Electrophysiological and Behavioral Evaluation of C-LTMR Plasticity Induced by Spinal Cord Injury: Transformation from Pleasure to Pain Afferents
Abstract
The overall objective of the study is to test the hypothesis that C-low threshold mechanoreceptors (C-LTMRs) are transformed into allodynia-encoding nociceptors after SCI. Because C-LTMRs can be selectively identified by their expression of tyrosine hydroxylase (TH), all studies were done in adult transgenic TH-Cre mice. During the year 1 funding period, we made significant progress with the proposed experiments. Using the ex-vivo skin-nerve preparation, C-LTMR-evoked neural responses were recorded in dorsal cutaneous nerves following mechanical and optogenetic stimulation of the trunk skin. Serendipitously, we found that our TH-Cre mice also express TH in faster conducting, myelinated A delta-LTMRs, afferents that innervate the same hair follicles as C-LTMRs. Preliminary studies further showed that receptive fields of C-LTMRs (and A delta-LTMRs) are enhanced after SCI. Simultaneous behavioral studies showed that SCI acutely increased respiratory rates (RR), and that brush stimulation induced a slight increase in RR at 21 days after SCI. However, as the studies were done in TH-Cre mice, we are unable to specifically associate these responses to C-LTMRs. Due to the lack to specificity of our TH-Cre strain, future electrophysiological and behavioral studies will be undertaken in an inducible Cre strain (TH-CreER). This will enable us to more selectively target C-LTMRs.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2016
- Accession Number
- AD1034593
Entities
People
- Sandra M Garraway
- Shawn Hochman
Organizations
- Emory University School of Medicine