Rhythmic spontaneous contractions in the rat proximal colon

Area of Science:

• Gastroenterology
• Cell Biology
• Physiology

Background:

• Interstitial cells of Cajal (ICCs) expressing c-kit are known pacemakers for gastrointestinal motility.
• Previous research identified c-kit positive ICCs in the proximal colon of guinea pigs and rats.
• Rhythmic spontaneous contractions (RSCs) in rat proximal colon are tetrodotoxin-insensitive.

Purpose of the Study:

• To investigate the role of c-kit positive ICCs in generating RSCs in the rat proximal colon.
• To determine if RSCs are absent in Ws/Ws mutant rats lacking c-kit positive ICCs (ICC(SM) and ICC(MY)).

Main Methods:

• Utilized Ws/Ws mutant rats, which lack c-kit positive ICCs.
• Recorded and analyzed spontaneous contractions in the proximal colon of Ws/Ws mutant and wild-type rats.
• Administered sarcoplasmic reticulum Ca(2+)-ATPase blockers (cyclopiazonic acid and thapsigargin) to assess effects on RSC frequency.

Main Results:

• RSCs were present in Ws/Ws mutant rats, contrary to the initial hypothesis.
• C-kit negative ICC(SM) remain functional in Ws/Ws mutant rats.
• Blockade of sarcoplasmic reticulum Ca(2+)-ATPase increased RSC frequency, with a more pronounced effect in Ws/Ws mutant rats.

Conclusions:

• RSCs in the rat proximal colon are likely generated by c-kit negative ICC(SM).
• Functional coordination between c-kit negative ICC(SM) and impaired c-kit positive ICCs is crucial for regulating spontaneous activity frequency.
• This suggests a more complex cellular network underlies gastrointestinal pacemaker activity than previously understood.