Changes in heart rate and forearm blood flow following intravenous boluses of isoprenaline in the presence of practolol and propranolol.

Publisher Website
Google Scholar
Abstract
Increases in heart rate and forearm blood flow following graded i.v. bolus injections of isoprenaline sulfate, were measured in a double-blind randomized study of 6 subjects who received either placebo, practolol 50 mg, practolol 200 mg, propranolol 10 mg or propranolol 40 mg. Dose related increases in forearm blood flow were produced by the graded boluses of isoprenaline sulfate. Practolol 50 mg attenuated the heart rate response to isoprenaline but did not significantly affect the changes in forearm blood flow. Practolol 200 mg further attenuated the heart rate responses but also decreased the forearm blood flow responses. Propranolol 10 mg and propranolol 40 mg significantly attenuated both the heart rate and forearm blood flow responses. The effect on forearm blood flow tended to be greater than the effect on heart rate. Practolol 200 mg had the same effect on heart rate responses as propranolol 10 mg but a significantly smaller effect on the forearm blood flow responses. The measurement of forearm blood flow following i.v. bolus injections of isoprenaline provides useful information about the .beta.2-adrenoceptor antagonism of propranolol and practolol. Application of the technique may be limited by the magnitude of the heart rate response and by the short-lived nature of the increase in forearm blood flow.