E. Wechsung

ENDOTOXIN IN THE CONSCIOUS PIGLET : ITS EFFECTS ON SOME GENERAL AND GASTROINTESTINAL MYOELECTRICAL PARAMETERS

The effect of an intravenous bolus injection of endotoxin, 0.1, 1 or 10 μg/kg, on rectal temperature, clinical appearance, haematological parameters, and on gastrointestinal electrical activity was examined in 11 conscious piglets of 4–5 weeks of age, with implanted electrodes in the antrum pylori, duodenum, jejunum and ileum. All doses resulted in a significant and dose-dependent increase in rectal temperature, in pronounced clinical signs and in distinct changes in haematological values. These included shivering, depression, respiratory distress, a leukopenia (0.1 μg/kg) or a leukocytosis (1 μg/kg) with a shift to the left, an accelerated sedimentation rate and a decreased packed cell volume. Doses of 1 and 10 μg/kg induced a transient inhibition of gastroduodenal electrical activity. These results suggest that, in the piglet, endotoxin primarily manifests general clinical signs and that the gastrointestinal effects coincide with these.

Effect of infusion of a diarrheogenic dose of PGE2 on gastrointestinal electrical activity in the conscious piglet

In 5 conscious piglets with electrodes implanted on the antrum pylori and small intestine, phasic and integrated electrical activity was daily recorded. PGE2, 10 micrograms/kg/min, was infused intravenously during 1.5 h and the induced changes in electrical activity were analyzed. Clinical appearance was also studied. PGE2 induced an inhibition in both antral and intestinal activity. In the antrum this inhibition was characterized by a decrease in the frequency of electrical control activity and fast oscillations, and an increase in the duration of the inhibitory phase. Small intestinal recordings revealed an increase in the quiescence phase for the duodenum and a decrease in the integrated total activity for the duodenum, jejunum and ileum, induced by a decrease in phase II activity. PGE2 was without influence on phase III activity and the recycling of the migrating myoelectrical complexes. All piglets developed a severe diarrhea. Vomiting, sedation, fever and shivering were observed in most animals. These data suggest that the diarrheogenic effect of PGE2 is not provoked by an increase in small intestinal motility. Moreover, the direct effect of this PG is a partial inhibition of gastrointestinal electrical activity.

Influence of prostaglandin E2 infusion on gastrointestinal electrical activity in the conscious piglet

In 5 conscious piglets with implanted electrodes in the antrum pylori, duodenum, jejunum and ileum, electromyographic activity was recorded daily on a multichannel recorder with a time constant of 0.03 s for intestinal and of 1 s for gastric recordings, and simultaneously integrated at 20 s intervals. PGE2 was infused for 2 h in relatively low doses of 0.1 and 1 microgram/kg/min, to avoid excessive hypersecretion, which would disguise direct effects. Each dose was tested once in each animal with a 1 week interval. Infusion of 0.1 microgram/kg/min revealed no significant changes in antral and small intestinal electrical activity. One microgram/kg/min however induced a strong depression of fast oscillations until the end of the infusion and prolongation of the inhibitory phase in the antrum following a duodenal phase of regular spiking activity. Intestinal segments displayed a prolongation of the quiescent phase and a decrease in the integrated area curve of the phase of irregular spiking activity. Recurrence of the phase of regular spiking activity was unaltered in either segment. These data suggest that the direct effect of PGE2 on gastrointestinal motility in the piglet is a partial inhibition of intestinal contractions.

Influence of substance P on in vitro motility of the oviduct and intestine in the domestic hen

The influence of bovine substance P (SP) on contractility of circular strips from the infundibulum, magnum, isthmus, vagina and utero-vaginal junction (UVJ), as well as of circular and longitudinal strips from the uterus, duodenum and caecum taken from laying hens was studied in vitro. SP was cumulatively added to the incubation media, reaching concentrations from 10−9 to 10−5M for the oviduct strips and from 10−10 to 10−5M for the intestinal strips. Significant tension increases (P<0.05) were observed in tissue strips from the isthmus, uterus and UVJ (from 10−7M on) and from the magnum (10−5M). For the infundibulum and vagina, tension changes in response to SP were not significant. In the intestine SP provoked a significant increase (P<0.05 to P<0.01) in tension in longitudinal (threshold concentration: 10−7M) and circular (10−5M) caecal strips and in longitudinal duodenal strips (10−6M). Tension increases in longitudinal uterine and caecal strips were neither potentiated by the endopeptidase inhibitor, phosphoramidon, nor inhibited by the SP-antagonist, [D-Pro2, D-Phe7, D-Trp9]-SP. It is concluded that the SP-induced tension increases are mainly restricted to the uterus as well as to the rectal caecum and that the neuropeptide may be involved in the complex mechanisms which regulate the contractility of these structures in the domestic hen.

