Involvement of monoaminergic systems in anxiolytic and antidepressive activities of the standardized extract of Cocos nucifera L.

Abstract

Extracts from the husk fiber of Cocos nucifera are used in folk medicine, but their actions on the central nervous system have not been studied. Here, the anxiolytic and antidepressant effects of the standardized hydroalcoholic extract of C. nucifera husk fiber (HECN) were evaluated. Male Swiss mice were treated with HECN (50, 100, or 200 mg/kg) 60 min before experiments involving the plus maze test, hole-board test, tail suspension test, and forced swimming test (FST). HECN was administered orally (p.o.) in acute and repeated-dose treatments. The forced swimming test was performed with dopaminergic and noradrenergic antagonists, as well as a serotonin release inhibitor. Administration of HECN in the FST after intraperitoneal (i.p.) pretreatment of mice with sulpiride (50 mg/kg), prazosin (1 mg/kg), or p-chlorophenylalanine (PCPA, 100 mg/kg) caused the actions of these three agents to be reversed. However, this effect was not observed after pretreating the animals with SCH23390 (15 µg/kg, i.p.) or yohimbine (1 mg/kg, i.p.) The dose chosen for HECN was 100 mg/kg, p.o., which increased the number of entries as well as the permanence in the open arms of the maze after acute and repeated doses. In both the forced swimming and the tail suspension tests, the same dose decreased the time spent immobile but did not disturb locomotor activity in an open-field test. The anxiolytic effect of HECN appears to be related to the GABAergic system, while its antidepressant effect depends upon its interaction with the serotoninergic, noradrenergic (α1 receptors), and dopaminergic (D2 dopamine receptors) systems.

Neuropharmacology of Secondary Metabolites from Plants with Anxiolytic and Antidepressant Properties

“…These findings indicate that in some cases it may be necessary to keep the metabolites together at the concentrations present in the original infusion or extract that has a proven therapeutic effect. As explained herein, some metabolites share pharmacological targets, which explains why they lose their effect when separated and emphasizes the importance of using standardized extracts with demonstrated therapeutic effects in animal and human studies [97,98]. Unfortunately, very few clinical studies have evaluated the potential antidepressant or anxiolytic effects of isolated metabolites, so a great deal of work remains to be done.…”