Identity of pulmonary artery pressure and lobeline-induced ventilatory reflex

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Abstract
Reflex ventilatory changes following pulmonary artery pressure reduction have been compared in the α-chloralose-anesthetized intact cat to those following the intravenous injection of lobeline, phenyldiguanide, and veratridine. These drugs stimulate different groups of sensory neurons in the pulmonary vascular bed. The reflex changes initiated by pulmonary artery pressure reduction and by small doses of lobeline are predominantly ventilatory, whereas those consequent on phenyldiguanide and veratridine are not. Using specific reflex blocking procedures, it was shown that although definite and consistent separation of the responses to the three drugs could be obtained, the responses to pulmonary artery pressure reduction and lobeline could not be differentiated. It is concluded that pulmonary artery pressure fall and lobeline probably act on the same reflex, which, since it is known that the reflexogenic lobeline-sensitive zone lies in the extrapleural pulmonary arteries, must be a ventilation-regulating reflex originating from a pressure-sensitive zone in the region of the pulmonary artery bifurcation.