Detection of stress and the effects of central nervous system depressants by gastrointestinal smooth muscle electromyography in wakeful rats

The effect of single and repeated doses of rivastigmine on gastric myoelectric activity in experimental pigs

BACKGROUND

Rivastigmine is a pseudo-irreversible cholinesterase inhibitor used for therapy of Alzheimer's disease and non-Alzheimer dementia syndromes. In humans, rivastigmine can cause significant gastrointestinal side effects that can limit its clinical use. The aim of this study was to assess the impact of rivastigmine on gastric motor function by means of electrogastrography (EGG) in experimental pigs.

METHODS

Six experimental adult female pigs (Sus scrofa f. domestica, hybrids of Czech White and Landrace breeds; 3-month-old; mean weight 30.7 ± 1.2 kg) were enrolled into the study twice and created two experimental groups. In group A, a single intragastric dose of 6 mg rivastigmine hydrogen tartate was administered in the morning to fasting pigs before EGG recording. In group B, rivastigmine was administered to overnight fasting animals in a dietary bolus in the morning for 7 days (6 mg per day). On day 8, an intragastric dose of 12 mg rivastigmine was given in the morning to fasting pigs before EGG. EGG recording was accomplished by means of an EGG standalone system. Recordings from both groups were evaluated in dominant frequency and EGG power (areas of amplitudes).

RESULTS

In total, 1,980 one-minute EGG intervals were evaluated. In group A, basal EGG power (median 1290.5; interquartile range 736.5-2330 μV2) was significantly higher in comparison with the power of intervals T6 (882; 577-1375; p = 0.001) and T10 (992.5; 385-2859; p = 0.032). In group B, the dominant frequency increased significantly from basal values (1.97 ± 1.57 cycles per minute) to intervals T9 (3.26 ± 2.16; p < 0.001) and T10 (2.14 ± 1.16; p = 0.012), respectively. In group B, basal EGG power (median 1030.5; interquartile range 549-5093) was significantly higher in comparison with the power of intervals T7 (692.5; 434-1476; p = 0.002) and T8 (799; 435-1463 μV2; p = 0.004).

CONCLUSIONS

Both single as well as repeated intragastric administration of rivastigmine hydrogen tartrate caused a significant decrease of EGG power (areas of amplitudes) in experimental pigs. EGG power may serve as an indirect indicator of gastric motor competence. These findings might provide a possible explanation of rivastigmine-associated dyspepsia in humans.

Non-invasive smooth muscle electromyography (SMEMG) as a novel monitoring technology of the gastrointestinal tract of awake, free-moving pigs-A pilot study

There are several mathematical models and measurements to determine the efficiency of the digestibility of different feedstuffs. However, there is lack of information regarding the direct methods or measurement techniques used to analyse the physical response of the different parts of the gastrointestinal tract (GIT) of growing pigs to different diets. Smooth muscle electromyography (SMEMG) is a non-invasive method for the measurement of gastrointestinal myoelectrical activity. In the present study, SMEMG methodology has been adapted from laboratory rats to pigs, and the effects of feedstuffs with control (CTR) or experimentally increased (EXP) amounts of fibre were investigated on gastrointestinal tract motility. Nine barrow pigs ((Danish Landrace × Danish Yorkshire) × Danish Duroc) were used (30 ± 3 kg), and their CTR and EXP feedstuffs contained 29 and 49 g/kg crude fibre (CF), respectively. Myoelectric activities of the stomach, ileum and caecum were detected in the awake pigs by a pair of electrodes. The recorded myoelectric signals were analysed with fast Fourier transformation (FFT), and the spectra were expressed in GIT section-specific cycles per minutes (cpm) values and the maximum power spectrum density (PsD_max). A significant increase (P < 0.001) was observed in the value of the PsD_max of the small intestine (20–25 cpm) as a consequence of the EXP diet. The PsDmax values of the stomach (3–5 cpm) and large intestine (1–3 cpm) did not show any significant change in pigs fed the EXP diet. As a direct and non-invasive method, SMEMG is suitable for the rapid evaluation of the effects of diets with different fibre contents on the GIT of non-anaesthetised, free-moving pigs.

Detection of acute stress by smooth muscle electromyography: A translational study on rat and human

AIMS

Non-invasive and simultaneous recording of gastrointestinal (GI) activity during stress induction is still an unexplored field. In our previous investigation, the stress-induced alteration of the gastrointestinal tract was explored in rats. Our aims were to expand our previous rat experiment and to induce stress response in rats (Study 1) and humans (Study 2) to detect the GI tract activity, heart rate and body temperature.

MATERIALS AND METHODS

In the preclinical sample, acute stress was induced by immobilization in Sprague-Dawley rats (N = 10). Acute stress response was generated by the Trier Social Stress Test among healthy volunteers (N = 16). Detection of acute stress was measured by using smooth muscle electromyography, which recorded the myoelectric waves of the gastrointestinal tract (stomach, ileum and colon) simultaneously with heart rate and body temperature in rats and humans.

KEY FINDINGS

The myoelectric waves of the stomach, the cecum and the ileum increased during immobilization in rats, rising in parallel with heart rate and the dermal temperature of the abdominal surface. The same alterations were found during the stress period among humans, except in the case of the colon, where no change was detected.

SIGNIFICANCE

The crucial role of the GI tract in stress response was revealed by translating the outcome of basic research into human results. The similar GI alterations during stress in rats and humans underpin the robustness of our findings. In summary, our preliminary translational-based study can serve as an appropriate basis for further human studies.