Chronic lithium chloride fails to prevent imipramine-induced sensitization to the dopamine D(2)-like receptor agonist quinpirole

[Bipolar affective disorder occurring with psychopharmacotherapy-induced manic phases]

To analyze the stages of development of the problem, identify the evolution of views and the main directions of current research in the field of bipolar affective disorder, which occurs with psychopharmacotherapy-induced manic phases, the search for publications by keywords «pharmaco-induced mania»", «bipolar affective disorder» was carried out in the PubMed/MEDLINE, Russian Citation index and other sources from the mid-19th century to the present. The issue of adequate treatment of bipolar depression became relevant back in the 20th century; numerous observations indicated the presence of associated risks when using antidepressants in patients with bipolar affective disorder, namely, the likelihood of affect inversion and aggravation of the course of the disease (accelerated cyclicity, continuum). In recent years, due to the expansion of research capabilities and the introduction of biological psychiatry, works have appeared that consider this problem from both clinical and pharmacodynamic, genetic and neurophysiological aspects, which opens up the prospect of developing advanced methods of personalized medicine for the diagnosis and treatment of bipolar disorder, taking into account the need to minimize iatrogenic effects.

Mood and behavior regulation: interaction of lithium and dopaminergic system

Lithium is one of the most effect mood-stabilizing drugs prescribed especially for bipolar disorder. Lithium has wide range effects on different molecular factors and neural transmission including dopaminergic signaling. On the other hand, mesolimbic and mesocortical dopaminergic signaling is significantly involved in the pathophysiology of neuropsychiatric disorders. This review article aims to study lithium therapeutic mechanisms, dopaminergic signaling, and the interaction of lithium and dopamine. We concluded that acute and chronic lithium treatments often reduce dopamine synthesis and level in the brain. However, some studies have reported conflicting results following lithium treatment, especially chronic treatment. The dosage, duration, and type of lithium administration, and the brain region selected for measuring dopamine level were not significant differences in different chronic treatments used in previous studies. It was suggested that lithium has various mechanisms affecting dopaminergic signaling and mood, and that many molecular factors can be involved, including brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), β-catenin, protein kinase B (Akt), and glycogen synthase kinase-3 beta (GSK-3β). Thus, molecular effects of lithium can be the most important mechanisms of lithium that also alter neural transmissions including dopaminergic signaling in mesolimbic and mesocortical pathways.

Antidepressant-induced Dopamine Receptor Dysregulation: A Valid Animal Model of Manic-Depressive Illness

Background: Mania seems to be associated with an increased dopamine (DA) transmission. Antidepressant treatments can induce mania in humans and potentiated DA transmission in animals, by sensitizing DA D2 receptors in the mesolimbic system. We have suggested that the sensitization of D2 receptors may be responsible of antidepressant-induced mania. This review aims to report the experimental evidence that led to the hypothesis that antidepressant-induced DA receptors dysregulation can be considered an animal model of bipolar disorder.

Methods: We reviewed papers reporting preclinical and clinical studies on the role of DA in the mechanism of action of antidepressant treatments and in the patho-physiology of mood disorders.

Results: A number of preclinical and clinical evidence suggests that mania could be associated with an increased DA activity, while a reduced function of this neurotransmission might underlie depression. Chronic treatment with imipramine induces a sensitization of DA D2 receptors in the mesolimbic system, followed, after drug discontinuation, by a reduced sensitivity associated with an increased immobility time in forced swimming test of depression (FST). Blockade of glutamate NMDA receptors by memantine administration prevents the imipramine effect on DA receptors sensitivity and on the FST.

Conclusion: We suggest that chronic treatment with antidepressants induces a behavioural syndrome that mimics mania (the sensitization of DA receptors), followed by depression (desensitization of DA receptors and increased immobility time in the FST), i.e. an animal model of bipolar disorder. Moreover the observation that memantine prevents the “bipolar-like” behavior, suggests that the drug may have an antimanic and mood stabilizing effect. Preliminary clinical observations support this hypothesis.

Failure of memantine to “reverse” quinpirole-induced hypomotility

AIM: To evaluate antidepressant-like effect of memantine in a rat model.

METHODS: Male Wistar rats were treated intraperitoneally with either vehicle, memantine (10 mg/kg) or imipramine (20 mg/kg), for 3 wk. Twenty-four hour after the last treatment animals were challenged with quinpirole (0.3 mg/kg s.c.) and tested for motor activity. After 1 h habituation to the motility cages, the motor response was recorded for the following 45-min and the data were collected in 5-min time bins.

