Phenylalanine in the caudate nucleus of dopamine depleted rats.
Dopamine depleting lesions of the substantia nigra result in a reduction of the striatal accumulation of 2-phenylethylamine following monoamine oxidase inhibition. It is established that this effect may not be due to a change in availability of aromatic L-amino acid decarboxylase in striatum. Nevertheless, the possibility remains that striatal concentrations of phenylalanine (the precursor of 2-phenylethylamine) may be altered by dopamine-depleting lesions. The present experiments assessed the effects of dopamine depletion induced by 6-OHDA (7 days following 8 micrograms/4 microliters unilateral substantia nigra injection) on striatal concentrations of phenylalanine, dopamine, 5-hydroxytryptamine and their metabolites. In addition, the effects of reserpine-induced (10 mg kg-1, 2h, sc) amine depletion on these striatal levels were also assessed. Under equivalent conditions reserpine is reported to increase striatal accumulation of 2-phenylethylamine. 6-OHDA induced a significant unilateral depletion of dopamine, DOPAC and HVA and increased 5-HIAA but had no significant effect on phenylalanine levels. Reserpine decreased dopamine and 5-hydroxytryptamine and increased DOPAC, HVA and 5-HIAA levels, no changes in phenylalanine were observed. This pattern of results was also observed when lesioned animals or reserpine-treated animals were pretreated with (-)-deprenyl (2 mg kg-1, 2 hr, sc), the treatment previously used to induce accumulation of 2-phenylethylamine. These data indicate that changes in 2-phenylethylamine previously observed under these conditions may not simply be secondary to a change in striatal phenylalanine concentrations.
Paetsch
P R
PR
Department of Psychiatry University of Alberta, Edmonton, Canada.
Greenshaw
A J
AJ
Juorio
A V
AV
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000172:deficiency*; D006719:Homovanillic Acid / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D010649:Phenylalanine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012110:Reserpine / Q000494:pharmacology*; D012701:Serotonin / Q000378:metabolism; D013378:Substantia Nigra / Q000502:physiology*
D008996:Monoamine Oxidase Inhibitors; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D010649:Phenylalanine; D006897:Hydroxyindoleacetic Acid; D012110:Reserpine; D004298:Dopamine; D006719:Homovanillic Acid