Different patterns between mechanical and electrical activities: an approach to investigate gastric motility in a model of long-term diabetic rats.

The relationship between time-courses of mechanical and electrical events in longstanding diabetes was investigated in rats. Magnetic markers and electrodes were surgically implanted in the gastric serosa of male rats. Simultaneous recordings were obtained by AC biosusceptometry, electromyography and electrogastrography one, three and six months after injections of saline (control) or alloxan (diabetic). Frequency and amplitude of contraction, abnormal rhythmic index and half-bandwidth were obtained (ANOVA P < 0.05). Antral hypomotility and gastric motility instability were observed in the signal waveform of diabetic rats at the three time points of study. The mean frequency (4.4 ± 0.4 cpm) was strictly similar, but the mechanical and electrical correlation was lowest for diabetics groups. Decreases in mechanical amplitude were observed for all diabetic groups compared with control; also the ranges of frequency were much wider in diabetes. The half-bandwidth increased since the first month in mechanical recordings and only after the third month in electrical. In diabetic animals, about 40% of gastric activity was abnormal (against 12% in control) and may reach 60% in the sixth month of mechanical recordings. The multi-instrumental approach showed a more substantial deterioration in mechanical activity and created an integrative view of gastric motility for longstanding diabetic model.

AC Biosusceptometry as a method for measuring gastric contraction.

The aim of this study was to validate the alternate current biosusceptometry (ACB) for monitoring gastric contractions in rats. In vitro data were obtained to establish the relationship between ACB and the strain-gauge (SG) signal amplitude. In vivo experiments were performed on rats with magnetic markers and SGs previously implanted under the gastric serosa. The effects of the prandial state in gastric motility profiles were obtained. The correlation between in vitro signal amplitudes was strong (R = 0.989). The temporal cross-correlation between the ACB and SG signal amplitude was higher in the postprandial than in the fasting state. Irregular signal profiles, low contraction amplitudes, and smaller signal-to-noise ratios explained the poor correlation for fasting-state recordings. The contraction frequencies using ACB were 0.068 ± 0.007 Hz (postprandial) and 0.058 ± 0.007 Hz (fasting) and those using SG were 0.066 ± 0.006 Hz (postprandial) and 0.059 ± 0.008 Hz (fasting) (P < 0.003). When a magnetic tracer was ingested, there was a strong correlation and a small phase-difference between techniques. We conclude that ACB provides an accurate and sensitive technique for studies of GI motility in the rat.

The ACB technique: a biomagentic tool for monitoring gastrointestinal contraction directly from smooth muscle in dogs.

The aim of this paper was to verify whether AC biosusceptometry (ACB) is suitable for monitoring gastrointestinal (GI) contraction directly from smooth muscle in dogs, comparing with electrical recordings simultaneously. All experiments were performed in dogs with magnetic markers implanted under the serosa of the right colon and distal stomach, and their movements were recorded by ACB. Monopolar electrodes were implanted close to the magnetic markers and their electric potentials were recorded by electromyography (EMG). The effects of neostigmine, hyoscine butylbromide and meal on gastric and colonic parameters were studied. The ACB signal from the distal stomach was very similar to EMG; in the colonic recordings, however, within the same low-frequency band, ACB and EMG signals were characterized by simultaneity or a widely changeable frequency profile with time. ACB recordings were capable of demonstrating the changes in gastric and colonic motility determined by pharmacological interventions as well as by feeding. Our results reinforce the importance of evaluating the mechanical and electrical components of motility and show a temporal association between them. ACB and EMG are complementary for studying motility, with special emphasis on the colon. ACB offers an accurate method for monitoring in vivo GI motility.