[The influence of aging on cerebral energy metabolism following post-hypoglycemic recovery in the rat. Pharmacologic application].

Abstract

Influence of aging on cerebral energetic metabolism was evaluated during and after severe hypoglycemia in rats respectively 20 (adults), 60 (matures) or 100 (senescents) week-old. Cerebral content of carbohydrates, amino-acids, ammonia, ATP, ADP, AMP, creatine phosphate and creatine was analysed after 20 min insulin induced hypoglycemia and after 20 min hypoglycemic recovery induced by glucose infusion. In the rats of different ages tested, effect of raubasine (0.85 mg X kg-1 i.p. and i.v.), almitrine (2.68 mg X kg-1 i.p. and i.v.) and association almitrine plus raubasine (at the same doses) on post-hypoglycemic recovery was tested. Aging does not affect the cerebral metabolic disorders occurring in severe hypoglycemia, but rather the metabolic changes during the post-hypoglycemic restitution. In fact there is lower restitution of the concentrations of cerebral cortical metabolites in older rats: the concentrations of many amino-acids and adenylate nucleotides remains largely abnormal. Compared with saline treated post-hypoglycemic rats, raubasine decreases by 15 to 20% cerebral glucose and pyruvate contents in "adults" and "matures" rats and by 10 to 15% glutamate content in rat of different ages tested. Almitrine decreases by 20% cerebral glucose concentration in "matures" and "senescent" rats. In this latter group, almitrine decreases lactate and ammonium contents and increases by 23% glutamine level. In rats of all ages that were submitted to 20 min insulin induced hypoglycemia followed by 20 min glucose induced post-hypoglycemic recovery, the association almitrine plus raubasine decreases by 20 to 30% cerebral glucose, pyruvate and lactate contents and decreases by 15% glutamate. In older brains the association almitrine plus raubasine decreases by 50% cerebral content in ammonium and concomitantly induces an equivalent increase in glutamine content. The effect of the combination almitrine plus raubasine is characterized by an increase in rate of metabolic recovery process in all ages tested.