Enteric reflexes and nitric oxide in the fish intestine

Area of Science:

• Gastroenterology
• Comparative Physiology
• Neurogastroenterology

Background:

• Peristalsis is crucial for intestinal motility in vertebrates.
• Understanding peristaltic regulation in diverse species like fish can reveal evolutionary conservation.

Purpose of the Study:

• To investigate the neural control mechanisms of intestinal peristalsis in the Atlantic cod (Gadus morhua).
• To identify the specific neurotransmitter pathways involved in cod intestinal motility.

Main Methods:

• Isolated Atlantic cod mid-intestine preparations were used.
• Spontaneous contractions, responses to balloon distension, and intramural electrical stimulation were recorded.
• Pharmacological agents including tetrodotoxin, atropine, methysergide, and L-NAME were applied.

Main Results:

• Spontaneous, anally propagating contractions were observed.
• Intramural stimulation induced oral contractions and anal relaxations, blocked by tetrodotoxin.
• Cholinergic and serotonergic pathways mediated oral contractions; nitrergic pathways mediated anal relaxations.

Conclusions:

• Atlantic cod intestine exhibits an ascending excitatory peristaltic reflex (cholinergic-serotonergic) and a descending inhibitory reflex (nitrergic).
• These findings suggest that the fundamental mechanisms of peristalsis are highly conserved across vertebrate evolution.