An in vitro technique has been developed for the simultaneous recording of vasoconstriction and transmitter release from small perfused blood vessels. To avoid excessive dilution of the released substances, 6-12-mg segments of rabbit ear arteries or rat tail arteries were mounted in 0.5-mL tissue chambers and perfusedsuperfused in a closed system. Drug administration and removal were performed by timer-controlled solenoid valves. Oscillation in the baseline generated by the roller pump was dampened by delivering Krebs' solution through a 4-mL buffer vial filled partly with air. Vasoconstriction was elicited by electrical stimulation and detected by pressure sensitive transducers. Transducer-generated electrical signals were amplified, digitalized, and recorded by a computerized system. Release of norepinephrine was measured after the tissue was preloaded with [3H]norepinephrine. This system allowed us to measure minimum vasoconstrictions of 1-2 mm Hgand [3H]norepinephrine efflux evoked by 4-8 electrical pulses. There was a good linear correlation (r = 0.98) between the contractile responses and tritiated norepinephrine release. Endogenous norepinephrine released by electrical stimulation into the perfusion media was determined by high-performance liquid chromatography (HPLC) in the low picogram range (80-100 pg). Our novel experimental setup permits computerized data acquisition and automated in vitro pharmacological experiments on isolated blood vessels.
- Endogenous norepinephrine release
- High-performance liquid chromatography
- Rabbit ear artery
- Rat tail artery
- [H]Norepinephrine overflow
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