In this study, 14 adult albino guinea pigs, weighing 300-350 g, were divided into two equal groups. The small intestinal segments (distal ileum)taken from the animals were kept in vitro in the isolated organ bath, and the isotonic contractions of the tissues produced by amitraz and acetylcholine were recorded on a polygraph. For the first group, tissues belonging to the seven animals, the cumulative concentration-response curves of amitraz were obtained and compared by applications at concentrations from 10-8 M to 10-3 M in three different conditions alone,in the presence of verapamil (3x10-5 M)and in Ca++ free solution. For the second group, tissues taken from the other seven animals, the responses to acetylcholine (3x10-3 M)were compared with it given alone (control), in the presence of amitraz at the effective dose for this tissue (10-3 M), verapamil (3x10-5 M)and finally in Ca++ free solution. The cumulative concentration-response curves of amitraz showed that amitraz at a concentration of 10-3 M created a contraction 3- 4-fold that of the others produced by a concentration of 10-8 -10-4 M. It was also observed that Ca++ played a big role in acetylcholine and amitraz-induced contractions while the contraction produced by acetylcoline was not reduced by the effective concentration of amitraz for the tissue.

In this study, 14 adult albino guinea pigs, weighing 300-350 g, were divided into two equal groups. The small intestinal segments (distal ileum)taken from the animals were kept in vitro in the isolated organ bath, and the isotonic contractions of the tissues produced by amitraz and acetylcholine were recorded on a polygraph. For the first group, tissues belonging to the seven animals, the cumulative concentration-response curves of amitraz were obtained and compared by applications at concentrations from 10-8 M to 10-3 M in three different conditions alone,in the presence of verapamil (3x10-5 M)and in Ca++ free solution. For the second group, tissues taken from the other seven animals, the responses to acetylcholine (3x10-3 M)were compared with it given alone (control), in the presence of amitraz at the effective dose for this tissue (10-3 M), verapamil (3x10-5 M)and finally in Ca++ free solution. The cumulative concentration-response curves of amitraz showed that amitraz at a concentration of 10-3 M created a contraction 3- 4-fold that of the others produced by a concentration of 10-8 -10-4 M. It was also observed that Ca++ played a big role in acetylcholine and amitraz-induced contractions while the contraction produced by acetylcoline was not reduced by the effective concentration of amitraz for the tissue.