The effect of emboli upon intrapulmonary receptors in the cat.

The effect of successive injections (on the activity from pulmonary stretch, irritant and type J receptors) of 0.1 g aliquots of either potato starch or plastic sheres was examined in artificially ventilated, anaesthetized, open chested cats. The discharge from nineteen pulmonary stretch receptors was altered after embolisation and mean maximum changes of 10% were observed in peak frequency and spike count per respiratory cycle. The activity from twelve of fourteen irritant receptors was changed after embolisation, mainly in the form of an increase of an existing, respiratory modulated discharge. O f ten type J receptors examined, six were stimulated after embolisation to produce an erratic pattern of discharge. The response of the three groups of receptors appeared to be independent of the size of the emboli. Histological examination showed scattered emboli in capillaries and columns in arterioles, according to particle size. It is likely that all three receptor types are involved in the reflex tachypnoea induced by pulmonary embolisation, since the changes in afferent vagal discharge occurred at or before the onset of the reflex respiratory events.