Aggravating effect of serotonin on gastric ulceration induced by thermocautery under the healing process in mice.

The influence of various ulcerogenic treatments on healing gastric ulcers induced by thermocautery was studied in mice. A low dose of serotonin (5HT) which did not produce ulceration, was found to aggravate gastric ulcers at 15th or 30th day after thermocauterization, but other ulcerogenic treatments including histamine, norepinephrine, vasopressin, acetic acid ingestion and cold-restraint stress did not affect this induced gastric ulcer. Bleeding and ulceration, however, occurred in the gastric glandular portion in addition to thermocauterization ulcer by the treatment of acetic acid ingestion or cold-restraint stress. Histological sections of gastric ulcers (15th and 30th day) 24 hr after 5HT injection, showed severe necrosis of the regenerated mucosal layer. Microvessel structure in the gastric mucosa as revealed by the Indian-ink infusion, showed a local obstruction of blood flow on the edge of ulcers 1 or 3 hr after 5HT injection. Although acetic acid ingestion increased transmucosal fluxes of Na+ and K+, 5HT had no effect on the ion flux in normal mice. Thus the healed ulcer area was resistant to various ulcerogenic stimulants, except for 5HT, and the vasoactive factor of 5HT may be involved in the aggravating process of gastric ulcers induced by thermocautery.