The prokinetic-like activity of the 5-HT4 receptor agonist prucalopride and the cholinesterase inhibitor donepezil in human isolated colon

John Broad, Samrat Mukherjee, George Boundouki, Charles Knowles, Gareth Sanger. Wingate Institute of Neurogastroenterology, Queen Mary, University of London, London, E1 2AJ, United Kingdom.

Lack of efficacious intestinal prokinetic drugs led to the acetylcholinesterase (AChE) inhibitor neostigmine being used to treat patients with severe intestinal hypomotility (eg. pseudo-obstruction or constipation after spinal injury [Saunders and Kimney, 2005; Rubiales et al., 2006]). The AChE inhibitor donepezil, used to treat Alzheimer’s disease, may stimulate gastrointestinal motility in a less severe manner [Jarvie et al., 2008] and may therefore be better-tolerated for a wider spectrum of patients. We examined the ability of donepezil to increase cholinergically-mediated contractions in human colon and compared this effect to that of the 5-HT4 receptor agonist prucalopride, registered in Europe for treatment of constipation.

Human colon tissue was obtained at surgery for cancer (macroscopically normal areas), ulcerative colitis (UC) and Crohn’s disease, following informed consent. After removing the mucosa, strips (∼4mm wide, 10mm long) were cut parallel to the circular muscle and suspended between 2 platinum ring electrodes in tissue baths (Kreb’s; 5% CO2 in O2; 37°C; 1g tension) for isometric recording. Electrical field stimulation (EFS) at different frequencies were applied every 1 min (0.5ms pulse width, 50V, 10s). Drugs were applied non-cumulatively.

Colon from patients with cancer or inflammatory bowel disease (IBD) responded to EFS over a range of frequencies. Low frequencies (1-2Hz) tended to induce relaxations whereas high frequencies (10-20Hz) induced contractions. The effects of drugs were studied against responses evoked by EFS at 5Hz, a frequency which evoked all phenotypes of response, prevented by 1µM tetrodotoxin (n = 2-4 patients for each condition). In colon from cancer patients 74% of strips contracted, 22% relaxed and 4% did not respond; termination of EFS was followed by a large after-contraction in 82% of tissues (n = 14 patients). There was a tendency for tissues from IBD patients to relax more readily in response to EFS. Thus, tissue from UC patients (n = 5) displayed contractions (59%) or relaxations (41%) followed by after-contractions in 65% of strips, and tissue from patients with Crohn’s disease (n = 3) displayed contractions (55%) or relaxations (45%) followed by after-contractions in 59% of strips. In each type of patient, contractions during EFS were prevented by atropine 1µM and relaxations prevented by the nitric oxide synthase inhibitor L-NAME 300µM (n = 2-3 each). Results obtained from IBD patients were combined for analysis of the prokinetic compounds. Donepezil 0.01-3µM did not change muscle tension but facilitated contractions during EFS in tissues from cancer and IBD patients by respectively 122±42% (EC50 = 357nM) and 107±35% (EC50 = 289nM); n = 3 each concentration. Similarly, prucalopride 0.1-30µM facilitated contractions during EFS by 35±23% (EC50 = 2.4µM) and 17±28% (EC50 = 9.0µM); n = 3-5 each concentration.

Differences between the balance of excitatory and inhibitory nerve-mediated responses in ‘normal’ and inflamed colon may indicate changes in the enteric nervous system. Donepezil promotes cholinergic contractility in normal and inflamed colon, to a greater degree than prucalopride and may therefore provide an alternative prokinetic agent.

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Rubiales et al (2006). J Pain Symptom Manage, 32, 204–205

Jarvie EM, Cellek S, Sanger GJ (2008). Pharmacol Res, 58, 297-301.