Slowing of intestinal transit by fat or peptide YY depends on beta-adrenergic pathway.
Although the enteric reflex pathway triggered by volume distension is known to depend on an adrenergic nerve, it is not known whether the slowing of intestinal transit by fat or peptide YY (PYY) also depends on an adrenergic pathway. The aim of this study was to test the hypotheses that the slowing of transit by fat or PYY may depend on a beta-adrenergic pathway, and this adrenergic pathway may act via the serotonergic and opioid pathways previously observed for the slowing of transit by fat. Eighteen dogs were equipped with duodenal and midgut fistulas. The small intestine was compartmentalized into the proximal and distal half of gut. The role of adrenergic, serotonergic, and opioid pathways was then tested in the slowing of intestinal transit by fat, PYY, and norepinephrine. Intestinal transit results were compared as the cumulative percent marker of recovery over 30 min. We found that the slowing of transit by fat, PYY, or norepinephrine was reversed by propranolol. In addition, the slowing effect of fat was reversed by metoprolol (beta1-adrenoreceptor antagonist) but not phentolamine (alpha-adrenoreceptor antagonist). Furthermore, norepinephrine-induced slowing of transit was reversed by ondansetron (5-HT3 receptor antagonist) or naloxone (opioid receptor antagonist). Extending these physiological results, we also found by immunohistochemistry that beta1-adrenoreceptors are expressed by neurons of the intrinsic plexuses of the small intestine. We conclude that the slowing of intestinal transit by fat or PYY depends on a beta-adrenergic pathway and that this adrenergic pathway acts on serotonergic and opioid pathways.
Lin
Henry C
HC
Division of Gastroenterology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA. henry.lin@cshs.org
Neevel
Corynn
C
Chen
Peng-Sheng
PS
Suh
Gina
G
Chen
Jin Hai
JH
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004285:Dogs; D004723:Endorphins / Q000378:metabolism; D005223:Fats / Q000494:pharmacology*; D005772:Gastrointestinal Transit / Q000187:drug effects* / Q000502:physiology; D007150:Immunohistochemistry; D009638:Norepinephrine / Q000494:pharmacology; D019894:Peptide YY / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism
D000319:Adrenergic beta-Antagonists; D004723:Endorphins; D005223:Fats; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D019894:Peptide YY; D012701:Serotonin; D011433:Propranolol; D009638:Norepinephrine