Direct injection into the dorsal root ganglion: Technical, behavioral, and histological observations

Abstract

Direct injection of agents into the dorsal root ganglia (DRGs) offers the opportunity to manipulate sensory neuron function at a segmental level to explore pathophysiology of painful conditions. However, there is no described method that has been validated in detail for such injections in adult rats. We have found that 2 (µl of dye injected through a pulled glass pipette directly into the distal DRG, exposed by a minimal foraminotomy, produces complete filling of the DRG with limited extension into the spinal roots. Injection into the spinal nerve required 3 µl to achieve comparable DRG filling, produced preferential spread into the ventral root, and was accompanied by substantial leakage of injected solution from the injection site. Injections into the sciatic nerve of volumes up to 10 (µl did not reach the DRG. Transient hypersensitivity to mechanical stimulation at threshold (von Frey) and noxious levels (pin) developed after 2 µl saline injection directly into the DRG that was in part attributable to the surgical exposure procedure alone. Only minimal astrocyte activation in the spinal dorsal horn was evident after DRG saline injections. Injection of adeno-associated virus (AAV) vector conveying green fluorescent protein (GFP) transgene resulted in expression as soon as 1 day after injection into the DRG, including fibers in the spinal dorsal horn and columns. AAV injection into the DRG produced additional thermal hypersensitivity and withdrawal from the stroke of a brush and compromised motor performance. These findings demonstrate a method for selective injection of agents into single DRGs for anatomically restricted actions.

Regulation of voltage-gated Ca2+ currents by Ca2+/calmodulin-dependent protein kinase II in resting sensory neurons

“…Control animals received midline lumbar skin incision during brief general anesthesia (Isoflurane 2% in O 2 ). Other rats were injected with vectors AAV8-EGFP or AAV8-EGFP-AIP, as described previously (Fischer et al, 2011). Briefly, after exposure through a midline lumbar incision, the intervertebral foramen was enlarged by removal of laminar bone to expose the distal pole of the right 4 th lumbar (L4) and L5 DRGs.…”

Painful nerve injury increases plasma membrane Ca2+-ATPase activity in axotomized sensory neurons

“…PMCA may be considered a novel site for altering mechanisms leading to the generation of neuropathic pain. The continuing development of molecular therapies and the tolerance of the DRG as a site for intraneuronal injections [45,46] make modulation of PMCA function in sensory neurons a potential future therapy for chronic pain.…”

Adeno-associated Virus Vectors Efficiently Transduce Mouse and Rabbit Sensory Neurons Coinfected with Herpes Simplex Virus 1 following Peripheral Inoculation

“…When certain capsid tyrosine residues were mutated to phenylalanine (Y733F), transduction efficiency was shown to be greatly increased relative to that seen with vectors with wild-type capsids (12)(13)(14)(15)(16)(17)(18)(19)(20). Most relevant to the current study, AAV is capable of transducing DRG sensory neurons via direct intraganglionic sciatic nerve injection (21,22) and intraperitoneal and intravenous injection (23), as well as via intrathecal injection following lumbar puncture (24)(25)(26)(27). Therefore, we sought to determine if rAAV vectors would be delivered to the same sensory neurons that HSV-1 infects when applied at an epithelial surface that has been treated to expose the underlying sensory nerve termini.…”