CORRELATION OF VISCERAL AND SOMATIC ACTIVITY FOLLOWING ADMINISTRATION OF HYPNOTICS (A) BARBITAL COMPOUNDS, AND (B) TRIBROMETHANOL (AVERTIN-CRYSTALS AND FLUID)

¹ From the Departments of Physiology and Pharmacology of the School of Medicine, Western Reserve University, Cleveland, Ohio

The effect of a range of doses of pentobarbital, amytal and barbital (intravenously administered) on tone and motility of the stomach, ileum and colon has been studied by the balloon method in trained, unanesthetized dogs. The action of barbital has been checked by direct observations using the paraffin bath method. The visceral response has been correlated with the hypnotic action of these compounds.

Motor activity of the gut was depressed in a qualitatively similar manner by each of the barbitals but maximal depression frequently developed most rapidly in the colon and latest in the stomach; complete recovery usually occurred early in the ileum and late in the stomach. With doses of the barbiturates producing equal degrees of hypnosis, gastro-intestinal depression was longest with barbital (1), intermediate with amytal (0.6) and shortest with pentobarbital (0.3).

Expressing the ratio between duration of hypnosis (taken as 1) and persistence of gastro-intestinal depression, pentobarbital, small and medium dosages, is 0.25 to 0.33 and completely anesthetic doses 0.25 to 0.5; amytal, small doses 1 or occasionally more, medium doses 0.5 to 1, maximal doses 0.25 to 1; anesthetic doses of barbital 0.08.

Excitation from barbital and pentobarbital was more frequent after small than with moderate dosages but the maximal dose of amytal produced marked restlessness. The frequency with which excitement or restlessness was observed was in the order amytal > barbital > pentobarbital.

The influence of avertin (crystals and fluid) administered rectally, on gastric, ileal and colonic motor activity of trained, unanesthetized dogs also was studied by the balloon method.

Dosages of avertin having a slight hypnotic action markedly depressed the gastro-intestinal tract (order of depression, stomach > ileum > colon), but the visceral effects persisted only 0.6 to 0.8 times as long as the period of hypnosis.

The somatic depression produced by avertin fluid exceeded that from avertin crystals, in that the maximal effects of the fluid developed somewhat earlier were of greater degree and persisted 1.5 to 2.0 times as long as with the crystals. This indicated that the rate of absorption of an aqueous solution of avertin fluid from the dog's colon equaled or exceeded that of a similar solution of the crystals. The amylene hydrate contained in the fluid may have produced a moderate irritation of the colon.