Evidence for vagal enkephalinergic neural control of the feline pylorus and stomach.
The atropine- and guanethidine-resistant contraction of the cat pyloric sphincter induced by efferent stimulation of the cervical vagi, was studied with a new method for measuring transpyloric flow. The pyloric contraction was blocked in a dose-dependent manner by the opiate antagonist naloxone infused intraarterially to the pyloric region. Local intraarterial injection of morphine or enkephalinamide elicited a pyloric and gastric contraction. Leu- and met-enkephalin intraarterially elicited a pyloric contraction and a gastric relaxation. These effects could be prevented or reversed by naloxone. Immunohistochemical studies revealed a particularly rich enkephalinergic innervation of the pylorus with dense networks of varicose nerve fibers with enkephalin-like immunoreactivity both in the circular smooth muscle layer and in the myenteric plexus. Furthermore, many cell bodies of the myenteric plexus with enkephalin-like material were demonstrated. The corpus-antrum was sparsely innervated by enkephalin-like nerves to the circular muscle layer and only few immunoreactive cell bodies were observed in the myenteric plexus. These results together suggest a vagal control of the feline pylorus and stomach mediated via enkephalinergic neurons.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D004558:Electric Stimulation; D004723:Endorphins / Q000502:physiology*; D004745:Enkephalins / Q000276:immunology / Q000502:physiology*; D005260:Female; D005455:Fluorescent Antibody Technique; D005769:Gastrointestinal Motility / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D011706:Pyloric Antrum / Q000187:drug effects / Q000294:innervation; D011708:Pylorus / Q000187:drug effects / Q000294:innervation*; D013270:Stomach / Q000187:drug effects / Q000294:innervation*; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone; D009020:Morphine; D001285:Atropine