RESULTS: As expected, chronic treatment with imipramine potentiated the locomotor stimulant effect of quinpirole. On the contrary, chronic memantine administration failed to induce the behavioral supersensitivity to the dopamine agonist.

CONCLUSION: The results show that memantine, at variance with antidepressant treatments, fails to induce dopaminergic behavioral supersensitivity. This observation is consistent with the results of preclinical and clinical studies suggesting that memantine does not have an acute antidepressant action but does have an antimanic and mood-stabilizing effect.

Modeling mania in preclinical settings: A comprehensive review

The current pathophysiological understanding of mechanisms leading to onset and progression of bipolar manic episodes remains limited. At the same time, available animal models for mania have limited face, construct, and predictive validities. Additionally, these models fail to encompass recent pathophysiological frameworks of bipolar disorder (BD), e.g. neuroprogression. Therefore, there is a need to search for novel preclinical models for mania that could comprehensively address these limitations. Herein we review the history, validity, and caveats of currently available animal models for mania. We also review new genetic models for mania, namely knockout mice for genes involved in neurotransmission, synapse formation, and intracellular signaling pathways. Furthermore, we review recent trends in preclinical models for mania that may aid in the comprehension of mechanisms underlying the neuroprogressive and recurring nature of BD. In conclusion, the validity of animal models for mania remains limited. Nevertheless, novel (e.g. genetic) animal models as well as adaptation of existing paradigms hold promise.

Memantine prevents "bipolar-like" behavior induced by chronic treatment with imipramine in rats

A great deal of evidence suggests that virtually all antidepressant treatments induce a dopaminergic behavioral supersensitivity. We have suggested that this effect may play a key role not only in the antidepressant effect of these treatments, but also in their ability to induce a switch from depression to mania. In 2003-4 we found that the sensitization of dopamine receptors induced by imipramine is followed, after imipramine withdrawal, by a desensitization of these receptors associated with a depressive-like behavior assessed in the forced swimming test. The dopamine receptor sensitization can be prevented by MK-801, an NMDA receptor antagonist, but not by currently used mood stabilizers (lithium, carbamazepine, valproate). These observations led us to suggest - and later confirm - with preliminary clinical observations that memantine may have an acute antimanic and a long-lasting mood-stabilizing effect in treatment-resistant bipolar disorder patients. Here we present data showing that memantine prevents not only the dopamine receptor sensitization induced by imipramine, as observed with MK-801, but also the ensuing desensitization and the associated depressive-like behaviorq observed after antidepressant withdrawal.

The role of memantine in the treatment of psychiatric disorders other than the dementias: a review of current preclinical and clinical evidence

Memantine, a non-competitive NMDA receptor antagonist approved for Alzheimer's disease with a good safety profile, is increasingly being studied in a variety of non-dementia psychiatric disorders. We aimed to critically review relevant literature on the use of the drug in such disorders. We performed a PubMed search of the effects of memantine in animal models of psychiatric disorders and its effects in human studies of specific psychiatric disorders. The bulk of the data relates to the effects of memantine in major depressive disorder and schizophrenia, although more recent studies have provided data on the use of the drug in bipolar disorder as an add-on. Despite interesting preclinical data, results in major depression are not encouraging. Animal studies investigating the possible usefulness of memantine in schizophrenia are controversial; however, interesting findings were obtained in open studies of schizophrenia, but negative placebo-controlled, double-blind studies cast doubt on their validity. The effects of memantine in anxiety disorders have been poorly investigated, but data indicate that the use of the drug in obsessive-compulsive disorder and post-traumatic stress disorder holds promise, while findings relating to generalized anxiety disorder are rather disappointing. Results in eating disorders, catatonia, impulse control disorders (pathological gambling), substance and alcohol abuse/dependence, and attention-deficit hyperactivity disorder are inconclusive. In most psychiatric non-Alzheimer's disease conditions, the clinical data fail to support the usefulness of memantine as monotherapy or add-on treatment However, recent preclinical and clinical findings suggest that add-on memantine may show antimanic and mood-stabilizing effects in treatment-resistant bipolar disorder.

