Protective effect of antihistamines on cerebral oedema induced by experimental pneumothorax in newborn piglets.

As a consequence of general hypoxaemia evoked experimentally by bilateral pneumothorax, brain oedema of vasogenic type developed in newborn piglets after 4 h survival. Histamine receptor antagonists, mepyramine (H1-receptor blocker), metiamide, cimetidine and ranitidine (H2-receptor antagonists) were administered either intraperitoneally or intrathecally to check to what extent the formation of brain oedema could be reduced. Mepyramine and ranitidine decreased the accumulation of water, sodium and albumin in the parietal cortex. By measuring the concentration of histamine, the presence of a histamine pool was demonstrated in the cerebral microvessels. The results suggest that histamine, if released upon hypoxic injury from the microvascular store, can take an important part in the development of vasogenic brain oedema.