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

1. The sensations evoked by the injection of lobeline into the right antecubital 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 approximately 10 s) followed by a late sensation of breathlessness (onset approximately 26 s) associated with involuntary hyperventilation. The early sensation was accompanied by respiratory and cardiovascular changes. 2. In contrast to control subjects, the early respiratory events and the noxious sensations evoked by injections of lobeline (18-60 microg kg(-1)) did not occur in subjects with recent bilateral lung transplantation. This suggests that the early respiratory sensations are mediated by the discharge of receptors in the lungs. 3. The late hyperventilation and the accompanying sensation of breathlessness occurred in both transplant and control subjects and are therefore likely to be mediated by receptors elsewhere in the body, presumably systemic arterial 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 lobeline had returned. This suggests that some functional reinnervation of pulmonary afferents may occur.