Project 8G: Role of D2L and D2S in Mediating Methamphetamine-Induced Behavior

Kim A. Neve, Ph.D., Principal Investigator

The overall objective of this research program is to characterize the mechanisms by which dopamine receptors transduce the dopamine signal into intracellular and behavioral responses. The specific aims of this proposal focus on testing the hypothesis that the long form of the D2 receptor, D2L, mediates postsynaptic effects of dopamine and abused drugs such as methamphetamine that elevate extracellular dopamine. A secondary aim is to test the hypothesis that binding of the receptor-interacting protein arrestin to D2L mediates methamphetamine-stimulated locomotor activity.

1) The first specific aim is to assess the hypothesis that D2L is the postsynaptic D2 receptor in the mouse neostriatum.Methamphetamine-stimulated locomotor activity in D2 receptor null-mutant (D2-KO) mice will be compared to wild type mice to confirm a deficit in this behavior in D2-KO mice. We will use herpes simplex virus- (HSV-) mediated expression of D2L or D2S in the neostriatum of to restore the expression of either D2L or D2S in neostriatal cells, which are postsynaptic to dopamine-containing nerve terminals, prior to measuring methamphetamine- or quinpirole-induced locomotor activity and D2 regulation of the phosphorylation of DARPP-32.

We predict that drug-stimulated locomotor activity will be reduced in D2-KO mice compared to wildtype littermates, and that expression of D2L, but not D2S or β-galactosidase, will partially restore responsiveness to methamphetamine and quinpirole.

2) The second specific aim will test the hypothesis that binding of arrestin to D2L contributes to methamphetamine-induced locomotor activity. We will express either D2L or an arrestin-insensitive mutant of D2L, D2-A4, in the neostriatum of D2-KO mice. Methamphetamine-induced locomotor activity will be measured in D2-KO mice treated with HSV-D2L or HSV-D2-A4.

We predict that methamphetamine-induced locomotor activity will be reduced in D2-KO mice compared to wild type littermates, and that expression of D2L, but not D2-A4, will partially restore methamphetamine-induced locomotor activity.