Atrial receptors in the dog and rabbit

Abstract

SUMMARY1. Action potentials were recorded from slips of the cervical vagi in anaesthetized dogs and rabbits. Single functional units with atrial patterns of discharge (Paintal Type A, B and intermediate) were obtained and then attempts were made to alter (i.e. convert) their patterns of discharge. Finally the points of origin of these action potentials were located.2. Thirty unselected units were investigated in thirty dogs. Twentyseven of these were located in the endocardium of the vein-atrial system and the ratio of the type A, type B and intermediate type receptors was 1: 16: 10; three units were located elsewhere in the chest. Conversion of the pattern of discharge was achieved in twenty of the twenty-seven units; conversion was achieved in the single type A unit.3. In a second series of experiments in dogs, eight Paintal Type A units were selectively studied in fifteen animals. Four of these were located in the endocardium and all were converted. The remaining four were located outside the endocardium and conversion could not be achieved in two of these. Thus in the entire investigation, the 'type A' units which could not be converted were all located at sites other than the atrial endocardium.4. In the corresponding unselected study in the rabbit, eleven units were studied in eleven animals. Nine of these units were located in the atrial endocardium and the ratio of the type A, type B and intermediate type receptors was 2:1:6. Conversion was achieved in both type A units, the sole type B unit and two of the intermediate units.

Type A atrial receptors in the cat: effects of changes in atrial volume and contractility.

“…An atrial receptor may have its endings functionally orientated so as to detect atrial filling ('in parallel' orientation), and it could be located in the atrial wall close to another receptor whose endings are functionally orientated so as to detect atrial contraction ('in series' orientation) (Whitteridge, 1953;Recordati et al 1976). Such orientation of atrial endings would explain the following findings, which are in apparent contradiction to those reported by Kappagoda et al (1976Kappagoda et al ( , 1977. First, in our present and previous studies, few type A atrial receptors have been located on the lateral free wall of the right atrium.…”

“…Pattern of discharge Kappagoda et al (1976Kappagoda et al ( , 1977, demonstrated that the pattern of spontaneous discharge of an atrial receptor is mainly dependent upon its anatomical location. The present study confirms this observation.…”

“…If the atrial endings have similar transducing properties (Arndt et al 1974), then for a given location (Kappagoda et al 1976(Kappagoda et al , 1977 and orientation (Chapman & Pankhurst, 1976) of the endings, atrial dynamics, namely atrial volume and the state of atrial contraction, are the determinants of the pattern of discharge. Changes in atrial volume mainly affect the diastolic discharge while changes in the inotropic state mainly influence the systolic burst of impulses.…”

“…Almost all type A receptors could be converted into Intermediate type or type B receptors Kappagoda et al 1976Kappagoda et al , 1977 (Kappagoda et al 1976(Kappagoda et al , 1977Rao, Fahim & Gupta, 1975;Gupta, 1977 …”

The Atrial Receptors Responsible for the Decrease in Plasma Vasopressin Caused by Distension of the Left Atrium in the Dog

“…2) Paintal, 1953;Kappagoda, Linden & Mary, 1977). On the left side of the heart, these receptors are situated mainly at the pulmonary vein-left atrial junctions (Coleridge, Hemingway, Holmes & Linden, 1957;Kappagoda et al 1977). Receptors with nonmyelinated vagal afferent fibres (e.g.…”