Some synaptosomal energy-requiring ATPases were evaluated in the cereb
ral cortex from 3- and 24-month-old normoxic rats and rats submitted t
o either mild or severe chronic (4 weeks) intermittent normobaric hypo
xia. Furthermore, 4-week treatment with saline or TRH analogue posatir
eline was performed. The activities of Na+,K+-ATPase, low- and high-af
finity Ca2+-ATPase, Mg2+-ATPase, and Ca2+,Mg2+-ATPase were assayed in
synaptosomes and synaptosomal subfractions, namely synaptosomal plasma
membranes and synaptic vesicles. With the exception of the high-affin
ity Ca2+-ATPase, aging induced a decrease in the ATPase activities fro
m normoxic rats. The adaptation to chronic intermittent mild hypoxia w
as characterized by an increase in the activity of Mg2+-ATPase in 3-mo
nth-old rats, concomitant with a decrease in the activities of: a) Na,K+-ATPase and high-affinity Ca2+-ATPase in both 3- and 24-month-old r
ats, and b) Ca2+,Mg2+-ATPase in 3-month-old ones. The TRH analogue pos
atireline increased the high-affinity Ca2+-ATPase in both 3- and 24-mo
nth-old hypoxic rats, concomitant with an increase in Mg2+-ATPase acti
vity in 24-month-old ones. The adaptation to chronic intermittent seve
re hypoxia was characterized by a decrease in the activities of: a) Na
+,K+-ATPase, Ca2+,Mg2+-ATPase and high-affinity Ca2+-ATPase in both 3-
and 24-month-old rats, and b) low-affinity Ca2+-ATPase only in 24-mon
th-old ones. The effect on Mg2+-ATPase activity was characterized by a
decrease in the enzymatic form located in the synaptic plasma membran
es, concomitant with an increase in the form located in the synaptic v
esicles. In both 3- and 24-month-old hypoxic rats, TRH analogue increa
sed the activity of the Na+,K+-ATPase and the enzymatic form of the Mg
2+-ATPase located in the synaptosomal plasma membranes, concomitant wi
th a decrease in the form of the Mg2+-ATPase located in the synaptic v
esicles.