Functional response to vasoactive intestinal peptide in piebald lethal mice

Area of Science:

• Gastroenterology
• Neurogastroenterology
• Developmental Biology

Background:

• Hirschsprung's disease is characterized by aganglionosis in the distal colon.
• Reduced concentrations of vasoactive intestinal peptide (VIP), a key gut neuropeptide, are observed in Hirschsprung's disease models.
• The functional role of VIP in aganglionic colonic tissue remains unclear.

Purpose of the Study:

• To investigate the functional response to VIP in the aganglionic colon.
• To compare VIP's effects on colonic motility in normal and aganglionic tissues.

Main Methods:

• In vitro study using distal colonic segments from piebald lethal (PLM) mice (aganglionic) and normal littermates (NLM).
• Tissues were subjected to electrical field stimulation (EFS), acetylcholine (ACh) challenge, and VIP administration in tissue baths.
• Motility index (MI) was used to quantify contractile activity and responses.

Main Results:

• Aganglionic PLM colonic tissues exhibited significantly higher basal contractile activity (MI = 19.5) compared to NLM tissues (MI = 6.5).
• VIP significantly reduced ACh-induced motility in NLM tissues (49% reduction) but showed a nonsignificant reduction in PLM tissues (22%).
• VIP inhibited EFS responses in NLM tissues, while PLM tissues showed no response to EFS, indicating impaired inhibitory innervation.

Conclusions:

• Aganglionic colonic tissue in PLM mice demonstrates a deficit in the inhibitory response to VIP.
• Increased basal activity and reduced VIP responsiveness in aganglionic colon support a generalized impairment of inhibitory innervation.
• These findings highlight VIP's crucial role in maintaining normal colonic motility and suggest its dysfunction contributes to Hirschsprung's pathophysiology.