Lithium effects on active and passive avoidance behavior in the rat

Mission impossible: Reach the carrion in a lithium pollution and marine warming scenario

In this study we investigated the independent and synergistic effects of lithium (Li, 0.08 mM) contamination and the rising seawater temperature (21 °C; control- 15 °C) on survival and trophic interactions (foraging behaviour, success, search time, carrion preference, feeding time, and tissue consumption-the dry weight basis) of the opportunistic intertidal scavenger Tritia neritea. Trophic interactions were assessed in a two-choice test using a Y-maze design using the same amount of two carrion species (Solen marginatus and Mytilus galloprovincialis) given to all snails simultaneously. Lithium pollution and synergestic warming have the effect of reducing the survival rate of T. neritea, triggering potential global change scenarios. The foraging behaviour of T. neritea under Li-contaminated conditions was characterised by a decrease in the snail's effectiveness in finding a carrion. Lithium changes the feeding behaviour as well as increasing the time it takes for snails to reach their food. T. neritea did not show preference for any of the carrion species offered in controls, but a shift in feeding behaviour towards more energetic carrion under Li contamination which may indicate a strategy to compensate for the greater energy expenditure necessary to survive. There were no differences in feeding time at the different treatments and regardless of the treatment tested T. neritea consumed more mussels tissue probably due to its greater palatability. Results showing foraging modifications in an intertidal scavenger mollusc in global change scenarios indicate potential changes in complex trophic interactions of marine food webs.

Lithium prevents REM sleep deprivation-induced impairments on memory consolidation

BACKGROUND

Pre-training rapid eye movement sleep (REMS) deprivation affects memory acquisition and/or consolidation. It also produces major REMS rebound at the cost of waking and slow wave sleep (SWS). Given that both SWS and REMS appear to be important for memory processes, REMS rebound after training may disrupt the organization of sleep cycles, i.e., excessive amount of REMS and/or little SWS after training could be harmful for memory formation.

OBJECTIVE

To examine whether lithium, a drug known to increase SWS and reduce REMS, could prevent the memory impairment induced by pre-training sleep deprivation.

DESIGN

Animals were divided in 2 groups: cage control (CC) and REMS-deprived (REMSDep), and then subdivided into 4 subgroups, treated either with vehicle or 1 of 3 doses of lithium (50, 100, and 150 mg/kg) 2 h before training on the multiple trial inhibitory avoidance task. Animals were tested 48 h later to make sure that the drug had been already metabolized and eliminated. Another set of animals was implanted with electrodes and submitted to the same experimental protocol for assessment of drug-induced sleep-wake changes.

SUBJECTS

Wistar male rats weighing 300-400 g.

RESULTS

Sleep deprived rats required more trials to learn the task and still showed a performance deficit during test, except from those treated with 150 mg/kg of lithium, which also reduced the time spent in REM sleep during sleep recovery.

CONCLUSION

Lithium reduced rapid eye movement sleep and prevented memory impairment induced by sleep deprivation. These results indicate that these phenomena may be related, but cause-effect relationship cannot be ascertained.

Anti-anhedonic activity of long-term lithium treatment in rats exposed to repeated unavoidable stress

Behavioural and neurochemical responses to palatable food exposure represent an index of hedonic competence. In rats, a palatable meal increases extra-neuronal dopamine levels in the nucleus accumbens shell (NAcS) that confers to it incentive salience and reinforcing value. Repeated stress exposure decreases dopamine output and impairs the NAcS dopaminergic response to palatable food and the competence to acquire a vanilla sugar (VS)-reinforced instrumental behaviour [VS-sustained appetitive behaviour (VAB)]. Moreover, chronic stress exposure disrupts reactivity to aversive stimuli. A 3-wk treatment with lithium, the gold-standard treatment in bipolar disorder, tonically reduces NAcS dopamine output and the reactivity to aversive stimuli. However, it does not affect the dopaminergic response to VS and the competence to acquire VAB. This study investigated whether repeated lithium administration is endowed with anti-anhedonic activity. The NAcS dopaminergic response to VS and the competence to acquire VAB and sucrose self-administration (SA), in terms of fixed-ratio (FR)1, FR5 and progressive ratio schedules of reinforcement, were studied in saline or lithium-treated groups of non-food-deprived rats exposed or not to repeated unavoidable stress. Chronic stress exposure impaired the NAcS dopaminergic response to VS, acquisition of VAB and sucrose SA, in terms of FR1 and FR5 schedules of reinforcement and breaking point score. Repeated lithium treatment restored these parameters to control group values, even when treatment began in rats already showing an anhedonia-like condition. Since the breaking point defines the reinforcement efficacy of a hedonic stimulus, the present data suggest that lithium treatment is endowed with anti-anhedonic activity in rats.

