Contribution of central μ-receptors to switching pulmonary C-fibers-mediated rapid shallow breathing into an apnea by fentanyl in anesthetized rats

► Systemic administration of fentanyl switches the pulmonary C-fibers-mediated rapid shallow breathing (RSB) into an apnea. ► Intracisternal injection of opioid receptor antagonists can prevent this fentanyl-induced RSB-apnea switch. ► Blocking PBC, but not mNTS, μ-receptors also prevents this fentanyl-induced switch.