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Adenosine 5'-triphosphate and its relationship with other mediators that activate pelvic nerve afferent neurons in the rat colorectum.

Wynn G, Burnstock G - Purinergic Signal. (2006)

Bottom Line: Seventy-seven percent of all units studied either responded to both ATP and capsaicin or to neither, giving the greatest degree of activity correlation.It is concluded that ATP activates pelvic nerve afferents and acts synergistically with protons, capsaicin and 5-hydroxytryptamine.The pattern of neuronal activation suggests that visceral afferents are polymodal but the receptor expression on their terminals is variable.

View Article: PubMed Central - PubMed

Affiliation: Autonomic Neuroscience Centre, Royal Free and University College School of Medicine, Rowland Hill Street, London, NW3 2PF, UK.

ABSTRACT
Evidence of a role for purinergic signalling in visceral afferents involving P2X(2), P2X(3) and P2Y(1) receptors exists, which appears to be important during inflammation. This study aimed to evaluate the degree of interaction between adenosine 5'-triphosphate (ATP) and other mediators that activate sensory nerves in the colorectum. Recordings from pelvic nerve afferents were made during application of agents to the in-vitro colorectal preparation. Analysis allowed calculation of single unit activity. When applied individually, bradykinin (78%) and 5-hydoxytryptamine (77%) activated the greatest number of neurons, followed by substance P, protons, ATP and capsaicin. Prostaglandin E(2) stimulated the least number (54%) and had a longer latency. Seventy-seven percent of all units studied either responded to both ATP and capsaicin or to neither, giving the greatest degree of activity correlation. Five percent of units were activated by all seven agents and no units were activated by a single agent alone. 5-hydroxytryptamine, capsaicin and protons, when co-applied with ATP, increased pelvic nerve activity to a greater degree than the sum of the individual responses. It is concluded that ATP activates pelvic nerve afferents and acts synergistically with protons, capsaicin and 5-hydroxytryptamine. The pattern of neuronal activation suggests that visceral afferents are polymodal but the receptor expression on their terminals is variable.

No MeSH data available.


An example of a single unit in the pelvic nerve that responds to both 5-HT and ATP individually. When the two mediators are applied together, the activity is greatly increased.
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Fig7: An example of a single unit in the pelvic nerve that responds to both 5-HT and ATP individually. When the two mediators are applied together, the activity is greatly increased.

Mentions: By studying the spike frequency of individual units during the application of one or more agents, it was possible to evaluate which units were contributing to the increased response of the nerve as a whole. The vast majority of units that contributed to a greater combined response were activated by both agents, but this was not exclusively the case. In the experiments involving 5-HT, 24% of units increased their firing frequency sufficiently in the presence of a combined bolus of ATP and 5-HT to surpass the responses of both single boluses put together. Of these, three quarters were activated by both single applications and a quarter of them by ATP only. None of the units studied were activated by 5-HT only and then went on to contribute to the increased response. An example of a single unit that contributed to the increased response when both agents were applied is shown in Figure 7. In this case, both ATP and 5-HT activated the unit. Thirty-one percent of units contributed to the combined increased response seen with ATP and capsaicin. All of these units were activated by both single applications. In the experiments involving ATP and protons, the larger combined response was mediated by those units responding to both agents or to protons alone; units exclusively activated by ATP did not contribute. The contribution of units activated by both ATP and protons was only slightly greater at pH 6.5 (34%) than pH 6.8 (32%). However, those responding to protons alone contributed to a greater extent at the lower pH: a further 12% of units at pH 6.8 but a further 21% at pH 6.5. This amounted to a total of 44% of units at pH 6.8 and 55% of units at pH 6.5 that made a contribution to the increased response to a combined bolus of ATP and protons.Figure 7


Adenosine 5'-triphosphate and its relationship with other mediators that activate pelvic nerve afferent neurons in the rat colorectum.

Wynn G, Burnstock G - Purinergic Signal. (2006)

An example of a single unit in the pelvic nerve that responds to both 5-HT and ATP individually. When the two mediators are applied together, the activity is greatly increased.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2104004&req=5

Fig7: An example of a single unit in the pelvic nerve that responds to both 5-HT and ATP individually. When the two mediators are applied together, the activity is greatly increased.
Mentions: By studying the spike frequency of individual units during the application of one or more agents, it was possible to evaluate which units were contributing to the increased response of the nerve as a whole. The vast majority of units that contributed to a greater combined response were activated by both agents, but this was not exclusively the case. In the experiments involving 5-HT, 24% of units increased their firing frequency sufficiently in the presence of a combined bolus of ATP and 5-HT to surpass the responses of both single boluses put together. Of these, three quarters were activated by both single applications and a quarter of them by ATP only. None of the units studied were activated by 5-HT only and then went on to contribute to the increased response. An example of a single unit that contributed to the increased response when both agents were applied is shown in Figure 7. In this case, both ATP and 5-HT activated the unit. Thirty-one percent of units contributed to the combined increased response seen with ATP and capsaicin. All of these units were activated by both single applications. In the experiments involving ATP and protons, the larger combined response was mediated by those units responding to both agents or to protons alone; units exclusively activated by ATP did not contribute. The contribution of units activated by both ATP and protons was only slightly greater at pH 6.5 (34%) than pH 6.8 (32%). However, those responding to protons alone contributed to a greater extent at the lower pH: a further 12% of units at pH 6.8 but a further 21% at pH 6.5. This amounted to a total of 44% of units at pH 6.8 and 55% of units at pH 6.5 that made a contribution to the increased response to a combined bolus of ATP and protons.Figure 7

Bottom Line: Seventy-seven percent of all units studied either responded to both ATP and capsaicin or to neither, giving the greatest degree of activity correlation.It is concluded that ATP activates pelvic nerve afferents and acts synergistically with protons, capsaicin and 5-hydroxytryptamine.The pattern of neuronal activation suggests that visceral afferents are polymodal but the receptor expression on their terminals is variable.

View Article: PubMed Central - PubMed

Affiliation: Autonomic Neuroscience Centre, Royal Free and University College School of Medicine, Rowland Hill Street, London, NW3 2PF, UK.

ABSTRACT
Evidence of a role for purinergic signalling in visceral afferents involving P2X(2), P2X(3) and P2Y(1) receptors exists, which appears to be important during inflammation. This study aimed to evaluate the degree of interaction between adenosine 5'-triphosphate (ATP) and other mediators that activate sensory nerves in the colorectum. Recordings from pelvic nerve afferents were made during application of agents to the in-vitro colorectal preparation. Analysis allowed calculation of single unit activity. When applied individually, bradykinin (78%) and 5-hydoxytryptamine (77%) activated the greatest number of neurons, followed by substance P, protons, ATP and capsaicin. Prostaglandin E(2) stimulated the least number (54%) and had a longer latency. Seventy-seven percent of all units studied either responded to both ATP and capsaicin or to neither, giving the greatest degree of activity correlation. Five percent of units were activated by all seven agents and no units were activated by a single agent alone. 5-hydroxytryptamine, capsaicin and protons, when co-applied with ATP, increased pelvic nerve activity to a greater degree than the sum of the individual responses. It is concluded that ATP activates pelvic nerve afferents and acts synergistically with protons, capsaicin and 5-hydroxytryptamine. The pattern of neuronal activation suggests that visceral afferents are polymodal but the receptor expression on their terminals is variable.

No MeSH data available.