Endogenous noradrenaline release from guinea-pig isolated trachea is inhibited by activation of M2 receptors.
Overflow of endogenous noradrenaline (NA) from guinea-pig isolated tracheae was evoked by electrical field stimulation (3 Hz, 540 pulses). The muscarinic receptor agonist oxotremorine inhibited the evoked overflow of NA in a concentration-dependent manner (EC50 84 nM). Methoctramine, pirenzepine and p-fluoro-hexahydrosiladiphenidol (each 1 microM) shifted the concentration-response curves of oxotremorine to the right with apparent pA2 values of 7.60, 6.74 and 6.18, respectively. It is concluded that sympathetic nerve terminals in the guinea-pig trachea are endowed with inhibitory muscarinic M2 receptors.
Racké
K
K
Department Pharmacology, University of Frankfurt, Germany.
Hey
C
C
Wessler
I
I
D000818:Animals; D003959:Diamines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D018727:Muscarinic Antagonists; D009638:Norepinephrine / Q000378:metabolism*; D010095:Oxotremorine / Q000494:pharmacology*; D010276:Parasympatholytics / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D010890:Pirenzepine / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000378:metabolism*; D014132:Trachea / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*
D003959:Diamines; D018727:Muscarinic Antagonists; D010276:Parasympatholytics; D010880:Piperidines; D011976:Receptors, Muscarinic; C058297:4-fluorohexahydrosiladifenidol; D010890:Pirenzepine; D010095:Oxotremorine; C054938:methoctramine; D009638:Norepinephrine