PHOSPHODIESTERASE INHIBITORS AND ENDOTHELIN AS MODULATORS OF RESPIRATORY NEUROTRANSMISSION

1. Airway smooth muscle receives cholinergic, adrenergic and non-adren ergic, non-cholinergic (NANC) neural input. In guinea-pig airways chol inergic and NANC nerves provide contractile innervation, while adrener gic and NANC nerves provide relaxant pathways. In contrast, the major relaxant innervation in human airways is NANC in nature. 2. The presen t review describes the effects or selective phosphodiesterase (PDE) in hibitors on NANC relaxant and contractile responses in guinea-pig trac hea as well as on NANC relaxations in human bronchus. 3. The effects o f endothelin-1 on cholinergic contractile responses obtained in a vari ety of species are also assessed.