[Peripheral mechanism of inhibitory effect of centrally administrated histamine on gastric acid secertion].

The present experiment is undertaken to study the peripheral mechanism of the inhibitory effect of intra third ventricular administration of histamine (HA, i.c.v.) on gastric acid secretion. Gastric acid was continuously washed with 37 degrees C saline by means of a perfusion pump in male adrenalectomized SD rats. Drugs were injected intravenously by a syringe pump and their effect on pentagastrin-induced [10 micrograms/(kg.h), i.v.] gastric acid secretion was measured. The results were as follows: (1) The inhibitory effect of HA on gastric acid secretion was abolished by subdiaphragmatic vagotomy. (2) The inhibitory effect of HA on gastric acid secretion could be abolished by pretreatment with atropine [0.05 mg/(kg.100 min), i.v.]. (3) Pretreatment with somatostatin antagonist, cyclo-[7-aminoheptanoyl-Phe-D-Trp-Lys-Thr (Bzl)], [2-4 micrograms/(kg.100 min), i.v.] could also block the inhibitory effect of HA on gastric acid secretion in a dose dependent manner. The above results suggest that the inhibitory effect of centrally administrated HA on gastric acid secretion is mediated by vagi, acetylcholine M receptor and somatostatin.