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Thread: Entry of drugs into peripheral nerve and dorsal root ganglia

  1. #1

    Entry of drugs into peripheral nerve and dorsal root ganglia

    Very interesting study from Wisconsin. The authors where drugs affect the nervous system. The dorsal root ganglia (DRG, where all the sensory axons come from) are situated outside the spinal cord. They therefore injected a fluorescent dye (fluorescein) into various places in animals and compared its presence in the DRG, peripheral nerve, or spinal cord. They found that extensive dye present in the DRGs, no matter where they injected (intravenous, peri-DRG, epidural). No dye was present in the spinal cord unless they injected it intrathecally. Minimal dye was present in the peripheral nerves, except when the nerves were injured. This suggests (to me anyway) that for drugs that share the water solubility of fluorescein affect primarily the DRG. They don't get into the spinal cord that readily, nor into the peripheral nerve.

    [*] Abram SE, Yi J, Fuchs A and Hogan QH (2006). Permeability of Injured and Intact Peripheral Nerves and Dorsal Root Ganglia. Anesthesiology 105: 146-153. BACKGROUND:: Nerve injury that produces behavioral changes of allodynia and hyperalgesia in animals is associated with electrophysiologic changes in dorsal root ganglion (DRG) cells. The introduction of drugs into the DRG or the peripheral nerve that alter calcium, sodium, or potassium channel activity may be of therapeutic benefit after nerve injury. For this reason, the authors sought to determine whether drugs that do not ordinarily cross the blood-nerve barrier will enter the DRG after intravenous or regional injection and to determine whether nerve injury alters drug access to DRGs or peripheral nerves METHODS:: Both intact and spinal nerve-ligated rats were injected with sodium fluorescein by intravenous, intrathecal, peri-DRG, perisciatic, and epidural routes. DRG, sciatic nerve, and spinal cord tissues were harvested and frozen, and histologic sections were analyzed quantitatively for tissue fluorescence. RESULTS:: In both intact and nerve-injured animals, fluorescein accumulated in DRGs after intravenous, peri-DRG, and epidural injection. There was accumulation in the proximal portion of the ganglion after intrathecal injection. Minimal amounts of fluorescein were found in the sciatic nerve in intact animals after intravenous or perineural injection, but substantial amounts were found in some nerve fascicles in nerve-injured animals after both intravenous and perineural injection. There was almost no fluorescein found in the spinal cord except after intrathecal administration. CONCLUSIONS:: In both intact and nerve-injured animals, fluorescein accumulates freely in the DRG after intravenous, epidural, or paravertebral injection. The sciatic nerve is relatively impermeable to fluorescein, but access by either systemic or regional injection is enhanced after nerve injury. * Professor, Department of Anesthesiology, dagger Medical Student, Medical College of Wisconsin. double dagger Staff Anesthesiologist, Department of Anesthesiology and Intensive Care Medicine, Medical University of Graz, Graz, Austria.

  2. #2
    Senior Member
    Join Date
    Aug 2004
    Tallahassee, FL

    Humm. Very intersting Doc

    OK... Doc... what is the practical application here. I mean to say... what is the best way we can put to use this info. I am in the high pain Club and my middlke name is Guinie POig! Lets do somethiong with it! LOL. Thanks Doc. Your the best. Mike (feeling OK these days). Colostomy best thing in the world. Cant imagine an SCI without one. That brings me to another point? Why arnt more Doctors pro active and suggest a Colostomy for every SCI!!! LOL Mike
    Mike (Florida)

    Cant we get 1 do over?

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