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Monoglyceride lipase deficiency causes desensitization of intestinal cannabinoid receptor type 1 and increased colonic μ-opioid receptor sensitivity.

Taschler U, Eichmann TO, Radner FP, Grabner GF, Wolinski H, Storr M, Lass A, Schicho R, Zimmermann R - Br. J. Pharmacol. (2015)

Bottom Line: Conversely, genetic deletion of MGL did not affect gut transit despite increased 2-AG levels.Finally, MGL-deficient mice displayed accelerated colonic propulsion and were hypersensitive to μ receptor agonist-mediated inhibition of colonic motility.This phenotype was reproduced by chronic pharmacological inhibition of MGL.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biosciences, University of Graz, Graz, Austria.

No MeSH data available.


Related in: MedlinePlus

MGL-KO mice are hypersensitive to μ receptor agonist-induced constipation. (A) Effect of loperamide on whole gut transit in wild-type and MGL-KO mice (n = 10 per genotype). Animals were kept in single cages without bedding and fasted overnight. Loperamide (5 mg·kg−1 mouse) or carrier solution were injected i.p. After 20 min, mice were gavaged with Evans Blue and received free access to food and water. The time period until the appearance of Evans Blue in the faeces was recorded. (B) Effect of loperamide on whole gut transit of wild-type and CB1-KO mice (n = 5–6 per genotype). The experiment was performed exactly as in (A). (C) Effect of loperamide on the contractility of ileal segments obtained from wild-type and MGL-KO mice. Explants were incubated in a physiological solution at 37°C and 5% CO2. Contractions were evoked using EFS (8 Hz). EFS-stimulated contractions were determined 20 min after pre-incubation with the indicated concentrations of loperamide (n = 3 per genotype). (D) Upper GI transit and colonic transit in loperamide-treated wild-type and MGL-KO mice. Animals were treated with loperamide and Evans Blue as in (A). After 3 and 6 h, mice were killed and the progression of the marker in the GI tract was determined. Progression of the dye was expressed as % of small intestine (left panel) or colon length (right panel). (E) Effect of loperamide on the colonic propulsion of plastic beads in wild-type and MGL-KO mice. Animals (n = 10 per genotype) were treated with loperamide and Evans Blue as in (A). After 20 min, a 2 mm plastic bead was inserted 2 cm into the colon under mild anaesthesia. Subsequently, the time periods until the appearance of the bead were monitored. Data are presented as means ± SEM. Statistical differences were determined using Student's unpaired t-test or two-way anova followed by Bonferroni's post hoc test, ***P < 0.001 for comparison of genotypes; ###P < 0.001 for comparison of treatments.
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fig04: MGL-KO mice are hypersensitive to μ receptor agonist-induced constipation. (A) Effect of loperamide on whole gut transit in wild-type and MGL-KO mice (n = 10 per genotype). Animals were kept in single cages without bedding and fasted overnight. Loperamide (5 mg·kg−1 mouse) or carrier solution were injected i.p. After 20 min, mice were gavaged with Evans Blue and received free access to food and water. The time period until the appearance of Evans Blue in the faeces was recorded. (B) Effect of loperamide on whole gut transit of wild-type and CB1-KO mice (n = 5–6 per genotype). The experiment was performed exactly as in (A). (C) Effect of loperamide on the contractility of ileal segments obtained from wild-type and MGL-KO mice. Explants were incubated in a physiological solution at 37°C and 5% CO2. Contractions were evoked using EFS (8 Hz). EFS-stimulated contractions were determined 20 min after pre-incubation with the indicated concentrations of loperamide (n = 3 per genotype). (D) Upper GI transit and colonic transit in loperamide-treated wild-type and MGL-KO mice. Animals were treated with loperamide and Evans Blue as in (A). After 3 and 6 h, mice were killed and the progression of the marker in the GI tract was determined. Progression of the dye was expressed as % of small intestine (left panel) or colon length (right panel). (E) Effect of loperamide on the colonic propulsion of plastic beads in wild-type and MGL-KO mice. Animals (n = 10 per genotype) were treated with loperamide and Evans Blue as in (A). After 20 min, a 2 mm plastic bead was inserted 2 cm into the colon under mild anaesthesia. Subsequently, the time periods until the appearance of the bead were monitored. Data are presented as means ± SEM. Statistical differences were determined using Student's unpaired t-test or two-way anova followed by Bonferroni's post hoc test, ***P < 0.001 for comparison of genotypes; ###P < 0.001 for comparison of treatments.

Mentions: To investigate whether MGL deficiency influences other signalling pathways, we treated mice with loperamide, a selective μ receptor agonist, which inhibits gut motility (De Luca and Coupar, 1996). In accordance with published data (Carai et al., 2006), loperamide decelerated whole gut transit in wild-type mice 4.4-fold (Figure 4A). In comparison with wild-type mice, MGL-KO animals exhibited a more than 4 h delay in gut transit (7.7-fold compared with carrier treated mice), indicating that MGL-KO mice are hypersensitive to μ receptor stimulation (Figure 4A). To examine whether this increased sensitivity is caused by desensitization of CB1 receptors, we compared the effect of μ receptor stimulation on gut transit in wild-type and CB1-KO mice. Although CB1-KO mice showed a trend towards delayed transit, we did not observe a significant difference between groups (Figure 4B). This observation suggests that a CB1 receptor-independent mechanism causes μ receptor hypersensitivity in MGL-KO mice.


