Difference between substance P- and acetylcholine-induced currents in mammalian smooth muscle cells.
The effects of substance P (SP) and acetylcholine (ACh) on membrane currents were compared using freshly isolated smooth muscle cells from guinea-pig ileum. Both SP (100 nM) and ACh (10 microM) induced inward currents at negative holding potentials. The ACh-induced current, but not the SP-induced current, showed relaxation upon voltage-stepping. The SP-induced current was increased by hyperpolarization more negative than -50 mV whereas the ACh-induced current was decreased by hyperpolarization. The results suggest that the SP-induced inward current is elicited via an ionic pathway different from that involved with ACh-activated channels.
Division of Pharmacology, National Institute of Hygienic Sciences, Tokyo, Japan.
K
K
Nakazawa
K
K
Inoue
K
K
Fujimori
A
A
Takanaka
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009529:Nicardipine / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology*
D007473:Ion Channels; D013373:Substance P; D009529:Nicardipine; D000109:Acetylcholine