The effect of various amino acids and drugs on thepara-andmeta-hydroxyphenylacetic acid concentrations in the mouse caudate nucleus |
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Authors: | P S McQuade A V Juorio |
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Institution: | (1) Psychiatric Research Division, University of Saskatchewan, Cancer and Medical Research Building, S7N 0W0 Saskatoon, Saskatchewan;(2) Present address: Douglas Hospital Research Centre, 6875 LaSalle Blvd., H4H 1R3 Verdun, Quebec |
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Abstract: | Injection ofl-p-tyrosine (800 mg/kg, 2 h) increased the mouse striatalpara-hydroxyphenylacetic acid (p-HPAA) concentrations. A smaller dose ofd,l-m-tyrosine (20 mg/kg, 2h) produced a larger increase in mouse striatalmeta-hydroxyphenylacetic acid (m-HPAA) concentrations. The administration ofl-phenylalanine to mice caused a slight increase in thep-HPAA concentrations in the corpus striatum after 2h while a larger dose ofl-phenylalanine (800 mg/kg) produced a greater increase. Eight hours followingl-phenylalanine injection,p-HPAA concentrations were still elevated. Withd-phenylalanine a significant increase was observed at eight hours after drug administration.Two drugs which reduce dopamine synthesis, -methyl-para-tyrosine and apomorphine, decreasedm-HPAA striatal concentrations without affectingp-HPAA concentrations. From these results, it is proposed that tyrosine hydroxylase activity determinesp-HPAA concentrations by regulatingp-tyrosine availability. This enzyme may also synthesizem-tyrosine which is subsequently decarboxylated to formm-tyramine and then oxidatively deaminated to formm-HPAA. |
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