Specific in-depth insights on features of immunohistochemistry and immunofluorescence in dorsal root ganglia and clinical signs in neuropathic and non-neuropathic dogs

Disorders of the somatosensory system causing neuropathic pain (NP) are common in people. In small animals medicine, this condition remains underestimated probably due to the lack of standardized assessment methods and studies focused on the description of structures playing a key role in developing and maintaining neuropathic pain, such as dorsal root ganglia (DRG). Hence, the aims of the present research project, structured in three different studies, were: a) investigate the possible effects of the reduction in radicular blood flow on the vascular density, ganglionic and endoneurial ischemia and shift in neuronal metabolism, in fifteen L7-DRG from a total of eight dogs suffering from painful compressed spinal L7 nerve roots (NRs) and DRG; b) perform a preliminary characterization of the expression of substance P, calcitonin gene-related peptide, calbindin D-28k, neuronal nitric oxide synthase and the colocalization of those molecules in lumbosacral DRG neurons of three neurologically normal dogs; c) Investigate the prevalence, risk factors and owners' perception of their pets quality of life of the Phantom Complex (PC) in a client-owned population of 107 dogs with limb amputation through an online survey. Main results were: a) Our findings highlight a significant neuronal distress in compressed DRG. Despite the similarity of vascular density between controls and compressed L7-DRG, we found a significant increased in neuronal immunoreactivity for hypoxia-related markers and for markers related to glycolytic cellular metabolism. b) The wide variability of CGRP-, SP-, CALB-, and nNOS-immunoreactivity among different species was confirmed. Further studies are required in order to better define the characterization of those markers in canine DRG. c) Our study demonstrates for the first time the presence of PC.Significant risk factors associated with the frequency of post-amputation pain episodes are duration of pain before amputation and time between diagnosis and amputation.