Conclusions
Our results provide in vivo evidence for agonist-induced D&sub2;R trafficking that is inversely related to CB&sub1;R distribution in postsynaptic neurons of Acb shell and in presynaptic axons in this region and in the CPu.
Methods
To address this question, we examined the electron microscopic immunolabeling of D&sub2; and CB&sub1; receptors in the Acb shell and CPu of male mice at 1 h following a single subcutaneous injection of quinpirole (0.5 mg/kg) or saline, a time point when quinpirole reduced locomotor activity.
Objective
We sought to determine whether quinpirole alters the surface/cytoplasmic partitioning of D&sub2;Rs in striatal neurons in vivo.
Results
Many neuronal profiles throughout the striatum of both treatment groups expressed the D&sub2;R and/or CB&sub1;R. As compared with saline, quinpirole-injected mice showed a significant region-specific decrease in the plasmalemmal and increase in the cytoplasmic density of D&sub2;R-immunogold particles in postsynaptic dendrites without CB&sub1;R-immunolabeling in the Acb shell. However, quinpirole produced a significant increase in the plasmalemmal density of D&sub2;R immunogold in CB&sub1;R negative axons in both the Acb shell and CPu. Conclusions: Our results provide in vivo evidence for agonist-induced D&sub2;R trafficking that is inversely related to CB&sub1;R distribution in postsynaptic neurons of Acb shell and in presynaptic axons in this region and in the CPu.