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Identification of the visceral pain pathway activated by noxious colorectal distension in mice.

Kyloh M, Nicholas S, Zagorodnyuk VP, Brookes SJ, Spencer NJ - Front Neurosci (2011)

Bottom Line: Also, lesions applied to the right or left hypogastric nerves failed to reduce VMRs.Electrical stimulation applied to either the lumbar colonic or hypogastric nerves in vivo, failed to elicit a VMR.The sensory neurons of this spinal afferent pathway lie primarily in the lumbosacral region of the spinal cord, between L6 and S1.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University Adelaide, SA, Australia.

ABSTRACT
In patients with irritable bowel syndrome, visceral pain is evoked more readily following distension of the colorectum. However, the identity of extrinsic afferent nerve pathway that detects and transmits visceral pain from the colorectum to the spinal cord is unclear. In this study, we identified which extrinsic nerve pathway(s) underlies nociception from the colorectum to the spinal cord of rodents. Electromyogram recordings were made from the transverse oblique abdominal muscles in anesthetized wild type (C57BL/6) mice and acute noxious intraluminal distension stimuli (100-120 mmHg) were applied to the terminal 15 mm of colorectum to activate visceromotor responses (VMRs). Lesioning the lumbar colonic nerves in vivo had no detectable effect on the VMRs evoked by colorectal distension. Also, lesions applied to the right or left hypogastric nerves failed to reduce VMRs. However, lesions applied to both left and right branches of the rectal nerves abolished VMRs, regardless of whether the lumbar colonic or hypogastric nerves were severed. Electrical stimulation applied to either the lumbar colonic or hypogastric nerves in vivo, failed to elicit a VMR. In contrast, electrical stimulation (2-5 Hz, 0.4 ms, 60 V) applied to the rectum reliably elicited VMRs, which were abolished by selective lesioning of the rectal nerves. DiI retrograde labeling from the colorectum (injection sites 9-15 mm from the anus, measured in unstretched preparations) labeled sensory neurons primarily in dorsal root ganglia (DRG) of the lumbosacral region of the spinal cord (L6-S1). In contrast, injection of DiI into the mid to proximal colon (injection sites 30-75 mm from the anus, measured in unstretched preparations) labeled sensory neurons in DRG primarily of the lower thoracic level (T6-L2) of the spinal cord. The visceral pain pathway activated by acute noxious distension of the terminal 15 mm of mouse colorectum is transmitted predominantly, if not solely, through rectal/pelvic afferent nerve fibers to the spinal cord. The sensory neurons of this spinal afferent pathway lie primarily in the lumbosacral region of the spinal cord, between L6 and S1.

No MeSH data available.


Related in: MedlinePlus

Distribution of retrogradely labeled DRG neurons following injection of DiI into the mouse distal colon. (A) Following DiI injections made 9–15 mm from the anal sphincter (measured from unstretched colorectum preparations), the distribution of retrogradely labeled DRG neurons were identified. The majority of labeled neurons were identified in the lumbosacral region of spinal cord. Primary labeling was identifiedat levels of L6 and S1. (B) Fluorescence micrograph showing labeledneurons at L6.
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Figure 3: Distribution of retrogradely labeled DRG neurons following injection of DiI into the mouse distal colon. (A) Following DiI injections made 9–15 mm from the anal sphincter (measured from unstretched colorectum preparations), the distribution of retrogradely labeled DRG neurons were identified. The majority of labeled neurons were identified in the lumbosacral region of spinal cord. Primary labeling was identifiedat levels of L6 and S1. (B) Fluorescence micrograph showing labeledneurons at L6.

Mentions: We injected the retrograde neuronal tracer, DiI, into a similar region of colorectum that was distended by the intraluminal balloon. Following laparotomy, DiI was injected through the serosa and into the muscularis externa a distance of 9–15 mm from the anus (measured in unstretched preparations). These same injection sites measured a distance of 19–30 mm in stretched preparations. In control mice, it was found that the greatest number of DRG neurons were located in the sacral spinal cord at the level of L6 and S1, with a small proportion of neurons labeled in T13-L1 (see Figure 3). On average, a mean number of 17 ± 6 DRG neurons were labeled in L6 per section (Figure 3, N = 5).


