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The guinea pig ileum lacks the direct, high-potency, M(2)-muscarinic, contractile mechanism characteristic of the mouse ileum.

Griffin MT, Matsui M, Ostrom RS, Ehlert FJ - Naunyn Schmiedebergs Arch. Pharmacol. (2009)

Bottom Line: Following 4-DAMP mustard treatment, the concentration-response curve of oxotremorine-M in wild-type ileum resembled that of the M(3) knockout mouse in terms of its pEC (50), E (max), and inhibition by selective muscarinic antagonists.Following 4-DAMP mustard treatment, the contractile response of the guinea pig ileum to oxotremorine-M exhibited low potency and a competitive-antagonism profile consistent with an M(3) response.The guinea pig ileum, therefore, lacks a direct, highly potent, M(2)-contractile component but may have a direct, lower potency M(2) component.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Chapman University, Orange, CA, USA.

ABSTRACT
We explored whether the M(2) muscarinic receptor in the guinea pig ileum elicits a highly potent, direct-contractile response, like that from the M(3) muscarinic receptor knockout mouse. First, we characterized the irreversible receptor-blocking activity of 4-DAMP mustard in ileum from muscarinic receptor knockout mice to verify its M(3) selectivity. Then, we used 4-DAMP mustard to inactivate M(3) responses in the guinea pig ileum to attempt to reveal direct, M(2) receptor-mediated contractions. The muscarinic agonist, oxotremorine-M, elicited potent contractions in ileum from wild-type, M(2) receptor knockout, and M(3) receptor knockout mice characterized by negative log EC(50) (pEC (50)) values +/- SEM of 6.75 +/- 0.03, 6.26 +/- 0.05, and 6.99 +/- 0.08, respectively. The corresponding E (max) values in wild-type and M(2) receptor knockout mice were approximately the same, but that in the M(3) receptor knockout mouse was only 36% of wild type. Following 4-DAMP mustard treatment, the concentration-response curve of oxotremorine-M in wild-type ileum resembled that of the M(3) knockout mouse in terms of its pEC (50), E (max), and inhibition by selective muscarinic antagonists. Thus, 4-DAMP mustard treatment appears to inactivate M(3) responses selectively and renders the muscarinic contractile behavior of the wild-type ileum similar to that of the M(3) knockout mouse. Following 4-DAMP mustard treatment, the contractile response of the guinea pig ileum to oxotremorine-M exhibited low potency and a competitive-antagonism profile consistent with an M(3) response. The guinea pig ileum, therefore, lacks a direct, highly potent, M(2)-contractile component but may have a direct, lower potency M(2) component.

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Effects of 4-DAMP mustard treatment on contractions elicited to oxotremorine-M in mouse ileum. a Responses were measured in ilea from the M3 KO mouse (open triangles) and from wild-type ileum before (open circles) and after (closed triangles) treatment with 4-DAMP mustard (40 nM) in combination with AF-DX 116 (4 μM) for 2 h followed by washing as described under “Methods.” b Responses were measured in ilea from the M2 KO mouse before (open circles) and after (closed triangles) treatment with 4-DAMP mustard as described in a. c Same as b except that responses were measured in ilea from the M3 KO mouse. d All responses were measured in ilea from wild-type mice that had been treated with 4-DAMP mustard as described in a. After this treatment, responses were measured in the absence (open circles) and presence of AF-DX 116 (1 μM; closed triangles) or 4-DAMP (10 nM; open triangles). Mean values ± SEM from five to seven experiments are plotted in a–d
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Fig3: Effects of 4-DAMP mustard treatment on contractions elicited to oxotremorine-M in mouse ileum. a Responses were measured in ilea from the M3 KO mouse (open triangles) and from wild-type ileum before (open circles) and after (closed triangles) treatment with 4-DAMP mustard (40 nM) in combination with AF-DX 116 (4 μM) for 2 h followed by washing as described under “Methods.” b Responses were measured in ilea from the M2 KO mouse before (open circles) and after (closed triangles) treatment with 4-DAMP mustard as described in a. c Same as b except that responses were measured in ilea from the M3 KO mouse. d All responses were measured in ilea from wild-type mice that had been treated with 4-DAMP mustard as described in a. After this treatment, responses were measured in the absence (open circles) and presence of AF-DX 116 (1 μM; closed triangles) or 4-DAMP (10 nM; open triangles). Mean values ± SEM from five to seven experiments are plotted in a–d

Mentions: bThe pKB was not determined because of the low log shift value


The guinea pig ileum lacks the direct, high-potency, M(2)-muscarinic, contractile mechanism characteristic of the mouse ileum.

