ENDOTHELIN-3 INCREASES TRANSMISSION IN THE RABBIT PULMONARY PARASYMPATHETIC NERVOUS-SYSTEM

The effect of endothelin-3 (ET-3) on the response to parasympathetic n erve stimulation of rabbit isolated bronchus was examined. The site of action of ET-3 in the pulmonary parasympathetic nervous system was al so investigated. ET-3 induced a concentration-dependent increase in th e response to electrical field stimulation. The response was atropine sensitive and therefore cholinergically mediated. At a concentration o f 10 nM, ET-3 increased the response to field stimulation to 205 +/- 4 2% of the initial response. The effect was concentration-related, as 1 00 nM further increased this response to 315 +/- 69%. The responsivene ss of the tissue to exogenous acetylcholine was not affected by ET-3. Therefore ET-3 has a neuromodulatory role on cholinergic parasympathet ic transmission in rabbit airways exerted at a prejunctional site.