Tachykinins and intestinal motility in different fish groups

Area of Science:

• Comparative physiology
• Gastrointestinal research
• Neuroendocrinology

Background:

• Tachykinins are peptides involved in various physiological processes, including gut motility.
• Their presence and function in fish gastrointestinal systems are not fully understood across diverse species.

Purpose of the Study:

• To investigate the presence and function of tachykinins, specifically substance P (SP), in the intestines of a wide range of fish species.
• To compare the effects of SP on intestinal motility across different vertebrate lineages.

Main Methods:

• Immunohistochemistry was used to detect SP-like material in the digestive tracts of hagfish, lamprey, starry ray, lungfish, bichir, and rainbow trout.
• Isolated intestinal muscle strips were used to assay the effects of SP on motility.

Main Results:

• SP-like material was found in the intestine of lamprey and lungfish, and the stomach of the ray.
• SP induced intestinal contractions in starry ray, lungfish, bichir, and rainbow trout, but not in hagfish or lamprey.
• In rainbow trout, SP's effect involved direct smooth muscle action and stimulation of cholinergic and serotonergic neurons.

Conclusions:

• Tachykinins play a role in regulating intestinal motility in several fish species, with varying mechanisms of action.
• The functional significance of tachykinins differs across fish taxa, reflecting evolutionary divergence in gastrointestinal control.