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Novel aspects of cholinergic regulation of colonic ion transport.

Bader S, Diener M - Pharmacol Res Perspect (2015)

Bottom Line: As a strong acetylcholinesterase activity was found in colonic epithelium, the effect of choline on I sc was examined.Although choline proved to be only a partial agonist, it concentration-dependently desensitized the response to acetylcholine, suggesting that it might act as a modulator of cholinergically induced anion secretion.Thus the cholinergic regulation of colonic ion transport - up to now solely explained by cholinergic submucosal neurons stimulating epithelial muscarinic receptors - is more complex than previously assumed.

View Article: PubMed Central - PubMed

Affiliation: Institute of Veterinary Physiology and Biochemistry, Justus-Liebig-University Giessen Giessen, Germany.

ABSTRACT
Nicotinic receptors are not only expressed by excitable tissues, but have been identified in various epithelia. One aim of this study was to investigate the expression of nicotinic receptors and their involvement in the regulation of ion transport across colonic epithelium. Ussing chamber experiments with putative nicotinic agonists and antagonists were performed at rat colon combined with reverse transcription polymerase chain reaction (RT-PCR) detection of nicotinic receptor subunits within the epithelium. Dimethylphenylpiperazinium (DMPP) and nicotine induced a tetrodotoxin-resistant anion secretion leading to an increase in short-circuit current (I sc) across colonic mucosa. The response was suppressed by the nicotinic receptor antagonist hexamethonium. RT-PCR experiments revealed the expression of α2, α4, α5, α6, α7, α10, and β4 nicotinic receptor subunits in colonic epithelium. Choline, the product of acetylcholine hydrolysis, is known for its affinity to several nicotinic receptor subtypes. As a strong acetylcholinesterase activity was found in colonic epithelium, the effect of choline on I sc was examined. Choline induced a concentration-dependent, tetrodotoxin-resistant chloride secretion which was, however, resistant against hexamethonium, but was inhibited by atropine. Experiments with inhibitors of muscarinic M1 and M3 receptors revealed that choline-evoked secretion was mainly due to a stimulation of epithelial M3 receptors. Although choline proved to be only a partial agonist, it concentration-dependently desensitized the response to acetylcholine, suggesting that it might act as a modulator of cholinergically induced anion secretion. Thus the cholinergic regulation of colonic ion transport - up to now solely explained by cholinergic submucosal neurons stimulating epithelial muscarinic receptors - is more complex than previously assumed.

No MeSH data available.


Related in: MedlinePlus

RT-PCR detection of mRNA expression of muscarinic M1 and M3 acetylcholine receptor subunits in isolated rat colonic crypts. The agarose gel shows bands of cDNA fragments amplified using specific primers for M1 (373 bp) and M3 receptors (434 bp). cDNA from spinal cord was used as positive control. The efficiency of RNA isolation and cDNA synthesis was verified by using GAPDH-specific primers (303 bp). Representative results from three independent experiments. Cry, colonic crypts; SC, spinal cord; RT-PCR, reverse transcription polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.
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fig09: RT-PCR detection of mRNA expression of muscarinic M1 and M3 acetylcholine receptor subunits in isolated rat colonic crypts. The agarose gel shows bands of cDNA fragments amplified using specific primers for M1 (373 bp) and M3 receptors (434 bp). cDNA from spinal cord was used as positive control. The efficiency of RNA isolation and cDNA synthesis was verified by using GAPDH-specific primers (303 bp). Representative results from three independent experiments. Cry, colonic crypts; SC, spinal cord; RT-PCR, reverse transcription polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.

Mentions: In murine colonic epithelium, the two isoforms M1 and M3 of the muscarinic receptors have been described (Haberberger et al. 2006). In order to find out, whether M1 receptors were involved, the effect of choline was tested in the absence or presence of pirenzepine or telenzepine, two M1 muscarinic receptor antagonists (Hammer and Giachetti 1980; Galvan et al. 1989). Telenzepine (10−7 mol/L) tended to reduce the choline-induced Isc as did pirenzepine (10−6 mol/L, Fig.8). However, these effects did not reach statistical significance. A significant inhibition, however, was observed, when the tissue was pretreated with darifenacin or J104129 (Fig.8), which inhibit M3 muscarinic receptors (Mitsuya et al. 1999; Zinner 2007). It can therefore be concluded that the choline-induced secretion is due to an activation of muscarinic receptors, particularly of the M3 subtype. Expression of both M1 and M3 muscarinic receptors in isolated rat colonic crypts was confirmed by RT-PCR experiments (Fig.9).


