title: Tyrosine augments acute clozapine- but not haloperidol-induced dopamine release in the medial prefrontal cortex of the rat: an in vivo microdialysis study.
abstract: Tyrosine availability can influence dopamine (DA) synthesis in highly electrophysiologically active DAergic neurons, such as those innervating the medial prefrontal cortex (MPFC). Whether tyrosine concentrations can also affect MPFC extracellular DA concentrations, measured in vivo, is not known. Since clozapine preferentially activates mesocortical DA neurons, we posited that tyrosine administration to a clozapine-pretreated rat would enhance the clozapine-induced augmentation of MPFC extracellular DA concentrations. Tyrosine alone (25-50mg/kg IP) did not affect mesocortical or striatal extracellular DA concentrations measured by in vivo microdialysis. Given 30 minutes after clozapine (10 mg/kg), tyrosine (50 mg/kg) significantly prolonged the clozapine-induced increase in MPFC extracellular DA concentrations but had no effect in the striatum. In contrast, tyrosine (50 mg/kg) significantly prolonged the haloperidol (1 mg/kg) induced increase in striatal extracellular DA concentrations but had no effect in the MPFC. These data constitute the first in vivo evidence that administration of tyrosine can selectively potentiate the clozapine-evoked increase in mesocortical extracellular DA concentrations.
authors.affiliation: Veterans Affairs Medical Center, Cleveland, OH 44141, USA. gxj5@po.cwru.edu
authors.forename: G E
authors.initials: GE
authors.lastname: Jaskiw
authors.forename: K A
authors.initials: KA
authors.lastname: Collins
authors.forename: E A
authors.initials: EA
authors.lastname: Pehek
authors.forename: B K
authors.initials: BK
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D003024:Clozapine / Q000494:pharmacology*; D004298:Dopamine / Q000096:biosynthesis*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004347:Drug Interactions / Q000502:physiology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006220:Haloperidol / Q000494:pharmacology*; D008297:Male; D017551:Microdialysis; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D014150:Antipsychotic Agents; D018492:Dopamine Antagonists; D004338:Drug Combinations; D014443:Tyrosine; D003024:Clozapine; D006220:Haloperidol; D004298:Dopamine