The involvement of histaminic and muscarinic receptors in the bronchoconstriction induced by myorelaxant administration in sensitized rabbits.
BACKGROUND
Muscle relaxants cause bronchospasm via histamine release and/or by acting on the muscarinic receptors; we sought to characterize the respective importance of these pathways in the presence of bronchial hyperreactivity.


METHODS
Ovalbumin-sensitized rabbits were randomly assigned to several protocol groups: Group C comprised untreated animals; in the other three groups, either H1 and H2 histaminic receptor blockade was performed, leaving the M1, M2, and M3 muscarinic receptors functional (Group M123), or combining this treatment with M3 muscarinic receptor blockade (Group M12), or with vagotomy (Group M3). Respiratory system impedance was measured over a 90-s period, during which succinylcholine, mivacurium or atracurium was administered. To monitor the changes in lung mechanics, respiratory system impedance was averaged in a 2-s time window and fitted by a model featuring airway resistance and inertance and tissue damping and elastance.


RESULTS
The peak increases in airway resistance in Group C were greatest with succinylcholine (79 +/- 17[SE]%) and mivacurium administration (75% +/- 12%), whereas they were lower after attracurium (40% +/- 11%). These changes were markedly attenuated by both histamine and muscarinic receptor blockade with the largest reduction in Group M3 for succinylcholine (14% +/- 5.2%), and in Group M123 for mivacurium (5.1% +/- 9.1%) and attracurium (7.8% +/- 4.0%).


CONCLUSIONS
Although the bronchospasm developing in the allergic airways after muscle relaxants is mediated primarily by the histaminic pathway, the interactions of succinylcholine on the M1, M2, and M3 receptors, those of atracurium on the M1 and M2 receptors, and those of mivacurium on the M3 receptors may also play a role.
Habre
Walid
W
Pediatric Anesthesia Unit, Geneva Children's Hospital, Switzerland.
Adamicza
Agnes
A
Lele
Enikõ
E
Novák
Tímea
T
Sly
Peter D
PD
Petak
Ferenc
F
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001279:Atracurium / Q000494:pharmacology; D016084:Bronchoconstriction / Q000187:drug effects*; D005260:Female; D006632:Histamine / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D000077590:Mivacurium; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D011817:Rabbits; D043585:Receptor, Muscarinic M2 / Q000502:physiology; D043587:Receptor, Muscarinic M3 / Q000502:physiology; D011968:Receptors, Histamine / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*; D013390:Succinylcholine / Q000494:pharmacology
D007546:Isoquinolines; D009466:Neuromuscular Blocking Agents; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D011968:Receptors, Histamine; D011976:Receptors, Muscarinic; D001279:Atracurium; D000077590:Mivacurium; D006632:Histamine; D013390:Succinylcholine; D000109:Acetylcholine