Enhancing effects of chronic lithium treatment on detour learning in chicks

Lithium is the first line of therapeutic drugs used to treat both mania and depression in bipolar disorder.Although a body of research suggests that lithium acts as a cognitive enhancer, other animal studies suggest that lithium induces cognitive deficits. Comparatively, the effects of lithium on cognitive behaviour in these studies are inconsistent and contradictory. Further investigations in different species of animals and behavioural tasks are important to evaluate the possibility that lithium may act as a cognitive enhancer. In the present study, the chicks were treated intraperitoneally with lithium chloride (120 mg/kg), and the effects of chronic lithium treatment on chick cognitive behaviour were examined using a detour learning task.Additionally, the effects of chronic lithium treatment on BDNF messenger RNA (mRNA) expression were measured in RTPCR. We found that chronic lithium treatment(120 mg/kg) had no effect on spontaneous motor activity or weight gain of the chicks and that the chicks had a general healthy appearance, while chronic lithium treatment significantly promoted the response latency of detour learning and BDNF mRNA expression. These results suggest that chronic lithium treatment may improve cognitive function.

Abnormalities in brain structure and behavior in GSK-3alpha mutant mice

BACKGROUND

Glycogen synthase kinase-3 (GSK-3) is a widely expressed and highly conserved serine/threonine protein kinase encoded by two genes that generate two related proteins: GSK-3alpha and GSK-3beta. Mice lacking a functional GSK-3alpha gene were engineered in our laboratory; they are viable and display insulin sensitivity. In this study, we have characterized brain functions of GSK-3alpha KO mice by using a well-established battery of behavioral tests together with neurochemical and neuroanatomical analysis.

RESULTS

Similar to the previously described behaviours of GSK-3beta(+/-) mice, GSK-3alpha mutants display decreased exploratory activity, decreased immobility time and reduced aggressive behavior. However, genetic inactivation of the GSK-3alpha gene was associated with: decreased locomotion and impaired motor coordination, increased grooming activity, loss of social motivation and novelty; enhanced sensorimotor gating and impaired associated memory and coordination. GSK-3alpha KO mice exhibited a deficit in fear conditioning, however memory formation as assessed by a passive avoidance test was normal, suggesting that the animals are sensitized for active avoidance of a highly aversive stimulus in the fear-conditioning paradigm. Changes in cerebellar structure and function were observed in mutant mice along with a significant decrease of the number and size of Purkinje cells.

CONCLUSION

Taken together, these data support a role for the GSK-3alpha gene in CNS functioning and possible involvement in the development of psychiatric disorders.

Lithium and cognitive enhancement: leave it or take it?

RATIONALE

Lithium is established as an effective treatment of acute mania, bipolar and unipolar depression and as prophylaxis against bipolar disorder. Accumulating evidence is also delineating a neuroprotective and neurotrophic role for lithium. However, its primary effects on cognitive functioning remain ambiguous.

OBJECTIVES

The aim of this paper is to review and combine the relevant translational studies, focusing on the putative cognitive enhancement properties of lithium, specifically on learning, memory, and attention.

DISCUSSION

These properties are also discussed in reference to research demonstrating a protective action of lithium against cognitive deficits induced by various challenges to the nervous system, such as stress, trauma, neurodegenerative disorders, and psychiatric disorders.

CONCLUSIONS

It is suggested on the basis of the evidence that the cognitive effects of lithium are best expressed and should, therefore, be sought under conditions of functional or biological challenge to the nervous system.

