Changes in respiratory sensations induced by lobeline after human bilateral lung transplantation

1. The sensations evoked by the injection of lobeline into the right antecu bital vein were studied in 8 subjects after bilateral lung transplantation and 10 control subjects. In control subjects, two distinct sensations were experienced. There was an early noxious sensation (onset similar to 10 s) f ollowed by a late sensation of breathlessness (onset similar to 26 s) assoc iated with involuntary hyperventilation. The early sensation was accompanie d by respiratory and cardiovascular changes. 2. In contrast to control subjects, the early respiratory events and the no xious sensations evoked by injections of lobeline (18-60 mug kg(-1)) did no t occur in subjects with recent bilateral lung transplantation. This sugges ts that the early respiratory sensations are mediated by the discharge of r eceptors in the lungs. 3. The late hyperventilation and the accompanying sensation of breathlessne ss occurred in both transplant and control subjects and are therefore likel y to be mediated by receptors elsewhere in the body, presumably systemic ar terial chemoreceptors stimulated by lobeline. 4. In control subjects, but not transplant subjects, there was a consistent decrease in mean arterial pressure associated with the lobeline injection. This suggests that pulmonary afferents mediate the hypotension. 5. For transplant subjects studied more than a year after transplantation, there was some evidence that the noxious respiratory sensations evoked by l obeline had returned. This suggests that some functional reinnervation of p ulmonary afferents may occur.