Sensory nerve depletion potentiates inhibitory non-adrenergic, non-cholinergic nerves in guinea-pig airways.

The effect of sensory neuropeptide depletion by systemic capsaicin pretreatment was studied both on inhibitory non-adrenergic, non-cholinergic responses elicited to electrical field stimulation and on bronchodilator responses to vasoactive intestinal peptide (the putative transmitter of these nerves), in guinea-pig trachea. Capsaicin pretreatment enhanced the relaxation responses induced by both electrical field stimulation and vasoactive intestinal peptide, whereas these responses were not significantly increased in vehicle-pretreated or in untreated animals. The bronchodilator response to isoprenaline was unaffected by capsaicin pretreatment. Sensory neuropeptide depletion therefore augments both inhibitory non-adrenergic, non-cholinergic responses and responses to exogenous vasoactive intestinal peptide, suggesting an effect on vasoactive intestinal peptide receptors.