Electrochemical measurements of serotonin (5-HT) release from the guinea pig mucosa using continuous amperometry with a boron-doped diamond microelectrode

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder characterized by chronic abdominal discomfort, including pain, bloating and changes in bowel habits. The pathophysiology of IBS is multi-factoral to be sure, but is not fully understood. Recent studies have shown that IBS may be associated with altered serotonin (5-hydroxytryptamine, 5-HT) levels within the GI tract. About 90% of 5-HT in the human body is produced and stored in enterochromaffin (EC) cells that reside in the mucosal layer of the intestine. Measurements of serotonin availability locally in the mucosa can provide insight on the functionality of these cells and potentially the pathophysiology of the disease. In this study, we used continuous amperometry with a diamond microelectrode to record serotonin levels in vitro in the ileum mucosa as an oxidation current. The boron-doped diamond (BDD) microelectrode is quite practical for these measurements because if its low background signal, low sensitivity to solution pH changes, and excellent resistance to fouling by adsorbed serotonin oxidation reaction products. In fact, the measurements are only possible because of the unique properties of diamond. We present electrochemical data that demonstrate the diamond microelectrode's utility for assessing 5-HT handling on the gut. Confirmation that the oxidation current measured was associated with endogenous serotonin release came from pharmacological studies. These types of in vitro electrochemical measurements may lead to a better understanding of the pathophysiology of IBS.