Ann Rehabil Med.  2011 Oct;35(5):589-598. 10.5535/arm.2011.35.5.589.

Changes in the Muscarinic Receptors on the Colonic Smooth Muscles of Rats with Spinal Cord Injury

• Joo MC
• Kim YS
• Choi ES
• Oh JT
• Park HJ
• Lee MY

• KMID: 2267219
• DOI: http://doi.org/10.5535/arm.2011.35.5.589

Abstract

OBJECTIVE
To investigate changes in (1) the colonic response to acetylcholine (Ach), (2) the muscarinic (M) receptors in the colon, and (3) the levels of colonic contraction-related proteins after a spinal cord injury (SCI). METHOD: We divided 16 Sprague-Dawley rats into 2 groups: the control group and the SCI group. A spinal cord transection was performed surgically at the T10 vertebral level. After 1 week, the entire colon was divided into 2 segments, the proximal and distal colon. Each segment was mounted in a longitudinal or circular muscle direction in a 10-ml organ bath. We determined the intergroup differences as percentage changes in contractility after Ach treatment alone, Ach treatment with M2 receptor antagonist (AQ-RA741) pretreatment, and Ach treatment with M3 receptor antagonist (4-DAMP) pretreatment. Western blot analyses were performed to determine the expression level of RhoA, and heat shock protein 27 (HSP27).
RESULTS
Compared to the control rats, the SCI rats showed an increased response to Ach along both the directions in the proximal colon (p<0.05). Compared to the control group, in the SCI group, the Ach response was significantly different in the proximal segment under AQ-RA741 pretreatment (p<0.05) and in the distal segment under 4-DAMP pretreatment (p<0.05). Findings of the western blot analyses showed a significant decrease in the level of protein gene product 9.5 in the proximal and distal colon and a significant increase in the level of RhoA and HSP27 in the proximal colon of the SCI rats.
CONCLUSION
Our results suggest that changes in colonic contractility after SCI are partly attributable to changes in the M receptor subtypes.

Keyword

Spinal cord injury; Colon; Muscarinic receptor subtype; M2; M3

MeSH Terms

Acetylcholine
Animals
Baths
Blotting, Western
Colon
HSP27 Heat-Shock Proteins
Muscle, Smooth
Muscles
Piperidines
Proteins
Rats
Rats, Sprague-Dawley
Receptors, Muscarinic
Spinal Cord
Spinal Cord Injuries
Acetylcholine
HSP27 Heat-Shock Proteins
Piperidines
Proteins
Receptors, Muscarinic

Figure

• 

  Fig. 1 Photographs of the colon of rats belonging to both groups. The upper and lower panels show the colons of the control (CON) spinal cord injured (SCI) rats, respectively. Note the fecal impaction in the distal colon of the SCI rats.

• 

  Fig. 2 Percentage changes in contractility after treatment with acetylcholine (Ach) for the control (CON) and spinal cord injury (SCI) groups. The intergroup difference in the percentage changes in contractility in the proximal colon along the longitudinal and circular muscle direction was significant. The values are expressed as mean±SD. *Denotes significant difference between the CON and SCI groups (*p<0.05).

• 

  Fig. 3 Percentage changes in contractility of the proximal and distal colon of the control (CON) and spinal cord injury (SCI) groups after acetylcholine (Ach) treatment of samples pretreated with AQ-RA741. The intergroup difference in the percentage changes in contractility in the proximal colon along the longitudinal and circular muscle direction was significant. The values are expressed as mean±SD. *Denotes significant difference between the CON and SCI groups (*p<0.05).

• 

  Fig. 4 Percentage changes in contractility of the proximal and distal colon of the CON and SCI groups after Ach treatment of samples pretreated with 4-DAMP. The intergroup difference in the percentage changes in contractility in the distal colon along the longitudinal muscle direction was significant. The values are expressed as mean±SD. *Denotes significant difference between the CON and SCI groups (*p<0.05).

• 

  Fig. 5 Results of western blot analysis for PGP 9.5 (B), RhoA (C), and HSP 27 (D) in the proximal and distal colon. (A) shows representative cases of each protein. The intergroup differences in the levels of PGP 9.5 in the proximal and distal colon and of RhoA and HSP 27 in the proximal colon were significant. The values are as expressed mean±SD. *Denotes significant difference between the CON and SCI groups (*p<0.05).

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