Effects of the (+) and (-) enantiomers of the antidepressant drug tianeptine on 5-HTP-induced behaviour

Long-term kindling of the basolateral amygdala impairs copulatory behavior in male rats

This experiment examined the consequences of long-term kindling of the basolateral amygdala on male sexual behavior and the frequency of both spontaneous wet dog shakes (WDS) and those induced by the 5-HT2A receptor agonist DOI. Results demonstrated that following 60 stimulations of the left basolateral amygdala over a 4-week period, male Long-Evans rats exhibited decrements in every aspect of sexual behavior. Specifically, latencies to mount, intromit and ejaculate were all prolonged following long-term kindling, and ejaculation frequencies were significantly reduced. Furthermore, spontaneous peri-copulatory WDS were increased in kindled rats, suggesting a possible role of the 5-HT2A receptor. However, countering this suggestion, there were no differences between sham and kindled rats on WDS induced by the 5-HT2A receptor agonist DOI. These results suggest that kindled rats may exhibit elevated levels of endogenous serotonin during exposure to a female rat, which would attenuate copulatory behavior, while concurrently increasing WDS expression.

Overcoming the effects of stress on synaptic plasticity in the intact hippocampus: rapid actions of serotonergic and antidepressant agents

Acute inescapable stress dramatically affects the inducibility of plasticity at glutamatergic synapses in the intact hippocampus. The present study examined the involvement of serotonergic mechanisms in mediating and modulating the block of long-term potentiation (LTP) in the CA1 area of anesthetized rats after exposure to an elevated platform stress. Fluoxetine and fenfluramine, agents that raise hippocampal extracellular 5-HT concentration, blocked the induction of LTP in nonstressed animals, thus mimicking the effect of stress. In contrast, (+/-)-tianeptine, a drug that decreases 5-HT levels, had no effect on LTP induction in nonstressed animals. Remarkably, (+/-) administration of tianeptine after the stress rapidly overcame the block of LTP induction without affecting baseline excitatory transmission. Consistent with a reduction of 5-HT levels being responsible for this effect of tianeptine, the (-) enantiomer, which is associated with the 5-HT uptake enhancing action of (+/-)-tianeptine, also caused a recovery of the induction of LTP in previously stressed animals, whereas the relatively inactive (+) enantiomer had no effect. Furthermore, fluoxetine prevented the effect of tianeptine in stressed animals. These findings show that antidepressants have rapid and powerful interactions with the mechanisms controlling the persistence of the block of LTP by inescapable stress.

Tianeptine: a review of its use in depressive disorders

Tianeptine is an antidepressant agent with a novel neurochemical profile. It increases serotonin (5-hydroxytryptamine; 5-HT) uptake in the brain (in contrast with most antidepressant agents) and reduces stress-induced atrophy of neuronal dendrites. Like the selective serotonin reuptake inhibitors (SSRIs) and in contrast with most tricyclic antidepressant agents, tianeptine does not appear to be associated with adverse cognitive, psychomotor, sleep, cardiovascular or bodyweight effects and has a low propensity for abuse. Tianeptine has a comparatively favourable pharmacokinetic profile. It is not subject to first-pass hepatic metabolism, has high bioavailability and limited distribution, and is rapidly eliminated. While this offers advantages for tianeptine over the tricyclic antidepressant agents in terms of dose titration, treatment changes and potential drug interactions, its rapid elimination makes adherence to dosage schedules more important. Tianeptine differs from most antidepressants in that it is not primarily metabolised by the hepatic cytochrome P450 system, indicating less likelihood of drug-drug interactions; this is of particular interest for elderly patients. Tianeptine, in dosages of 25 to 50 mg/day, has been investigated in patients with major depression, depressed bipolar disorder, dysthymia or adjustment disorder. It has equivalent antidepressant efficacy to several classical antidepressant agents (amitriptyline, clomipramine, imipramine, mianserin) and the SSRIs fluoxetine (in most patients), paroxetine and sertraline. Comparison with maprotiline indicated superior efficacy for tianeptine but dothiepin appeared superior in another study. Extended treatment with tianeptine decreases the incidence of relapse/recurrence of depression. Tianeptine appears to be as effective as fluoxetine, sertraline, amitriptyline, clomipramine and mianserin and more effective than maprotiline in improving associated anxiety in patients with depressive disorders. Depression and anxiety symptoms in alcohol dependant patients also respond well to tianeptine. The adverse effects associated with tianeptine are similar in many respects to those of the SSRIs and minimal in comparison with the tricyclic antidepressants. The most common adverse effects are nausea, constipation, abdominal pain, headache, dizziness and changes in dreaming. Anticholinergic effects occur less often with tianeptine than with tricyclic agents. Hepatoxicity is rare. The dosage should be decreased in elderly patients and those with severe renal failure, but adjustment is not necessary in patients with alcoholism or hepatic impairment, or those undergoing haemodialysis.

