[Activity of several the mediator systems of the brain during hyperbaric oxygenation]

Dynamics of noradrenalin, adrenalin, dipeptide homocarnosine, GABA, hystidine, MAO activity (with noradrenalin as substrate), and homocarnosincarnosinsynthetase in the rat brain under hyperbaroxygenation, was studied. Exposure of the rats to 4 atm of oxygen for 1 hr leads to the 70--80% decrease of noradrenalin content in all brain areas. Adrenalin level does not change. MAO activity increases in hypothalamus remaining at the control level in cortex, decreases significantly in medulla oblongata, and complete inhibition of the enzyme activity occurs in the midbrain. The hyperbaric conditions cause no considerable changes in homocarnosine, GABA, and hystidine levels in all the areas under study. A profound decrease of homocarnosine content and inhibition of homocarnosine--carnosinesynthetase follows the convulsive phase of oxygen intoxication especially in the midbrain (69.9% and 50.3%, resp.).