Calcium signalling and removal mechanisms in myenteric neurones.
To characterize further the Ca2+ signalling mechanisms of myenteric neurones, we studied the effect of thapsigargin, a blocker of the Ca2+-store ATPase, and the mechanisms involved in restoring the intracellular Ca2+ concentration ([Ca2+]i) after activation. Thapsigargin (5 x 10(-6) mol L(-1)) induced an oscillatory [Ca2+]i response in 86.6% of the neurones (n=276), which was blocked by the removal of extracellular Ca2+ and by omega-conotoxin MVIIA (5 x 10(-7) mol L(-1)). The IP3-blocker, 2-aminoethyl-diphenyl-borate (75 x 10(-6) mol L(-1)), blocked or reduced the responses in 74.5% of the neurones. The oscillatory responses induced by the depletion of Ca2+ stores suggest that myenteric neurones might recruite N-type Ca2+ channels as a refill mechanism. Thapsigargin pretreatment increased the amplitude, the upstroke and duration of the K+-induced [Ca2+]i responses. Mitochondrial blockers (rotenone and antimycin/oligomycin) also prolonged the responses, but without affecting the amplitude. Furthermore, it was found that for high [Ca2+]i, the thapsigargin-sensitive Ca2+ uptake was crucial, while mitochondrial blockade affected the Ca2+ uptake over a wide range of concentrations. The Ca2+-sequestering components might also have been compensating for each other, as most drugs only delayed and not inhibited Ca2+ removal.
Vanden Berghe
P
P
Center for Gastroenterological Research, Katholieke Universiteit Leuven, Leuven, Belgium. pieter@physio.unr.edu
Missiaen
L
L
Janssens
J
J
Tack
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D007421:Intestine, Small / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D019284:Thapsigargin; D002118:Calcium