Electrophysiological and Behavioral Evaluation of C-LTMR Plasticity Induced by Spinal Cord Injury: Transformation from Pleasure to Pain Afferents
Technical Report,30 Sep 2015,29 Sep 2016
Emory University School of Medicine Atlanta United States
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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.
- Medicine and Medical Research
- Anatomy and Physiology