posttransection with and without passive cycling lumbar flexor and extensor motoneurons Serotonin receptor and KCC2 gene expression in

113: 1369–1376, 2015. First published Decem-ber 10, 2014; doi:10.1152/jn.00550.2014.—Sacrocaudal motoneurongene expression is altered following a spinal transection. Of interesthere is the regulation of serotonin (5-HT) receptors (R), glutamatereceptor, metabotropic 1 (mGluR1), and potassium-chloride cotrans-porter (KCC2), which mediate motoneuron excitability, locomotorrecovery, and spasticity posttransection. The examination of thesegenes in lumbar motoneurons posttransection has not been studied,which is necessary for developing potential pharmacological interven-tions aimed at restoring locomotion and/or reducing spasticity. Also,if activity is to be used to promote recovery or reduce spasticitypostinjury, a further examination of neuromuscular activity on geneexpression posttransection is warranted. The purpose of this study wasto examine motoneuronal gene expression of 5-HT receptors, KCC2,and mGluR1 at 3 mo following a complete thoracic spinal cordtransection, with and without the inclusion of daily passive cycling.Physiological hindlimb extensor and flexor motoneurons were differ-entially identified with two retrograde fluorescent tracers, allowing forthe identification and separate harvesting of extensor and flexormotoneurons with laser capture microdissection and the subsequentexamination of mRNA content using quantitative RT-PCR analysis.We demonstrate that posttransection 5-HT