Multiple muscarinic pathways mediate the suppression of voltage‐gated Ca²⁺ channels in mouse intestinal smooth muscle cells

Abstract

Background and purpose: Stimulation of muscarinic receptors in intestinal smooth muscle cells results in suppression of voltage-gated Ca 2+ channel currents (ICa). However, little is known about which receptor subtype(s) mediate this effect. Experimental approach: The effect of carbachol on ICa was studied in single intestinal myocytes from M2 or M3 muscarinic receptor knockout (KO) and wild-type (WT) mice. Key results: In M2KO cells, carbachol (100 mM) induced a sustained ICa suppression as seen in WT cells. However, this suppression was significantly smaller than that seen in WT cells. Carbachol also suppressed ICa in M3KO cells, but with a phasic time course. In M2/M3-double KO cells, carbachol had no effect on ICa. The extent of the suppression in WT cells was greater than the sum of the ICa suppressions in M2KO and M3KO cells, indicating that it is not a simple mixture of M2 and M3 receptor responses. The Gi/o inhibitor, Pertussis toxin, abolished the ICa suppression in M3KO cells, but not in M2KO cells. In contrast, the Gq/11 inhibitor YM-254890 strongly inhibited only the ICa suppression in M2KO cells. Suppression of ICa in WT cells was markedly reduced by either Pertussis toxin or YM-254890.

Flavonoid galetin 3,6-dimethyl ether attenuates guinea pig ileum contraction through K + channel activation and decrease in cytosolic calcium concentration

“…Contractile agents such as acetylcholine, histamine and KCl cause a biphasic contractile response consisting of a transient contraction (phasic) followed by a sustained one (tonic) maintained during exposure to the contractile agent (Horie et al, 2005;Tanahashi et al, 2009). It has been reported that the phasic contraction is caused by inositol 1,4,5-trisphosphate (IP 3 )-mediated Ca 2+ release from intracellular stores (Abdel-Latif, 1989;Kobayashi et al, 1989), whereas the tonic contraction is attributed to a Ca 2+ influx through Ca V (Jim et al, 1981).…”

Ent-7α-acetoxytrachyloban-18-oic acid and ent-7α-hydroxytrachyloban-18-oic acid from Xylopia langsdorfiana A. St-Hil. & Tul. modulate K+ and Ca2+ channels to reduce cytosolic calcium concentration on guinea pig ileum

“…The ileal smooth muscle is known to present biphasic contraction where, in the first phase, the muscle exhibits a fast and transient contraction followed by a long-lasting second phase characterized by the maintained tonic contraction (Horie et al, 2005;Tanahashi et al, 2009). However, both phasic and tonic antagonist-induced contractions depend on extracellular calcium since both are inhibited in its absence (Honda et al, 1996).…”

Roles of M2 and M3 muscarinic receptors in the generation of rhythmic motor activity in mouse small intestine

“…The generation and breeding of the M 2 and M 3 muscarinic receptor single-KO, M 2 /M 3 double-KO and their WT mice has been previously described. [21][22][23][24] The WBB6F1-W/W v (W/W v ) mice, which selectively lack ICC-MY in the small intestine, 18,[25][26][27] and the WBB6F1-+/+ (+/+) control mice were purchased from Japan SLC (Hamamatsu, Shizuoka, Japan).…”