Lack of effect of Z-butylidenephthalide on presynaptic N-type Ca²⁺ channels in isolated guinea-pig ileum.
Naunyn Schmiedebergs Arch Pharmacol 2016;
389:159-66. [PMID:
26497186 DOI:
10.1007/s00210-015-1183-5]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 10/07/2015] [Indexed: 01/23/2023]
Abstract
Z-Butylidenephthalide (Bdph) was reported to more potently inhibit electrically induced twitch responses than acetylcholine-induced tonic contraction in isolated guinea-pig ileum (GPI). The aim of the present study was to investigate the inhibitory effects of Z-Bdph on Ca2+ and K+ channels on GPI. In Locke-Ringer’s solution, both responses were isometrically recorded on a polygraph. Incubation of ω-conotoxin MVIIC, but not Z-Bdph, in the electrically stimulated GPI prior to adding ω-conotoxin GVIA, an irreversible blocker of N-type voltage-dependent Ca2+ channels (VDCCs), protected the binding sites and resulted in the twitch responses reversible by washing, suggesting that Z-Bdph did not bind to the N-type VDCCs. Interestingly, we found Z-Bdph concentration dependently delayed the onsets of K+-induced twitch responses, suggesting that Z-Bdph may be a blocker of K+ channels to interfere extracellular K+ across through the pre-junctional membrane of nerve ending in K+-free medium. Z-Bdph similar to nifedipine non-competitively inhibited cumulative ACh-induced phasic contractions, suggesting that Z-Bdph may bind to L-type of inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ channels on the endoplasmic reticulum (ER) membrane. In the presence of verapamil, a L-type Ca2+ channel blocker or Z-Bdph, the twitch inhibitions by either were effectively reversed by exogenous Ca2+, suggesting that they may freely pass through pre-junctional N-type, but not L-type which was blocked at least a part by either, of VDDCs open when each electrical coaxial stimulation (ECS) into intracellular space of cholinergic nerve terminal and trigger release of transmitters. In conclusion, results confirm that Z-Bdph more potently inhibits ECS-induced twitch responses than ACh-induced PCs in GPI and suggest that this effect is not mediated by interaction with presynaptic N-type VDCCs.
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