Amphetamine Increases Phosphorylation of Extracellular Signal-regulated Kinase and Transcription Factors in the Rat Striatum via Group I Metabotropic Glutamate Receptors

Amphetamine Increases Phosphorylation of Extracellular Signal-regulated Kinase and Transcription Factors in the Rat Striatum via Group I Metabotropic Glutamate Receptors Eun Sang Choe, Ph.D., Kyung Tae Chung, Ph.D., Limin Mao, M.D., and John Q. Wang, Ph.D. Amphetamine is an indirect dopamine receptor agonist and increases glutamate release in the striatum. Activation of group I metabotropic glutamate receptors (mGluRs) upregulates cAMP response element-binding protein (CREB) and Elk-1 phosphorylation via extracellular signal-regulated kinase 1 and 2 (ERK1/2) in the striatum in vivo. In the present study the role of mGluRs in the regulation of ERK1/2 pathways leading to CREB and Elk-1 phosphorylation by amphetamine was investigated using immunohistochemistry and Western blot in the rat dorsal striatum. Acute administration of amphetamine (5 mg/kg, i.p.) caused increases in phosphorylated (p)CREB, pElk-1, and pERK1/2 immunoreactivity. Intrastriatal blockade of group I mGluRs with N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1acarboxamide (PHCCC; 25 nmol) significantly attenuated amphetamine-induced pCREB, pElk-1, pERK1/2, and Fos immunoreactivity in both medial and lateral areas of the striatum. Systemic injection of an mGluR5 antagonist, From the Division of Pharmacology (ESC, LM, JQW), School of Pharmacy, University of Missouri-Kansas City, 2411 Holmes St., M3-C15, Kansas City, MO 64108, USA; and Department of Tumor Cell Biology (KTC), St. Jude Children’s Research Hospital, 332 North Lauderdale St., Memphis, TN 38105, USA. Address correspondence to: John Q. Wang, Ph.D., Division of Pharmacology, School of Pharmacy, University of Missouri-Kansas City, 2411 Holmes St., M3-225, Kansas City, MO 64108. Tel.: (816) 235-1786; Fax: (816) 235-1776; E-mail: Received November 27, 2001; revised March 18, 2002; accepted April 1, 2002. Online publication: 4/03/02 at www.acnp.org/citations/ Npp040302277. NEUROPSYCHOPHARMACOLOGY 2002–VOL. 27, NO. 4 © 2002 American College of Neuropsychopharmacology Published by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP; 10 mg/kg, i.p.), also blocked the amphetamine induction of these phosphoproteins. In contrast, intrastriatal blockade of group II/III mGluRs with (RS)--methylserine-o-phosphate monophenyl ester (MSOPPE; 25 nmol) did not affect amphetamine-induced increases in all the four markers. Similarly, intrastriatal dantrolene (2 or 20 nmol) that blocks intracellular Ca2 release from ryanodine-sensitive stores did not affect amphetamine effects. Injection of PHCCC, MPEP, MSOPPE, or dantrolene alone did not alter basal levels of the three phosphoproteins and Fos. These data suggest that acute amphetamine is able to facilitate the phosphorylation of CREB, Elk-1, and ERK1/2 signaling proteins and Fos gene expression via a group I mGluR-dependent mechanism in the dorsal striatum. [Neuropsychopharmacology 27:565–575, 2002] © 2002 American College of Neuropsychopharmacology. Published by Elsevier Science Inc. KEY WORDS: Calcium; CREB; Dopamine; Drugs of abuse; ERK; Elk-1; Fos Amphetamine, an indirect dopamine receptor agonist, increases glutamate release in the striatum (Nash and Yamamoto 1993; Del Arco et al. 1999; Rawls and McGinty 2000). Activation of metabotropic glutamate receptors (mGluRs) transduces extracellular glutamatergic signals to second messengers in a subtype-specific manner. Activation of group I mGluRs (mGluR1/5) mobilizes intracellular Ca2 release (Dale et al. 2001; Kawa- 0893-133X/02/$–see front matter PII S0893-133X(02)00341-X 566 E.S. Choe et al. bata et al. 1998; Schnabel et al. 1999) and activates mitogen-activated protein kinases (MAPK) (Choe and Wang 2001). In contrast, activation of group II/III receptors downregulates the adenylate cyclase (AC) and cyclic adenosine monophosphate (cAMP) cascades. Previous studies show that mGluRs are involved in the regulation of amphetamine-induced behaviors in a subgroup specific manner (Cartmell et al. 1999, 2000; Mao and Wang 1999, 2000; Mao et al. 2000; Spooren et al. 2000). Cyclic AMP response element-binding protein (CREB) and Elk-1 are major transcriptional regulators in striatal projection neurons and are phosphorylated by one member of MAPK family: extracellular signal-regulated kinase 1/2 (ERK1/2) (Sgambato et al. 1998; Vanhoutte et al. 1999). Stimulation of group I mGluRs with the selective agonist, 3,5-dihydroxyphenylglycine (DHPG), upregulates CREB, Elk-1, and ERK1/2 phosphorylation in the dorsal striatum (Choe and Wang 2001). Like DHPG, amphetamine increases CREB phosphorylation in the striatum (Konradi et al. 1994). Numerous studies show that CREB is necessary for c-fos mRNA induction by amphetamine, and Fos protein is induced by glutamatergic signals (Konradi et al. 1994; Vanhoutte et al. 1999). A recent study also shows that cocaine or methamphetamine increases pERK1/2 immunoreactivity (IR) in the striatum (Adams et al. 2001). These findings suggest that both dopaminergic and glutamatergic inputs are capable of regulating the ERK1/2 signaling pathways leading to the phosphorylation of CREB and Elk-1 and thus gene expression in striatal neurons. However, the role of mGluRs in regulating ERK1/2 pathways leading to CREB and Elk-1 phosphorylation in response to dopamine stimulation remains to be documented. In this study, potential roles of group I mGluRs were therefore examined by investigating whether amphetamine upregulates CREB, Elk-1 and ERK1/2 phosphorylation and Fos expression via a group I mGluRdependent way in striatal neurons. Experiments were performed in freely moving rats treated with: (1) an acute injection of amphetamine; (2) intrastriatal infusion of the group I selective antagonist, n-phenyl-7-(hydroxyimino) cyclopropa[b]chromen-1a-carboxamide (PHCCC), followed by an acute amphetamine injection; (3) intrastriatal infusion of the group II/III selective antagonist, (RS)-methylserine-o-phosphate monophenyl ester (MSOPPE), followed by an acute amphetamine injection; (4) systemic injection of the mGluR5 selective antagonist 2-methyl-6(phenylethynyl)pyridine hydrochloride (MPEP), followed by an acute amphetamine injection; and (5) intrastriatal infusion of the ryanodine receptor antagonist, dantrolene, followed by an acute amphetamine injection. Immunohistochemistry and Western blot were applied to quantify alterations in the levels of the phosphorylated or unphosphorylated signaling molecules in the selected areas of ipsilateral dorsal striatum. NEUROPSYCHOPHARMACOLOGY 2002–VOL. 27, NO. 4 METHODS Animals Adult male Wistar rats (200–250 g) were obtained from Charles River Laboratories (New York, NY). Rats were individually housed in a controlled environment during all experimental treatments. Food and water were provided ad libitum and rats were maintained on a 12/12-h light/dark cycle (lights on at 7:00 A.M.). On the day of the experiment injection was made in the quie (...truncated)