Location of pulmonary stretch receptors in the guinea-pig.

The site of pulmonary slowly adapting stretch receptors (SRs) was investigated in anaesthetized, thoracotomized and artificially ventilated guinea-pigs. The location of SRs within the lungs and airways was determined by analyzing the changes of SR single fibres discharge patterns in response to (a) occlusion of the airways, (b) local probing, and (c) microinjection of the non-diffusible local anaesthetic cinchocaine into the presumed receptor site. The great majority (92%) of the 79 SRs examined was localized in small airways or in lung parenchyma ('peripheral SRs'), whereas only 8% were located in large airways, i.e., in the trachea, main bronchi and lobar bronchi ('central SRs'). The discharge responses to lung inflation and to ammonia inhalation slightly differed between these two SR groups. With the pronounced prevalence of peripheral SRs, the guinea-pig seems to take a unique position among the species examined hitherto.