The sustained mood-stabilizing effect of memantine in the management of treatment resistant bipolar disorders: findings from a 12-month naturalistic trial

BACKGROUND

We have recently provided preliminary clinical observations indicating that memantine, as augmenting agent, was associated with a meaningful antimanic and mood-stabilizing effect in treatment-resistant bipolar disorders. To further investigate the therapeutic and prophylactic action of the drug we administered memantine, as augmenting agent, to 40 treatment-resistant bipolar disorder patients, monitored and evaluated for 12 months.

METHODS

The sample population encompassed 40 treatment-resistant bipolar disorder patients monitored for 12 months. Memantine, at the dose of 10-30 mg/day, was added to the ongoing treatment, which was left unmodified. The severity of the patients' condition before memantine and the changes after memantine addition were evaluated on the Clinical Global Impression Bipolar (CGI-BP) Overall Bipolar Illness Scale. The severity of patients' condition was scored before memantine and the change was evaluated after memantine addition at 6 and 12 months.

LIMITATIONS

The present study has the limitations of an open clinical study and the observed effects require testing in a blinded, randomized, controlled trial which is planned.

RESULTS

The average CGI-BP score of the patients was 6.7 (SD=0.58, range: 5-7) before the addition of memantine. After 6 months of memantine treatment, 72.5% of patients were very much or much improved. Among the rapid cyclers 68.4% of patients reached stability, defined by the absence of recurrences. Patients very much or much improved were 72.5% at 12 months; while 12.5% discontinued memantine or were lost to follow-up.

CONCLUSIONS

The results confirm our previous observations and strongly suggest that memantine, as augmenting agent, was associated with a clinically substantial antimanic and sustained mood-stabilizing effect, with excellent safety and tolerability profile.

Alcohol-induced depressive-like behavior is associated with cortical norepinephrine reduction

Although strong positive association between alcoholism and depression is a common epidemiological observance, the causal relationship and the neurobiological substrates of such observations are far from clear. We have reported that chronic daily exposure to a relatively high dose of alcohol in rats can induce or exacerbate an already existing depressive-like behavior (Pharm Biochem Behav 91:97-103, 2008). Moreover, these effects of alcohol were blocked by pretreatment with desipramine, a tricyclic antidepressant, implicating a role for the biogenic amines in this type of depressive symptoms. In order to further delineate the involvement of specific neurotransmitters in alcohol-induced depressive symptoms, we examined the concentrations of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) in the frontal cortex and hippocampus following alcohol administration as well as pretreatment with two antidepressants, nomifensine and imipramine selective NE/DA and NE/5-HT uptake inhibitors, respectively. Adult female Wistar and Wistar-Kyoto (WKY) rats were exposed to alcohol via inhalation chambers (3h/day for 10 days) to achieve daily blood alcohol concentration of approximately 150 mg%. On day 11, the animals were evaluated for general locomotor activity (LCA) and performance in the forced swim test (FST), followed by neurochemical analyses. As expected WKY rats had lower LCA and higher immobility in the FST compared to Wistar rats. WKY rats also had lower levels of all three biogenic amines compared to Wistar rats in both areas. However, only cortical NE was reduced in both strains following alcohol administration. Treatments with nomifensine and imipramine blocked the behavioral and most of the neurochemical deficits caused by alcohol in both strains. These results implicate cortical NE as a major player in alcohol-induced depression. Moreover, it is suggested that selective NE uptake inhibitors may be of particular therapeutic potential in co-morbid condition of alcoholism and depression.

Effects of mood stabilizers on the inhibition of adenylate cyclase via dopamine D(2)-like receptors

OBJECTIVE

The mood stabilizing drugs lithium, carbamazepine and valproate modulate brain adenosine monophosphate (cAMP) levels, which are assumed to be elevated in bipolar disorder patients. The aim of this work was to investigate how these three mood stabilizing agents affect the regulation of cAMP levels by dopamine D(2)-like receptors in vitro in rat cortical neurons in culture and in vivo in the rat prefrontal cortex.

METHODS

The production of cAMP was measured in the cultured cortical neurons or in microdialysis samples collected from the prefrontal cortex of freely moving rats using the [8-(3)H] and [(125)I] radioimmunoassay kits.

