The influence of one hyperbaric oxygen-induced seizure on brain eicosanoid content

The levels of prostaglandin F1 (6-keto-PGF1 alpha), thromboxane B2 (11-dehydro-TxB2), and peptidoleukotriene C4 (LTC4) were measured (acetylcholinesterase immunoassay) in the frontal cortex (FC) and the striatum (SA) of the rat brain to study the possible role of eicosanoids in seizures induced by hyperbaric oxygen (HBO). The rats were exposed to (1) hyperbaric oxygen (HBO, 6 ATA O2) up to the first seizure (2) compressed air (6 ATA air, i.e., approximately equal to 1.25 ATA O2) or (3) atmospheric pressure (1 ATA air, i.e., 0.21 ATA O2); there was no seizure in groups 2 and 3. Transition from 6 ATA to atmospheric pressure was obtained in 15 min; the rats were then decapitated and their heads frozen in liquid nitrogen before extraction and analysis of prostanoids. Whatever the conditions, cortical levels of 6-keto-PGF1 alpha and 11-dehydro-Tx B2 are higher than striatal levels; considering the same area, 11-dehydro-Tx B2 and LTC4 concentrations were not significantly different whatever the condition, but there is a trend for lower 6-keto-PGF1 alpha levels in FC after HBO seizure. Biochemical mechanisms are discussed. Eicosanoids do not seem to play a major role in HBO seizures, although some modifications of their metabolism may take place.