Involvement of serotonin in the antidepressant-like effect of extract from Kielmeyera coriacea stems

The stems of Kielmeyera coriacea Mart. ( Clusiaceae) ( syn. pau-santo'') are a therapeutic herbal in Brazilian folk medicine. This study investigates the effects of a hydroethanoli extract ( HE) from Kielmeyera coriacea stems on the central nervous system ( CNS) of rats. Chronic administration by gavage of the extract ( 60.0 mg/kg) revealed decreased immobility time in the forced swimming test ( FST). This effect of the extract was compared with chronic treatment by gavage of fluoxetine ( 10.0 mg/kg) and nortriptyline ( 15.0 mg/kg). The anti-immobility effect of the HE from Kielmeyera coriacea in the FST was also investiged in association with the intra-dorsal raphe nucleus microinjection of 5-hydroxytryptamine ( serotonin; 5-HT) or R( +)-8-hydroxyl-2( di-n-propylamino) tetralin ( 8-OHDPAT), a 5-HT1A specific agonist receptor. The ligands, 5-HT ( 5.0 nmol) and 8-OHDPAT ( 0.6 and 1.0 nmol), significantly increased immobility time per se and blocked the anti-immobility effect of the extract. Biochemical investigations employing an in vitro synaptosomal assay showed uptake inhibition by the extract of [ H-3] 5-HT, [ H-3] noradrenaline ( NA), and [ H-3] dopamine ( DA) in the rat brain. These results suggest that serotonergic neurotransmission is involved in the antidepressant-like activity of the extract, as shown by the interaction with microinjected 5-HT and 8-OHDPAT, and that 5-HT, NA, and DA uptake inhibition may contribute to this effect.