Mechanism of action of vasoactive intestinal polypeptide on myometrial smooth muscle of rabbit and guinea-pig.

摘要: 1. The action of vasoactive intestinal peptide (VIP) on the electrical and mechanical activity strips longitudinal myometrial smooth muscle from rabbits guinea-pigs treated with oestradiol was studied in sucrose-gap apparatus. 2. In which spontaneously exhibited regular contractions, or were induced to contract rhythmically application oxytocin, VIP reduced both frequency force contraction. 3. Contractions associated bursts potential discharge. guinea-pig, membrane reached its most negative value shortly following a burst slow decay negativity followed ("generator potential'). inhibited this increased duration period between bursts. rabbit myometrical strips, discharges occurred less regularly but also had an inhibitory action. not affected by beta-adrenoreceptor blocker propranolol, tetrodotoxin, apamin. 4. Using double apparatus, potentials contractions elicited depolarizing pulses absence oxytocin. Changes resistance estimated eliciting hyperpolarizing electrotronic potentials. hyperpolarized as now failed reach threshold for discharge fewer discharged. A small (about 10%) reduction freqeuently observed during hyperpolarization. 5. If single presence VIP, tension generated than absence. 6. calcium-free high-potassium (126 mM) solution, readmitting calcium produced contraction; Activation beta-receptors means isoprenaline similar effect unlike blocked propranolol. 7. It is suggested that primary economy cell, possibly accelerate sequestration and/or extrusion cell. some way inhibition generator potential, hyperpolarization, increase permeability potassium.