Mechanisms Underlying Methamphetamine-Induced Dopamine Transporter Complex Formation

Abstract

Repeated, high-dose methamphetamine (METH) administrations cause persistent dopaminergic deficits in rodents, nonhuman primates, and humans. In rats, this treatment also causes the formation of high-molecular mass (greater than approximately 120 kDa) dopamine transporter (DAT)-associated complexes, the loss of DAT monomer immunoreactivity, and a decrease in DAT function, as assessed in striatal synaptosomes prepared 24 h after METH treatment. The present study extends these findings by demonstrating the regional selectivity of DAT complex formation and monomer loss because these changes in DAT immunoreactivity were not observed in the nucleus accumbens. Furthermore, DAT complex formation was not a consequence limited to METH treatment because it was also caused by intrastriatal administration of 6-hydroxydopamine. Pretreatment with the D2 receptor antagonist, eticlopride [S-(Ϫ)-3-chloro-5-ethyl-N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-hydroxy-2-methoxybenzamide hydrochloride], but not the D1 receptor antagonist, SCH23390 [R(ϩ)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride], attenuated METH-induced DAT complex formation. Eticlopride pretreatment also attenuated METH-induced DAT monomer loss and decreases in DAT function; however, the attenuation was much less pronounced than the effect on DAT complex formation. Finally, results also revealed a negative correlation between METH-induced DAT complex formation and DAT activity. Taken together, these data further elucidate the underlying mechanisms and the functional consequences of repeated administrations of METH on the DAT protein. Furthermore, these data suggest a multifaceted role for D2 receptors in mediating METH-induced alterations of the DAT and its function.Repeated, high-dose methamphetamine (METH) administrations cause persistent striatal dopaminergic deficits (for review, see Gibb et al., 1994;Brown and Yamamoto, 2003). Although mechanisms contributing to this phenomenon remain to be elucidated fully, dopamine (DA) (Wagner et al., 1983;, the DA transporter (DAT) Fumagalli et al., 1998), hyperthermia (Bowyer et al., 1992), glutamate (Sonsalla et al., 1989;Mark et al., 2004), microglial activation (LaVoie et al., 2004;Thomas et al., 2004), and reactive species (Giovanni et al., 1995;Yamamoto and Zhu, 1998;Gluck et al., 2001;Imam et al., 2001) are among the contributing factors. Repeated, highdose METH injections also rapidly (within 1 h after the final METH administration) decrease plasmalemmal DA uptake, as assessed in striatal synaptosomes prepared from treated rats. As with METH-induced striatal dopaminergic deficits, DA, reactive species, and hyperthermia contribute to this rapid decrease in DAT function (for review, see Fleckenstein et al., 2000). In addition to effects described above, repeated, high-dose METH administrations also cause the formation of high molecular mass (greater than approximately 120 kDa) DATassociated complexes, as assessed 24 h after treatment. This phenomenon is attenuated by either ...

Methamphetamine-Induced Dopamine Transporter Complex Formation and Dopaminergic Deficits: The Role of D2 Receptor Activation

“…In particular, both the METH-induced increase in DAT complex formation and decrease in DAT activity observed after 24 h (Hadlock et al, 2009) and 72 h (Fig. 4) are attenuated by D2 antagonist pretreatment.…”

“…As demonstrated for METH-induced DAT complex formation (Hadlock et al, 2009), pretreatment with the D2 receptor antagonist eticlopride (Fig. 3A), but not the D1 receptor antagonist SCH23390 (Fig.…”

“…Samples were then transferred to a polyvinylidene difluoride hybridization transfer membrane (PerkinElmer Life and Analytical Sciences, Waltham, MA). Western blot analysis was performed as described previously (Hadlock et al, 2009). Overall DAT complex immunoreactivity was defined as immunoreactivity more than ϳ120 kDa and determined for data presented in Fig.…”

“…However, the relationship among these factors has not been elucidated fully. In addition, an association between METH-induced DAT complex formation and persistent dopaminergic deficits has been suggested (Baucum et al, 2004;Hadlock et al, 2009) but has not been studied specifically. Accordingly, the purpose of this study was to investigate possible associations among three of these phenomena and METH-induced persistent dopaminergic deficits, in particular, METH-induced DAT complex formation, alterations in VMAT2 immunoreactivity, and astrocytic activation.…”

“…Studies involving rodents indicate there are many effects caused by repeated high-dose administrations of METH including, but not limited to, oxidative stress (for review, see Brown and Yamamoto, 2003;Krasnova and Cadet, 2009), astrocytic/microglial activation (O'Callaghan and Miller, 1994;LaVoie et al, 2004;Thomas et al, 2004), DAT complex formation (Baucum et al, 2004;Hadlock et al, 2009), and alterations in vesicular monoamine transporter 2 (VMAT2) function (Brown et al, 2000;Eyerman and Yamamoto, 2007;Guillot et al, 2008). However, the relationship among these factors has not been elucidated fully.…”