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EFFECTS OF ADRENOCEPTOR BLOCKADE ON PLASMA CATECHOLAMINE LEVELS DURING ADRENALINE INFUSION
Author(s) -
BRITTON B.J.,
IRVING M.H.,
WOOD W.G.
Publication year - 1977
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1977.tb06969.x
Subject(s) - phenoxybenzamine , premedication , propranolol , epinephrine , liter , saline , catecholamine , endocrinology , basal (medicine) , medicine , anesthesia , insulin
1 The present experiments investigate the effects of phenoxybenzamine and propranolol, singly and in combination, on plasma catecholamine levels in sheep receiving a three‐hour adrenaline infusion. 2 Five groups of five anaesthetized sheep were studied for a period of 3 h each. One group acted as a control and received only a saline (0.9% w/v NaCl solution) infusion. A second group received a constant infusion of adrenaline (2 μg kg body weight −1 min −1 ). A third group received a similar adrenaline infusion, having been premedicated with phenoxybenzamine (1 mg/kg body weight). A fourth group received a similar adrenaline infusion following premedication with (±)‐propranolol hydrochloride (7 μg/kg body weight). The fifth group received the adrenaline infusion following premedication with both the α‐ and β‐blocker in the above doses. 3 Plasma catecholamines were measured on blood samples taken at seven intervals before, during and following the infusion. 4 Control animals receiving only a saline infusion remained physiologically and biochemically stable throughout the experimental period. 5 Adrenaline infusion in animals not receiving adrenoceptor blocking drugs caused a rise in plasma adrenaline levels from a low basal value of 1 μg/litre to a maximum level of 19.8 μg/litre. Animals premedicated with phenoxybenzamine exhibited a similar response. 6 Animals premedicated with propranolol before the infusion of adrenaline did not demonstrate as marked a rise of plasma adrenaline levels as the two previous groups. The maximum mean plasma adrenaline level recorded in this group was 6.88 μg/litre. 7 Animals premedicated with phenoxybenzamine and propranolol before the infusion of adrenaline showed only a small rise in plasma adrenaline levels compared with animals receiving adrenaline infusion alone. The maximum mean plasma adrenaline level in the group was only 3.43 μg/litre. 8 The studies demonstrate that by an unknown mechanism β‐adrenoceptor blockade with (±)‐propranolol, either alone or in combination with phenoxybenzamine, lowers the plasma adrenaline response evoked by adrenaline infusion.