Location-dependent characteristics of pulmonary stretch receptor activity in the rabbit.

In anaesthetized, thoracotomized and artificially ventilated rabbits, the location of pulmonary stretch receptors (SR) was established by means of local mechanical stimulation as well as by micro-injections of the local anaesthetic cinchocaine. Differences in SR activity were analyzed in relation to the receptor site during specific stimulation by lung inflation, as well as during nonspecific activation by ammonia inhalation. Out of 107 SR, 55% were located in larger airways, i.e., in the trachea, main bronchus and lobar bronchi ("central SR"), whereas 45% were found to lie more peripherally ("peripheral SR"). There were several differences with respect to the discharge pattern evoked by lung inflation and by ammonia inhalation between SR of different locations. The increase of discharge rate evoked by lung inflation and by ammonia inhalation was significantly greater in peripheral than in central SR. Significantly more central than peripheral SR discharged throughout the whole respiratory cycle, i.e., even at end-expiratory lung volume. Furthermore, a delayed inspiratory recruitment as well as a transient cessation of firing after the initial increase of activity, which followed ammonia inhalation, occurred more frequently in central than in peripheral SR.