Gastric stimulation is effective in reversing vasopressin induced gastroparesis

The aim of this study was to determine the most effective current parameters reversing vasopressin (VP) induced gastroparesis by gastric electrical stimulation IGES).

Twenty male healthy Wistar rats were included into the study (weight 227 +/- 24 g). Animals were subjected to gastric fistula placement and implantation of two monopolar electrodes for EGG-studies and GES. After 5 days of recovery VP was applied (terlipressin 0.1 mg/kg i.p.) The gastric motility was measured by means of balloon introduced into the stomach through the fistula. The gastric electrical and motor activity were recorded by the PowerLab/8SP system and software. Electrical signals were cleared by 3000 AC/DC differential amplifier A-M System Inc. Gastric electrical stimulation (GES) was generated by Zimmer stimulator SINUS5. The following currents: S01 (monopolar): ampl 2.2 mA, freq 29 Hz, on/off 1 s / 10 s; S02 (bipolar): ampl 2.2 mA, freq 29 Hz, on/off 1s/10s: S03 (monopolar): ampl 2.2 mA, freq 0.5 Hz: S04 (monopolar): ampl 2.2 mA, freq 34 Hz, on/off 5.5 s/15 s were used.

The phasic contractions almost disappeared and amplitude decreased from 12 +/- 5 to 2.9 +/- 1.5 cm H20. The motility index decreased from 276,3 +/- 76.4 to 154.6 +/- 63 cm H2O x s/min. GES S01-S04 increased motility index to: 167.6 +/- 60.8: 155.1 +/- 89.3; 170.3 +/- 92.3: 301.9 +/- 70.5 cm H2O x s/min respectively. The frequency of gastric slow wave increased from 0.04 +/- 0.02 to 0.07 +/- 0.02 Hz after VP administration. GES S01-S04 reversed VP induced increase of slow wave frequency to 0.06 +/- 0.02, 0.055 +/- 0.02, 0.06 +/- 0.01 and 0.04 +/- 0.02 Hz, respectively.

This effectiveness of local GES and the pressure pattern of induced gastroparesis suggest peripheral complex inhibitory-excitatory action of vasopressin on gastric smooth muscles. The mechanism of this action may involve the enteric nervous system, gastric and vasal smooth muscles. The most effective in reversing VP induced functional gastroparesis is high frequency current applied in timing of the natural slow wave.