title: Enhanced amphetamine- and K+-mediated dopamine release in rat striatum after repeated amphetamine: differential requirements for Ca2+- and calmodulin-dependent phosphorylation and synaptic vesicles.
abstract: After cessation of repeated, intermittent amphetamine, we detected an emergent Ca2+-dependent component of amphetamine-induced dopamine release and an increase in calmodulin and Ca2+- and calmodulin-dependent protein kinase activity in rat striatum. This study examined the involvement of calmodulin-dependent protein kinase II (CaM kinase II) and synaptic vesicles in the enhanced Ca2+-dependent dopamine release in response to amphetamine or K+ in rat striatum. Rats were pretreated for 5 d with 2.5 mg/kg amphetamine or saline and withdrawn from drug for 10 d. The selective CaM kinase II inhibitor KN-93 (1 microM), but not the inactive analog KN-92, attenuated the Ca2+-dependent amphetamine-mediated dopamine release from amphetamine-pretreated rats but had no effect in saline-pretreated controls. [3H]Dopamine uptake was unaltered by repeated amphetamine or KN-93 and was Ca2+ independent. Striatal dopamine release stimulated by 50 mM KCl was enhanced twofold after repeated amphetamine compared with that in saline controls but was unaffected by KN-93. To examine the requirement for dopaminergic vesicles in the Ca2+-dependent dopamine release, we administered reserpine to saline- and amphetamine-pretreated rats 1 d before killing. Reserpine pretreatment did not affect amphetamine-mediated dopamine release from either pretreatment group but completely ablated K+-mediated dopamine release. Reserpine did not disrupt the ability of 1 microM KN-93 to block the Ca2+-dependent amphetamine-mediated dopamine release from amphetamine-pretreated rats. The results indicate that the enhanced dopamine release elicited by amphetamine from chronically treated rats is dependent on Ca2+- and calmodulin-dependent phosphorylation and is independent of vesicular dopamine storage. On the contrary, the enhanced depolarization-mediated vesicular dopamine release is independent of Ca2+- and calmodulin-dependent phosphorylation.
authors.affiliation: Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0634, USA.
authors.forename: L
authors.initials: L
authors.lastname: Kantor
authors.forename: G H
authors.initials: GH
authors.lastname: Hewlett
authors.forename: M E
authors.initials: ME
authors.lastname: Gnegy
mesh_terms: D000661:Amphetamine / Q000378:metabolism*; D000818:Animals; D001596:Benzylamines / Q000494:pharmacology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003342:Corpus Striatum / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D008564:Membrane Potentials / Q000187:drug effects; D010766:Phosphorylation; D011188:Potassium / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D012110:Reserpine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000378:metabolism*; D000096926:Benzenesulfonamides
chemical_list: D000661:Amphetamine; D001596:Benzylamines; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004298:Dopamine; D004791:Enzyme Inhibitors; D011188:Potassium; D011493:Protein Kinase C; D012110:Reserpine; D013449:Sulfonamides; C072105:KN 93; D000096926:Benzenesulfonamides