Identification of bladder and colon afferents in the nodose ganglia of male rats

Abstract

The sensory neurons innervating the urinary bladder and distal colon project to similar regions of the central nervous system and often are affected simultaneously by various diseases and disorders, including spinal cord injury. Anatomical and physiological commonalities between the two organs involve the participation of shared spinal-derived pathways, enabling mechanisms of communication between the bladder and colon. Prior electrophysiological data from our lab suggests that the bladder also may receive sensory innervation from a non-spinal source through the vagus nerve, which innervates the distal colon as well. The present study therefore aimed to determine if anatomical evidence exists for vagal innervation of the male rat urinary bladder and assess whether those vagal afferents also innervate the colon. Additionally, the relative contribution to bladder and colon sensory innervation of spinal and vagal sources was determined. Using lipophilic tracers, neurons that innervated the bladder and colon in both the nodose ganglia (NG) and L6/S1 and L1/L2 dorsal root ganglia (DRG) were quantified. Some single vagal and spinal neurons provided dual innervation to both organs. The proportions of NG afferents labeled from the bladder did not differ from spinal afferents labeled from the bladder when considering the collective population of total neurons from either group. Our results demonstrate evidence for vagal innervation of the bladder and colon and suggest that dichotomizing vagal afferents may provide a neural mechanism for cross-talk between the organs.

Evidence of vagus nerve sprouting to innervate the urinary bladder and clitoris in a canine model of lower motoneuron lesioned bladder

“…In the normal un‐operated control dogs, we found no evidence for sensory or motor vagal innervation of the urinary bladder, urethral sphincter, anal sphincter nor clitoris. This is in contrast to findings in the normal control Wistar rat in which substantial electrophysiological and anatomical evidence exists for vagal innervation of the urinary bladder, distal colon, uterus, cervix, and vagina . Studies recording brain activity during bladder filling using fMRI find no evidence of vagal innervation of the urinary bladder in healthy female volunteers, or in female patients with urinary frequency .…”

Chronic stress and peripheral pain: Evidence for distinct, region-specific changes in visceral and somatosensory pain regulatory pathways

“…In painful diabetic neuropathy animal model, enhanced somatosensory pain perception was associated with increased expression and function of both tetrodotoxin (TTX)-sensitive Na v 1.7 and TTX-resistant Na v 1.8 sodium channels (Hong et al , 2004). Here we examined the expression of Na v 1.7 and Na v 1.8 in L4-L5 DRGs of control and WA stressed rats by immunofluorescence staining.…”

“…Corticosterone also increased the expression levels of Na v 1.7 and Na v 1.8 sodium channels in L4-L5 but not L6-S2 DRGs in vitro , supporting a “hard-wired” mechanism in DRG neurons. This differential response may reflect the distinct development fates of these DRGs and/or the bidirectional influence of the target organs, including the colon and bladder compared to the somatosensory distribution (Herrity et al , 2014;La et al , 2011;Christianson et al , 2007). Future studies will need to examine whether stress-response transcription factor binding sites (for example, GR binding regions) demonstrate altered epigenetic regulation, such as enhanced methylation in L4-L5 DRGs which could explain the absence of response in CB1 gene expression to chronic stress.…”

Axotomy of tributaries of the pelvic and pudendal nerves induces changes in the neurochemistry of mouse dorsal root ganglion neurons and the spinal cord

“…Thus, axotomy of the glossopharyngeal and carotid sinus nerves in the rat (innervating head and neck structures) results in down-regulation in the number of neurons expressing CGRP protein (Helke and Rabchevsky 1991) and transcript (Huang et al 1994). Axotomy of the vagus nerve, innervating the entire length of the gut (Grundy 2006), including the urinary bladder and the distal colon and rectum (Herrity et al 2014), has been shown to reduce the number of nodose ganglion neurons expressing CGRP transcript (Huang et al 1994), but not protein (Helke and Rabchevsky 1991). Here, we demonstrate that axotomy of the L6-S1 trunk results in downregulation of the number of CGRP-IR DRG neurons in the mouse.…”