Relationship between dihydroetorphine and cholinergic system in the inhibition of respiration and heart rate

The respiratory inhibition caused by dihydroetorpine (DHE) was fully antagonized by pilocarpine or physostigmine, but the bradycardia was not. When atropine (icv) was combined with DHE, the respiratory inhibition was antagonized but the bradycardia persisted. However, intravenous atropine antagonized both the respiratory and cardiac inhibition caused by DHE.