct EGFP fluorescence in pyramidal cells of layers V and VI of auditory cortex in a guinea pig. The fluorescence is the result of an injection of rgAAV-CAG-EGFP into the ipsilateral inferior colliculus of this animal.

Image attribution: Taken by Brett Schofield.

Virus & Injection

Primary Virus
Promoter
CAG
Injected Titer
5.00E+12 GC/ml
Injected Volume
two 0.05 μl injections (0.1 μl total)
Injection Rate
0. 05 μl over about 2. 5 min
Injection Site
Brain parenchyma
Brain Region
Midbrain: Tectum
Injection Site Comments
The injection was made into the inferior colliculus in an attempt to label neurons in other brain regions (e. G. Contralateral inferior colliculus, lower brainstem auditory nuclei, auditory cortex) that make projections to the inferior colliculus
View in Addgene Catalog

Subject

Species / Strain
Guinea pig
Age at Injection
subject weighed 358 g, (corresponding to an approximate age of 6-7 weeks)

Data Collection

Time After Injection
5 weeks
Detection Method
Direct fluorescence
Expression Site
Of all neuronal types that could potentially have expressed the virus, only pyramidal cells in the auditory cortex were detectable by observing direct fluorescence
Genetic Tool Outcome
We expected that any neurons that make projections to the inferior colliculus might express EGFP in the tissue due to the general CAG promoter present in the virus, but only pyramidal cells in the auditory cortex were detectable by observing direct fluorescence
Other Information
Very little toxicity or inflammation were present at the injection site
Tips & Comments
This virus seems to work in a very pathway-specific manner (at least in guinea pigs). There were multiple brain areas where we should have seen fluorescent cells, and we only observed them in one area. The areas of input from these nuclei overlap in the injected nucleus, so the best explanation for this observation is cell-type specificity in either infection or expression