The behavioral actions of lithium in rodent models: leads to develop novel therapeutics

For nearly as long as lithium has been in clinical use for the treatment of bipolar disorder, depression, and other conditions, investigators have attempted to characterize its effects on behaviors in rodents. Lithium consistently decreases exploratory activity, rearing, aggression, and amphetamine-induced hyperlocomotion; and it increases the sensitivity to pilocarpine-induced seizures, decreases immobility time in the forced swim test, and attenuates reserpine-induced hypolocomotion. Lithium also predictably induces conditioned taste aversion and alterations in circadian rhythms. The modulation of stereotypy, sensitization, and reward behavior are less consistent actions of the drug. These behavioral models may be relevant to human symptoms and to clinical endophenotypes. It is likely that the actions of lithium in a subset of these animal models are related to the therapeutic efficacy, as well the side effects, of the drug. We conclude with a brief discussion of various molecular mechanisms by which these lithium-sensitive behaviors may be mediated, and comment on the ways in which rat and mouse models can be used more effectively in the future to address persistent questions about the therapeutically relevant molecular actions of lithium.

Enhancing effects of chronic lithium on memory in the rat

BACKGROUND

In spite of recent enrichment of neurochemical and behavioural data establishing a neuroprotective role for lithium, its primary effects on cognitive functioning remain ambiguous. This study examines chronic lithium effects on spatial working memory and long-term retention.

METHODS

In three discrete experiments, rats subjected to 30 daily intraperitoneal injections (2mmol/kg) of lithium (lithium groups: serum lithium=0.5+/-0.4mEq/l, 12h post-injection) or saline (controls) were trained in 0-s delay T-maze alternation and then tested in 30-, 45- and 60-s delay alternation (Experiments 1, 2, 3, respectively). Animals from Experiment 1 were further tested in one-trial step-through passive avoidance under mild shock parameters (0.5mA, 1s). Retention was assessed 6h later. Daily lithium or saline injections continued throughout behavioural testing.

RESULTS

Lithium animals were indistinguishable from controls during 0-delay alternation baseline (Experiments 1-3, accuracy>88%) but showed significantly higher accuracy than controls at 30- and 45-s delays (93% versus 85% and 92% versus 82%, Experiments 1 and 2, respectively). At 60-s delay (Experiment 3) this beneficial effect of lithium was no longer apparent (lithium and control accuracy=78%). In Experiment 4, the shock used did not support 6-h passive avoidance retention in controls, whereas lithium animals showed significant step-through latency increases.

CONCLUSIONS

Chronic lithium enhanced spatial working memory and promoted long-term retention of a weak aversive contingency. The results suggest that lithium may have potential as a cognitive enhancer.

Lithium effects on adjunctive alcohol consumption. III: FT-shock as the inducing schedule

Under conditions in which a mild shock (0.5 mA, 200 msec) was delivered, independently of the subject's behavior, every 90 sec (an FT 90-sec shock schedule), subjects receiving chronic lithium chloride in their drinking water (25 mEq/l), showed a rapid acquisition of an adjunctive alcohol consumption, while subjects in the control groups did not. Following termination of the FT-shock condition (extinction), subjects in all groups showed an increase in alcohol consumption, relative to both baseline and adjunctive levels.

Effects of lithium on appetitive discrimination in the rat

1. The present study attempted to test the hypothesis that lithium (as chloride, 0.15 mEq/kg) promotes an attentional focus onto stimulation of high salience (Cappeliez and Moore 1988). 2. The effect of lithium treatment was studied within the context of discrimination learning in a Y-maze. 3. When the brightness cue (illuminated/dark goal arm) signalled reinforcement (food) and the spatial cue (right/left location of goal arm) acted as a distractor, lithium-treated rats showed evidence of increased readiness to focus onto the brightness cue. 4. When these experimental conditions were reversed in a second experiment, with the brightness cue now acting as a distractor, the performance of the lithium-treated rats was adversely affected. 5. These results are interpreted as supporting the hypothesis that, under the influence of this dose of lithium, rats are more likely to maintain their attention on stimulation of high salience, with accompanying reduction in the processing of peripheral stimulation. The implications of this theory for the understanding of lithium's action and manic-depressive conditions are discussed.

