Both the cholinergic and non-cholinergic components of airway excitation are inhibited by morphine in the guinea-pig.
In order to investigate the effect of morphine on the excitatory and inhibitory non-adrenergic, non-cholinergic (NANC) neurotransmission and cholinergic neurotransmission in airways, ring preparations from guinea-pig trachea and bronchi were studied. The preparations were stimulated by electrical field stimulation to elicit contractions and relaxations. Both cholinergic and NANC contractions were reduced by morphine in a dose-dependent way, while the inhibitory NANC neurotransmission was unaffected. A morphine concentration of 10(-4) M reduced the NANC contractions to 20.8 +/- 1.5% of the control contractions and the cholinergic contractions to 49.7 +/- 4.2%. The effect of morphine on cholinergic neurotransmission was completely inhibited by naloxone (10(-5) M) while the effect of morphine on NANC contractions only was reduced to 67.6 +/- 5.6% of the control contractions. It is suggested that morphine influences the excitatory neurotransmission via pre-junctional sites, since morphine had no effect on the acetylcholine-induced contractions.
Johansson
I G
IG
Department of Pharmacology, Faculty of Health Sciences, University of Linköping, Sweden.
Grundström
N
N
Andersson
R G
RG
D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000294:innervation; D004558:Electric Stimulation; D006168:Guinea Pigs; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects; D011950:Receptors, Cholinergic / Q000187:drug effects*; D012132:Respiratory Muscles / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D014132:Trachea / Q000187:drug effects / Q000294:innervation
D011950:Receptors, Cholinergic; D009020:Morphine