Submitted on June 12, 2008
Revised on September 15, 2008
Accepted on October 9, 2008
Serotonin (5-HT) release and uptake measured by real-time electrochemical techniques in the rat ileum
Paul Page Bertrand1*, Xiaoya Hu1, John Mach1, and Rebecca L Bertrand1
1 University of New South Wales
* To whom correspondence should be addressed. E-mail: p.bertrand{at}gmail.com.
Serotonin (5-HT) is released from the enterochromaffin (EC) cells and plays an important role in regulating intestinal function. Whilst the release of 5-HT is well-documented, the contribution of the serotonin reuptake transporter (SERT) to the levels and actions of 5-HT in the intestine is unclear. This study aimed to demonstrate real-time SERT activity in ileal mucosa and to assess the effects of SERT inhibition using fluoxetine. Electrochemical recordings were made from the mucosa in full thickness preparations of rat ileum using a carbon fiber electrode to measure 5-HT oxidation current and a force transducer to record circular muscle (CM) tension. Compression of the mucosa stimulated a peak 5-HT release of 12 ± 6 µM which decayed to 7 ± 4 µM. Blockade of SERT with fluoxetine (1 µM) increased the peak compression-evoked release to 19 ± 9 µM and the background levels of 5-HT increased to 11 ± 7 µM (P < 0.05; n = 7). When 5-HT was exogenously applied to the mucosa, fluoxetine caused a significant increase in the time to 50% and 80% decay of the oxidation current. Fluoxetine also increased the spontaneous CM motility (P < 0.05; n = 7) but did not increase the CM-contraction evoked 5-HT release (P > 0.05; n = 5). In conclusion, this is the first characterization of the real-time uptake of 5-HT into the rat intestine. These data suggest that SERT plays an important role in the modulation of 5-HT concentrations that reach intestinal 5-HT receptors.
