Neuropeptides in the human appendix. Distribution and motor effects

Area of Science:

• Neuroscience
• Gastroenterology
• Immunohistochemistry

Background:

• Knowledge of human enteric peptide-containing neurons is limited.
• The appendix's role in enteric innervation requires further investigation.

Purpose of the Study:

• To characterize the peptidergic innervation of the human appendix using immunocytochemistry and in vitro pharmacology.
• To investigate the functional roles of identified peptides in modulating appendix smooth muscle activity.

Main Methods:

• Human appendix samples were analyzed using immunocytochemistry and immunochemistry (RIA, HPLC).
• In vitro pharmacological experiments assessed the effects of peptides on electrically evoked contractions and exogenous acetylcholine responses.
• Tetrodotoxin was used to differentiate direct smooth muscle effects from neural modulation.

Main Results:

• Numerous nerve fibers containing VIP/PHI, SP/NKA, galanin, and enkephalin were identified. Unexpected VIP/PHI and NPY co-expression was observed.
• Galanin and GRP induced concentration-dependent contractions, suggesting direct smooth muscle action.
• GRP enhanced cholinergic contractions, while met-enkephalin reduced them, indicating modulation of acetylcholine release.

Conclusions:

• The human appendix exhibits a complex peptidergic innervation with novel peptide co-expressions.
• Specific peptides like galanin and GRP directly influence smooth muscle, while others modulate cholinergic neurotransmission.
• This research provides crucial insights into the neurochemical control of the human appendix.