Journal of Neuroscience, Vol 6, 2941-2949, Copyright © 1986 by Society for Neuroscience
3H-3-N-methylspiperone labels D2 dopamine receptors in basal ganglia and S2 serotonin receptors in cerebral cortex
RA Lyon, M Titeler, JJ Frost, PJ Whitehouse, DF Wong, HN Wagner Jr, RF Dannals, JM Links and MJ Kuhar
Detailed studies of the properties of 3H-3-N-methylspiperone (NMSP) binding
in rat and human brain homogenates were performed at 37 degrees C. In
homogenates of rat striatum and frontal cortex and human caudate and
frontal cortex tissues, the specific binding was found to be saturable. Rat
caudate contained 33.2 pmol/gm wet-weight tissue and displayed an
equilibrium dissociation constant (Kd) of 8.7 X 10(-11) M; rat frontal
cortex contained 18.5 pmol/gm wet-weight tissue and displayed a Kd of 1.5 X
10(-10) M. Human caudate contained 8.96 pmol/gm wet-weight tissue and
displayed a Kd of 1.1 X 10(-10) M; human frontal cortex possessed 9.8
pmol/gm wet-weight tissue and a Kd of 4.4 X 10(- 10) M. Kinetic studies
revealed a very rapid rate of association in all the tissues studied. The
rate of dissociation was relatively slow in all 4 tissue preparations; the
dissociation rate was somewhat slower in rat striatum and human caudate
relative to rat and human frontal cortex. This was consistent with the
somewhat higher affinity, relative to frontal cortex, displayed by 3H-NMSP
in rat striatal and human caudate tissue. The pharmacological properties of
the specific binding in rat striatal and human caudate tissues were very
similar and indicated the presence of brain D2 dopamine receptors. In rat
and human frontal cortex tissue homogenates, the pharmacological
characteristics of the specific binding indicated the presence of 5-HT2
receptors.