1. Oral administration of [14C]histamine induced the presence of small amounts of [14C]histamine in stomach and ileal tissues of control guinea-pigs. In contrast, much larger amounts were found after 8 h infusion. 2. Similar amounts of [14C]histamine were found in the tissues when [14C]histamine was given by intravenous infusion from 24-30 h after chlorpromazine injection.
1. Acid secretion for each dog has reached a near maximum (100%) at the 6th samples, 90 min after the intravenous infusion of histamine (10 mu ghr-1, or approximately equal to 0.3 mghr-1). 2. 0.5 mgkg-1 Cimetidine had produced a mean inhibition of 47% on the stomach. 3. 0.1 mgkg-1 Ranitidine (D 14,951) could only inhibit a maximum of 28%, and the secretion had return to normal in just 30 min. 4. 0.025 mgkg-1 Tiotidine (D 15,104) had inhibited 53% acid secretion within 15 min of exposure. Recovery was quite similar to that of Cimetidine, at 150 min. 5. At a dosage one fifth of Cimetidine (0.1 mgkg-1) D 15,144 had depressed 35% of acid secretion at the first 15 min. The inhibition is gradually increased to about 43% (at 30 min), and was maintained for the next 105 min.
1. 30 mg kg-1 chlorpromazine (CPZ) depleted more than half of the tissue histamine from lungs, stomach, ileum and skin of the normal guinea-pigs. However, the drug increased the tissue histamine content in scorbutic animals. 2. In contrast, reserpine depleted histamine from the four tested tissues in both normal and scorbutic animals, except those in the lungs of the control animals. 3. Ascorbic acid only depleted histamine from the stomach and ileum. 4. A 24 hr period was the time limit for CPZ to deplete the histamine in all the four tested tissues. 5. Histamine partially or completely recovered in the tissues after the next 24 hr.
1. In vitro studies of non-specific histidine decarboxylase activity was low or absent in control guinea-pigs and unchanged 9 or 27 hr after chlorpromazine (CPZ) injection intraperitoneally. 2. However, specific histidine decarboxylase activity was found in the control tissues and was increased 9 hr but not 27 hr after CPZ injection.