Article date: July 1996
By: Masaya Yoshimura, Yasuko S‐Yamashita, Shukei Kan, Masami Niwa, Kohtaro Taniyama, in Volume 118, Issue 5, pages 1171-1176
The type of endothelin (ET) receptor located on the myenteric neurones of guinea‐pig ileum was determined by receptor autoradiography and function of the receptor was examined by release experiments of acetylcholine (ACh) from the longitudinal muscle myenteric plexus (LM‐MP) preparations.
Specific [125I]‐ET‐1 binding sites were distributed in muscle layers, myenteric and submucous plexuses, and mucosa layers. High‐grain densities were detected in both myenteric and submucous plexuses.
Binding in the myenteric plexus was abolished by incubation with either IRL 1620 (endothelin ETB receptor agonist) or BQ 788 (endothelin ETB receptor antagonist), but not with BQ 123 (endothelin ETA receptor antagonist). The [125I]‐IRL 1620 binding sites were evident in the myenteric plexus. Thus, the endothelin receptor located on the myenteric neurones is of the ETB type.
ET‐1 (10−10‐3 × 10−8m) and ET‐3 (10−10‐3 × 10−8m) evoked 3H outflow from LM‐MP preparations of ileum preloaded with [3H]‐choline, in a concentration‐dependent manner. There was no significant difference between maximum amounts of ET‐1‐evoked and ET‐3‐evoked 3H outflow.
ET‐1 and ET‐3 evoked outflow of 3H was BQ 788‐sensitive, but BQ 123‐insensitive. Both evoked outflows of 3H were Ca2+‐dependent and tetrodotoxin‐sensitive.
These results indicate that the endothelin ETB receptor is located on the enteric cholinergic neurones and that stimulation evokes the release of ACh.
The type of endothelin (ET) receptor located on the myenteric neurones of guinea‐pig ileum was determined by receptor autoradiography and function of the receptor was examined by release experiments of acetylcholine (ACh) from the longitudinal muscle myenteric plexus (LM‐MP) preparations.
Specific [125I]‐ET‐1 binding sites were distributed in muscle layers, myenteric and submucous plexuses, and mucosa layers. High‐grain densities were detected in both myenteric and submucous plexuses.
Binding in the myenteric plexus was abolished by incubation with either IRL 1620 (endothelin ETB receptor agonist) or BQ 788 (endothelin ETB receptor antagonist), but not with BQ 123 (endothelin ETA receptor antagonist). The [125I]‐IRL 1620 binding sites were evident in the myenteric plexus. Thus, the endothelin receptor located on the myenteric neurones is of the ETB type.
ET‐1 (10−10‐3 × 10−8m) and ET‐3 (10−10‐3 × 10−8m) evoked 3H outflow from LM‐MP preparations of ileum preloaded with [3H]‐choline, in a concentration‐dependent manner. There was no significant difference between maximum amounts of ET‐1‐evoked and ET‐3‐evoked 3H outflow.
ET‐1 and ET‐3 evoked outflow of 3H was BQ 788‐sensitive, but BQ 123‐insensitive. Both evoked outflows of 3H were Ca2+‐dependent and tetrodotoxin‐sensitive.
These results indicate that the endothelin ETB receptor is located on the enteric cholinergic neurones and that stimulation evokes the release of ACh.
DOI: 10.1111/j.1476-5381.1996.tb15520.x
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