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Factors modifying the frequency of spontaneous activity in gastric muscle
Author(s) -
Suzuki H.,
Kito Y.,
Hashitani H.,
Nakamura E.
Publication year - 2006
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2006.117093
Subject(s) - chemistry , neuroscience , medicine , biology
The cellular mechanisms that determine the frequency of spontaneous activity were investigated in gastric smooth muscles isolated from the guinea‐pig. Intact antral muscle generated slow waves periodically; the interval between slow waves was decreased exponentially by depolarization of the membrane to reach a steady interval value of about 7 s. Isolated circular muscle bundles produced slow potentials spontaneously or were evoked by depolarizing current stimuli. Evoked slow potentials appeared in an all‐or‐none fashion, with a refractory period of ∼2–3 s. Low concentrations of chemicals that modify intracellular signalling revealed that the refractory period was causally related to the activity of protein kinase C (PKC). Activation of PKC increased and inhibition of PKC activity decreased the frequency of slow potentials. Chemicals that inhibit mitochondrial functions reduced the frequency of slow waves. Inhibition of internal Ca 2+ ‐store activity decreased the amplitude, but not the frequency of slow potentials, suggesting that the amplitude is causally related to Ca 2+ release from the internal store. The results suggest that changes in [Ca 2+ ] i caused by the activity of mitochondria may play a key role in determining the frequency of spontaneous activity in gastric pacemaker cells.