CONCLUSIONS

The antidepressant efficacy and favourable tolerability and pharmacokinetic profiles of tianeptine in patients with depression, including those with associated anxiety, have been proven; the data indicate that it may have additional potential in specific subgroups of depressed patients such as the elderly and those with chronic alcoholism.

Tianeptine and its enantiomers: effects on spatial memory in rats with medial septum lesions

Tianeptine, an atypical antidepressant that exhibits clinical efficacy in measures of depression and anxiety, has been reported to enhance learning and memory in rats under certain conditions, an effect not observed with other tricyclic antidepressants. The present study explores further the possibility that tianeptine or its enantiomers (S 16190 and S 16191) can enhance either learning or retention in animals in which the hippocampus has been made partially dysfunctional. The effects of tianeptine and its enantiomers were tested using an open field watermaze test, in rats with partial lesions of the medial septum/diagonal band of Broca (MSDB). When given to normal rats, tianeptine (10 mg/kg, i.p.) did not significantly affect learning as compared to animals injected with saline. We therefore created, in other animals, partial ibotenic acid lesions of MSDB and showed histochemically that these lesions reduced but did not abolish the density of acetylcholinesterase staining in the hippocampus. They impaired both the acquisition of place-navigation and the long-term retention of spatial information over 7 days. Against the baseline of impaired performance in animals with these lesions, neither tianeptine (10 mg/kg) nor its enantiomers (5 mg/kg) affected the rate of acquisition of place navigation. However, tianeptine did enhance the retention of spatial memory over 7 days. These results are discussed in relation to different effects that tianeptine may have on learning including its ability to block stress-induced dendritic re-modelling of the hippocampus.

Effects of antidepressants and benzodiazepine treatments on the dendritic structure of CA3 pyramidal neurons after chronic stress

Both repeated stress and corticosterone administration induce remodeling of apical dendrites of hippocampal CA3 pyramidal neurons. Circulating glucocorticoids are involved in the mechanism that produces atrophy, along with excitatory amino acids and serotonin (5-hydroxytryptamine, 5-HT). We used 5-HT-related antidepressants and a benzodiazepine in order to explore indirectly the role of serotonin and GABA(A)-benzodiazepine receptors in the stress-induced structural changes visualized by the Golgi impregnation of the rat hippocampus. The 5-HT reuptake enhancer (+/-)-tianeptine prevented the dendritic atrophy caused by repeated restraint stress in a non-stereoselective fashion and two 5-HT reuptake antagonists, fluoxetine and fluvoxamine, failed to block dendritic atrophy. Tianeptine also functions as a therapeutic tool since it reversed the already established hippocampal atrophy caused by treatment with corticosterone for 3 weeks. Finally, the benzodiazepine agonist adinazolam was effective in preventing the stress-induced dendritic atrophy. These findings suggest that the synaptic availability of 5-HT is involved in the mechanism leading to stress-induced dendritic remodeling and supports the idea that the hippocampal inhibitory GABAergic tone may play a regulatory role.