L-glutamate reduces the affinity of [ 3H]N-propylnorapomorphine binding sites in striatal membranes

Abstract

l-Glutamate but not methyl-D-aspartate (NMDA) or quisqualate (Quis) (10 −6 M) in vitro with or without preincubation increased significantly the K D value of the [ 3H]N-propylnorapomorphine ([ 3H]NPA) binding sites by 21 and 36% respectively in striatal membranes of rat without influencing the striatal [ 3H]spiperone binding sites. The number of striatal [ 3H]NPA binding sites was not changed by l-glutamate (10 −6 and 10 −5 M) in vitro. There may thus exist interactions between striatal glutamate receptors — not related to excitatory amino-acid receptors of the NMDA or the QUIS type - and high affinity striatal DA receptors.