Journal of Neuroscience, Vol 6, 3218-3228, Copyright © 1986 by Society for Neuroscience
Characterization, distribution, and ontogenesis of adenosine binding sites in cat visual cortex
C Shaw, SE Hall and M Cynader
In vitro autoradiographic techniques were used to characterize binding
sites for 3H-cyclohexyladenosine (CHA) and 3H-5'-N-
ethylcarboxamidoadenosine (NECA) in cat and kitten visual cortex. 3H- CHA
binding sites in adult cat have a Bmax of 1,363 fmol/mg protein and a Kd of
6.8 nM. Displacement experiments indicate that 3H-CHA binds to an adenosine
receptor similar to the A1-adenosine receptor described by other
investigators. 3H-NECA binding sites in adult cat have a Bmax of 518
fmol/mg protein and a Kd of 15.4 nM. Displacement experiments do not allow
us to identify this binding site unambiguously. Bmax values increase during
postnatal development for both binding sites, peaking in adulthood for
3H-CHA and at 30 d for 3H-NECA. Kd values show neither consistent nor
significant differences during postnatal development for either binding
site. 3H-CHA and 3H-NECA binding sites are concentrated in layers 1-3 and
upper layer 5 in the visual cortex of adult cats. These laminar patterns,
however, change during postnatal development, showing the densest binding
in the deep cortical layers (5 and 6) in kittens younger than 30 d of age
and a fairly homogeneous binding in older kittens before achieving the
adult distribution.