Involvement of Serotonin in the Antidepressant-like Effect of Extract from Kielmeyera coriacea. Stems

Abstract

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-HT_1A 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 [³H]5-HT, [³H]noradrenaline (NA), and [³H]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.

Keywords:

• Antidepressant activity
• dorsal raphe nucleus
• forced swimming test
• Kielmeyera coriacea
• open-field test
• rat
• serotonin uptake