Effects of metoclopramide on gastrointestinal myoelectric activity in rats

To investigate the effects of metoclopramide (MCP) action on myoelectric activity in the antrum and small intestine.

Ten healthy male Wistar rats, weighing 250-350 g, were anesthetized with ketamine hydrochloride (100 mg/kg, intramuscularly). Four pairs of bipolar stainless steel electrodes 3 mm apart were implanted on the serosal surface of the antrum at one, 10 and 20 cm distal to the pylorus. Five to ten days following the operation, the gastrointestinal myoelectric activity of fasted rats after intramuscular injection of 2.5, six and 12 mg/kg MCP was recorded using a 8-channel EEG machine, and these values were quantitatively compared with the myoelectric activity after saline injection.

In fasted rats, 2.5 mg/kg MCP increased the amplitude of spike activity (402.0 ± 138.4 μV, vs 345 ± 163.4 μV, P < 0.05) and the percentage of the slow wave-containing spike bursts (60.4% ± 22.0% vs 47.4% ± 22.5%, P < 0.01) of small intestine (1 cm distal to the pylorus), but did not affect the myoelectric activity of the antrum. Six and 12 mg/kg MCP increased the amplitude of both the slow wave (332.8 ± 200.1 μV vs 191.2 ± 143.9 μV, P < 0.01; 330.0 ± 197.1 μV vs 191.2 ± 143.9 μV, P < 0.05) and the spike activity of the antrum (180.5 ± 69.7 μV vs 121.8 ± 63.3 μV, P < 0.05; 174.5 ± 71.7 μV vs 123.8 ± 63.3 μV, P < 0.05), while in small intestine (1 cm distal to the pylorus) only the amplitude of spike activity (407.3 ± 179.0 μV vs 345.0 ± 163.4 μV, P < 0.05; 456.0 ± 145.4 μV vs 345.0 ± 163.4 μV, P < 0.05) and the percentage of the slow wave containing spike bursts (61.7% ± 26.5% vs 47.4% ± 22.5%, P < 0.01; 59.1% ± 17.3% vs 47.4% ± 22.5%, P < 0.01) was increased and the latent period significantly prolonged (2.5 ± 0.35 min vs 0.77 ± 0.18 min, P < 0.01).

Different mechanisms may be involved in enhancing the myoelectric activity of the antrum and small intestine following MCP administration.