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. 2002 Jul;51(Suppl 1):i2–i5. doi: 10.1136/gut.51.suppl_1.i2

Neuroanatomy of visceral nociception: vagal and splanchnic afferent

D Grundy
PMCID: PMC1867719  PMID: 12077054

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Figure 1 .

Figure 1

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Arrangement of the primary afferent neurones within the intestine. DRG, dorsal root ganglion. Reproduced with permission from Furness and colleagues.1

Figure 2 .

Figure 2

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Potential receptor mechanisms underlying activation (depolarisation) and sensitisation of visceral sensory afferents. Some mediators, for example, serotonin (5-HT) acting on 5-HT3 receptors, cause activation while some (prostaglandin E2 (PGE2)) cause sensitisation. Others, for example adenosine, cause both stimulation and sensitisation. Bradykinin has a self sensitising action, stimulating discharge through activation of phospholipases (PLs) and enhancing excitability via PGs. Inflammatory mediators can be released from a variety of cell types (for example, sympathetic varicosities, mast cells, and blood vessels) present in or around the afferent nerve terminal. 5-HT, adenosine triphosphate (ATP), and capsaicin can directly activate non-selective cation channels (NSCCs) while adenosine, histamine, PGs (not PGE2), and proteases such as tryptase and thrombin act on G protein coupled receptors leading to a Ca2+ dependent modulation of ion channel activity. Sensitisation may be mediated via cyclic adenosine 3,5-monophosphate (cAMP). Adenosine and PGE2 can generate cAMP directly through G protein coupled stimulation of adenyl cyclase (AC). In contrast, histamine may act indirectly through generation of PGs. The actions of cAMP downstream are currently unknown but may involve modulation of ion channels, interaction with other second messengers, such as Ca2+, or even changes in receptor expression. COX, cyclooxygenase; DAG, diacylglycerol; IP3, inositol 1,4,5-triphosphate; PARs, protease activated receptors; PLC, phospholipase C; PLA2, phospholipase A2; PKC, protein kinase C. Modified from Kirkup and colleagues.12

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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