Injection of WGA-Alexa 488 into the ipsilateral hemidiaphragm of acutely and chronically C2 hemisected rats reveals activity-dependent synaptic plasticity in the respiratory motor pathways

WGA-Alexa transsynaptic labeling in the phrenic motor system of adult rats: Intrapleural injection versus intradiaphragmatic injection

“…However, following intradiaphragmatic injection, neither WGA-Alexa 594 (red, N=8) or WGA-Alexa 488 (green, N=2) were detected in the thoracic spinal cord (fig. 3B) confirming the results of our previous study (Buttry and Goshgarian, 2014). The labeling of intercostal motoneurons following intrapleural injection, but not after intradiaphragmatic injection indicates that the tracer is exposed to phrenic axons exclusively when injected into the diaphragm (Buttry and Goshgarian, 2014).…”

“…Moreover, there was no evidence of spinal interneurons labeled with either WGA-Alexa 488 or 594 following intrapleural or intradiaphragmatic injection. The lack of spinal interneurons confirms the findings in our previous study examining WGA-Alexa 488 labeling following intradiaphragmatic injection (Buttry and Goshgarian, 2014). Of the WGA-Alexa 488 labeled cells observed in the PN following a right intrapleural injection, 86 ± 17.9% displayed a dual label with WGA-Alexa 594 (left intradiaphragmatic injection) (table 2).…”

The Therapeutic Effectiveness of Delayed Fetal Spinal Cord Tissue Transplantation on Respiratory Function Following Mid-Cervical Spinal Cord Injury

“…Both CT-B and WGA tracers have been used to investigate the neural control of the phrenic motor system [28,37]. Our data indicate that phrenic motoneurons are robustly labeled by these tracers.…”

“…Bregman [40] demonstrated that in newborn rats, host serotonergic fibers can grow into the graft and re-innervate the host spinal cord caudal to the injury. Although the capacity for axonal growth is relatively weaker in adult rats than in newborn rats [38], our recent study demonstrated that transplantation of fetal medullary cells can improve respiratory outputs in high-cervical hemisected rats [37]. These results indicated that fetal grafts may provide a trophic microenvironment that enables serotonergic fibers to grow through the transplant and/or grow around the host-graft interface to reach the ventral horn and then modulate phrenic motoneuron excitability.…”

“…The weak expression of GFP-positive fibers may be attributed to several factors: 1) the graft axons did not extensively project to the host tissue owing to the formation of the glia scar at the host-graft interface; 2) the graft neuronal axon did not express robust GFP as well as neuronal cell body or glial cell and therefore the innervation pattern of the graft axon may not be effectively revealed in the host tissue; 3) our current data demonstrated that the proportion of oligodendrocytes was very low in the graft, which may influence the graft axonal projection to the host tissue. Additionally, Buttry and Goshgarian [37] demonstrated that WGA conjugated with Alexa Fluor dyes may detect the activity state of the synapse and label the physiologically active pathway. This suggested that FSC-derived graft neurons may have a physiological impact on phrenic bursting.…”