Thiopental induces contraction of rat aortic smooth muscle through Ca(2+) release from the sarcoplasmic reticulum

• Published in: Anesthesia and analgesia Vol. 91; no. 1; pp. 62 - 67
• Main Authors: Mousa, W F, Enoki, T, Fukuda, K
• Format: Journal Article
• Language: English
• Published: United States 01.07.2000
• Subjects: Animals; Aorta, Thoracic - drug effects; Aorta, Thoracic - physiology; Caffeine - pharmacology; Calcium - metabolism; Hypnotics and Sedatives - pharmacology; In Vitro Techniques; Male; Muscle Contraction - drug effects; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - physiology; Rats; Rats, Wistar; Sarcoplasmic Reticulum - metabolism; Thapsigargin - pharmacology; Thiopental - pharmacology; Vasoconstriction - drug effects
• ISSN: 0003-2999
• DOI: 10.1213/00000539-200007000-00012

Little is known about the mechanism of thiopental-induced contraction in vascular smooth muscle. This study aimed to clarify this question by conducting isometric tension experiments and (45)Ca(2+) flux measurements in endothelium-denuded rat aortic rings. Thiopental induced a concentration-dependent contraction under basal tension. This contraction was enhanced when rings were precontracted with phenylephrine in the presence of verapamil. In Ca(2+)-free solution, thiopental-induced contraction was reduced but not abolished with high concentrations. Ca(2+) store depletion with a maximum dose of caffeine in Ca(2+)-free solution further reduced the contraction by subsequent thiopental. Ca(2+) store depletion with thapsigargin completely abolished contraction by thiopental. (45)Ca(2+) influx experiment in the presence of verapamil showed that thiopental could not induce any Ca(2+) influx with or without phenylephrine prestimulation. The (45)Ca(2+) efflux experiment showed more evidence of thiopental-induced Ca(2+) release, which was abolished by thapsigargin. In conclusion, thiopental induces contraction in rat aortic smooth muscle by releasing Ca(2+) from the sarcoplasmic reticulum without Ca(2+) influx. This is the first study providing evidence that thiopental-induced vascular contraction is caused by Ca(2+) release from the sarcoplasmic reticulum of the smooth muscle.