Abstract
1 In anaesthetized mice prostaglandins E1 and E2 reduced the bradycardia caused by electrical stimulation of the sectioned peripheral vagus nerve; prostaglandin F produced only a slight inhibition of the vagal response. 2 None of the prostaglandins studied affected acetylcholine-induced bradycardia. 3 Prostaglandins modify para sympathetic nerve activity in vivo presumably by a pre-synaptic action.