Recent studies have shown the importance of the GABA-ergic transmission in the pathophysiology of anxiety and depressive disorders in humans. Our present study aims to investigate the interaction of melatonin (MEL) wi...Recent studies have shown the importance of the GABA-ergic transmission in the pathophysiology of anxiety and depressive disorders in humans. Our present study aims to investigate the interaction of melatonin (MEL) with this system by exploring the effects of MEL with or without a facilitator of GABA-ergic neurotransmission, diazepam (DZ) on the levels of depression and anxiety in Wistar rats. For this purpose, different doses of MEL (2, 4 or 16 mg/kg) or DZ (2 mg/kg) are subchronically administered during 15 days. After pharmacological treatments, anxiety levels are evaluated in behavioral tests of Open Field (OFT) and elevated plus maze (EPM) and depression levels are evaluated by the forced swim test (FST). The results showed that MEL produces anxiolytic-like and antidepressant-like effects in a dose-dependent manner;the maximum effect was obtained at a dose of 16 mg/kg. However, a dose of 4 mg/kg is necessary to induce an effect. The effect of MEL and DZ reported in this study concerns selective modulation of behavioral anxiety and depression since locomotor activity assessed by the OFT and EPM was not affected. The subchronic injection of MEL at 4 mg/kg, DZ at 2 mg/kg or the two combined molecules also induces also anxiety-like and antidepressant-like behavior. In addition, a potentiating effect between MEL and DZ was observed. These effects suggest that psychopharmacological actions of MEL are due, at least in part, to its ability to improve the central GABA-ergic transmission.展开更多
The aim of this study was to determine the effect of pharmacological doses of melatonin (MEL) and L-tryptophan (L-TRP) on depression-like behavior in female rats submitted to the forced swimming test (FST) after 2, 4,...The aim of this study was to determine the effect of pharmacological doses of melatonin (MEL) and L-tryptophan (L-TRP) on depression-like behavior in female rats submitted to the forced swimming test (FST) after 2, 4, 6 or 8 weeks of treatment. This will allow exploring the different mechanisms of L-TRP actions particularly that due to its conversion into MEL. For this purpose, four groups of 24 rats each were constituted;(Group 1: Control): received saline solution NaCl (0.9%), (Group 2: MEL4): received 4 mg/Kg of MEL, (Group 3: L-TRP4): received 4 mg/Kg of L-TRP and (Group 4: L-TRP20): received 20 mg/Kg of L-TRP. Animals of each group were distributed on 4 subgroups of 6 rats submitted to different time treatments. The duration of immobility (TIM) and struggling period (TST) of rats in FST were measured after 2, 4, 6 and 8 weeks of drug treatment and the effects of MEL and L-TRP were compared. Chronical administration of different doses of MEL or L-TRP failed to induce any anti-depressant activity in rats subjected to FST after 2 weeks of treatment. However, after 4 weeks, daily administration of MEL at 4 mg/Kg significantly reduced the immobility period and enhanced struggling time. After 6 weeks, MEL at 4 mg/Kg and L-TRP at 20 mg/Kg were both effective in reducing immobility and increasing struggling movement, their effects being statistically comparable. All treatments were able to significantly reduce immobility time and increase struggling duration after 8 weeks, but L-TRP at 4 mg/Kg was less potent than MEL and L-TRP at 20 g/Kg. The antidepressant-like activity of L-TRP was dose and time dependent, and that of MEL was time dependent. In conclusion, the study showed that at pharmacological doses, MEL and L-TRP have anti-depressant action, and such effect is dependent on time treatment;MEL?is more effective than L-TRP. In conclusion, L-TRP, through MEL, 5-HT or by itself could modulate aminergic neurotransmission in the different brain areas to ensure its behavioral effects.展开更多
文摘Recent studies have shown the importance of the GABA-ergic transmission in the pathophysiology of anxiety and depressive disorders in humans. Our present study aims to investigate the interaction of melatonin (MEL) with this system by exploring the effects of MEL with or without a facilitator of GABA-ergic neurotransmission, diazepam (DZ) on the levels of depression and anxiety in Wistar rats. For this purpose, different doses of MEL (2, 4 or 16 mg/kg) or DZ (2 mg/kg) are subchronically administered during 15 days. After pharmacological treatments, anxiety levels are evaluated in behavioral tests of Open Field (OFT) and elevated plus maze (EPM) and depression levels are evaluated by the forced swim test (FST). The results showed that MEL produces anxiolytic-like and antidepressant-like effects in a dose-dependent manner;the maximum effect was obtained at a dose of 16 mg/kg. However, a dose of 4 mg/kg is necessary to induce an effect. The effect of MEL and DZ reported in this study concerns selective modulation of behavioral anxiety and depression since locomotor activity assessed by the OFT and EPM was not affected. The subchronic injection of MEL at 4 mg/kg, DZ at 2 mg/kg or the two combined molecules also induces also anxiety-like and antidepressant-like behavior. In addition, a potentiating effect between MEL and DZ was observed. These effects suggest that psychopharmacological actions of MEL are due, at least in part, to its ability to improve the central GABA-ergic transmission.
文摘The aim of this study was to determine the effect of pharmacological doses of melatonin (MEL) and L-tryptophan (L-TRP) on depression-like behavior in female rats submitted to the forced swimming test (FST) after 2, 4, 6 or 8 weeks of treatment. This will allow exploring the different mechanisms of L-TRP actions particularly that due to its conversion into MEL. For this purpose, four groups of 24 rats each were constituted;(Group 1: Control): received saline solution NaCl (0.9%), (Group 2: MEL4): received 4 mg/Kg of MEL, (Group 3: L-TRP4): received 4 mg/Kg of L-TRP and (Group 4: L-TRP20): received 20 mg/Kg of L-TRP. Animals of each group were distributed on 4 subgroups of 6 rats submitted to different time treatments. The duration of immobility (TIM) and struggling period (TST) of rats in FST were measured after 2, 4, 6 and 8 weeks of drug treatment and the effects of MEL and L-TRP were compared. Chronical administration of different doses of MEL or L-TRP failed to induce any anti-depressant activity in rats subjected to FST after 2 weeks of treatment. However, after 4 weeks, daily administration of MEL at 4 mg/Kg significantly reduced the immobility period and enhanced struggling time. After 6 weeks, MEL at 4 mg/Kg and L-TRP at 20 mg/Kg were both effective in reducing immobility and increasing struggling movement, their effects being statistically comparable. All treatments were able to significantly reduce immobility time and increase struggling duration after 8 weeks, but L-TRP at 4 mg/Kg was less potent than MEL and L-TRP at 20 g/Kg. The antidepressant-like activity of L-TRP was dose and time dependent, and that of MEL was time dependent. In conclusion, the study showed that at pharmacological doses, MEL and L-TRP have anti-depressant action, and such effect is dependent on time treatment;MEL?is more effective than L-TRP. In conclusion, L-TRP, through MEL, 5-HT or by itself could modulate aminergic neurotransmission in the different brain areas to ensure its behavioral effects.
