Dibutyrul cyclic AMP (dbcAMP) was injected intracerebroventricularly into rats in doses of 50, 100 or 200 microgram. Noradrenaline (NA), dopamine (DA), 5-hydroxytryptamine (5-HT) or 5-hydroxy indoleacetic acid (5-HIAA) concentrations were measured spectrophotofluorimetrically in discrete brain areas: cortex, hypothalamus, striatum, hippocampus with nucleus amygdala and nucleus accumbens (limbic system) and pons with medulla oblongata. DbcAMP (in each dosage administered) decreased, NA content of cortex and of pons with medulla oblongata. NA content in the hypothalamus and striatum was decreased only after the largest dose of dbcAMP. In the limbic system NA concentration was diminished after a dose of 100 or 200 microgram of dbcAMP. There was a decrease in DA level measured in the striatum alone after a dose of 100 microgram of dbcAMP. 5-HT concentration was increased in the striatum and the pons with medulla oblongata after each dose level of dbcAMP; in the cortex after a dose of 50 and 100 microgram; and in the hypothalamus after a dose of 200 microgram. 5-HIAA level was increased in the striatum, limbic system, pons with medulla oblongata after all doses of dbcAMP. We conclude that dbcAMP affects presynaptic central catecholaminergic and serotoninergic neurons in an opposite, manner, although discrete brain areas have a different susceptibility to dbcAMP action. These findings provide some explanation for the behavioural effects of dbcAMP.