Autoradiographic visualization of A1 adenosine receptors in rat brain
with 3H8-cyclopentyl-1,3-dipropylxanthine
J Neurochem, 54 (4):
1344-53 (April 1990)Weber, R G Jones, C R Lohse, M J Palacios, J M Research Support,
Non-U.S. Gov't United states Journal of neurochemistry J Neurochem.
1990 Apr;54(4):1344-53..Abstract
A1 adenosine receptors were labeled in rat brain sections with the
antagonist 3H8-cyclopentyl-1,3-dipropylxanthine (3HDPCPX) and
visualized at the light microscopic level using autoradiography.
The specific binding of 3HDPCPX to the sections showed the pharmacological
characteristics of A1 adenosine receptors and was accompanied by
very low levels of nonspecific binding. Whereas GTP had no significant
effect on 3HDPCPX binding to rat brain membranes, the addition
of 100 microM GTP increased the apparent affinity of 3HDPCPX to
tissue sections fivefold (from 1.83 to 0.35 nM), enhancing it to
the affinity measured in membranes. However, GTP altered neither
the binding capacity nor the distribution of binding sites in tissue
sections. It is suggested that a competitive antagonism with endogenous
adenosine explains the lower affinity of 3HDPCPX in the absence
of GTP. The autoradiographic pattern of 3HDPCPX binding was characteristic
for A1 adenosine receptors. Distinct labeling of the different layers
of the cerebellar cortex was shown by photomicrographs generated
with the coverslip technique. In addition, several fiber tracts were
found to be labeled. The high selectivity for A1 adenosine receptors
and low nonspecific binding of 3HDPCPX, the ability to produce
high-resolution autoradiograms, together with the fact that the effects
of endogenous adenosine can be eliminated by the addition of GTP
make 3HDPCPX a very useful tool in the autoradiographic study of
A1 adenosine receptors.