Effects of lithium on latent inhibition in the rat

1. A latent inhibition paradigm was used to test the proposition that lithium increases rats' capacity to ignore an irrelevant stimulation. 2. In latent inhibition, non-reinforced presentations of the stimulus in the preexposure phase are said to lead the animal to ignore this stimulus, therefore reducing its later associability with a UCS. 3. Lithium (as chloride, 0.15 mEq/kg, for 6 days) counteracted the latent inhibition and impaired the acquisition of the conditioned response in the nonpreexposed condition. These results were attributed to an increased focus on stimuli of high salience, produced by lithium. 4. This interpretation was supported in a second experiment which demonstrated that enhancing opportunities for detailed inspective exploration of the apparatus before the initiation of conditioning markedly impaired the learning of rats treated for up to 7 days with 0.15 mEq/kg lithium chloride. 5. These findings are discussed within the context of the hypothesis that lithium narrows the breadth of attention onto stimuli of high salience at the expense of the processing of stimuli of low salience.

Lithium chloride stabilizes systolic blood pressure and increases adrenal catecholamines in the spontaneously hypertensive rat

The effects of daily, intraperitoneal injections of LiCl (3 mEq/kg) on systolic blood pressure (SBP) and adrenal catecholamine levels were measured in spontaneously hypertensive rats (SHR) and in normotensive Wistar-Kyoto rats (WKY). Control animals from each strain were injected with equivalent volumes (0.1 ml/100 g b.wt.) of 0.9% saline (0.15 mEq/kg). SBP in LiCl-treated SHR was significantly lower (p less than 0.05) than that of saline-treated SHR (177 +/- 7 vs. 196 +/- 4 mm Hg, respectively) after one week. After two weeks SBP was lower in LiCl SHR than in saline controls, but this difference was not significant. While SBP of both LiCl and saline treated WKY was not significantly different (146 +/- 4 vs. 147 +/- 8 mm Hg, respectively), SBP in both WKY groups remained lower than the SBP for either group of SHR. LiCl induced a significant weight loss in the SHR, but not in the WKY. Adrenal norepinephrine and epinephrine were significantly (p less than 0.05) higher in LiCl-treated rats of both strains; dopamine was also higher in LiCl-treated rats of both strains, but significant only between SHR-LiCl and SHR controls. It appears that LiCl's effect in slowing the development of hypertension is independent of its action on adrenal catecholamines. The SHR's increased sensitivity to LiCl, relative to weight loss and SBP, may reflect differences in genetic or physiological status of the animal compared to WKY. These differences may be associated with alterations in membrane ion transport systems.

Lithium effects on adjunctive alcohol consumption. II: Effects of adding concurrent shock

Rats receiving chronic administration of lithium chloride (20 mEq/l) in their drinking water were tested for adjunctive alcohol (10% v/v) consumption in which temporally scheduled, noncontingent shock delivery was added following the establishment of food delivery-based adjunctive alcohol intake. The addition of shock to the eliciting schedule produced an initial reduction in alcohol consumption (Lithium subjects took longer to reach maximal suppression of drinking than did Controls), with a subsequent return to preshock levels for both groups. The reduction in alcohol consumption seen in control subjects following the discontinuation of food and shock delivery (extinction) was interpreted as suggesting that adding conflict/stress to established drinking conditions may facilitate subsequent extinction of that drinking behavior. Lithium subjects produced an initial suppression of drinking, with alcohol consumption returning to adjunctive levels by the end of the extinction series, suggesting that lithium decreases conflict/stress effects, that it impairs extinction processes, that it increases the reinforcing value of alcohol, or that it produces a combination of the three outcomes.

Effects of lithium and rubidium on shock-induced changes in open-field activity

Lithium chloride and rubidium chloride were tested under conditions in which the effects of their chronic administration on aversively-controlled behavior could be assessed. Lithium attenuated shock-induced suppression of open-field activity when that suppression was under the control of mild or moderate stimulus parameters, but had no effect on the suppression produced by the presence of shock itself. Rubidium, on the other hand, increased shock-induced suppression under all conditions. When shock was removed and extinction of the activity suppression was investigated, lithium subjects failed to return to their original baseline activity levels, while subjects receiving rubidium recovered baselines in a manner indistinguishable from that observed in control animals.

Lithium effects on position learning with exploratory and aversive goal-box conditions

Under conflict conditions in which reinforcement occurred within mildly aversive white goal-boxes, the chronic administration of lithium chloride (20 meg/l, in drinking water) to rats, while reducing avoidance of the goal boxes, impaired acquisition of an exploration-reinforced position discrimination. These results were interpreted as supporting the concept that lithium salts reduce the individual's reaction to general environmental stimulation--an effect which may account for its therapeutic action in the treatment of manic disorders.