DEMONSTRATION OF DEPRESSANT EFFECT OF PROPRANOLOL AND ACEBUTOLOL ON THE CONTRACTILE RESPONSE OF RAT ISOLATED DIAPHRAGM WITH ELECTRICAL STIMULATION
Abstract
Background: Propranolol is a non-selective, while acebutolol is a cardioselective beta blocker. This study wasdesigned to implore into the effect of nonselective and cardioselective beta blockers on the electrically stimulatedcontractile response of isolated diaphragm of rat. Methods: Study was conducted on male and female rats of albinovariety, weighing 150-200 grams, in Jinnah Postgraduate Medical Centre Karachi. Diaphragmatic strips wereprepared. Tissue was transferred to a tissue bath containing oxygenated Krebs solution kept at 32°C. One end of thestrip was connected to the electrodes of an electric stimulator, while its other end was connected to a polygraph througha force displacement transducer. Normal recordings of the response of tissue to electrical stimulation was obtained.The response was observed with 10-8 – 10-3 M concentrations of propranolol and acebutolol separately and in series.Contractile response of the tissue was measured in millimeters. Arithmetic mean for each set of observation wasdetermined.T test was performed and P value was determined from the t table Results: Both propranolol and acebutolol producedsignificant depression of the contraction of rat isolated diaphragm as a result of electrical stimulation. Conclusion:Our study has shown that the depressant effect of beta adrenoceptor blocking drugs. perhaps, do not play importantrole in the etiology of respiratory distress produced by these drugs, because the depressant effect of both propranololand acebutolol on diaphragm are only produced in high doses.References
Hoffman. B.B. (1998). Adrenoceptor antagonist drugs,
in basic and clinical Pharmacology. Edited by Bertram
G. Katzung. 7th ed Stanford. Connecticut. Appleton and
lange. pp. 136-1 51.
Macdonald. A.G., Ingram. C.G. and McNeil. R.S.
(1967). The effect of propranolol on airway resistance.
Br. J. Anaesth. 39:919-926.
Besterman. E.. V1. M. (1966). Precipitation of asthma
in chronic bronchitis. Am .1 Cardiol. 18:475
(Discussion).
Bongrani. S.. Folca. C.G.. Razzetti. Razzetti. R. and
Schiantarelli. P (1983). Beta adrenoceptor blockade U
the basis of the guinea-pig hyper responsiveness to
leukotriene C4 and other agonists. Br .1. Pharmacol.
:839-948.
Harry. J D. Linden. R.J. and Snow. H.M. (1974). The
effects of three beta adrenoceptor blocking drugs on
isolated preparation of skeletal and cardiac muscle. Br
.1 Pharmacol. 52:275-281.
Drazen. J.M.. Lacouture. P.G. and Miller. M.J. (198.3).
Inhibition In propranolol of the contractile response of
the rat diaphrgm to tetanic field stimulation in vitrol.
Br. .1. Pharmacol. 80: 613-618.
Tang. HP.. Gale. M.M. and Ritteer. J.M. (1999).
Noradrenergic Transmission, in Pharmacology. Edited
by II P. Rang et al. 4th edition. Edinburgh. Churchill
Livingstone. PP 139-163.
Laurence. D. R. Bennet. P.N. Brown. M.J. (1997).
Arterial hypertension, angina pectoris. Myocardial
infarction in clinical Pharmacology. Edited by D.R.
Larence et al. 8 editions. London. Churchill
Livingstone. PP. 425-457.
Staufer. J.L. (1998). Lung in current medical diagnosis
and treatment. Edited by Lawrence M. Tierney. Jr. Et
al 37 edition. Stamford. Appleton and Lange. PP.251 -
