Decrease in tumour growth by injections of histamine or serotonin in fibrosarcoma-bearing mice: Influence of H1 and H2 histamine receptors

C3H and C57 BL/6 mice carrying methylcholanthrene-induced fibrosarcomas were injected i.p. daily with histamine, metiamide (anti-histamine type-2 receptor), histamine + metiamide, mepyramine (anti-histamine type-1 receptor), serotonin and methysergide (anti-serotonin). Inhibition of tumour growth and lengthened survival were observed with histamine and histamine + metiamide. The best results (both on tumour growth and survival) were obtained with serotonin. Survival was increased by metiamide and decreased by mepyramine and methysergide. In histamine-treated and in serotonin-treated mice, histological studies of the tumours showed large and numerous foci of haemorrhagic necrosis. Stimulation of histamine type-1 or serotonin receptors and inhibition of histamine type-2 receptors play a beneficial role in the host's defence against tumours.