Evaluation of acetylcholinesterase in an animal model of mania induced by D-amphetamine

Quercetin relieves D-amphetamine-induced manic-like behaviour through activating TREK-1 potassium channels in mice

BACKGROUND AND PURPOSE

Quercetin is a well-known plant flavonoid with neuroprotective properties. Earlier work suggested it may relieve psychiatric disorders, cognition deficits and memory dysfunction through anti-oxidant and/or radical scavenging mechanisms. In addition, quercetin modulated the physiological function of some ion channels. However, the detailed ionic mechanisms of the bioeffects of quercetin remain unknown.

EXPERIMENTAL APPROACH

Effects of quercetin on neuronal activities in the prefrontal cortex (PFC) and its ionic mechanisms were analysed by calcium imaging using mice bearing a green fluorescent protein, calmodulin, and M13 fusion protein and patch clamp in acute brain slices from C57BL/6 J mice and in HEK 293 cells. The possible ionic mechanism of action of quercetin on D-amphetamine-induced manic-like effects in mice was explored with c-fos staining and the open field behaviour test.

KEY RESULTS

Quercetin reduced calcium influx triggered by PFC pyramidal neuronal activity. This effect involved increasing the rheobase of neuronal firing through decreasing membrane resistance following quercetin treatment. Spadin, a blocker of TREK-1 potassium channels, also blocked the effect of quercetin on the membrane resistance and neuronal firing. Further, spadin blocked the neuroprotective effects of quercetin. The effects of quercetin on TREK-1 channels could be mimicked by GF109203X, a protein kinase C inhibitor. In vivo, injection of quercetin relieved the manic hyperlocomotion in mice, induced by D-amphetamine. This action was partly alleviated by spadin.

CONCLUSION AND IMPLICATIONS

TREK-1 channels are a novel target for quercetin, by inhibiting PKC. This action could contribute to both the neuroprotective and anti-manic-like effects.

Coadministration of lithium and celecoxib attenuates the behavioral alterations and inflammatory processes induced by amphetamine in an animal model of mania

The present study evaluated the effects of the coadministration of lithium (Li) and Cel on inflammatory parameters in an animal model of mania induced by dextroamphetamine (D-amph). It was used Wistar rats 60 days old (250-350 g). The animals (n = 10 per group) received D-amph (2 mg/kg) or saline solution of NaCl 0.9% (Sal) intraperitoneally once a day for 14 days. From day eight until 14, the animals from the D-amph and Sal groups received Li (24 mg/kg), Cel (20 mg/kg), Li + Cel or water via gavage. Behavioral analyses were performed using the open-field test. The levels of IL-1β, IL-4, IL-10, and TNF-α were evaluated. The administration of D-amph induced hyperactivity in the rats, as well increased the IL-4, IL-10, and TNF-α levels in the serum, frontal cortex, and striatum of rats compared to those of the controls, and treatment with Li plus Cel reversed these alterations. In general, the administration of Li or Cel per se did not have effects on the behavioral and biochemical parameters. However, the treatment with Cel per se decreased only the IL-10 levels in the serum of animals. Besides, the treatment with Li or Cel decreased the IL-4 levels in the serum and reversed the effects of D-amph on this parameter in the frontal cortex. The treatment with Li reversed the effects of D-amph on the TNF-α levels in all tissues evaluated, and the administration of Cel reversed this alteration only in the striatum. It can be observed that treatment with Li plus Cel was more effective against damages caused by D-amph when compared to the administration of both treatments per se, suggesting that the coadministration can be more effective to treat BD rather than Li or Cel itself. The treatment with Li plus Cel was effective against the inflammation induced by D-amph.

Animal models for bipolar disorder: from bedside to the cage

Bipolar disorder is characterized by recurrent manic and depressive episodes. Patients suffering from this disorder experience dramatic mood swings with a wide variety of typical behavioral facets, affecting overall activity, energy, sexual behavior, sense of self, self-esteem, circadian rhythm, cognition, and increased risk for suicide. Effective treatment options are limited and diagnosis can be complicated. To overcome these obstacles, a better understanding of the neurobiology underlying bipolar disorder is needed. Animal models can be useful tools in understanding brain mechanisms associated with certain behavior. The following review discusses several pathological aspects of humans suffering from bipolar disorder and compares these findings with insights obtained from several animal models mimicking diverse facets of its symptomatology. Various sections of the review concentrate on specific topics that are relevant in human patients, namely circadian rhythms, neurotransmitters, focusing on the dopaminergic system, stressful environment, and the immune system. We then explain how these areas have been manipulated to create animal models for the disorder. Even though several approaches have been conducted, there is still a lack of adequate animal models for bipolar disorder. Specifically, most animal models mimic only mania or depression and only a few include the cyclical nature of the human condition. Future studies could therefore focus on modeling both episodes in the same animal model to also have the possibility to investigate the switch from mania-like behavior to depressive-like behavior and vice versa. The use of viral tools and a focus on circadian rhythms and the immune system might make the creation of such animal models possible.

