Opposing effects on the phrenic motor pathway attributed to dopamine-D1 and -D3/D2 receptor activation

► Dopamine-D1 agonists stimulate bulbar inspiratory motor output in two stages. ► Dopamine-D1 agonists increase excitatory synaptic coupling in respiratory network. ► Dopamine-D3/D2 agonist depresses and slows phrenic nerve discharges. ► D1-agonist counteracts D3/D2-agonist-mediated depression of phrenic nerve activity.