RESULTS

In vitro and in vivo data showed that the treatment with the mood stabilizing drugs had no effect on basal cAMP levels in vitro, but had differential effects in vivo. Direct stimulation of adenylate cyclase (AC) with forskolin increased cAMP levels both in vitro and in vivo, and this effect was significantly inhibited by all three mood stabilizers. Activation of dopamine D(2)-like receptors with quinpirole partially inhibited forskolin-induced increase in cAMP in untreated cultures, but no effect was observed in cortical neuron cultures treated with the mood stabilizing drugs. Similar results were obtained by chronic treatment with lithium and valproate in the prefrontal cortex in vivo. However, surprisingly, in carbamazepine-treated rats the activation of dopamine D(2)-like receptors enhanced the responsiveness of AC to subsequent activation by forskolin, possibly as a consequence of chronic inhibition of the activity of the enzyme.

CONCLUSIONS

It was shown that each of these drugs affects basal- and forskolin-evoked cAMP levels in a distinct way, resulting in differential responses to dopamine D(2)-like receptors activation.

Chronic valproate fails to prevent imipramine-induced behavioural sensitization to the dopamine D2-like receptor agonist quinpirole

Based on experimental evidence suggesting a relationship between dopamine and mania, we proposed the antidepressant-induced dopaminergic supersensitivity as a model of antidepressant-related mania. We have previously shown the ability of carbamazepine, but not lithium, to prevent this phenomenon. Here we show that sodium valproate (50 mg/kg/day for 3 weeks) fails to prevent imipramine (20 mg/kg/day for 3 weeks)-induced sensitization to the locomotor response to the dopamine D2-like receptor agonist quinpirole (0.15 mg/kg). Since lithium, carbamazepine and valproate are all considered poorly effective in the treatment of antidepressant-related mania, the validity of the proposed model should be disproved by the carbamazepine results, to which, however, a pharmacokinetic mechanism might have concurred.

The serotonin/noradrenaline reuptake inhibitor venlafaxine attenuates acquisition, but not maintenance, of intravenous self-administration of heroin in rats

Opioids and antidepressants are frequently used for the treatment of various pain conditions. A combination of both drug classes may be more effective than either treatment alone, and combined treatment with an antidepressant may result in an opiate-sparing effect. Although it has been shown that antidepressants can attenuate self-administration of psychomotor stimulant and depressant drugs, it is not known whether they also attenuate self-administration of opiates. To determine whether venlafaxine, a serotonin/noradrenaline reuptake inhibitor with antidepressive and analgesic properties, affects acquisition and maintenance of intravenous heroin self-administration in rats, male Long-Evans rats were trained to press a lever in order to receive heroin (0.05 mg/kg/infusion) under a fixed ratio or a progressive ratio schedule. A control group was trained in a fixed ratio food-reinforced operant procedure. The effect of venlafaxine on operant responding for heroin and food was assessed both during acquisition and, in separate groups of rats, during maintenance (i.e., after acquisition) of self-administration behaviour. Daily treatment with venlafaxine (10 mg/kg i.p.) before the operant session attenuated the acquisition of responding for heroin, but not for food. However, when tested during the maintenance phase in rats showing stable responding, acute treatment with venlafaxine only marginally affected operant responding for heroin under a fixed ratio:10 schedule of reinforcement, and neither acute nor subchronic (once daily during 4 weeks) venlafaxine treatment affected responding under a progressive ratio schedule. Thus, daily treatment with an antidepressant attenuates the acquisition of heroin self-administration in a behaviourally specific manner, while having only marginal effects on maintenance of heroin self-administration.

Central monoamines and their role in major depression

The role of the monoamines serotonin and noradrenaline in mental illnesses including depression is well recognized. All antidepressant drugs in clinical use increase acutely the availability of these monoamines at the synapse either by inhibiting their neuronal reuptake, inhibiting their intraneuronal metabolism, or increasing their release by blocking the alpha(2) auto- and heteroreceptors on the monoaminergic neuron. This acute increase in the amount of the monoamines at the synapse has been found to induce long-term adaptive changes in the monoamine systems that end up in the desensitization of the inhibitory auto- and heteroreceptors including the presynaptic alpha(2) and 5-HT(1B) receptors and the somatodendritic 5-HT(1A) receptors located in certain brain regions. The desensitization of these inhibitory receptors would result in higher central monoaminergic activity that coincides with the appearance of the therapeutic response. These adaptive changes responsible for the therapeutic effect depend on the availability of the specific monoamine at the synapse, as depletion of the monoamines will either reverse the antidepressant effect or causes a relapse in the state of drug-free depressed patient previously treated with antidepressant drugs. Furthermore, blocking the somatodendritic 5-HT(1A) or nerve terminal alpha(2) receptors proved to increase the response rate in the treatment of major and treatment-resistant depression, providing further support to the assumption that the antidepressant effect results from the long-term adaptive changes in the monoamine auto- and heteroregulatory receptors. On the other hand, the chronic treatment with antidepressants resulted in D(2) receptors supersensitivity in the nucleus accumbens. This supersensitivity might play a role in the mechanisms underlying antidepressant induced mood switch and rapid cycling.

