Incomplete cardiac vagal blockade with atropine in the anesthetized dog.
In dogs in neurolept-anesthesia the successive administration of alpha- and beta-adrenergic blocking agents and atropine, which should cause the functional equivalent of surgical denervation of the heart, always results in a marked tachycardia. The same is observed in conscious dogs, but not during methoxyflurane anesthesia. Bilateral vagotomy and administration of hexamethonium abolish the tachycardia. These observations demonstrate the presence of a vagally mediated chronotropic effect which becomes manifest when the inhibitory vagal effect is eliminated through blockade of the muscarinic receptors with atropine.
D000758:Anesthesia; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D003714:Denervation; D004285:Dogs; D005260:Female; D006321:Heart / Q000294:innervation* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008733:Methoxyflurane / Q000494:pharmacology; D009609:Nitrous Oxide / Q000494:pharmacology; D014630:Vagus Nerve / Q000502:physiology*
D014150:Antipsychotic Agents; D008733:Methoxyflurane; D001285:Atropine; D009609:Nitrous Oxide