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Chlorpromazine at comparatively low concentrations potentiates carbachol‐induced tonic contraction of ileal longitudinal smooth muscle of the guinea‐pig
Author(s) -
Nasu Tetsuyuki,
Ou Shuichi
Publication year - 2000
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.2000.tb00015.x
Subject(s) - carbachol , tonic (physiology) , contraction (grammar) , endocrinology , chemistry , medicine , chlorpromazine , muscle contraction , stimulation , biology
— The neuroleptic phenothiazine derivative chlorpromazine (CPZ) at high concentration (1 × 10 −5 M) decreased either the phasic or tonic contraction in response to carbachol and the carbachol‐induced increase in [Ca 2+ ]i in both phases in ileal muscle. In contrast, CPZ at low concentrations (8 × 10 −7 – 5 × 10 −6 M) decreased only the phasic contraction and potentiated the tonic contraction induced by carbachol. However, CPZ at these concentrations dose‐dependently decreased the carbachol‐induced increase in [Ca 2+ ]i in both phases. These results suggested that CPZ dose‐dependently decreased the initial phasic contraction in response to carbachol by inhibition of Ca 2+ release from the intracellular storage sites. CPZ at low concentrations appears to increase Ca 2+ sensitivity to contractile proteins in the carbachol‐induced tonic phase. CPZ dose‐dependently reduced the 60 mM K+‐induced phasic and tonic responses and a concomitant decrease in [Ca 2+ ]i in ileal muscle.