Ra. Cunha et al., MODIFICATION OF A(1) AND A(2A) ADENOSINE RECEPTOR-BINDING IN AGED STRIATUM, HIPPOCAMPUS AND CORTEX OF THE RAT, NeuroReport, 6(11), 1995, pp. 1583-1588
AGE-related changes of A(1) and A(2a) adenosine receptor binding chara
cteristics were investigated in three regions of the rat brain using t
he A(1) selective antagonist [H-3]DPCPX, and the A(2a) selective agoni
st [H-3]CGS 21680. The density of A(1) binding sites in aged rats (24
months) was decreased by 33% in the hippocampus and by 60% in the cort
ex and was unchanged in the striatum when compared with young adult ra
ts (6 weeks), with no change in K-D. There were also age-related chang
es in the density of A(2a) binding sites: in the cortex, there was a 9
4% increase in the number of [H-3]CGS 21680 binding sites in aged rats
compared with young rats, and a similar tendency was observed in the
hippocampus (32% increase in A(2a) binding sites in aged rats), with n
o change in K-D; in the striatum there was a tendency for a decrease (
22%) in the number of [H-3]CGS 21680 binding sites in aged rats, and a
decrease in K-D. These results suggest that there are age-related cha
nges in the balance between inhibitory A(1)- and excitatory A(2a)-aden
osine receptor-mediated actions, which vary in different brain areas:
in the cortex and hippocampus, the balance might be shifted towards ad
enosine-mediated excitatory actions, since there is an increase in the
number of A(2a) receptors and a decrease in the number of A(1) recept
ors upon ageing. In contrast, in the striatum, the A(1)/A(2a) ratio mi
ght be only slightly affected upon ageing.