Paradoxical response of pulmonary slowly adapting units during constant pressure lung inflation

Typically, unit discharge of slowly adapting receptors (SARs) declines slowly when lung inflation pressure is constant, although in some units it increases instead-a phenomenon hereinafter referred to as creeping. These studies characterize creeping behavior observed in 62 of 137 SAR units examined in anesthetized, open-chest, and mechanically ventilated rabbits. SAR units recorded from the cervical vagus nerve were studied during 4 s of constant lung inflation at 10, 20, and 30 cmH(2)O. Affected SAR units creep more quickly as inflation pressure increases. SAR units also often deactivate after creeping, i.e., their activity decreases or stops completely. Creeping likely results from encoder switching from a low discharge to a high discharge SAR, because it disappears in SAR units with multiple receptive fields after blocking a high discharge encoder in one field leaves low discharge encoders intact. The results support that encoder switching is a common mechanism operating in lung mechanosensory units.

Automated summary

In the study, creeping behavior was observed in 62 out of 137 SAR units examined in anesthetized rabbits. Creeping refers to the phenomenon where unit discharge either declines slowly or increases when lung inflation pressure is constant. Creeping is likely the result of encoder switching from low to high discharge SAR units.