Contractile actions of L-type Ca2+-agonists in human vas deferens and effects of structurally different Ca2+-antagonists Export

@article{citeulike:6052073, abstract = {The actions of L-type Ca 2+ agonists, FPL 64176 and Bay K 8644 were investigated in human vas deferens in the presence of structurally different L-type Ca 2+ antagonists. The L-type Ca 2+ agonists (≤3 µM, \~{} 10 min) produced no detectable contractions but higher concentrations evoked intermittent rhythmic contractility of longitudinal and circular muscles. Exposure to the drugs (1 µM,≥20 min) evoked only rhythmic contractility even in moderately depolarizing ([K + ] O , 10 mM) medium. These findings suggest low basal activity of L-type Ca 2+ channels (VOCs) in both muscle types. In the presence of L-type Ca 2+ agonists (1 µM), high [K + ] O (30 or 120 mM) evoked contractions with different profiles. Circular muscle had a predominance of rhythmic activity ([K + ] O 30 mM) and slow time to peak and decline ([K + ] O 120 mM). Longitudinal muscle was more tonic ([K + ] O 30 mM) with a rapid time to peak and decline ([K + ] O 120 mM). The contractions in both muscle types were blocked by nifedpine or methoxyverapamil; indicating the involvement of L-type VOCs and suggests that the distinct contractile profiles originate from differences in mechanisms that regulate contractility. In comparison to the conventional L-type Ca 2+ antagonists, fendiline, prenylamine and thioridazine were more effective against longitudinal than circular muscle contractions. Structurally similar diphenylalkylamines (cinnarizine, flunarizine, pimozide) and phenothiazines (sulphoridazine, chlorpromazine, trifluoperazine) inhibited the contractions comparably in both muscle types. These findings are discussed in relation to inhibition of muscle type-specific mechanisms that may contribute more to L-type VOC activation and contractility in longitudinal than in circular muscle.}, author = {Amobi, Nnaemeka and Guillebaud, John and Smith}, citeulike-article-id = {6052073}, citeulike-linkout-0 = {http://dx.doi.org/10.1016/j.ejphar.2009.10.043}, citeulike-linkout-1 = {http://linkinghub.elsevier.com/retrieve/pii/S0014299909009509}, day = {28}, doi = {10.1016/j.ejphar.2009.10.043}, issn = {00142999}, journal = {European Journal of Pharmacology}, month = {October}, posted-at = {2009-10-31 23:05:39}, title = {Contractile actions of L-type Ca2+-agonists in human vas deferens and effects of structurally different Ca2+-antagonists}, url = {http://dx.doi.org/10.1016/j.ejphar.2009.10.043}, year = {2009} }

TY - JOUR ID - citeulike:6052073 L3 - citeulike-article-id:6052073 N2 - The actions of L-type Ca 2+ agonists, FPL 64176 and Bay K 8644 were investigated in human vas deferens in the presence of structurally different L-type Ca 2+ antagonists. The L-type Ca 2+ agonists (≤3 µM, ~ 10 min) produced no detectable contractions but higher concentrations evoked intermittent rhythmic contractility of longitudinal and circular muscles. Exposure to the drugs (1 µM,≥20 min) evoked only rhythmic contractility even in moderately depolarizing ([K + ] O , 10 mM) medium. These findings suggest low basal activity of L-type Ca 2+ channels (VOCs) in both muscle types. In the presence of L-type Ca 2+ agonists (1 µM), high [K + ] O (30 or 120 mM) evoked contractions with different profiles. Circular muscle had a predominance of rhythmic activity ([K + ] O 30 mM) and slow time to peak and decline ([K + ] O 120 mM). Longitudinal muscle was more tonic ([K + ] O 30 mM) with a rapid time to peak and decline ([K + ] O 120 mM). The contractions in both muscle types were blocked by nifedpine or methoxyverapamil; indicating the involvement of L-type VOCs and suggests that the distinct contractile profiles originate from differences in mechanisms that regulate contractility. In comparison to the conventional L-type Ca 2+ antagonists, fendiline, prenylamine and thioridazine were more effective against longitudinal than circular muscle contractions. Structurally similar diphenylalkylamines (cinnarizine, flunarizine, pimozide) and phenothiazines (sulphoridazine, chlorpromazine, trifluoperazine) inhibited the contractions comparably in both muscle types. These findings are discussed in relation to inhibition of muscle type-specific mechanisms that may contribute more to L-type VOC activation and contractility in longitudinal than in circular muscle. JF - European Journal of Pharmacology SN - 00142999 TI - Contractile actions of L-type Ca2+-agonists in human vas deferens and effects of structurally different Ca2+-antagonists AU - Amobi, Nnaemeka AU - Guillebaud, John AU - Smith PY - 2009/10/28/ UR - http://dx.doi.org/10.1016/j.ejphar.2009.10.043 ER -