Gene Delivery to Neurons of the Dorsal Root Ganglia Using Adeno-Associated Viral Vectors - Gene Delivery and Therapy for Neurological Disorders - page 179

Fig. 1 Confi guration of the stereotactic frame for injection of rat dorsal root ganglia. ( a ) First the electrode
holder is placed in inverted orientation. ( b ) The manipulator is swiveled 180° about the vertical axis so that the
electrode holder is held outside the frame. ( c ) The manipulator is then rotated 90° in the vertical plane to bring
the electrode holder to a horizontal position. ( d ) The injection needle is then mounted on the electrode holder
using adhesive putty
crest ( see Fig. 2 ). The L4 DRG will be approximately 8 mm rostral
in a young adult rat. An area of about 6-7 cm long centered over
the DRG should be shaved, cleaned, and sterilized with alcohol.
A longitudinal skin incision of about 4 cm is made over the
position of the L4/L5 DRG to the left of the spinous processes,
and the muscles attached to these processes on the left side are
separated from the vertebrae by cutting. Retractors (17008-07;
Fine Science Tools, Heidelberg, Germany) can be inserted to keep
the muscles apart. To expose the L5 DRG, fi rst remove the acces-
sory process and the caudal articular process of the L5 vertebra
using Friedman-Pearson rongeurs (16021-14; Fine Science Tools).
This will expose the L6 cranial articular process ( see Fig. 2 ). From
here remove 1-2 mm more of the L5 vertebral lamina in the rostral
direction, exposing the proximal edge of the DRG. To fully expose
the DRG it is then necessary to remove at least the rostral half of
the L6 cranial articular process.
The area containing the DRG is now exposed although the
ganglion itself may not be visible due to overlying connective tissue
and more laterally, muscle, containing the dorsal ramus of the spi-
nal nerve. Care should be taken not to damage this. A small inci-
sion in the muscle parallel to the line of the spinal nerve and slightly
rostral to it can help to make the DRG visible.
The DRG is identifi able as a cream-colored enlargement as
compared to the surrounding dorsal root and spinal nerve. Often
a microscopically small capillary network is visible on top of the
DRG in the center.
It is important to open the epineurium of the DRG prior to
insertion of the injection needle. This must be done without
damaging the endoneurial tissue of the ganglion itself—as this will
result in poor retention of the injected liquid. Insertion of the
needle through the intact epineurium, on the other hand, will risk
considerable compression of the ganglion which may compromise
the viability of the tissue.