Neurochemical features of boar lumbo-sacral dorsal root ganglion neurons and characterization of sensory neurons innervating the urinary bladder trigone.

Porcine lumbo-sacral dorsal root ganglion (DRG) neurons were neurochemically characterized using six neuronal markers: calcitonin gene-related peptide (CGRP), substance P (SP), neuronal nitric oxide synthase (nNOS), neurofilament 200kDa (NF200), transient receptor potential vanilloid 1 (TRPV1), and isolectin B4 (IB4) from Griffonia simplicifolia. In addition, the phenotype and cross sectional area of DRG neurons innervating the urinary bladder trigone (UBT) were evaluated by coupling retrograde tracer technique and immunohistochemistry. Lumbar and sacral DRG neuronal subpopulations were immunoreactive (IR) for CGRP (30±3% and 29±3%, respectively), SP (26±8% and 27±12%, respectively), nNOS (21±4% and 26±7%, respectively), NF200 (75±14% and 81±7%, respectively), TRPV1 (48±13% and 43±6%, respectively), and labeled for IB4 (56±6% and 43±10%, respectively). UBT sensory neurons, which were distributed from L2 to Ca1 DRG, presented a segmental localization, showing their highest density in L4-L5 and S2-S4 DRG. Lumbar and sacral UBT sensory neurons expressed similar percentages of NF200-IR (64±33% and 58±12%, respectively) but showed a significantly different immunoreactivity for CGRP, SP, nNOS, and TRPV1 (56±9%, 39±15%, 17±13%, 62±10% vs 16±6%, 16±11%, 6±1%, 45±24%, respectively). Lumbar and sacral UBT sensory neurons showed also different IB4-labeling (67±19% and 48±16, respectively). Taken together, these data indicate a probably different role of lumbar and sacral pathways in the sensory transmission from the UBT. The findings related to cell size also reinforced this hypothesis, since lumbar UBT sensory neurons were significantly larger than sacral ones (1112±624 μm2 vs 716±421 μm2).