Effects of methyl-4-ethyl-6,7-dimethoxy-(3-carboline-3-carboxylate on the release of monoamine neurotransmitters from rat brain slices

HPLC with electro-chemical detection was employed to analyse the release of monoamine neurotransmitters from rat brain slice preparations. An inverse benzo-diazepine receptor agonist, methyl-4-ethyl- 6 , 7-dimethoxy-3-carboline-3-carboxylate (DMCM, 10 Umol/L). significantly increased the release of norepinephrine (NE) and serotonin (5-HT) from the frontal cortex, hippocampus, amygdala and brain stem. However. it only increased the release of dopamine from the amygdala. These effects of DMCM were reversed by R0 15-1788 (5 vmol/L), clonidine (5 vmol/L) and muscimol (5 vmol/L). A higher concentration of R0 15-1788 (10 vmol/L), a putative benzodiazepine receptor antagonist. also significantly increased the release of NE from the hippocampus and 5-HT from the amygdala and hippocampus. Our results suggest that both central NE and 5-HT systems may be involved in the anxiogenic action of DMCM.