Decrease of duodenal calcitonin gene-related peptide- and substance P-like immunoreactivity in rat duodenal ulcers

Area of Science:

• Gastroenterology
• Neuroscience
• Pharmacology

Background:

• Calcitonin gene-related peptide (CGRP) and Substance P (SP) are neuropeptides involved in various physiological processes, including gastrointestinal function.
• The role of these neuropeptides in the pathogenesis of duodenal ulcers remains incompletely understood.

Purpose of the Study:

• To investigate the endogenous levels of duodenal CGRP and SP following the induction of duodenal ulcers in a rat model.
• To explore the origin and mechanisms of CGRP and SP changes during ulcer formation.

Main Methods:

• Induction of duodenal ulcers using three different ulcerogens: cysteamine, dulcerozine, and mepirizole.
• Quantification of CGRP and SP like immunoreactivity (li) in duodenal tissues.
• Pretreatment with capsaicin, a selective sensory neurotoxin, to investigate the origin of CGRP and SP.

Main Results:

• A significant decrease in duodenal CGRP-li and SP-li was observed after ulcer induction by all three agents.
• Time-course studies demonstrated a concomitant decrease in CGRP-li and SP-li with ulcer formation after cysteamine administration.
• Capsaicin pretreatment abolished the cysteamine-induced decrease in CGRP-li, indicating a capsaicin-sensitive origin, whereas SP-li reduction was independent of capsaicin, suggesting an intrinsic source.

Conclusions:

• CGRP and SP levels are reduced during duodenal ulcerogenesis in rats.
• CGRP depletion appears to originate from capsaicin-sensitive nerves, while SP depletion is from an intrinsic source.
• These findings suggest that CGRP and SP play a significant local role in the development of duodenal ulcers.