Bass, Paul

Recordings of pressure and electric potentials from Biebl loops of the duodenum of trained dogs were used to quantitate and to determine relationships among basic electric rhythm (BER), irregular bursts of spike potentials, and motor action of the duodenum. After control periods, morphine was used to stimulate rhythmic motor activity. The omnipresence of a stable, longitudinally propagated BER was demonstrated, each phase of which was detected simultaneously by electrodes arranged radially in the wall of the gut. Spike potentials were recorded whenever contraction of the gut wall was detected. The spikes occurred during a limited segment of the BER. Their number and amplitude were directly related to the strength of the contractions. Under control conditions, duodenal contractions associated with the spike potentials produced type I waves in the pressure record. Neither the spike potentials nor the type I contractions were conducted more than a few centimeters. With morphine only the latter portion of the BER showed minor changes. Incidence of spike potentials and contractions was increased. Occasionally morphine induced motor spasms, accompanied by a prolonged series of spike-like potentials and disruption of the BER.

In preparation for a study of the electric activity in the wall of the gastroduodenal junction in unanesthetized trained dogs, the pyloric portion of the stomach (antrum), the pylorus, and the first portion of the duodenum were exteriorized surgically. When the animals were fully recovered, needle electrodes were inserted into the wall of the bowel for the detection of electric activity. The pylorus was found to act as an "electric insulator" between the stomach and the duodenum. The basic electric rhythm (BER) and the fast or spike activity detected in both the pyloric canal and the duodenal bulb became attenuated in the pylorus and usually disappeared in it. The BER of the antrum had a mean frequency of 4.4 cycle/min and spike potentials sometimes were associated with it. The frequency of the BER in the duodenal bulb was the same as in the duodenum but its voltage was less and its form more irregular. Spike potentials in the bulb occurred during a greater portion of the BER and had a greater tendency to distort the BER than in the more distal duodenum.

The rates of movement of isotopically labeled water, sodium and potassium from the contents of segments of duodenum and ileum into the blood (insorption) and from blood to the contents (exsorption) were determined in dogs. The insorption of labeled water and sodium from the duodenal and ileal segments was exponential in character. Calculation of insorption and exsorption using the exponential rate and the Visscher formulation gave similar values. Anesthesia produced by pentobarbital sodium had no effect on the insorption of water and sodium from the intestinal segments, but it caused a small decrease in exsorption into the duodenum. Acidification of the contents of the intestinal segments decreased insorption of water, sodium and potassium, whereas it increased the exsorption of sodium and potassium without altering that of water. The results indicate that the mucosa of the duodenum fulfills the function of equilibrating its contents by maintaining nearly equal and large movements of water and sodium in both directions, while that of the ileum is fixed to serve absorption (a net gain to the body) of water and sodium.