Premium
Effects of calcium modulators on vagally‐mediated constriction in the guinea‐pig isolated trachea
Author(s) -
McCaig Dorothy J.,
Aitken Susan
Publication year - 1991
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1991.tb12433.x
Subject(s) - nifedipine , verapamil , constriction , medicine , endocrinology , stimulation , chemistry , calcium , guinea pig , efferent , anesthesia , afferent
1 The effects of calcium modulators on tracheal constriction evoked by vagal stimulation were examined in the isolated, innervated trachea of the guinea‐pig. Responses were assessed in the Krebs‐filled trachea as changes in intraluminal pressure (ILP), increases and decreases reflecting constriction and dilatation, respectively. 2 Preparations had a positive resting ILP, indicating significant spontaneous tone. Verapamil and nifedipine reduced baseline ILP, whilst Bay K 8644 had mixed effects. 3 Verapamil and nifedipine attenuated vagal responses in a concentration‐dependent manner. At lower concentrations attenuation was due entirely to postjunctional effects but at higher concentrations prejunctional effects may have contributed to attenuation. 4 Verapamil and nifedipine attenuated vagal responses in the absence or presence of flurbiprofen, indicating that their effects are largely independent of the generation of cyclo‐oxygenase products. Nifedipine, however, was less effective in reducing responses to low frequency vagal stimulation (up to 5 Hz) when flurbiprofen was present. 5 Bay K 8644 augmented vagal responses, the degree varying widely between preparations. 6 It was concluded that influx of Ca 2+ through voltage‐operated Ca 2+ channels contributes significantly to vagally‐mediated tracheal constriction in normal trachea and in trachea where endogenous release of cyclo‐oxygenase products is inhibited.