Acceleration by stress of dopamine synthesis and metabolism in prefrontal cortex: antagonism by diazepam

Abstract

Using liquid chromatography and electrochemical detection (LCEC), we have measured the accumulation of 3,4-dihydroxyphenylalanine (DOPA) (after L-aromatic amino acid decarboxylase inhibition), dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the frontal cortex and in the corpus striatum of the rat. Mild-footshock stress increased frontal cortex DOPA accumulation, as well as DA and DOPAC, without changing the concentration of these substances in the corpus striatum. The increases in cortical DA synthesis and metabolism were antagonized by diazepam which, given alone, tended to decrease DOPA accumulation to a small degree. In addition, we have measured the indoles serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and the noradrenergic metabolite MHPG, none of which were altered by stress. The accumulation of 5-hydroxytryptophan (5-HTP) was also unaffected by stress but, like DOPA accumulation, was reduced to a small degree by diazepam. This study directly demonstrates a selective activation of frontal cortex catechol synthesis (in vivo tyrosine hydroxylation) by a mild stress, which did not significantly alter cortical noradrenergic or serotonergic metabolism.