Acute post-injury blockade of a2d-1 calcium channel subunits on pathological autonomic plasticity after T3 crush spinal cord injury in female mice

STUDY PURPOSE: After a spinal cord injury (SCI), normally innocuous visceral or somatic stimuli can trigger uncontrolled reflex activation of sympathetic circuitry, causing pathological dysautonomia. Here, we tested the hypothesis that SCI causes remarkable structural remodeling and synaptic plasticity, creating abnormal spinal sympathetic reflexes that promote dysautonomia. We also tested whether treating mice with prophylactic gabapentin (GBP), an FDA-approved drug that inhibits a2d-1-mediated synaptogenesis in the brain, can prevent these pathologies. DATA COLLECTED: The dataset includes n = 183 adult female mice on a C57BL/6J background and n=16 adult female mice on a 129SVE background with a2d-1 overexpression or wild type littermates. Mice received a T3 crush SCI or sham control surgery. Mice were injected subcutaneously 3x/d with GBP (66.7 mg/kg) or Saline from 1 day post-injury (dpi) until 28 or 35 days post-injury, and were perfused at 28, 35, 42, or 56 dpi. Additional mice were used for pharmacokinetic studies and time-course studies of anatomical reorganization (sham, 7 dpi, 14 dpi, 21 dpi, 28 dpi). Anatomical reorganization was assessed using Vglut2+ pre-synaptic puncta, Vglut2+Homer1+ excitatory synapse count, quantification of spinal PRV+ neurons that control lymphoid tissue, lumbar CGRP fiber sprouting, and FosB+ neuron counts. Dysautonomia was assessed using spleen weight, spleen B and T cell quantification, and spontaneous and induced autonomic dysreflexia experiments. Additional outcome measures include a2d-1+ cell number, percent a2d-1+ area, thrombospondin mRNA and protein levels, and principal component analysis results (spinal sympathetic reflex index). DATA USAGE NOTES: We show that remarkable structural remodeling and synaptic plasticity occur within spinal autonomic circuitry after SCI, creating abnormal spinal sympathetic reflexes that promote dysautonomia. If SCI mice are treated with human equivalent doses of GBP, beginning at one day post-injury, well before the onset of post-injury plasticity and dysautonomia, both structural plasticity and pathological dysautonomia can be prevented. This prophylactic GBP regimen blocks multi-segmental excitatory synaptogenesis, and abolishes sprouting of autonomic neurons that innervate immune organs and sensory afferents that trigger pain and autonomic dysreflexia (AD). Prophylactic GBP decreases the frequency and severity of AD and protects against SCI-induced immune suppression. These benefits persist even one month after stopping GBP treatment. GBP could be repurposed to prevent dysautonomia in at-risk individuals with a high-level SCI.