Use of electrogastrography in preclinical studies of cholinergic and anticholinergic agents in experimental pigs

Electrogastrography measurement systems and analysis methods used in clinical practice and research: comprehensive review

Electrogastrography (EGG) is a non-invasive method with high diagnostic potential for the prevention of gastroenterological pathologies in clinical practice. In this study, a review of the measurement systems, procedures, and methods of analysis used in electrogastrography is presented. A critical review of historical and current literature is conducted, focusing on electrode placement, measurement apparatus, measurement procedures, and time-frequency domain methods of filtration and analysis of the non-invasively measured electrical activity of the stomach. As a result, 129 relevant articles with primary aim on experimental diet were reviewed in this study. Scopus, PubMed, and Web of Science databases were used to search for articles in English language, according to the specific query and using the PRISMA method. The research topic of electrogastrography has been continuously growing in popularity since the first measurement by professor Alvarez 100 years ago, and there are many researchers and companies interested in EGG nowadays. Measurement apparatus and procedures are still being developed in both commercial and research settings. There are plenty variable electrode layouts, ranging from minimal numbers of electrodes for ambulatory measurements to very high numbers of electrodes for spatial measurements. Most authors used in their research anatomically approximated layout with two++ active electrodes in bipolar connection and commercial electrogastrograph with sampling rate of 2 or 4 Hz. Test subjects were usually healthy adults and diet was controlled. However, evaluation methods are being developed at a slower pace, and usually the signals are classified only based on dominant frequency. The main review contributions include the overview of spectrum of measurement systems and procedures for electrogastrography developed by many authors, but a firm medical standard has not yet been defined. Therefore, it is not possible to use this method in clinical practice for objective diagnosis.

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A non-invasive tool to collect small intestine content in post weaning pigs: validation study

The Capsule for Sampling (CapSa) is an ingestible capsule that collects small intestine content while transiting through the natural digestive pathway. In this study, 14 Swiss Large White pigs weighing less than 12 kg (Category < 12 kg) and 12 weighing between 12 and 20 kg (Category [12-20 kg]) were given two CapSas and monitored for three days. The animals were euthanized for post-mortem sampling, allowing us to directly obtain gut microbiota samples from the gastrointestinal tract. This post-mortem approach enabled a direct comparison between the microbial content from the gut and the samples collected via the CapSas, and it also facilitated precise identification of the CapSas' sampling sites within the gastrointestinal tract. For the category under 12 kg, only 2.3% of the administered CapSas were recovered from the feces. In contrast, in the 12-20 kg category, 62.5% of the CapSas were successfully retrieved from the feces within 48 h. Of these recovered CapSas, 73.3%-equating to 11 capsules from eight pigs-had a pH > 5.5 and were therefore selected for microbiome analysis. Bacterial composition of the CapSas was compared with that of the three segments of the small intestine, the large intestine and feces of the corresponding pig. The results were tested using a PERMANOVA model (Adonis) including sample type as a factor, and then pairwise comparisons were made. The bacterial composition found in the CapSas differed from that of the large intestine and feces (P < 0.01), while it did not differ from the first segment of the small intestine (P > 0.10). This study provides evidence that the CapSa effectively samples the intestinal microbiota from the upper section of the small intestine in post-weaning pigs. Furthermore, it was found that the collection of CapSas could only be successfully achieved in pigs classified within the heavier weight category.

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.

Dextran Sodium Sulphate-Induced Gastrointestinal Injury Further Aggravates the Impact of Galantamine on the Gastric Myoelectric Activity in Experimental Pigs

Galantamine has been used as a treatment for Alzheimer disease. It has a unique, dual mode of action (inhibitor of acetylcholinesterase and allosteric modulator of nicotinic acetylcholine receptors). Nausea (in about 20%), vomiting (10%) and diarrhoea (5–7%) are the most common side effects. The aim of this study was to assess the effect of galantamine on porcine gastric myoelectric activity without (Group A) and with (Group B) dextran sodium sulphate (DSS)-induced gastrointestinal injury. Galantamine hydrobromide was administrated to twelve pigs as a single intragastric dose (24 mg). Gastric myoelectric activity was investigated by electrogastrography (EGG). Basal (15 min before galantamine administration) and study recordings after galantamine administration (300 min) were evaluated using a running spectral analysis. Results were expressed as dominant frequency of gastric slow waves and power analysis (areas of amplitudes). Altogether, 3780 one-minute EGG recordings were evaluated. In Group A, power was steady from basal values for 180 min, then gradually decreased till 270 min (p = 0.007). In Group B, there was a rapid gradual fall from basal values to those after 120 min (p = 0.007) till 300 min (p ˂ 0.001). In conclusion, galantamine alone revealed an unfavourable effect on porcine myoelectric activity assessed by gastric power. It can be a plausible explanation of galantamine-associated dyspepsia in humans. DSS caused further profound decrease of EGG power. That may indicate that underlying inflammatory, ischaemic or NSAIDs-induced condition of the intestine in humans can have aggravated the effect of galantamine on gastric myoelectric activity.

The pharmacokinetic parameters and the effect of a single and repeated doses of memantine on gastric myoelectric activity in experimental pigs

Background

Memantine, currently available for the treatment of Alzheimer's disease, is an uncompetitive antagonist of the N-methyl-D-aspartate type of glutamate receptors. Under normal physiologic conditions, these unstimulated receptor ion channels are blocked by magnesium ions, which are displaced after agonist-induced depolarization. In humans, memantine administration is associated with different gastrointestinal dysmotility side effects (vomiting, diarrhoea, constipation, motor-mediated abdominal pain), thus limiting its clinical use. Mechanism of these motility disorders has not been clarified yet. Pigs can be used in various preclinical experiments due to their relatively very similar gastrointestinal functions compared to humans. The aim of this study was to evaluate the impact of a single and repeated doses of memantine on porcine gastric myoelectric activity evaluated by means of electrogastrography (EGG).

Methods

Six adult female experimental pigs (Sus scrofa f. domestica, mean weight 41.7±5.0 kg) entered the study for two times. The first EGG was recorded after a single intragastric dose of memantine (20 mg). In the second part, EGG was accomplished after 7-day intragastric administration (20 mg per day). All EGG recordings were performed under general anaesthesia. Basal (15 minutes) and study recordings (120 minutes) were accomplished using an EGG stand (MMS, Enschede, the Netherlands). Running spectral analysis based on Fourier transform was used. Results were expressed as dominant frequency of gastric slow waves (DF) and power analysis (areas of amplitudes).

Results

Single dose of memantine significantly increased DF, from basic values (1.65±1.05 cycles per min.) to 2.86 cpm after 30 min. (p = 0.008), lasting till 75 min. (p = 0.014). Basal power (median 452; inter-quartile range 280–1312 μV^2) raised after 15 min. (median 827; IQR 224–2769; p = 0.386; NS), lasting next 30 min. Repetitively administrated memantine caused important gastric arrhythmia. Basal DF after single and repeated administration was not different, however, a DF increase in the second part was more prominent (up to 3.18±2.16 after 15 and 30 min., p<0.001). In comparison with a single dose, basal power was significantly higher after repetitively administrated memantine (median 3940; IQR 695–15023 μV^2; p<0.001). Next dose of 20 mg memantine in the second part induced a prominent drop of power after 15 min. (median 541; IQR 328–2280 μV^2; p<0.001), lasting till 120 min. (p<0.001).

Conclusions

Both single and repeated doses of memantine increased DF. Severe gastric arrhythmia and long-lasting low power after repeated administration might explain possible gastric dysmotility side effects in the chronic use of memantine.