Monoglyceride lipase deficiency causes desensitization of intestinal cannabinoid receptor type 1 and increased colonic μ-opioid receptor sensitivity.

Taschler U, Eichmann TO, Radner FP, Grabner GF, Wolinski H, Storr M, Lass A, Schicho R, Zimmermann R - Br. J. Pharmacol. (2015)

MGL-KO mice are hypersensitive to μ receptor agonist-induced constipation. (A) Effect of loperamide on whole gut transit in wild-type and MGL-KO mice (n = 10 per genotype). Animals were kept in single cages without bedding and fasted overnight. Loperamide (5 mg·kg−1 mouse) or carrier solution were injected i.p. After 20 min, mice were gavaged with Evans Blue and received free access to food and water. The time period until the appearance of Evans Blue in the faeces was recorded. (B) Effect of loperamide on whole gut transit of wild-type and CB1-KO mice (n = 5–6 per genotype). The experiment was performed exactly as in (A). (C) Effect of loperamide on the contractility of ileal segments obtained from wild-type and MGL-KO mice. Explants were incubated in a physiological solution at 37°C and 5% CO2. Contractions were evoked using EFS (8 Hz). EFS-stimulated contractions were determined 20 min after pre-incubation with the indicated concentrations of loperamide (n = 3 per genotype). (D) Upper GI transit and colonic transit in loperamide-treated wild-type and MGL-KO mice. Animals were treated with loperamide and Evans Blue as in (A). After 3 and 6 h, mice were killed and the progression of the marker in the GI tract was determined. Progression of the dye was expressed as % of small intestine (left panel) or colon length (right panel). (E) Effect of loperamide on the colonic propulsion of plastic beads in wild-type and MGL-KO mice. Animals (n = 10 per genotype) were treated with loperamide and Evans Blue as in (A). After 20 min, a 2 mm plastic bead was inserted 2 cm into the colon under mild anaesthesia. Subsequently, the time periods until the appearance of the bead were monitored. Data are presented as means ± SEM. Statistical differences were determined using Student's unpaired t-test or two-way anova followed by Bonferroni's post hoc test, ***P < 0.001 for comparison of genotypes; ###P < 0.001 for comparison of treatments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556478&req=5

fig04: MGL-KO mice are hypersensitive to μ receptor agonist-induced constipation. (A) Effect of loperamide on whole gut transit in wild-type and MGL-KO mice (n = 10 per genotype). Animals were kept in single cages without bedding and fasted overnight. Loperamide (5 mg·kg−1 mouse) or carrier solution were injected i.p. After 20 min, mice were gavaged with Evans Blue and received free access to food and water. The time period until the appearance of Evans Blue in the faeces was recorded. (B) Effect of loperamide on whole gut transit of wild-type and CB1-KO mice (n = 5–6 per genotype). The experiment was performed exactly as in (A). (C) Effect of loperamide on the contractility of ileal segments obtained from wild-type and MGL-KO mice. Explants were incubated in a physiological solution at 37°C and 5% CO2. Contractions were evoked using EFS (8 Hz). EFS-stimulated contractions were determined 20 min after pre-incubation with the indicated concentrations of loperamide (n = 3 per genotype). (D) Upper GI transit and colonic transit in loperamide-treated wild-type and MGL-KO mice. Animals were treated with loperamide and Evans Blue as in (A). After 3 and 6 h, mice were killed and the progression of the marker in the GI tract was determined. Progression of the dye was expressed as % of small intestine (left panel) or colon length (right panel). (E) Effect of loperamide on the colonic propulsion of plastic beads in wild-type and MGL-KO mice. Animals (n = 10 per genotype) were treated with loperamide and Evans Blue as in (A). After 20 min, a 2 mm plastic bead was inserted 2 cm into the colon under mild anaesthesia. Subsequently, the time periods until the appearance of the bead were monitored. Data are presented as means ± SEM. Statistical differences were determined using Student's unpaired t-test or two-way anova followed by Bonferroni's post hoc test, ***P < 0.001 for comparison of genotypes; ###P < 0.001 for comparison of treatments.
Mentions: To investigate whether MGL deficiency influences other signalling pathways, we treated mice with loperamide, a selective μ receptor agonist, which inhibits gut motility (De Luca and Coupar, 1996). In accordance with published data (Carai et al., 2006), loperamide decelerated whole gut transit in wild-type mice 4.4-fold (Figure 4A). In comparison with wild-type mice, MGL-KO animals exhibited a more than 4 h delay in gut transit (7.7-fold compared with carrier treated mice), indicating that MGL-KO mice are hypersensitive to μ receptor stimulation (Figure 4A). To examine whether this increased sensitivity is caused by desensitization of CB1 receptors, we compared the effect of μ receptor stimulation on gut transit in wild-type and CB1-KO mice. Although CB1-KO mice showed a trend towards delayed transit, we did not observe a significant difference between groups (Figure 4B). This observation suggests that a CB1 receptor-independent mechanism causes μ receptor hypersensitivity in MGL-KO mice.

Bottom Line: Conversely, genetic deletion of MGL did not affect gut transit despite increased 2-AG levels.Finally, MGL-deficient mice displayed accelerated colonic propulsion and were hypersensitive to μ receptor agonist-mediated inhibition of colonic motility.This phenotype was reproduced by chronic pharmacological inhibition of MGL.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biosciences, University of Graz, Graz, Austria.

No MeSH data available.


Related in: MedlinePlus