VALPROIC ACID AND BICUCULLINE AFFECT TREFORMATION OF GLYCEROLIPID IN RAT BRAIN

To ascertain the effects of bicuculline and of sodium valproate on the incorporation of glycerol into rat brain lipid, rats were divided into 5 groups: (a) controls; (b) treated with sodium valproate (400 mg/kg body wt); (c) treated with bicuculline (12.5 umol/kg body wt); (d) treated with sodium valproate as in (b) + bicuculline as in (c); and (e) treated with bicuculline (25 umol/jkg body wt). Only rats of group (e) had seizures, which lasted until the end of the experiment. Each animal received 20 uCi of [2-3H]glycerol by intraventricular route and was sacrificed 12 min afterwards. Hippocampi and cerebella were taken and lipid extracted and separated by chromatography. The type of treatment infiuenced very much the fate of injected, labeled glycerol. Indeed, total recovered radioactivity increased following either convulsions or the administration of valproate, whereas both treatments decreased the amount of radioactivity incorporated into lipid. These effects were more evident in cerebella than in hippocampi. The distribution of radioactivity among lipid classes (diglyceride, triglyceride and total phospholipid) was also affected by seizures, which decreased the labeling ratio phospholipid/neutral lipid. The distribution of radioactivity among phospholipid classes was infiuenced by bicuculline (both at convulsant . and non-convulsant doses) and these effects were sometimes antagonized by valproate. We conclude that some effects ofbicuculline are exerted through the systemic modifications due to seizures and that other effects are probably connected to neuronal hyperfiring. The data reported in this paper are consistent with both mechanisms of action proposed for valproate, i.e. increased membrane permeability and modifications of GABAergic systems.