Relationship between the spike activities of the small and large intestines.

Experiments were performed using chronically implanted electrodes on the dog smooth muscle wall of the stomach and of the small and large intestines. Electrical activity of the muscle wall was recorded before and after feeding. When reaching the terminal ileum the active part of the migrating myoelectrical complex (MMC) continuously induced bursts of spike potentials superimposed on the slow waves. This electrical activity spread to the ascending colon. We also showed the existence of a spike activity on the terminal ileum independent of the MMC (appearing during the phase 1) and propagating to the colon. A relationship between the spike activities of the small and large intestines was also present after feeding. Beside the well-known gastro-colic reflex, we observed an increase in the spike activity of the terminal ileum and ascending colon between the 4th-5th hours after feeding. This probably corresponds to the arrival of the first portions of contents, evacuated from the arrival of the first portions of contents, evacuated from the stomach, and of the last portions of small intestinal contents. In conclusion, there is a relationship between the spike activities of the small and large intestines in starving animals and after feeding, and the terminal ileum plays a substantial role in this relationship.

The role of the pelvic nerves in the realization of the reservoir function of the colon.

In situ experiments were made on a group of dogs and in vivo experiments on another group of dogs with implanted electrodes for recording the electrical activity of the colonic muscle wall. A bipolar platinum electrode implanted in the pelvic nerve entering into the distal area of descending colon was used for electrical stimulation of the nerve (1 ms impulse duration, frequency of 2, 8, 10 and 15 Hz and amplitude of 10, 15 or 20 V). Electrical stimulation of the pelvic nerve with a frequency of 2 Hz resulted in inhibition of the spike activity. However, groups of spike potential burst in the distal part of the descending colon in response to electrical stimulation with frequencies of 8, 10 or 15 Hz. Repeated stimulation caused spreading of the spike activity of the descending colon in oral direction until the transverse colon. These antiperistaltic waves probably prevented the propulsion of the content of the descending colon. Thus, in addition to the inhibitory effect exercised by the sympathetic and noncholinergic nonadrenergic inhibitory part of the intrinsic nervous system, the reservoir function of the colon is influenced by these orally spreading waves of spike activity (antiperistaltic waves), which are caused by impulses along the pelvic nerves.

On the mechanism of the smooth-muscle action of rosanol.

In vivo and in vitro experiments were performed to clarify some aspects of the mechanism of the smooth-muscle action of rosanol prepared from rose oil. On dogs (in vivo) and on isolated segments from guinea-pig ileum (in vitro) rosanol at high doses exerted a slight inhibitory effect on the activated gastrointestinal motility. The cholinolytic rosanol action proved in in vitro experiments, was found to play an essential role in the mechanism of its gastrointestinal motility-inhibiting effect. The present studies showed a pronounced antagonistic effect of rosanol on the KCl-increased Ca2+ level in rabbit aorta. It might be suggested that this effect of rosanol is also involved in the inhibitory action of rosanol on the activated gastrointestinal motility.

Development of innervation in cat gastrointestinal sphincters during the postnatal period. (Functional studies).

The development of function in the intramural nerves was investigated by evaluating the mechanical responses of the smooth muscle of cat gastrointestinal sphincters to transmural electrical stimulation (2-20 Hz, 0.5 msec, supramaximal intensity for 20 sec) between 1 and 60 days postnatal. The intramural nervous system of the gastrointestinal sphincters was found to develop functionally in a cranio-caudal sequence. The cholinergic innervation in the lower esophageal sphincter (LES) was well developed in the first postnatal days. The development of the non-cholinergic, non-adrenergic innervation, however, proceeded further. An age-determined increase in the amplitude of the adrenoblocker-resistant primary relaxation of LES evoked by switching on the electrical stimulation, was established. The cholinergic innervation in the pyloric sphincter (PS) and ileocecal sphincter (ICS) was developed in the first postnatal days. The non-cholinergic, non-adrenergic innervation appeared in PS between 10- and 15-days postnatal and in ICS between 15- and 60-days postnatal. Noradrenaline (1 mumol) elicited responses typical of adult cats as early as the first postnatal days: contraction in LES and relaxation in PS. In ICS it did not evoke the typical response, contraction, until 15 days after birth.

Analysis of the innervation of the gastroduodenal region.

Under isometric conditions simultaneous recordings are made of the contractile activity of smooth-muscle strips isolated along the circular axis from the pyloric sphincter (PS) and at 1 cm proximally an distally from it -- from the antrum (A) and duodenum (D). The effect of transmural electrical stimulation is studied after the method of Burn and Rand (1960) (duration of the impulses 0.5 ms, frequency from 2 to 20 Hz and supramaximal current values for 20 s). The responses of the smooth-muscle strips isolated from A and D to transmural electrical stimulation are similar. Switching on of the stimulation causes contraction (on-response) throughout the entire stimulation period, while its switching off leads to additional last contraction (off-response). A dependence is observed between the amplitudes of the on- and off-responses and the frequency of the impulses, the maximum being reached in the high-frequency range (16-20 Hz). After Atropinum sulfuricum (5 x 10(-6)M) the on-response is considerably reached, no off-response being observed. In PS triggering of the stimulation results in inhibition of the phasic activity, accompanied by marked relaxation (on-response). The amplitude and the duration of the relaxation depend on the frequency of the impulses applied, the amplitude being maximal at 4-6 Hz, while its duration reaches the maximum between 16 and 18 Hz. Atropinum sulfuricum (5 x 10(-6)M) does not change essentially the amplitude of the relaxation. After Atropinum sulfuricum, Phentolamine and Propranolol (10(-5)M) the amplitude of the relaxation increases significantly in the low-frequency region (4-8 Hz), while its duration decreases considerably.

Specific features in the electrical and contractile activities of the gastro-intestinal sphincters.

Muscle strips (2/20 mm) are isolated from cat gastro-intestinal sphincters (GIS): lower esophageal sphincter (LES), pyloric sphincter (PS), ileo-caecal sphincter (ICS) and from the fundus. The activity of the four fibres is recorded simultaneously under isometric conditions in a bath. In another series of experiments the electrical and contractile activity of GIS was traced by the sucrose gap method. LES manifests only tonic changes which are associated only with changes in the membrane potential (MP); PS - rhythmic spike-dependent phasic contractions, ICS - in one part of the preparations both tonic and phasic contractions. The tonic changes in LES and ICS are sensitive both to nitroprusside-Na (10-6M) and to Verapamil (10-6 to 5X10-6 M). GIS sensitivity to external Ca2+ is different: maximum contractions in LES and ICS occur at Ca=2.5 mM, in PS at Ca=1.5mM. Ba2+ and Sr2+ (at CA=0) increase the sensitivity of LES and ICS to polarizing currents. After several stimulations there appear spontaneous spike-dependent phasic contractions in LES. TEA (5 mM) induces spike-dependent phasic contractions in LES and ICS. In PS the stimulating effect of TEA is manifested at very low concentrations (0.05-0.4 mM), while higher concentrations inhibit the electrical and contractile activity.