Reversal of antidepressant-induced dopaminergic behavioural supersensitivity after long-term chronic imipramine withdrawal

Chronic antidepressant treatments enhance dopaminergic neurotransmission in the mesolimbic dopamine system. We suggested that this potentiation might underlie both the antidepressant therapeutic effect and the antidepressant-induced switch from depression to mania, which in turn, might be involved in the development of rapid cycling in bipolar patients. In this study, we investigated the changes occurring in the sensitivity of the mesolimbic dopamine system up to 40 days after antidepressant withdrawal. Male Sprague-Dawley rats were treated for 3 weeks with imipramine (20 mg/kg) and tested for motor activity 24 h, 12, 33 and 40 days after treatment withdrawal. Ambulatory activity and rearing counts were recorded after challenge with the dopamine D2-like receptor agonist quinpirole (0.15 mg/kg). Imipramine increased the motor response to quinpirole, 24 h after treatment discontinuation. No relevant differences between the groups were found after 12 and 33 days. After 40 days, a decreased level of rearing was observed in the group treated with imipramine. These results show a reversal of the imipramine-induced dopaminergic supersensitivity after 40 days of chronic imipramine withdrawal and suggest that the mood-switches observed in bipolar patients following antidepressant treatment and subsequent withdrawal, i.e. mania followed by rebound depression, might depend upon parallel changes in the mesolimbic dopamine system sensitivity.

Carbamazepine prevents imipramine-induced behavioural sensitization to the dopamine D(2)-like receptor agonist quinpirole

Chronic treatment with antidepressants potentiates the behavioural sensitivity to the administration of dopamine receptor agonists. Such supersensitivity might be involved in the mechanism of action of antidepressant drugs, but it has also been suggested to play a role in the mechanisms underlying antidepressant treatment-related mania (i.e. antidepressant-induced mood switch and rapid cycling). Consistently to this hypothesis, we have recently shown that lithium salts, which are poorly effective in antidepressant-related mania, fail to prevent the development of imipramine-induced supersensitivity to the locomotor effect of the dopamine D(2)-like receptor agonist quinpirole. In the present paper, we report the ability of carbamazepine, an anticonvulsant with antimanic and mood stabiliser properties, to prevent the development of supersensitivity to the locomotor response to quinpirole induced by chronic treatment with imipramine. The present results, together with the results of our previous study, might contribute to explain the different responsiveness to lithium and carbamazepine observed in some manic patients, and are consistent with the clinical data suggesting that carbamazepine might be more effective than lithium in antidepressant-related mania.

Long-term lithium administration abolishes the resistance to stress in rats sensitized to morphine

Morphine sensitized rats appear protected from the sequelae of an unavoidable stress: when exposed to stress (after a 7-day morphine wash-out) and then tested for escape, they perform like naive animals. This protection appears similar to that induced by chronic imipramine treatment, as it is antagonized by the inhibition of D(1)-dopamine receptors before exposure to unavoidable stress. Repeated unavoidable stress induces in rats a condition characterized by hyporeactivity to noxious stimuli and reverted by long-term antidepressant treatments, and this state is regarded as an experimental model of depression. The resistance to stress in morphine sensitized rats could be considered as the behavioral counterpart of the sensitivity to stress in control rats, i.e. as a model of mania. The aim of the present study was to validate such a putative model by studying whether the resistance to stress induced by morphine sensitization would respond to a long-term administration of lithium, the reference antimanic drug. Long-term lithium treatment induces in rats a condition of hyporeactivity to noxious stimuli, accompanied by decreased levels of dopamine in the nucleus accumbens shell. In morphine sensitized rats chronic lithium abolished the resistance to stress, but it did not modify the D(1)-dopamine receptor mediated response to morphine, nor did it modify the levels of extraneuronal dopamine in the nucleus accumbens shell. Thus, lithium treatment abolished the resistance to stress in morphine sensitized rats, conferring predictive validity to the paradigm. Moreover, it did so through a mechanism which appeared to be independent of D(1)-dopamine receptor activity.