Ghrelin stimulates motility in the small intestine of rats through intrinsic cholinergic neurons

doi:10.1016/j.regpep.2004.04.001

Regulatory Peptides

Volume 121, Issues 1–3, 15 September 2004, Pages 25-30

https://doi.org/10.1016/j.regpep.2004.04.001 Get rights and content

Abstract

Background and purpose: Ghrelin is a peptide discovered in endocrine cells of the stomach. Since ghrelin mRNA expression and plasma levels are elevated in the fasting state, we investigated the effects of ghrelin on the interdigestive migrating myoelectric complex (MMC) in the small intestine in vivo and compared with motor effects of ghrelin in vitro. Methods: Sprague–Dawley rats were supplied with a venous catheter and bipolar electrodes in the duodenum and jejunum for electromyography of small intestine in awake rats. In organ baths, isometric contractions of segments of rat jejunum were studied. Results: Ghrelin dose-dependently shortened the MMC cycle length at all three recording points. At the duodenal site, the interval shortened from 17.2±2.0 to 9.9±0.8 min during infusion of ghrelin (1000 pmol kg⁻¹ min⁻¹) and at the jejunal site from 17.5±2.2 to 10.5±0.8 min. Ghrelin contracted the muscle strips with a pD₂ of 7.97±0.47. Atropine (10⁻⁶ M) in vitro and (1 mg kg⁻¹) in vivo blocked the effect of ghrelin. Conclusion: Ghrelin stimulates interdigestive motility through cholinergic neurons. Ghrelin also stimulates motility, in vitro, suggesting that ghrelin receptors are present in the intestinal neuromuscular tissue and mediate its effects via cholinergic mechanisms.

Introduction

Ghrelin is a 28-amino acid peptide, predominantly produced by endocrine cells in the oxyntic mucosa of the stomach [1], [2], [3], [4]. Ghrelin-producing endocrine cells are also found in the small intestine with decreasing expression in the distal direction [3]. Ghrelin has also been found in hypothalamus, pituitary gland, pancreas, liver, kidney, testis, ovary and placenta in both humans and rodents [2], [3]. The ghrelin receptor is found throughout the body including the heart, lungs, pancreas, stomach and the small and large intestine [3], [4].

Ghrelin was initially found due to its growth hormone (GH)-releasing properties [5]. Studies show that infusion of ghrelin increases circulating plasma GH in both rodents and humans [6], [7], [8], [9], [10]. However, other actions of ghrelin have emerged such as effects on glucose metabolism and insulin release [11], [12], gastric acid secretion and motility [13], fasting and fed motility [14], cardiovascular actions [15], [16], and food intake and control of energy balance [17], [18].

As ghrelin is shown to increase gastric emptying rate and small intestinal transit in normal rats [19] and induces fasting motor activity in fed rats [14], ghrelin might be of importance in the physiological regulation of gastrointestinal motility as a pro-kinetic.

The aim of this study was to extend previous investigations to involve effects of ghrelin on (i) the contractility of smooth muscle strips in vitro as well as effects on (ii) the migrating myoelctrical complex (MMC) in vivo.

Section snippets

Material and methods

The regional animal Ethics committee approved the experiments.

Organ bath

Ghrelin caused concentration-dependent contractions of jejunum segments, with a pD₂ of 7.97±0.47. At 10⁻⁶ M, ghrelin contracted the muscle strips to 97±7% of the maximal contraction amplitude with Ach. Atropine (10⁻⁶ M) blocked the effect of ghrelin Fig. 1, Fig. 2 (p<0.01).

The ghrelin receptor antagonist (10⁻⁶ M) blocked the effect of ghrelin at 10⁻⁸ M, but had no effect on the higher ghrelin concentrations (not shown). The contractile response to ghrelin at 10⁻⁸ was 40.6±9.0% of maximal Ach

Discussion

The present study confirms the finding by Fujino et al. [14] that ghrelin not only stimulates fasting motility by increasing the frequency of phase III of MMC through cholinergic mechanisms, but also that the effect depends on intact vagal function. Furthermore, our study shows that ghrelin stimulates motility in vitro in the rat small intestine and that this effect is mediated by cholinergic neurons.

Fujino et al. [14] used bolus injections up to 3 nmol, whereas we used continuous infusion of

Acknowledgements

The technical assistance of Berndt Wallin is gratefully acknowledged. The study was supported by Swedish Research Council, The Professor Nanna Svartz Fund, the Bengt Ihre Foundation, the Ruth and Richard Julin Foundation and the Novonordisk Foundation.

References (24)

H. Hosoda et al.
Ghrelin and des-acyl ghrelin: two major forms of rat ghrelin peptide in gastrointestinal tissue
Biochem. Biophys. Res. Commun.
(2000)
G. Wang et al.
Ghrelin—not just another stomach hormone
Regul. Pept.
(2002)
Y. Masuda et al.
Ghrelin stimulates gastric acid secretion and motility in rats
Biochem. Biophys. Res. Commun.
(2000)
I. Bedendi et al.
Cardiac effects of ghrelin and its endogenous derivatives des-octanoyl ghrelin and des-Gln14-ghrelin
Eur. J. Pharmacol.
(2003)
N. Nagaya et al.
Ghrelin, a novel growth hormone-releasing peptide, in the treatment of chronic heart failure
Regul. Pept.
(2003)
H.B. Schïoth et al.
Characterization of the binding of MSH-B, HB-228, GHRP-6 and 153N-6 to the human melanocortin receptor subtypes
Neuropeptides
(1997)
M. Kojima et al.
Purification and distribution of ghrelin: the natural endogenous ligand for the growth hormone secretagogue receptor
Horm. Res.
(2001)
Y. Date et al.
Ghrelin, a novel growth hormone-releasing acylated peptide, is synthesized in a distinct endocrine cell type in the gastrointestinal tracts of rats and humans
Endocrinology
(2000)
M. Kojima et al.
Ghrelin is a growth-hormone-releasing acylated peptide from stomach
Nature
(1999)
E. Arvat et al.
Preliminary evidence that ghrelin, the natural GH secretagogue (GHS)-receptor ligand, strongly stimulates GH secretion in humans
J. Endocrinol. Invest.
(2000)

R. Peino et al.

Ghrelin-induced growth hormone secretion in humans

Eur. J. Endocrinol.

(2000)

K. Takaya et al.

Ghrelin strongly stimulates growth hormone release in humans

J. Clin. Endocrinol. Metab.

(2000)

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Ghrelin stimulates motility in the small intestine of rats through intrinsic cholinergic neurons

Abstract

Introduction

Section snippets

Material and methods

Organ bath

Discussion

Acknowledgements

Biochem. Biophys. Res. Commun.

Regul. Pept.

Biochem. Biophys. Res. Commun.

Eur. J. Pharmacol.

Regul. Pept.

Neuropeptides

Purification and distribution of ghrelin: the natural endogenous ligand for the growth hormone secretagogue receptor

Horm. Res.

Ghrelin, a novel growth hormone-releasing acylated peptide, is synthesized in a distinct endocrine cell type in the gastrointestinal tracts of rats and humans

Endocrinology

Ghrelin is a growth-hormone-releasing acylated peptide from stomach

Nature

Preliminary evidence that ghrelin, the natural GH secretagogue (GHS)-receptor ligand, strongly stimulates GH secretion in humans

J. Endocrinol. Invest.

Ghrelin-induced growth hormone secretion in humans

Eur. J. Endocrinol.

Ghrelin strongly stimulates growth hormone release in humans

J. Clin. Endocrinol. Metab.