title: Acute lithium administration selectively lowers tyrosine levels in serum and brain.
abstract: Lithium exerts anti-dopaminergic behavioral effects. We examined whether some of these might be mediated by changes in brain levels of tyrosine (TYR), the precursor to dopamine. Lithium chloride (LiCl(2)) 3.0mEq/kg IP acutely lowered serum TYR and the ratio of serum TYR to other large neutral amino acids (LNAAs); it also selectively lowered striatum TYR levels as measured in tissue or in vivo. While LiCl(2) 3.0mEq/kg IP also augmented haloperidol (0.19mg/kg SC)-induced catalepsy, this lithium effect was not attenuated by administration of TYR 100mg/kg IP. We conclude that lithium acutely and selectively lowers brain TYR by lowering serum levels of tyrosine relative to the LNAAs that compete with it for transport across the blood-brain barrier. However, the lowering of TYR does not appear to significantly contribute to the ability of lithium to potentiate haloperidol-mediated catalepsy.
authors.affiliation: Department of Psychology, Kenyon College, Gambier, OH 43022, USA. mcfarlaneh@kenyon.edu
authors.forename: Hewlet G
authors.initials: HG
authors.lastname: McFarlane
authors.forename: John
authors.initials: J
authors.lastname: Steele
authors.forename: Keenan
authors.initials: K
authors.lastname: Vinion
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Bongiovanni
authors.forename: Manda
authors.initials: M
authors.lastname: Double
authors.forename: George E
authors.initials: GE
authors.lastname: Jaskiw
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D002375:Catalepsy / Q000139:chemically induced / Q000188:drug therapy; D004347:Drug Interactions; D006220:Haloperidol / Q000494:pharmacology; D018021:Lithium Chloride / Q000494:pharmacology*; D008297:Male; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014443:Tyrosine / Q000097:blood* / Q000378:metabolism*
chemical_list: D014150:Antipsychotic Agents; D014443:Tyrosine; D018021:Lithium Chloride; D006220:Haloperidol