Griffin MT, Matsui M, Ostrom RS, Ehlert FJ - Naunyn Schmiedebergs Arch. Pharmacol. (2009)

Effects of 4-DAMP mustard treatment on contractions elicited to oxotremorine-M in mouse ileum. a Responses were measured in ilea from the M3 KO mouse (open triangles) and from wild-type ileum before (open circles) and after (closed triangles) treatment with 4-DAMP mustard (40 nM) in combination with AF-DX 116 (4 μM) for 2 h followed by washing as described under “Methods.” b Responses were measured in ilea from the M2 KO mouse before (open circles) and after (closed triangles) treatment with 4-DAMP mustard as described in a. c Same as b except that responses were measured in ilea from the M3 KO mouse. d All responses were measured in ilea from wild-type mice that had been treated with 4-DAMP mustard as described in a. After this treatment, responses were measured in the absence (open circles) and presence of AF-DX 116 (1 μM; closed triangles) or 4-DAMP (10 nM; open triangles). Mean values ± SEM from five to seven experiments are plotted in a–d
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2749929&req=5

Fig3: Effects of 4-DAMP mustard treatment on contractions elicited to oxotremorine-M in mouse ileum. a Responses were measured in ilea from the M3 KO mouse (open triangles) and from wild-type ileum before (open circles) and after (closed triangles) treatment with 4-DAMP mustard (40 nM) in combination with AF-DX 116 (4 μM) for 2 h followed by washing as described under “Methods.” b Responses were measured in ilea from the M2 KO mouse before (open circles) and after (closed triangles) treatment with 4-DAMP mustard as described in a. c Same as b except that responses were measured in ilea from the M3 KO mouse. d All responses were measured in ilea from wild-type mice that had been treated with 4-DAMP mustard as described in a. After this treatment, responses were measured in the absence (open circles) and presence of AF-DX 116 (1 μM; closed triangles) or 4-DAMP (10 nM; open triangles). Mean values ± SEM from five to seven experiments are plotted in a–d
Mentions: bThe pKB was not determined because of the low log shift value

Bottom Line: Following 4-DAMP mustard treatment, the concentration-response curve of oxotremorine-M in wild-type ileum resembled that of the M(3) knockout mouse in terms of its pEC (50), E (max), and inhibition by selective muscarinic antagonists.Following 4-DAMP mustard treatment, the contractile response of the guinea pig ileum to oxotremorine-M exhibited low potency and a competitive-antagonism profile consistent with an M(3) response.The guinea pig ileum, therefore, lacks a direct, highly potent, M(2)-contractile component but may have a direct, lower potency M(2) component.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Chapman University, Orange, CA, USA.

ABSTRACT
We explored whether the M(2) muscarinic receptor in the guinea pig ileum elicits a highly potent, direct-contractile response, like that from the M(3) muscarinic receptor knockout mouse. First, we characterized the irreversible receptor-blocking activity of 4-DAMP mustard in ileum from muscarinic receptor knockout mice to verify its M(3) selectivity. Then, we used 4-DAMP mustard to inactivate M(3) responses in the guinea pig ileum to attempt to reveal direct, M(2) receptor-mediated contractions. The muscarinic agonist, oxotremorine-M, elicited potent contractions in ileum from wild-type, M(2) receptor knockout, and M(3) receptor knockout mice characterized by negative log EC(50) (pEC (50)) values +/- SEM of 6.75 +/- 0.03, 6.26 +/- 0.05, and 6.99 +/- 0.08, respectively. The corresponding E (max) values in wild-type and M(2) receptor knockout mice were approximately the same, but that in the M(3) receptor knockout mouse was only 36% of wild type. Following 4-DAMP mustard treatment, the concentration-response curve of oxotremorine-M in wild-type ileum resembled that of the M(3) knockout mouse in terms of its pEC (50), E (max), and inhibition by selective muscarinic antagonists. Thus, 4-DAMP mustard treatment appears to inactivate M(3) responses selectively and renders the muscarinic contractile behavior of the wild-type ileum similar to that of the M(3) knockout mouse. Following 4-DAMP mustard treatment, the contractile response of the guinea pig ileum to oxotremorine-M exhibited low potency and a competitive-antagonism profile consistent with an M(3) response. The guinea pig ileum, therefore, lacks a direct, highly potent, M(2)-contractile component but may have a direct, lower potency M(2) component.

Show MeSH
Related in: MedlinePlus