Lack of effect of Z-butylidenephthalide on presynaptic N-type Ca2+ channels in isolated guinea-pig ileum

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.

Mechanisms of butylidenephthalide for twitch facilitation in electrically stimulated mouse vas deferens

“…Thus, Bdph and verapamil did not influence their facilitations each other ( Figure 3(a) ). In contrast to MVD, we recently reported Bdph or verapamil (5 µM) inhibited, but not facilitated, the twitch response in electrically stimulated guinea-pig ileum (Chen and Ko 2016 ). Thus, the facilitation induced by Bdph or verapamil seems dependent on tissue preparation.…”

“… 2011 ). Z -Bdph has been reported to inhibit pre-junctional R-type, but not N-type, VDCCs of cholinergic nerve endings (Chen and Ko 2016 ). Furthermore, TEA (10 or 100 µM) or 4-AP (10 µM) significantly augmented log concentration-facilitation curve of Bdph ( Figure 4(a) ), but not verapamil with an exception that 4-AP significantly augmented verapamil-induced twitch facilitation at the least concentration of 1 µM ( Figure 4(b) ).…”

Butylidenephthalide facilitates contractions via nonspecific binding to receptors in isolated guinea-pig vas deferens

“…1997). Z -Bdph may inhibit the prejunctional R-type, but not the N-type, VDCCs of cholinergic nerve endings (Chen and Ko 2016). By contrast, the binding of Z -Bdph to the nonadrenergic prejunctional VDCCs of the cell membrane was more potent than that of E -Bdph in the electrically stimulated prostatic portion of rat vas deferens with stereoselectivity during twitch inhibition (Shih et al.…”