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Electrical rhythmicity and spread of action potentials in longitudinal muscle of guinea pig distal colon.
- Source :
-
American journal of physiology. Gastrointestinal and liver physiology [Am J Physiol Gastrointest Liver Physiol] 2002 May; Vol. 282 (5), pp. G904-17. - Publication Year :
- 2002
-
Abstract
- Using simultaneous intracellular recordings, we have characterized 1) electrical activity in the longitudinal muscle (LM) of isolated segments of guinea pig distal colon free to contract spontaneously and 2) extent of propagation of spontaneous action potentials around the circumference of the colon. In all animals, rhythmical spontaneous depolarizations (SDs) were recorded that are usually associated with the generation of action potentials. Recordings from pairs of LM cells, separated by 100 microm in the circumferential axis, revealed that each action potential was phase locked at the two electrodes (mean propagation velocity: 3 mm/s). However, at an increased electrode separation distance of 1 mm circumferentially, action potentials and SDs became increasingly uncoordinated at the two recording sites. No SDs or action potentials ever propagated from one circumferential edge to the other (i.e., 13 mm apart). When LM strips were separated from the myenteric plexus and circular muscle, rhythmically firing SDs and action potentials were still recorded. Atropine (1 microM) or tetrodotoxin (1 microM) either reduced the frequency of SDs or temporarily abolished activity, whereas nifedipine (1 microM) always abolished SDs and action potentials. Kit-positive interstitial cells of Cajal were present at the level of the myenteric plexus and circular and longitudinal muscle. In summary, SDs and action potentials in LM propagate over discrete localized zones, usually <1 mm around the circumference of the colon. Furthermore, in contrast to the classic slow wave, rhythmic depolarizations in LM appear to be generated by an intrinsic property of the smooth muscle itself and are critically dependent on opening of L-type Ca(2+) channels.
- Subjects :
- Action Potentials drug effects
Anesthetics, Local pharmacology
Animals
Atropine pharmacology
Calcium Channel Blockers pharmacology
Colon innervation
Electrophysiology
Enteric Nervous System physiology
Guinea Pigs
Muscle, Smooth innervation
Nifedipine pharmacology
Parasympatholytics pharmacology
Periodicity
Sodium metabolism
Tetrodotoxin pharmacology
Action Potentials physiology
Colon physiology
Gastrointestinal Motility physiology
Muscle, Smooth physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0193-1857
- Volume :
- 282
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- American journal of physiology. Gastrointestinal and liver physiology
- Publication Type :
- Academic Journal
- Accession number :
- 11960786
- Full Text :
- https://doi.org/10.1152/ajpgi.00345.2001