Meeting Abstract
P1.92 Thursday, Jan. 3 Botulinum toxin complex does not diffuse across muscle fascia during in vivo skeletal muscle denervation experiments in Rana pipens MELVILLE, B.*; O’NEILL, M.; GIBB, A.C.; Northern Arizona University; NAU; NAU jm348@nau.edu
Current methods used to study skeletal muscle function often disrupt the integrity of the underlying musculoskeletal system (e.g., cutting connective tissue to transect motor neurons). Our goal is to develop and refine the methods to chemically denervate (remove the nerve that stimulates muscle contraction) the skeletal muscle using a neurotoxin; this technique should cause minimal disruption to the underlying musculoskeletal system as neurotoxin can be injected directly into the muscle using a small-bore syringe. We ask two questions: (1) how localized are the effects of botulinum toxin? and (2) can a more complex form of the toxin be used to minimize diffusion across muscle fascia, thus reducing incidental paralysis of non-target muscle? We used the metabolism of glycogen stores in the gastrocnemius muscle of Rana pipens as an index of denervation, as a paralyzed muscle will not deplete its glycogen stores. Rana were anesthetized and the gastrocnemius muscle bilaterally exposed. On one gastrocnemius, the muscle fascia was surgically disrupted while the muscle of the other leg remained intact. Botulinum type A complex (5 mouse units in 5 uL saline) was dripped onto each muscle and the sciatic nerve of each muscle was stimulated by 5 to 7 volts for two hours. After the experiment, muscles were frozen, sectioned and stained for glycogen using PAS stain. Preliminary results are promising; two individuals demonstrate paralysis in the muscle with damaged fascia, with as much as 60% of the muscle paralyzed within 48 hours of injection. Muscles with intact fascia show little paralysis after 48 hours. This outcome suggests that the botulinum toxin complex is an excellent agent for chemical denervation, as it does not readily diffuse across undamaged muscle fascia.
