Inhibitions by 6-hydroxydopamine and neostigmine singly or together of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats.

The effects of chemical sympathectomy induced by 6-hydroxydopamine (6-OHDA) and administration of the acetylcholinesterase inhibitor neostigmine, singly or together, on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and on the tissue catecholamine concentration of the gastric wall and the labeling index of the gastric mucosa, were investigated in inbred Wistar rats. Rats received s.c. injections of neostigmine (0.075 mg/kg), and/or i.p. injections of 6-OHDA (42 mg/kg twice within 24 hr, and then 105 mg/kg every 2 weeks from 1 week later) 25 weeks after oral treatment with MNNG. Prolonged administration of 6-OHDA or neostigmine significantly reduced the incidence of gastric cancers by week 52, and in combination they had a significantly greater inhibitory effect. 6-OHDA and/or neostigmine had no influence on the histology of gastric cancers. Administration of 6-OHDA, but not neostigmine, significantly decreased the norepinephrine concentration in the antral portion of the gastric wall. The labeling index of the antral mucosa was decreased significantly by treatment with 6-OHDA or neostigmine, and decreased even more significantly by 6-OHDA plus neostigmine. Our findings indicate that 6-OHDA and neostigmine have protective effects against gastric carcinogenesis and that in combination their effects are additive. These results imply that the activities of the sympathetic and parasympathetic autonomic systems together influence gastric carcinogenesis.