Transducer properties of atrial receptors in the dog after 60 min of increased atrial pressure

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Abstract
This investigation was undertaken to examine the effect of a period of increased atrial pressure lasting 60 min on the ability of atrial receptors to transduce changes in atrial pressure. The experiments were performed on dogs anesthetized with pentobarbitone. Action potentials were recorded from branches of the cervical vagi and the atrial pressure was increased by distending a balloon in the lumen of the left atrium. Twelve receptors were examined in 14 dogs. For each receptor, stimulus–response curves relating the action potentials generated (number per cardiac cycle) to the mean left atrial pressure (centimetres of H2O) were obtained under three experimental conditions: (a) during an initial control period, (b) after 60 min of increased atrial pressure (i.e. 10–12 cm H2O), and (c) 60 min after restoration of the atrial pressure to its control value. It was found that in all 12 units the ability of the receptors to transduce changes in atrial pressure was impaired after 60 min of increased atrial pressure, i.e., the number of action potentials generated by a receptor for the same atrial pressure was smaller than that in the control period. This effect was partially restored in the 12 units 60 min after restoration of the atrial pressures to their respective control values.In four units the stimulus–response curves were repeated 60 min after obtaining the initial control response. It was found that there was no significant difference in each pair of curves. It is concluded that relatively short periods of increased atrial pressure impair transducer properties of the atrial receptors.