PGE 2 inhibits acetylcholine release from cholinergic nerves in canine but not equine airways

Abstract

The effects of exogenous prostaglandin E 2 (PGE 2) and endogenous prostanoids on cholinergic neurotransmission were determined by measurement of acetylcholine (ACh) release from canine and equine airway tissues. Trachealis strips and bronchial segments were suspended in 2 ml tissue baths. ACh release was induced by electrical field stimulation (EFS), and its content in tissue bath liquid was measured by high pressure liquid chromatography (HPLC) with electrochemical detection. In canine airways, exogenous PGE 2 (10 −9 to 10 −7 M) inhibited ACh release concentration-dependently, whereas inhibition of endogenous prostanoid production by indomethacin (3 × 10 −6 M) augmented ACh release. By contrast, in equine airways, exogenous PGE 2 had no effect on ACh release in bronchi but at 10 −7 M augmented ACh release in the trachea. Cyclooxygenase inhibition by either indomethacin or meclofenamate (10 −6 M) did not influence ACh release. We conclude that exogenous PGE 2 and endogenous prostanoids inhibit ACh release from cholinergic nerves in canine but not equine airways.