Identification of the visceral pain pathway activated by noxious colorectal distension in mice.

Kyloh M, Nicholas S, Zagorodnyuk VP, Brookes SJ, Spencer NJ - Front Neurosci (2011)

Distribution of retrogradely labeled DRG neurons following injection of DiI into the mouse distal colon. (A) Following DiI injections made 9–15 mm from the anal sphincter (measured from unstretched colorectum preparations), the distribution of retrogradely labeled DRG neurons were identified. The majority of labeled neurons were identified in the lumbosacral region of spinal cord. Primary labeling was identifiedat levels of L6 and S1. (B) Fluorescence micrograph showing labeledneurons at L6.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3046361&req=5

Figure 3: Distribution of retrogradely labeled DRG neurons following injection of DiI into the mouse distal colon. (A) Following DiI injections made 9–15 mm from the anal sphincter (measured from unstretched colorectum preparations), the distribution of retrogradely labeled DRG neurons were identified. The majority of labeled neurons were identified in the lumbosacral region of spinal cord. Primary labeling was identifiedat levels of L6 and S1. (B) Fluorescence micrograph showing labeledneurons at L6.
Mentions: We injected the retrograde neuronal tracer, DiI, into a similar region of colorectum that was distended by the intraluminal balloon. Following laparotomy, DiI was injected through the serosa and into the muscularis externa a distance of 9–15 mm from the anus (measured in unstretched preparations). These same injection sites measured a distance of 19–30 mm in stretched preparations. In control mice, it was found that the greatest number of DRG neurons were located in the sacral spinal cord at the level of L6 and S1, with a small proportion of neurons labeled in T13-L1 (see Figure 3). On average, a mean number of 17 ± 6 DRG neurons were labeled in L6 per section (Figure 3, N = 5).

Bottom Line: Also, lesions applied to the right or left hypogastric nerves failed to reduce VMRs.Electrical stimulation applied to either the lumbar colonic or hypogastric nerves in vivo, failed to elicit a VMR.The sensory neurons of this spinal afferent pathway lie primarily in the lumbosacral region of the spinal cord, between L6 and S1.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University Adelaide, SA, Australia.

ABSTRACT
In patients with irritable bowel syndrome, visceral pain is evoked more readily following distension of the colorectum. However, the identity of extrinsic afferent nerve pathway that detects and transmits visceral pain from the colorectum to the spinal cord is unclear. In this study, we identified which extrinsic nerve pathway(s) underlies nociception from the colorectum to the spinal cord of rodents. Electromyogram recordings were made from the transverse oblique abdominal muscles in anesthetized wild type (C57BL/6) mice and acute noxious intraluminal distension stimuli (100-120 mmHg) were applied to the terminal 15 mm of colorectum to activate visceromotor responses (VMRs). Lesioning the lumbar colonic nerves in vivo had no detectable effect on the VMRs evoked by colorectal distension. Also, lesions applied to the right or left hypogastric nerves failed to reduce VMRs. However, lesions applied to both left and right branches of the rectal nerves abolished VMRs, regardless of whether the lumbar colonic or hypogastric nerves were severed. Electrical stimulation applied to either the lumbar colonic or hypogastric nerves in vivo, failed to elicit a VMR. In contrast, electrical stimulation (2-5 Hz, 0.4 ms, 60 V) applied to the rectum reliably elicited VMRs, which were abolished by selective lesioning of the rectal nerves. DiI retrograde labeling from the colorectum (injection sites 9-15 mm from the anus, measured in unstretched preparations) labeled sensory neurons primarily in dorsal root ganglia (DRG) of the lumbosacral region of the spinal cord (L6-S1). In contrast, injection of DiI into the mid to proximal colon (injection sites 30-75 mm from the anus, measured in unstretched preparations) labeled sensory neurons in DRG primarily of the lower thoracic level (T6-L2) of the spinal cord. The visceral pain pathway activated by acute noxious distension of the terminal 15 mm of mouse colorectum is transmitted predominantly, if not solely, through rectal/pelvic afferent nerve fibers to the spinal cord. The sensory neurons of this spinal afferent pathway lie primarily in the lumbosacral region of the spinal cord, between L6 and S1.

No MeSH data available.


Related in: MedlinePlus