Substance P, like acetylcholine, augments one type of Ca2+ current in isolated smooth muscle cells.
Electrophysiological recordings from freshly-dissociated smooth muscle cells from toad stomach revealed that substance P enhances one of two types of Ca2+ currents. That is, substance P enhances the slowly inactivating, high-threshold current but not the fast inactivating, low-threshold current. Acetylcholine has the same effect, but the acetylcholine action is blocked by atropine whereas the substance P action is not, indicating that the two agents act at different receptor sites. Thus, substance P, like acetylcholine, has a dual excitatory action on the smooth muscle cells employed in these studies, enhancing a specific type of Ca2+ current, as demonstrated here, and suppressing a voltage-sensitive K+ conductance, as previously described [Sims, S.M., Walsh, J.V., Jr. & Singer, J.J. (1986) Am. J. Physiol. 251, C580-C587].
Clapp
L H
LH
Department of Physiology, University of Massachusetts Medical School, Worcester 01655.
Vivaudou
M B
MB
Singer
J J
JJ
Walsh
J V
JV
D000109:Acetylcholine / Q000502:physiology; D000818:Animals; D002024:Bufo marinus; D002118:Calcium / Q000502:physiology*; D004075:Diglycerides / Q000502:physiology; D004594:Electrophysiology; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000502:physiology*; D013373:Substance P / Q000502:physiology*
D004075:Diglycerides; D013373:Substance P; D000109:Acetylcholine; D002118:Calcium