Novel aspects of cholinergic regulation of colonic ion transport.

Bader S, Diener M - Pharmacol Res Perspect (2015)

RT-PCR detection of mRNA expression of muscarinic M1 and M3 acetylcholine receptor subunits in isolated rat colonic crypts. The agarose gel shows bands of cDNA fragments amplified using specific primers for M1 (373 bp) and M3 receptors (434 bp). cDNA from spinal cord was used as positive control. The efficiency of RNA isolation and cDNA synthesis was verified by using GAPDH-specific primers (303 bp). Representative results from three independent experiments. Cry, colonic crypts; SC, spinal cord; RT-PCR, reverse transcription polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492755&req=5

fig09: RT-PCR detection of mRNA expression of muscarinic M1 and M3 acetylcholine receptor subunits in isolated rat colonic crypts. The agarose gel shows bands of cDNA fragments amplified using specific primers for M1 (373 bp) and M3 receptors (434 bp). cDNA from spinal cord was used as positive control. The efficiency of RNA isolation and cDNA synthesis was verified by using GAPDH-specific primers (303 bp). Representative results from three independent experiments. Cry, colonic crypts; SC, spinal cord; RT-PCR, reverse transcription polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.
Mentions: In murine colonic epithelium, the two isoforms M1 and M3 of the muscarinic receptors have been described (Haberberger et al. 2006). In order to find out, whether M1 receptors were involved, the effect of choline was tested in the absence or presence of pirenzepine or telenzepine, two M1 muscarinic receptor antagonists (Hammer and Giachetti 1980; Galvan et al. 1989). Telenzepine (10−7 mol/L) tended to reduce the choline-induced Isc as did pirenzepine (10−6 mol/L, Fig.8). However, these effects did not reach statistical significance. A significant inhibition, however, was observed, when the tissue was pretreated with darifenacin or J104129 (Fig.8), which inhibit M3 muscarinic receptors (Mitsuya et al. 1999; Zinner 2007). It can therefore be concluded that the choline-induced secretion is due to an activation of muscarinic receptors, particularly of the M3 subtype. Expression of both M1 and M3 muscarinic receptors in isolated rat colonic crypts was confirmed by RT-PCR experiments (Fig.9).

Bottom Line: As a strong acetylcholinesterase activity was found in colonic epithelium, the effect of choline on I sc was examined.Although choline proved to be only a partial agonist, it concentration-dependently desensitized the response to acetylcholine, suggesting that it might act as a modulator of cholinergically induced anion secretion.Thus the cholinergic regulation of colonic ion transport - up to now solely explained by cholinergic submucosal neurons stimulating epithelial muscarinic receptors - is more complex than previously assumed.

View Article: PubMed Central - PubMed

Affiliation: Institute of Veterinary Physiology and Biochemistry, Justus-Liebig-University Giessen Giessen, Germany.

ABSTRACT
Nicotinic receptors are not only expressed by excitable tissues, but have been identified in various epithelia. One aim of this study was to investigate the expression of nicotinic receptors and their involvement in the regulation of ion transport across colonic epithelium. Ussing chamber experiments with putative nicotinic agonists and antagonists were performed at rat colon combined with reverse transcription polymerase chain reaction (RT-PCR) detection of nicotinic receptor subunits within the epithelium. Dimethylphenylpiperazinium (DMPP) and nicotine induced a tetrodotoxin-resistant anion secretion leading to an increase in short-circuit current (I sc) across colonic mucosa. The response was suppressed by the nicotinic receptor antagonist hexamethonium. RT-PCR experiments revealed the expression of α2, α4, α5, α6, α7, α10, and β4 nicotinic receptor subunits in colonic epithelium. Choline, the product of acetylcholine hydrolysis, is known for its affinity to several nicotinic receptor subtypes. As a strong acetylcholinesterase activity was found in colonic epithelium, the effect of choline on I sc was examined. Choline induced a concentration-dependent, tetrodotoxin-resistant chloride secretion which was, however, resistant against hexamethonium, but was inhibited by atropine. Experiments with inhibitors of muscarinic M1 and M3 receptors revealed that choline-evoked secretion was mainly due to a stimulation of epithelial M3 receptors. Although choline proved to be only a partial agonist, it concentration-dependently desensitized the response to acetylcholine, suggesting that it might act as a modulator of cholinergically induced anion secretion. Thus the cholinergic regulation of colonic ion transport - up to now solely explained by cholinergic submucosal neurons stimulating epithelial muscarinic receptors - is more complex than previously assumed.

No MeSH data available.


Related in: MedlinePlus