A double-blind placebo-controlled trial of BRL 24924 on lower oesophageal sphincter pressure and gastro-oesophageal reflux in healthy volunteers

The importance of 5-hydroxytryptamine receptors in the gut

Most of the 5-hydroxytryptamine (5-HT) present in the adult human body is located in the gastrointestinal tract. The vast majority is contained in enteroendocrine cells, the rest exists mainly in myenteric interneurons separated from the mucosa by an intraenteric barrier. Physiological studies suggest that 5-HT plays a vital role in mediating both sensory and reflex responses to gastrointestinal stimuli and, thus, this transmitter is closely implicated in gut reactions. This review outlines some of the evidence for different 5-HT receptors, summarizes the role of 5-HT in mediating gut sensitivity and motor activity, secretion and more complex activities, such as emesis and diarrhoea and identifies the clinical role of drugs acting on 5-HT receptors in the treatment of emesis, diarrhoea, the control of abdominal pain and discomfort and the rectification of gastrointestinal motility.

Gastrointestinal effects of 5-hydroxytryptamine and related drugs

This paper deals with the effects of 5-hydroxytryptamine (5-HT; serotonin) and related drugs on the gastrointestinal tract (GIT). The nomenclature and classification of 5-HT receptors, as well as their putative role in the GIT are updated in this review. Besides its effects on the cardiovascular system, which have been extensively described, several lines of evidence suggest a role for 5-HT in regulating gastrointestinal functions. 5-HT is present in the gastrointestinal tissues, and can elicit contraction or relaxation by activation of a wide variety of mechanisms and receptors. At least four main types of receptors (5-HT1, 5-HT2, 5-HT3 and 5-HT4) have been described and all the four types seem to influence the GIT. In this respect, the 5-HT2, and in some cases the 5-HT1 receptors, appear to be present on the gastrointestinal smooth muscle, while 5-HT3 and 5-HT4 are mainly neuronal.

A double-blind dose ranging study of BRL 24924 and metoclopramide on lower oesophageal sphincter pressure in healthy volunteers

1. A double-blind placebo controlled dose ranging study of the effect of single oral doses of 1 and 2 mg BRL 24924 and 10 mg metoclopramide on lower oesophageal sphincter pressure has been performed in 20 healthy volunteers. 2. The 2 mg dose of BRL 24924 caused a statistically significant increase in mean lower oesophageal sphincter pressure (P less than 0.05) at 30-45 min post-dose (20.8 +/- 7.1 cm H2O BRL 24924; 16.4 +/- 5.7 cm H2O placebo). BRL 24924 1 mg and metoclopramide 10 mg failed to increase lower oesophageal sphincter pressure at any time. However, eight volunteers with a hypotensive resting lower oesophageal sphincter pressure (less than 15 cm H2O) showed a statistically significant rise in pressure at 120 min for both 1 mg, 2 mg (P less than 0.01; P less than 0.001) BRL 24924 and 10 mg metoclopramide (P less than 0.01). No other significant effect was detected on oesophageal manometry. 3. BRL 24924 (2 mg) has statistically significant effects on lower oesophageal sphincter pressure. However, further studies in patients with gastro-oesophageal reflux disease and oesophagitis are needed to evaluate its clinical efficacy, especially where a hypotensive lower oesophageal sphincter pressure predominates.