[Acute and latent influenzal infection in mice with altered endogenous serotonin metabolism]

A steady and long-term increase of the endogenous serotonine concentration in the lungs, spleen, and brain achieved by administration of nontoxic doses of indopan, an inhibitor of monoamineoxidase, caused a significant decrease of resistance of animals to influenza virus in acute infection. After natural route of inoculation with 20 LD50 of the allantoic influenza A3/WSN (HON1) virus strain in the animals treated with indopan the area of lung affection with specific influenza pneumonia increased, the virus concentration in the lungs and spleen rose sharply, the titre of IgM antibody in the blood decreased; the animal mortality in this group also increased. The level of serotonin in the blood and organs of latently infected animals became normal 6 weeks after virus inoculation. In some of these animals, however, indopan caused a greater increase of serotonin level in the lungs than in intact mice of the same weight and age. Without changing the amine levels in the spleen and the brain, indopan caused 4-16-fold increase in the titer of specific antihemagglutinins in the blood, mostly of IgM fraction, as compared with the controls. In latent influenza infection the balance of serotonin metabolism in the lungs in unstable.