Serotonin-induced short-circuit current in pig jejunum

Area of Science:

• Gastrointestinal physiology
• Neurogastroenterology
• Ion transport mechanisms

Background:

• Serotonin (5-HT) plays a crucial role in regulating gastrointestinal function.
• Understanding 5-HT's impact on jejunal ion transport is vital for comprehending digestive processes.

Purpose of the Study:

• To investigate the effects of serotonin (5-HT) on short-circuit current (SCC), ion fluxes, and prostaglandin E2 (PGE2) release in pig jejunum.
• To elucidate the mechanisms underlying 5-HT-mediated changes in jejunal function.

Main Methods:

• The Ussing-chamber technique was employed to measure SCC, sodium, and chloride fluxes in isolated pig jejunum.
• Dose-response studies were conducted to determine the effects of 5-HT.
• The roles of prostaglandin E2, octreotide, and tetrodotoxin (TTX) were assessed using specific inhibitors and analogues.

Main Results:

• 5-HT induced a dose-dependent increase in SCC, with an EC50 of 6 +/- 4 microM and Emax of 77 +/- 8 microA.cm-2.
• The 5-HT-induced SCC was partially attributed to inhibited sodium absorption and stimulated chloride secretion.
• 5-HT stimulated PGE2 release in a dose-independent manner, and indomethacin reduced the 5-HT effect by 40%.
• Octreotide also reduced 5-HT-induced SCC by approximately 40%, whereas TTX had no significant effect.

Conclusions:

• Serotonin (5-HT) significantly increases SCC in the pig jejunum through a TTX-insensitive pathway.
• The 5-HT effect involves both inhibition of sodium absorption and stimulation of chloride secretion.
• Prostaglandin E2 and somatostatin pathways (modulated by octreotide) are implicated in mediating the 5-HT response in the jejunum.