Investigation of usefulness of electroreticulograms obtained from the sheep body surface in estimation of reticulum electrical activity.

The experiments were carried out on 3 sheep with one pair of platinum electrodes chronically implanted in the reticulum wall. The reticulum action potentials were recorded simultaneously from the body surface (using the needle electrodes placed subcutaneously) and from the implanted electrodes using an electroencephalograph Reega XVI Duplex TR. It was found that the two- or three-phase deflections on the electroreticulograms obtained from the body surface were exactly correlated with the series of potential spikes on the records from the implanted electrodes. The number of phases in each deflection was equal to the number of the series of potential spikes during the reticulum excitation. During the reticulum hypotony the decrease in action potentials was observed. That is why we were not able to record the electrical activity from the body surface, while it was still possible to record electroreticulograms from the implanted electrodes.

[Effect of dopamine on cecum motility in sheep]. / Wplyw dopaminy na motoryke jelita slepego u owiec.

The influence of dopamine on the motility of the caecum were studied. The experiments were carried out on 4 sheep with chronic fistulas of the caecum. The contractions of the caecum were recorded by the balloon method. Dopamine infused intravenously at a rate 29-38 micrograms.kg-1.min-1 inhibited the motility of the caecum. Dopamine infused after beta-adrenergic blocker propranolol (0.5-1.0 mg.kg-1) inhibited the movements of the caecum, however administrated after domperidone (0.2-0.4 mg.kg-1) didn't change its movements. It has been concluded that dopamine inhibits the caecum motility in sheep through specific dopaminergic receptors.

[Effect of dopamine on small-intestinal motility in sheep]. / Wplyw dopaminy na motoryke jelita cienkiego u owiec.

The receptors involved in dopamine effect on the motility of the ileum were studied. The experiments were carried out on 3 sheep with chronic fistulas of the ileum and rumen. The contractions of the fistulated parts of the alimentary tract were recorded by the balloon method. Dopamine infused intravenously at a rate 28-38 micrograms.kg-1.min-1 inhibited the motility of the ileum. Domperidone (0.4-0.8 mg.kg-1) did not abolish this inhibiting influence of dopamine. Dopamine infused after propranolol (0.5-0.7 mg.kg-1) inhibited the motility of the ileum, however administrated after phentolamine (0.6-0.8 mg.kg-1) did not change its movements. It has been concluded that dopamine inhibits the ileum motility in sheep through alpha-adrenergic receptors.

The phenomenon of reversal of reticulum action potentials recorded from the body surface of sheep.

The experiments were carried out on sheep with reticulum fistula. The biopotentials and transformed mechanogram of the reticulum were recorded simultaneously on the body surface with an electrocardiograph. Lactic acid solution 1.6 mol/l was administered through the fistula into the reticulum in an amount of 15 mmol/kg of body weight. It was found that administration of this acid caused reversal of the biopotentials of the reticulum. This phenomenon lasted from 10 to several scores of hours and occurred with pH of reticulum contents below the normal range as well as after return of normal pH.

Participation of the beta-adrenergic receptor in the enteroruminal reflex and enteroenteric reflex.

In sheep with chronic fistulae of the small intestine and rumen the participation of the beta-adrenergic receptor was investigated in the enteroruminal reflex and enteroenteric reflex using the method of pharmacological analysis. The movements of the segments of the digestive tract with fistulae were recorded by the balloon method. A solution of hydrochloric acid administered into the ileum caused a reflex stimulation of its motor activity and inhibited the movements of the rumen. Intravenous administration of propranolol before instillation of the acid into the intestine abolished or reduced greatly the reflex inhibition of the movements of the rumen and in the small intestine it enhanced significantly the studied reflex reaction. Thus stimulation of the beta-adrenergic receptor plays an important role in the reflex stimulation of the motor activity of the rumen, and stimulation of the motor activity of the small intestine in the enteroenteric reflex is limited by the effects derived from this receptor.

Analysis of the role of adrenergic receptors in the regulation of small intestine motor activity in sheep.

In sheep with chronic fistulae of the small intestine and rumen the participation of alpha- and beta-adrenergic receptors in the regulation of the motor activity of the small intestine was studied by the method of pharmacological analysis. The movements of the fistulated parts of the alimentary tract were recorded by the balloon method. Slow intravenous infusion of isoprenaline inhibited the contractions of the small intestine. This inhibitory effect of isoprenaline was abolished by propranolol. Intravenous phenylephrine inhibited the motor activity of this intestinal part as well. The effect of phenylephrine was abolished by pretreatment with dihydroergotamine. In the small intestine of sheep stimulation of the alpha and beta adrenergic receptors decrease the motor activity of intestine.

Participation of the adrenergic receptors in the regulation of large bowel motor activity in sheep.

In sheep with long-standing fistulae of the caecum, proximal loop of the colon and rumen the motor activity of these parts of the intestine was studied using the balloon method. Slow isoprenaline infusion caused first inhibition of caecal contractions, followed by gradually decreasing intensity of contractions of the colon and rumen. This inhibitory effect of isoprenaline was eliminated by propranolol. Intravenous infusion of phenylephrine failed to inhibit the colonic motor activity. A small dose of atropine, similarly as isoprenaline, caused an irregular inhibition of the contractions of the caecum, colon and rumen. In sheep, in contrast to other animal species, the effects inhibiting large intestine motility are mediated only by the beta-adrenergic receptors. The inhibitory effect of the beta-adrenergic receptors was strongest in the caecum.

Regulation of motor activity of omasum after blockade of vagus nerves.

In 3 sheep with subcutaneously exposed vagus nerves and with chronic large fistula of the rumen pharmacological analysis of the motor activity of omasum was carried out after blockade of vagus nerves. The contractions of omasal canal, reticulum and rumen were recorded by the baloon method. After blockade of the vagus nerves with anesthetics the proper pharmacological agents were administered in intravenous injections. In the light of the obtained results it was found that contractions of the omsal canal, persisting after vagal blockade, are independent of the influence of the autonomic system and they are probably due to myogenic automatism. It has been also demonstrated that both alpha and beta adrenergic receptors participate in regulation of the tonous of omasum musclular layers.