Responses of the Sino-atrial Node to Change in Pressure in the Sinus Node Artery

Abstract

The sino-atrial node area was perfused selectively through the right atrial artery in 76 dogs. The relationship between changes in the blood pressure in this artery and sinus node rhythmicity was studied in 56 hearts in which the major blood supply to the sinus node artery came from the right atrial artery. A reciprocal relation was observed between changes of blood pressure in the sinus node artery and the sinus rate. Some characteristics were: (1) The negative chronotropic effect induced by raising the blood pressure was linearly related to the Degrees of pressure change and more prominent than the positive chronotropic effect induced by reducing the pressure. (2) This relationship was most prominent in a limited range between 20 and 100 mm Hg. (3) Dichloroisoproterenol, atropine, hexamethonium, reserpine and vagotomy did not modify these responses. It is concluded that this localized mechanosensitivity of the sinus node to changes in arterial pressure may be responsible for the regulation of the heart rate in the lower range of blood pressure and that complete regulation of the heart rate is achieved physiologically in combination with the reflexes through the carotid and aortic nerves.

Comparison of Beta-Adrenergic Blocking Effect of Dci, Methoxamine, Propranolol, Mj 1999, H 56/28, Lb 46 and I.C.I. 50 172 on the Chronotropic Response to Isoprenaline

“…Previously the authors arranged the constant pressure perfusion of the sinus node artery in situ in vagotomized dogs (12). This proce dure in combination with the use of a micrometer-injector permitted us to observe drug response without interference from the chronotropic response to the pressure change caused by injection volume of drug solution.…”

“…The direct perfusion of the sinus node artery reported by James and Nadeau (11) was modified by the present authors. The details of preparation were described in previous papers (12,14), but all experiments were performed under a constant pressure at 100 mmHg. The arrangement of the constant pressure perfusion is shown in Fig.…”

Comparison of the chronotropic responses to local anesthetics (procaine, lidocaine, prilocaine, mepivacaine and bupivacaine) of the canine sinus node in situ.

“…The chest was opened through the right fourth intercostal space and the heart was cradled in the pericardial sac. The dorsal right atrial artery (sinus node artery) was then dissected free from the atrial wall and after proximal ligation, it was cannulated with a non-slip catheter with an outer diameter of about 0.5 mm at its tip (5)(6)(7).…”

Effect of Sodium Pentobarbital on the SA Nodal Activity of the Dog Heart <i>in vivo</i>

“…In 1964, Schaer reported that the rate decrease caused by a given concentration of sodium pentobarbital is dependent upon the rate before the administration of the drug in the dog heart-lung preparation accelerated by infusion of norepinephrine, i.e., only if the pacemaker activity exceeds a certain level, sodium pentobarbital can exert a negative chronotropic effect (Schaer 1964). In the present study, we investigated the direct effects of sodium pentobarbital on the SA nodal activity, using a method for in situ perfusion of the sinus node artery of the dog (Hashimoto et al 1967). In addition, the rate-increasing effect of norepinephrine injected into the sinus node artery was examined on the pacemaker depressed by injecting sodium pentobarbital into the sinus node artery.…”