We used complexes between a fourth generation polyamidoamine (PAMAM) dendrimer and one of two heterocyclic compounds — 1-(6-hydroxyhexyl)-3-(5-phenyl-isoxazole-3-yl)-urea or 5-phenyl-isoxazole-3-carboxylic acid — to reduce oxygen consumption in transverse slices of the hippocampus taken from 4-week old male rats. In vitro electrophysiological experiments revealed that the inhibitory effect of the hypoxic state on the evoked responses was enhanced in the presence of the complexes. The data were analyzed in terms of the potential antitumor effects of these complexes.