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Luminal Cholera Toxin Alters Motility in Isolated Guinea-Pig Jejunum via a Pathway Independent of 5-HT(3) Receptors.

Fung C, Ellis M, Bornstein JC - Front Neurosci (2010)

Bottom Line: Its effects on intestinal motor patterns are less well understood.Luminal CT also reduced the pressure threshold for saline distension evoked propulsive reflexes, an effect resistant to granisetron.In contrast, CT prevented the induction of segmenting contractions by luminal decanoic acid, so its effects on propulsive and segmenting contractile activity are distinctly different.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Melbourne Parkville, VIC, Australia.

ABSTRACT
Cholera toxin (CT) is well established to produce diarrhea by producing hyperactivity of the enteric neural circuits that regulate water and electrolyte secretion. Its effects on intestinal motor patterns are less well understood. We examined the effects of luminal CT on motor activity of guinea-pig jejunum in vitro. Segments of jejunum were cannulated at either end and mounted horizontally. Their contractile activity was video-imaged and the recordings were used to construct spatiotemporal maps of contractile activity with CT (1.25 or 12.5 μg/ml) in the lumen. Both concentrations of CT induced propulsive motor activity in jejunal segments. The effect of 1.25 μg/ml CT was markedly enhanced by co-incubation with granisetron (5-HT(3) antagonist, 1 μM), which prevents the hypersecretion induced by CT. The increased propulsive activity was not accompanied by increased segmentation and occurred very early after exposure to CT in the presence of granisetron. Luminal CT also reduced the pressure threshold for saline distension evoked propulsive reflexes, an effect resistant to granisetron. In contrast, CT prevented the induction of segmenting contractions by luminal decanoic acid, so its effects on propulsive and segmenting contractile activity are distinctly different. Thus, in addition to producing hypersecretion, CT excites propulsive motor activity with an entirely different time course and pharmacology, but inhibits nutrient-induced segmentation. This suggests that CT excites more than one enteric neural circuit and that propulsive and segmenting motor patterns are differentially regulated.

No MeSH data available.


Related in: MedlinePlus

Propulsive (A) and segmentation (B) contractions in control (black), CT (1. 25 μg/ml, red), CT plus gran (blue). Curve differs from control (*P < 0.0001), curve differs from CT alone (†P < 0.0001), CT plus gran differs from CT alone (‡P < 0.001, propulsive; P < 0.05 segmentation).
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Figure 2: Propulsive (A) and segmentation (B) contractions in control (black), CT (1. 25 μg/ml, red), CT plus gran (blue). Curve differs from control (*P < 0.0001), curve differs from CT alone (†P < 0.0001), CT plus gran differs from CT alone (‡P < 0.001, propulsive; P < 0.05 segmentation).

Mentions: We counted the numbers of propulsive and segmenting contractions in each map to determine whether CT enhanced one or both types of activity. The increased activity induced by CT (1.25 μg/ml) alone or with granisetron was almost entirely due to increased propulsive activity (Figure 2A).


Luminal Cholera Toxin Alters Motility in Isolated Guinea-Pig Jejunum via a Pathway Independent of 5-HT(3) Receptors.

Fung C, Ellis M, Bornstein JC - Front Neurosci (2010)

Propulsive (A) and segmentation (B) contractions in control (black), CT (1. 25 μg/ml, red), CT plus gran (blue). Curve differs from control (*P < 0.0001), curve differs from CT alone (†P < 0.0001), CT plus gran differs from CT alone (‡P < 0.001, propulsive; P < 0.05 segmentation).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2967348&req=5

Figure 2: Propulsive (A) and segmentation (B) contractions in control (black), CT (1. 25 μg/ml, red), CT plus gran (blue). Curve differs from control (*P < 0.0001), curve differs from CT alone (†P < 0.0001), CT plus gran differs from CT alone (‡P < 0.001, propulsive; P < 0.05 segmentation).
Mentions: We counted the numbers of propulsive and segmenting contractions in each map to determine whether CT enhanced one or both types of activity. The increased activity induced by CT (1.25 μg/ml) alone or with granisetron was almost entirely due to increased propulsive activity (Figure 2A).

Bottom Line: Its effects on intestinal motor patterns are less well understood.Luminal CT also reduced the pressure threshold for saline distension evoked propulsive reflexes, an effect resistant to granisetron.In contrast, CT prevented the induction of segmenting contractions by luminal decanoic acid, so its effects on propulsive and segmenting contractile activity are distinctly different.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Melbourne Parkville, VIC, Australia.

ABSTRACT
Cholera toxin (CT) is well established to produce diarrhea by producing hyperactivity of the enteric neural circuits that regulate water and electrolyte secretion. Its effects on intestinal motor patterns are less well understood. We examined the effects of luminal CT on motor activity of guinea-pig jejunum in vitro. Segments of jejunum were cannulated at either end and mounted horizontally. Their contractile activity was video-imaged and the recordings were used to construct spatiotemporal maps of contractile activity with CT (1.25 or 12.5 μg/ml) in the lumen. Both concentrations of CT induced propulsive motor activity in jejunal segments. The effect of 1.25 μg/ml CT was markedly enhanced by co-incubation with granisetron (5-HT(3) antagonist, 1 μM), which prevents the hypersecretion induced by CT. The increased propulsive activity was not accompanied by increased segmentation and occurred very early after exposure to CT in the presence of granisetron. Luminal CT also reduced the pressure threshold for saline distension evoked propulsive reflexes, an effect resistant to granisetron. In contrast, CT prevented the induction of segmenting contractions by luminal decanoic acid, so its effects on propulsive and segmenting contractile activity are distinctly different. Thus, in addition to producing hypersecretion, CT excites propulsive motor activity with an entirely different time course and pharmacology, but inhibits nutrient-induced segmentation. This suggests that CT excites more than one enteric neural circuit and that propulsive and segmenting motor patterns are differentially regulated.

No MeSH data available.


Related in: MedlinePlus