ADAPTATION CAPACITY OF BIOGENIC-AMINES TURNOVER TO HYPOXIA IN DIFFERENT BRAIN-AREAS OF OLD RATS

Catecholamines and indoleamines serve in the CNS as neurotransmitters in a great number of functional pathways. In order to contribute findings which might help to understand differences in functioning and behavioral performances with aging, the concentrations of dopa, dopamine, noradrenaline, 5-hydroxytryptophane (5-HTP), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) in four brain regions (hypothalamus, c. striatum, hippocampus, cortex) of young and old rats were determined 30 min after i.p. injection of NSD1015 (3-hydroxybenzylhydrazine hydrochloride). The influence of 12 h hypoxia of 10 and 8% O2 as well as 36 h hypoxia of 10% was investigated. Accumulation of dopa and 5-HTP under normoxic conditions is reduced in old rats compared to young rats; the concentration of dopamine, noradrenaline and 5-HT is not significantly different between the age groups. After 12 h of 10% O2 in young rats a drop of dopa accumulation occurs, only at 8% O2 in both groups can a significant reduction be observed; dopamine and noradrenaline do not show a uniform tendency. Under the same conditions 5-HTP accumulation is reduced in both groups, 5-HT and 5-HIAA decrease at 10% O2 but are in the range of controls at 8% O2. After 36 h 10% O2 hypoxia dopa accumulation in young rats returns to normal whereas in the striatum of old rats the decrease continues, but in the hypothalamus an increase above normal occurs. Dopamine and noradrenaline return to normal. Besides, in the hypothalamus of young rats 5-HTP accumulation is compensated. 5-HT and 5-HIAA rise even above control values. © 1990.