RESPONSES OF INTESTINAL SMOOTH MUSCLE OF THE DOG TO BENZEDRINE SULPHATE (PHENYL-1, AMINO-2 PROPANE SULPHATE)

¹ From the Department of Pharmacology, School of Medicine, American University of Beirut, Beirut, Lebanon

1 (a) In forty-six experiments on isolated segments of the small intestine and colon from ten dogs (three to twelve weeks old), employing the technique of Trendelenburg or Magnus, the usual response to benzedrine sulphate in doses of from 0.3 to 150 gamma per cubic centimeter of bath fluid was a generalized relaxation (decrease of "tone") and a decrease in the amplitude of the pendular and peristaltic movements (see fig. 1 A, B, and C).

(b) The isolated segments from the colon were much more sensitive to benzedrine than were those from the small intestine. The minimal effective dose for the former was 0.3 gamma, for the latter, 1.5 gamma. The general nature of the response was similar in the two cases.

2 (a) In sixty experiments (balloon technique) on five unanesthetized dogs with Thiry-Vella fistulae of the ileum, benzedrine sulphate in doses of 0.25 to 5 mgm. per kilogram usually caused a generalized relaxation (decrease of "tone") (see fig. 2). One animal of the series gave no response even with doses of 5 mgm. per kilogram.

(b) Three dogs with fistulae of the colon were studied. In twenty experiments without anesthesia, benzedrine in doses of 0.1 to 2 mgm. per kilogram consistently caused marked inhibition of spontaneous movements (see fig. 3).

3. The variations in the response of the gastrointestinal tract to benzedrine sulphate are discussed and it is concluded from the present experiments that the colon is the most sensitive portion of the intestine to benzedrine and consistently shows a definite inhibition of spontaneous movements.