title: A clinically relevant BTX-A injection protocol leads to persistent weakness, contractile material loss, and an altered mRNA expression phenotype in rabbit quadriceps muscles.
abstract: Botulinum toxin type-A (BTX-A) injections have become a common treatment modality for patients suffering from muscle spasticity. Despite its benefits, BTX-A treatments have been associated with adverse effects on target muscles. Currently, application of BTX-A is largely based on clinical experience, and research quantifying muscle structure following BTX-A treatment has not been performed systematically. The purpose of this study was to evaluate strength, muscle mass, and contractile material six months following a single or repeated (2 and 3) BTX-A injections into the quadriceps femoris of New Zealand white rabbits. Twenty three skeletally mature rabbits were divided into four groups: experimental group rabbits received 1, 2, or 3 injections at intervals of 3 months (1-BTX-A, 2-BTX-A, 3-BTX-A, respectively) while control group rabbits received volume-matched saline injections. Knee extensor strength, quadriceps muscle mass, and quadriceps contractile material of the experimental group rabbits were expressed as a percentage change relative to the control group rabbits. One-way ANOVA was used to determine group differences in outcome measures (α=0.05). Muscle strength and contractile material were significantly reduced in experimental compared to control group rabbits but did not differ between experimental groups. Muscle mass was the same in experimental BTX-A and control group rabbits. We concluded from these results that muscle strength and contractile material do not fully recover within six months of BTX-A treatment.
authors.affiliation: Human Performance Laboratory, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Rafael
authors.initials: R
authors.lastname: Fortuna
authors.affiliation: Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Brazil.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Vaz
authors.affiliation: Human Performance Laboratory, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Sawatsky
authors.affiliation: McCaig Institute for Bone & Joint Health, University of Calgary, Calgary, Alberta, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Hart
authors.affiliation: Human Performance Laboratory, University of Calgary, Calgary, Alberta, Canada. Electronic address: wherzog@ucalgary.ca.
authors.forename: Walter
authors.initials: W
authors.lastname: Herzog
mesh_terms: D000818:Animals; D019274:Botulinum Toxins, Type A / Q000009:adverse effects* / Q000494:pharmacology; D005260:Female; D007273:Injections, Intramuscular; D007719:Knee Joint / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D053580:Muscle Strength / Q000187:drug effects; D018908:Muscle Weakness / Q000139:chemically induced*; D010641:Phenotype; D052097:Quadriceps Muscle / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits
chemical_list: D012333:RNA, Messenger; D019274:Botulinum Toxins, Type A
keywords: Botulinum toxin; Cerebral palsy; Fibrosis; Muscle atrophy; Muscle weakness; Spasticity