Oxidative capacity of rat masseter muscle after implantation of thyrotropin-releasing hormone microspheres in proximity to trigeminal motoneurones.
Earlier work has shown that two important consequences of implanting thyrotropin-releasing hormone (TRH) microspheres near motoneurones within the trigeminal motor nucleus of actively growing rats are increased muscle mass and a darkening of the implant-side masticatory muscles. These phenomena have been associated with altered neuromuscular activity patterns and biomechanical forces that directly influence craniofacial growth and development. Now, whether the implantation of TRH microspheres in proximity to trigeminal motoneurones would affect the oxidative capacity of the implant-side masseter muscles was investigated. Cytochrome C oxidase (COX) assays were carried out for both implant- and non-implant-side masseters of TRH (n = 5) and blank microsphere (n = 6) Sprague-Dawley rats after stereotactic surgery at 35 days of age. Analyses of both groups at 14 days post-implantation revealed that the COX activity levels of implant-side masseters in TRH-implanted rats was significantly (P< or =0.05) greater than that of non-implant-side masseters; rats implanted with blank microsphere exhibited no significant difference between implant- and non-implant-side masseter COX activity levels. The stated null hypothesis was therefore rejected. These data suggest that TRH implants in proximity to trigeminal motoneurones effect increased oxidative capacity of the masseter muscle as measured by COX activity.
Department of Anatomy, Indiana University School of Medicine, Indianapolis 46202-5120, USA. kbyrd@topaz.iupui.edu
K E
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Byrd
M J
MJ
Sukay
D R
DR
Swartz
D000818:Animals; D001696:Biomechanical Phenomena; D004343:Drug Implants; D003576:Electron Transport Complex IV / Q000032:analysis / Q000187:drug effects; D008406:Masseter Muscle / Q000187:drug effects* / Q000201:enzymology / Q000294:innervation / Q000378:metabolism; D008445:Maxillofacial Development / Q000187:drug effects; D008863:Microspheres; D009046:Motor Neurons / Q000187:drug effects*; D009434:Neural Pathways / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013238:Stereotaxic Techniques; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D014278:Trigeminal Nuclei / Q000187:drug effects*
D004343:Drug Implants; D013973:Thyrotropin-Releasing Hormone; D003576:Electron Transport Complex IV