title: Increased c-fos gene expression in alpha motoneurons in rat loaded hindlimb muscles with inclined locomotion.
abstract: The potential usefulness of c-fos gene expression as an indicator of the activity level of spinal alpha motoneurons was examined in loaded locomotive rats. The motor pools of the plantaris (PL) and soleus muscles (SOL), mainly composed respectively of fast- and slow-twitch muscle fibers, were investigated in rats under locomotion at 25 m/min on a 20% incline. We first labeled motoneurons with a retrograde tracer, Nuclear Yellow (NY), and then quantified the c-fos mRNA expression level in the NY-labeled alpha motoneurons by means of in situ hybridization. Electromyographic (EMG) activities were also recorded. The c-fos expression level per alpha motoneuron showed a greater increase in the PL (75%) than in the SOL motor pool (38%). EMG activities also showed a greater increase in the PL (159%) than in the SOL (43%). Taken together, these results suggest that c-fos expression levels in alpha motoneurons are associated with the activity levels of their corresponding muscle. This cytochemical method for identifying the c-fos expression level has potential for use as a tool for estimating the activity level of large populations of alpha motoneurons in unrestricted animals.
authors.affiliation: Laboratory of Exercise Biochemistry, University of Tsukuba Graduate School of Comprehensive Human Sciences, 1-1-1 Tennôdai, Tsukuba, Ibaraki 305-8574, Japan.
authors.forename: Takenori
authors.initials: T
authors.lastname: Omori
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kawashima
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kizuka
authors.forename: Nao
authors.initials: N
authors.lastname: Ohiwa
authors.forename: Masaru
authors.initials: M
authors.lastname: Tateoka
authors.forename: Hideaki
authors.initials: H
authors.lastname: Soya
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation / Q000502:physiology; D016762:Genes, fos; D006614:Hindlimb / Q000294:innervation*; D008124:Locomotion / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation*; D051381:Rats