Influence of PGF2α on gastrointestinal activity in the conscious piglet

Abstract In 5 conscious piglets with electrodes implanted on the antrum pylori, duodenum, jejunum and ileum, the effect of intravenous infusion of PGF 2α 1 and 10 μg/kg/min during 2 h, on gastrointestinal electrical activity was studied. The influence of the PG, 10 −8 to 10 −4 M, on longitudinal tissue strips from the same segments was also examined. The in vitro results demonstrate that PGF 2α has only a weak contractile effect on duodenal and jejunal strips. This effect was enhanced in the presence of atropine and indomethacin. In the in vivo part of the study PGF 2α induced an inhibition of antral electrical activity as evidenced by a prolongation of the inhibitory phases and a reduction of the frequency of the fast oscillations. In the small intestine only ileal activity was changed significantly. PGF 2α provoked an increase in the phase II or irregular spiking activity and an increase in the interval of the migrating myoelectrical complexes in this segment.

Influence of indomethacin on endotoxin-induced changes in gastrointestinal myoelectrical activity and some haematological and clinical parameters in the conscious piglet

The effect of indomethacin, administered intravenously at 5 mg/kg, on the changes in gastrointestinal myoelectrical activity, rectal body temperature, clinical appearance and some haematological parameters induced by intravenous bolus injection of endotoxin, at 10 µg/kg, was examined in conscious piglets with electrodes implanted in the antrum pylori, duodenum, jejunum and ileum. Indomethacin inhibited the endotoxin-induced febrile response and the accompanying clinical signs. However, it was without influence on the induced leukopenia and shift to the left. Indomethacin both delayed the onset of and shortened the endotoxin-induced increase in the duration of the antral inhibitory phase and the duodenal phase I activity. It therefore appears that prostanoids are probably not the main factors involved in the endotoxin-induced haematological and gastrointestinal myoelectrical activity changes in the piglet.

Influence of leukotriene D4 on arterial pressure and gastrointestinal electrical activity in the conscious piglet

In 6 conscious weaned piglets with implanted electrodes in the corpus and antrum of the stomach, the duodenum, jejunum, ileum and caecum the influence of intravenous infusion of leukotriene (LT)D4, 0.1 and 1 microgram kgmin for 10 min, on mean arterial pressure and gastrointestinal electrical activity was examined. LTD4 induced a significant increase in arterial pressure. Gastrointestinal electrical activity, however, was little influenced, since only the antrum pylori revealed a transient decrease.

The influence of substance P on oviductal, duodenal and blood pressure in the anaesthetized domestic hen

In 13 anaesthetized hens in the peak phase of their first laying year the influence of intravenously injected substance P (SP), 1–10 μg/animal, on oviductal pressure, duodenal pressure, blood pressure and heart rate has been studied within 5 h of oviposition. The neuropeptide induced a significant pressure increase in the different segments of the oviduct (infundibulum, magnum, isthmus, uterus and vagina) as well as in the duodenum. Blood pressure revealed a distinct biphasic response: a short period of hypotension accompanied by a tachycardia and a more pronounced and sustained hypertension, inducing a subsequent bradycardia. The complexity of the observed effects demonstrates the overall impact of intravenously administered SP on the anaesthetized hen.

Influence of substance P on myoelectrical activity of the infundibulum, uterus and vagina in the conscious domestic hen

Abstract In five conscious hens (±2 kg) in the peak phase of their first laying year, with implanted electrodes in the infundibular, uterine and vaginal wall, the influence of intravenously injected substance P (SP), at a dose rate of 1, 3 and 10 μg/hen, on oviduct and electrical activity and on arterial pressure was studied within 5 h following oviposition. The neuropeptide induced a significant increase in the frequency of bursts of spike potentials in the oviductal segments studied. In the vagina this stimulatory effect was followed by a secondary inhibition. SP provoked a biphasic response in arterial pressure: a short hypotension followed by a long-lasting hypertension.