ABSTRACT
Acetylcholine was injected into the common carotid artery of 15 mongrel dogs. In the animals with tied internal carotid artery, hyperpnoea, bradycardia and hypotension was observed, and in the animals with free internal carotid artery the hyperphoea was followed by apnoea. The administration of phentolamine provokes a temporary decrease or abolition of the reflexes produced by acetylcholine. This action of the alpha-blocker is due to a local effect because when phentolamine is injected intravenously it does not happen and the reflexes produced by acetylcholine with starting place at the carotid sinus of the opposite side are not affected.
Subject(s)
Acetylcholine/antagonists & inhibitors , Phentolamine/pharmacology , Pressoreceptors/drug effects , Reflex/drug effects , Respiration/drug effects , Animals , Carotid Artery, Internal , Dogs , Female , Injections, Intra-Arterial , MaleABSTRACT
1. On the carotid reflexogenic zone, pindolol provokes a proper action which consists in a respiratory excitation and a diminution of cardiac rate accompanied by decrease of blood pressure. 2. The infiltration of the tissues of the carotid bifurcation with a solution of propranolol annuls temporarily the carotid lobeline reflexes probably by the propranolol local anaesthetic action. 3. The beta blockers propranolol and pindolol, when injected in the vessels of the carotid zone, inhibits temporarily the carotid reflexes of lobeline by a local action on the carotid body. These results suggest that in the excitation of the receptor system of the carotid body by lobeline interferes an adrenergic mechanism.
Subject(s)
Carotid Body/physiology , Lobeline/pharmacology , Pindolol/pharmacology , Propranolol/pharmacology , Reflex/drug effects , Animals , Blood Pressure/drug effects , Carotid Body/drug effects , Dogs , Female , Heart Rate/drug effects , MaleABSTRACT
On the carotid reflexogenic zone lobeline provoques : 1) a increase of amplitude and rate of respiratory movements with bradycardia and hypotension ; 2) a secondary decrease of amplitude and rate of breathing with tachycardia. Acting on the reflexogenic zone, phentolamine and dibenamine provoque a transitory weakening or disappearance of these reflexes. These effects are induced by a local action, because they are not observed by intravenous injection of the drugs and the lobeline reflexes starting from the carotid sinus of the other side are not affected.
