An automated superfusion technique for measuring circular muscle contraction. Effects of serotonin on intra- and extracranial arteries

A new in vitro technique is described and its advantages are demonstrated: “true” circular contraction is measured; arteries are in cascade, permitting comparison of intra- and extracranial arteries from the same animal; the mechanical influences on contractility are reduced; long-lasting experiments of up to 50 h can be performed; the procedure is fully automated. The maximal effect of an agonist was not only markedly modified during the first 2–4 h after fixing the arteries in the apparatus but also slightly during the next 3–4 h. After the initial stabilization period, the arterial response to an agonist remained highly reproducible for 24–48 h (standard deviation not exceeding 7%). This was demonstrated in all the types of arteries tested. With serotonin as agonist, there was a significant difference in −log ED 50 values for intracranial arteries (basilar 8.70, middle cerebral 8.72) vs. extracranial (lateral nasal 8.15; facial 8.14) and peripheral (branch of saphenous 8.14) arteries.