Characterization of the Antinociceptive Mechanisms of Khat Extract (Catha edulis) in Mice

This study investigated the antinociceptive mechanisms of khat extract (100, 200, and 400 mg/kg, i.p.) in four pain models: two thermic (hot plate, tail-flick) and two chemical (acetic acid, formalin) models. Male mice were pretreated intraperitoneally (i.p.) with the opioid receptor blocker naloxone (5 mg/kg), the cholinergic antagonist atropine (2 mg/kg), the selective α₁ blocker prazosin (1 mg/kg), the dopamine D₂ antagonist haloperidol (1.5 mg/kg), or the GABA_A receptor antagonist, bicuculline (1 mg/kg) 15 minutes prior to i.p. injection of khat extract (400 mg/kg). Khat extract reduced the nociceptive response of mice in the four pain tests. Naloxone significantly inhibited the antinociceptive effect of khat extract in the hot plate, tail-flick, and the first phase of formalin tests. Bicuculline significantly antagonized the antinociceptive effect of khat extract on the hot plate and tail-flick tests. Haloperidol significantly reversed the antinociceptive effect of khat extract on the tail-flick test and the first phase of formalin test. These results provide strong evidence that the antinociceptive activity of khat extract is mediated via opioidergic, GABAergic, and dopaminergic pathways. The mechanism of the antinociceptive action of khat may be linked to the different types of pain generated in animal models.

Modeling bipolar disorder in mice by increasing acetylcholine or dopamine: chronic lithium treats most, but not all features

RATIONALE

Bipolar disorder (BD) is a disabling and life-threatening disease characterized by states of depression and mania. New and efficacious treatments have not been forthcoming partly due to a lack of well-validated models representing both facets of BD.

OBJECTIVES

We hypothesized that cholinergic- and dopaminergic-pharmacological manipulations would model depression and mania respectively, each attenuated by lithium treatment.

METHODS

C57BL/6 J mice received the acetylcholinesterase inhibitor physostigmine or saline before testing for "behavioral despair" (immobility) in the tail suspension test (TST) and forced swim test (FST). Physostigmine effects on exploration and sensorimotor gating were assessed using the cross-species behavioral pattern monitor (BPM) and prepulse inhibition (PPI) paradigms. Other C57BL/6 J mice received chronic lithium drinking water (300, 600, or 1200 mg/l) before assessing their effects alone in the BPM or with physostigmine on FST performance. Another group was tested with acute GBR12909 (dopamine transporter inhibitor) and chronic lithium (1000 mg/l) in the BPM.

RESULTS

Physostigmine (0.03 mg/kg) increased immobility in the TST and FST without affecting activity, exploration, or PPI. Lithium (600 mg/l) resulted in low therapeutic serum concentrations and normalized the physostigmine-increased immobility in the FST. GBR12909 induced mania-like behavior in the BPM of which hyper-exploration was attenuated, though not reversed, after chronic lithium (1000 mg/ml).

CONCLUSIONS

Increased cholinergic levels induced depression-like behavior and hyperdopaminergia induced mania-like behavior in mice, while chronic lithium treated some, but not all, facets of these effects. These data support a cholinergic-monoaminergic mechanism for modeling BD aspects and provide a way to assess novel therapeutics.

The catecholaminergic-cholinergic balance hypothesis of bipolar disorder revisited

Bipolar disorder is a unique illness characterized by fluctuations between mood states of depression and mania. Originally, an adrenergic-cholinergic balance hypothesis was postulated to underlie these different affective states. In this review, we update this hypothesis with recent findings from human and animal studies, suggesting that a catecholaminergic-cholinergic hypothesis may be more relevant. Evidence from neuroimaging studies, neuropharmacological interventions, and genetic associations support the notion that increased cholinergic functioning underlies depression, whereas increased activations of the catecholamines (dopamine and norepinephrine) underlie mania. Elevated functional acetylcholine during depression may affect both muscarinic and nicotinic acetylcholine receptors in a compensatory fashion. Increased functional dopamine and norepinephrine during mania on the other hand may affect receptor expression and functioning of dopamine reuptake transporters. Despite increasing evidence supporting this hypothesis, a relationship between these two neurotransmitter systems that could explain cycling between states of depression and mania is missing. Future studies should focus on the influence of environmental stimuli and genetic susceptibilities that may affect the catecholaminergic-cholinergic balance underlying cycling between the affective states. Overall, observations from recent studies add important data to this revised balance theory of bipolar disorder, renewing interest in this field of research.