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Evidence for functional NK 1 ‐tachykinin receptors on motor neurones supplying the circular muscle of guinea‐pig small and large intestine
Author(s) -
Bian Xc,
Paul Bertrand,
John B. Furness,
Joel C. Bornstein
Publication year - 2000
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1046/j.1365-2982.2000.00200.x
Subject(s) - tetrodotoxin , inhibitory postsynaptic potential , agonist , medicine , excitatory postsynaptic potential , receptor , endocrinology , chemistry , enteric nervous system , ileum , biology , tachykinin receptor , myenteric plexus , substance p , neuropeptide , immunohistochemistry
The guinea‐pig intestine was investigated to determine which neurones are excited via NK 1 receptors. The specific NK 1 receptor agonists [Sar 9 , Met(O 2 ) 11 ]‐SP and septide contracted the circular muscle of all regions via a tetrodotoxin (TTX)‐insensitive mechanism. In the proximal colon, they also evoked a TTX‐sensitive relaxation; in the distal colon, the contractions were larger when nerve impulses were blocked with TTX, indicating that the agonists excited inhibitory motor neurones. In the duodenum and ileum, TTX reduced agonist‐evoked contractions indicating that excitatory motor neurones were activated. In the presence of indomethacin, TTX enhanced contractions of ileal circular muscle evoked by these agonists suggesting that NK 1 receptors were on inhibitory motor neurones. Blockade of nitric oxide synthase (NOS) enhanced NK 1 receptor agonist evoked contractions of duodenal circular muscle, indicating that the agonists excite inhibitory motor neurones in duodenum. Neurones immunoreactive for NK 1 receptors were studied in the duodenum and distal colon. As reported previously for the ileum, 1 some neurones were immunoreactive for NOS and had Dogiel type I morphology; features characteristic of inhibitory motor neurones. In conclusion, there are functional NK 1 receptors on excitatory and inhibitory motor neurones in the guinea‐pig small intestine and on inhibitory motor neurones in the colon.