PHOSPHORYLATION OF NEUROMODULIN IN RAT STRIATUM AFTER ACUTE AND REPEATED, INTERMITTENT AMPHETAMINE

Citation
Me. Gnegy et al., PHOSPHORYLATION OF NEUROMODULIN IN RAT STRIATUM AFTER ACUTE AND REPEATED, INTERMITTENT AMPHETAMINE, Molecular brain research, 20(4), 1993, pp. 289-298
Citations number
60
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences
Journal title
ISSN journal
0169-328X
Volume
20
Issue
4
Year of publication
1993
Pages
289 - 298
Database
ISI
SICI code
0169-328X(1993)20:4<289:PONIRS>2.0.ZU;2-T
Abstract
Repeated, intermittent treatment of rats with amphetamine results in a sensitization of locomotor and stereotyped behaviors that is accompan ied by an enhancement in stimulus-induced dopamine release. Increased phosphorylation of the neural specific calmodulin-binding protein, neu romodulin (GAP-43, B-50, F1) has been demonstrated in other forms of s ynaptic plasticity and plays a role in neurotransmitter release. To de termine whether neuromodulin phosphorylation was altered during amphet amine sensitization, the in vivo phosphorylated state of neuromodulin was examined in rat striatum in a post hoc phosphorylation assay. Fema le, Holtzman rats received saline or 2.5 mg/kg amphetamine twice weekl y for 5 weeks. One week after the last dose of amphetamine, rats were challenged with either 1 mg/kg or 2.5 mg/kg amphetamine or saline and the rats were sacrificed 30 min later. Purified synaptic plasma membra nes were prepared in the presence of EGTA and okadaic acid to inhibit dephosphorylation, and were subsequently phosphorylated in the presenc e of purified protein kinase C and [gamma-P-32]ATP. The protein kinase C-mediated post hoc phosphorylation of neuromodulin was significantly reduced in groups that received either acute or repeated amphetamine suggesting that neuromodulin in those groups contained more endogenous phosphate, The acute, challenge dose of amphetamine increased neuromo dulin phosphorylation in the saline-treated controls but not in the re peated amphetamine-pretreated group. Anti-neuromodulin immunoblots sho wed no change in neuromodulin levels in any group. There was no signif icant change in protein kinase C activity in any treatment group. To f urther investigate the effect of acute amphetamine, the ability of amp hetamine to alter neuromodulin phosphorylation in P-32(i)-preincubated Percoll-purified rat striatal synaptosomes was examined. Amphetamine (10 muM) significantly increased phosphorylation of a 53 kDa band that migrated with authentic neuromodulin in the synaptosomes by 22% while 500 nM 12-O-tetradecanoylphorbol 13-acetate (TPA) increased neuromodu lin phosphorylation by 45%. These data suggest that one injection of a mphetamine can increase neuromodulin phosphorylation in rat striatum a nd that this increase is maintained for at least 1 week following a re peated, sensitizing regimen of amphetamine. Since sensitization can be induced with one dose of amphetamine, it is possible that enhanced ne uromodulin phosphorylation could contribute to neurochemical events le ading to enhanced release of dopamine and/or behavioral sensitization.