Properties of rapidly adapting receptors of the airways in monkeys ( Macaca mulatta)

Abstract

The properties of rapidly adapting receptors (RARs) of the airways were examined in anaesthetised, artificially ventilated, paralysed and thoracotomised monkeys. The RARs were identified (i) by their rapid adaptation to a maintained inflation and forced deflation of the lungs and (ii) by their conduction velocity measurements. Right atrial ( n = 17) and left atrial ( n = 13) injections of histamine (10 μg/kg) stimulated the RARs. The stimulation was associated with an increase in peak intratracheal pressure. Right atrial injections of phenyl diguanide ( n = 6, 10 μg/kg) and 5-hydroxytryptamine ( n = 6, 10 μg/kg) did not produce a significant stimulation of the RARs. Administration of irritant vapours such as ammonia, ( n = 12), cigarette smoke ( n = 8), alcohol ( n = 10), acetone ( n = 10) and ether ( n = 7), caused a significant stimulation of the RARs. This stimulation occurred in spite of a significant decrease or no change in peak intratracheal pressure. During mild degrees of pulmonary venous congestion produced by graded increments in mean left atrial pressure (+ 5 and + 10 mmHg), there was a graded increase in RAR ( n = 6) activity. The present study shows the existence of the RARs in the airways of the rhesus monkey. These receptors are stimulated (i) by administration of agents which cause bronchoconstriction (ii) by vapours which cause airway irritation and (iii) in conditions which cause an expansion of the extravascular space in airways.