Glucocorticoid effects on mesotelencephalic dopamine neurotransmission

Multiple neurochemical estimates were used to examine peripheral corticosterone (CORT) effects in dopaminergic terminal regions. Acute CORT administration, which elevated plasma CORT (5 h), slightly decreased dihydroxyphenylacetic acid (DOPAC) to dopamine (DA) ratios in the striatum but not in other regions examined. Two weeks of adrenalectomy (ADX) increased both medial prefrontal cortex DOPAC/DA and homovanillic acid (HVA)/DA and striatal HVA/DA. A reciprocal pattern of changes was observed with CORT replacement in ADX animals. In contrast, CORT replacement in ADX animals did not significantly influence tyrosine hydroxylase content, basal dihydroxyphenylalanine (DOPA) accumulation after NSD 1015 treatment or the decline in DA after alpha-methyl-para-tyrosine, suggesting that neither DA neuronal activity nor release are altered by CORT. Moreover, neither gamma-hydroxybutyric acid lactone-induced increases in DOPA accumulation or stress-induced increases in DA utilization were influenced by CORT replacement, indicating that neither autoreceptor regulation of DA synthesis nor acute stress regulation of DA utilization are changed by CORT. The findings are most consistent with direct inhibition of basal DA metabolism in the medial prefrontal cortex and striatum. The possible physiological and behavioral significance of this inhibition is being further explored.