Investigation of the antidepressant-like effect of echinatin using In Vivo methods

In this thesis study, the potential antidepressant-like activity of echinatin, a phytochemical isolated from the roots and rhizomes of Glycyrrhiza (licorice) species, was investigated. Additionally, possible monoaminergic mechanisms mediating this effect were explored through pharmacological antagonism studies. The antidepressant-like activity of echinatin (20 and 30 mg/kg, i.p.) was evaluated using the tail suspension test and the modified forced swimming test, while its potential effects on motor performance were assessed via the rota-rod and activity meter tests. The findings demonstrated that echinatin, at a dose of 30 mg/kg, exhibited an antidepressant-like effect comparable to that of fluoxetine (10 mg/kg, i.p.) and reboxetine (20 mg/kg, i.p.) without affecting the animals' motor activity. Pre-treatment with p-chlorophenylalanine methyl ester, α-methyl-para-tyrosine methyl ester, WAY-100635, phentolamine, propranolol, SCH-23390, and sulpiride abolished the anti-immobility effect of echinatin in the tail suspension test, whereas pre-treatment with ketanserin had no significant effect. Taken together, these findings suggest that the antidepressant-like effect of echinatin is mediated through the modulation of monoaminergic neurotransmission and that α- and β-adrenergic, 5-HT₁A serotonergic, and D₁, D₂, and D₃ dopaminergic receptor subtypes are involved in this pharmacological activity. This study provides the first comprehensive pharmacological evidence supporting the antidepressant-like properties of echinatin mediated via these neurotransmitter systems.