Central orexin-A increases colonic motility in conscious rats

Abstract

Increasing evidence has indicated that brain orexin plays a vital role in the regulation of gastrointestinal physiology such as gastric secretion, gastric motility and pancreatic secretion. However, little is known whether orexin in the brain is involved in the physiology of the lower gastrointestinal tract. The aim of this study was therefore to elucidate whether orexin-A in the brain is involved in the regulation of colonic motility. In this study, we measured fecal pellet output and recorded intraluminal colonic pressure waves in freely moving conscious rats to evaluate the effects of central orexin-A on colonic motor functions. Intracisternal but not intraperitoneal injection of orexin-A dose-dependently (1-10 μg) increased fecal pellet output. Findings obtained from manometric recordings revealed that intracisternal administration of orexin-A at a dose of 10 μg significantly enhanced colonic motor contractions. These results suggest for the first time that orexin-A acts centrally in the brain to enhance fecal pellet output and stimulate colonic motility in conscious rats. The present study would furthermore support our hypothesis that orexin-A in the brain may be an important candidate as a mediator of the cephalic phase gut stimulation including stimulated colonic motility in addition to well known physiological response such as stimulation of gastric acid and pancreatic acid secretion, and gastric motility.

Endogenous orexin-A in the brain mediates 2-deoxy-d-glucose-induced stimulation of gastric motility in freely moving conscious rats

“…The present data clearly demonstrated that ip injection of orexin-A failed to stimulate gastric motility, strongly confirming that ic orexin-A acts centrally in the brain to stimulate gastric motility in freely moving conscious rats. We have very recently demonstrated that ic injection of orexin-A significantly enhanced colonic motor function in conscious rats [22]. The present study therefore provides evidence that orexin-A in the brain stimulates not only colonic but also gastric contractility in conscious rats.…”

The Orexin System in the Enteric Nervous System of the Bottlenose Dolphin (Tursiops truncatus)

“…OXA stimulates gastric acid secretion throughout vagal pathways [46], regulates intestinal bicarbonate secretion [32], and gastrointestinal and colon motility [33], [35], [47]. Studies on the dose-dependent peripheral effects of OXA and OXB on intestinal wall show that they slow down intestinal motility by extending of duration of migrating motor complex (MMC) [22,23,48 7].…”

“…In addition to a key role in food intake, orexins are also involved in the control of several biological functions such as arterial blood pressure and heart rate [24], sleep/wake cycle [25], water assumption [26], plasma corticosteroid levels [27], testosterone production [28], and endocrine and exocrine pancreatic secretions [29]–[31]. A series of recent studies [32]–[35] proposed a role of the orexin system in the central and peripheral control of gastrointestinal secretion and motility.…”

Antinociceptive action against colonic distension by brain orexin in conscious rats

“…With regard to the role of central orexin in digestive functions, it has been reported that orexin acts in the brain to stimulate gastric and pancreatic secretion, and increase gastric and colonic motility in rats (Takahashi et al, 1999;Okumura et al, 2001;Yamada et al, 2005;Nozu et al, 2011;Nozu et al, 2012;Bülbül et al, 2010a and2010b;Kobashi et al, 2002;Krowicki et al, 2002;Miyasaka et al, 2002). The present study therefore provided a novel evidence that central orexin plays a role in not only gastrointestinal secretion and motility but also gut sensation.…”