The role of substance P in arterial chemoreflex control of ventilation

The postulate that Substance P (SP) plays a neurotransmitter-like role in the arterial chemo- and thermoreflex control of ventilation was examined in conscious rabbits. The investigation was based on CNS neurotransmitter criteria and involved morphological studies using a monoclonal SP antibody, and functional experiments which compared within-animal responses to severe arterial hypoxia (PaO2 less than 35 mm Hg) and to intracisternal SP infusions. Experiments were performed in normal rabbits, and in rabbits pretreated at birth with capsaicin. The data support a neurotransmitter-like role for SP in the arterial chemo- and the thermoreflex control of ventilation, and there appear to be SP-dependent collateral chemoreflex pathways which block thermoregulatory panting through an inhibitory interneuron system.