Two-way Active Avoidance Test Research Articles

Neuroinflammation in the prefrontal-amygdala-hippocampus network is associated with maladaptive avoidance behaviour

Maladaptive avoidance behaviour is often observed in patients suffering from anxiety and trauma- and stressor-related disorders. The prefrontal-amygdala-hippocampus network is implicated in learning and memory consolidation. Neuroinflammation in this circuitry alters network dynamics, resulting in maladaptive avoidance behaviour. The two-way active avoidance test is a well-established translational model for assessing avoidance responses to stressful situations. While some animals learn the task and show adaptive avoidance (AA), others show strong fear responses to the test environment and maladaptive avoidance (MA). Here, we investigated if a distinct neuroinflammation pattern in the prefrontal-amygdala-hippocampus network underlies the behavioural difference observed in these animals. Wistar rats were tested 8 times and categorized as AA or MA based on behaviour. Brain recovery followed for the analysis of neuroinflammatory markers in this network. AA and MA presented distinct patterns of neuroinflammation, with MA showing increased astrocyte, EAAT-2, IL-1β, IL-17 and TNF-ɑ in the amygdala. This neuroinflammatory pattern may underlie these animals' fear response and maladaptive avoidance. Further studies are warranted to determine the specific contributions of each inflammatory factor, as well as the possibility of treating maladaptive avoidance behaviour in patients with psychiatric disorders with anti-inflammatory drugs targeting the amygdala.

A Modified Two-Way Active Avoidance Test for Combined Contextual and Auditory Instrumental Conditioning.

Available two-way active avoidance paradigms do not provide contextual testing, likely due to challenges in performing repetitive trials of context exposure. To incorporate contextual conditioning in the two-way shuttle box, we contextually modified one of the chambers of a standard two-chamber rat shuttle box with visual cues consisting of objects and black and white stripe patterns. During the 5 training days, electrical foot shocks were delivered every 10 s in the contextually modified chamber but were signaled by a tone in the plain chamber. Shuttling between chambers prevented an incoming foot shock (avoidance) or aborted an ongoing one (escape). During contextual retention testing, rats were allowed to freely roam in the box. During auditory retention testing, visual cues were removed, and tone-signaled shocks were delivered in both chambers. Avoidance gradually replaced escape or freezing behaviors reaching 80% on the last training day in both chambers. Rats spent twice more time in the plain chamber during contextual retention testing and had 90% avoidance rates during auditory retention testing. Our modified test successfully assesses both auditory and contextual two-way active avoidance. By efficiently expanding its array of outcomes, our novel test will complement standard two-way active avoidance in mechanistic studies and will improve its applications in translational research.

Hyperactive behavioral phenotypes and an altered brain monoaminergic state in male offspring mice with perinatal hypothyroidism.

Thyroid hormone (TH) is essential for normal brain development. TH insufficiency during early stages of development may increase the risk for attention deficit/hyperactivity disorder, in which malfunction of brain monoaminergic systems is likely involved. However, little is known about the effects of perinatal hypothyroidism on behaviors and brain monoaminergic systems in offspring mice. The present study examined in mice (1) whether perinatal hypothyroidism causes hyperactive behavioral phenotypes, (2) how perinatal hypothyroidism influences brain monoaminergic systems, and (3) whether hyperactive behavioral phenotypes are associated with the state of brain monoaminergic systems. When dams were exposed to propylthiouracil, offspring mice developed hypothyroidism during the perinatal period. Offspring mice with perinatal hypothyroidism exhibited hyperactive behavioral phenotypes such as hyper-ambulatory activity and an increased response rate in the two-way active avoidance test in a male-specific manner. Significant decreases in dopamine (DA) and serotonin turnover were observed in the striatum (ST), nucleus accumbens, hypothalamus, and hippocampus in male mice with perinatal hypothyroidism. A significant correlation between ambulatory activity and DA turnover in the ST and an augmented ambulatory response to the DA reuptake inhibitor bupropion suggested that DA in the ST was involved in the hyper-ambulatory activity in mice with perinatal hypothyroidism.

Gene expression analysis of Arc mRNA as a neuronal cell activity marker in the hippocampus and amygdala in two-way active avoidance test in rats

IntroductionImmediate early genes are widely used as neuronal cell activity markers in neuroscience. The present study investigated the relationship between their expression and abnormality in context fear conditioning. MethodsThe learning test (two-way active avoidance test) was conducted in male rats administered with nonselective muscarinic antagonist scopolamine or selective dopamine D1-like receptor antagonist SCH 23390 at a dose level of 2.0 or 0.1mg/kg, respectively, for 4days. Expression levels of Arc and Fos mRNA in the hippocampus and amygdala were also evaluated on the second day of dosing by fluorescent in situ hybridization (FISH) and reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR). ResultsScopolamine had no effect on avoidance rate, but decreased freezing in the two-way active avoidance test. SCH 23390 decreased avoidance rate and increased freezing. In FISH and RT-qPCR assays, scopolamine decreased Arc mRNA in the hippocampus and amygdala, whereas SCH 23390 increased Arc mRNA in the hippocampus. By contrast, scopolamine and SCH 23390 did not change Fos mRNA expression compared to Arc mRNA expression. DiscussionThe results of the learning test indicated that scopolamine or SCH 23390 respectively inhibited fear or context conditioning in rats. Furthermore, alteration of the expression of Arc mRNA but not of Fos mRNA in the hippocampus and amygdala of the brain was suggested to be a sensitive neuronal cell activity marker to detect behavioral abnormality in the two-way active avoidance test.

A Window on the Study of Aversive Instrumental Learning: Strains, Performance, Neuroendocrine, and Immunologic Systems.

The avoidance response is present in pathological anxiety and interferes with normal daily functions. The aim of this article is to shed light on performance markers of active avoidance (AA) using two different rat strains, Sprague-Dawley (SD) and Wistar. Specifically, good and poor performers were evaluated regarding anxiety traits exhibited in the elevated plus maze (EPM) and corticosterone levels and motor activity in the open field test. In addition, the plasma levels of Interleukin-6 (IL-6), Interleukin-1Beta (IL-1beta), Nerve Growth Factor Beta (NGF-beta), Tumor Necrosis Factor-Alpha (TNF-alpha) and cytokine-induced neutrophil chemoattractant 1 (CINC-1) were compared in the good and poor performers to better understand the role of the immunologic system in aversive learning. Behavioral criteria were employed to identify subpopulations of SD and Wistar rats based on their behavioral scores during a two-way AA test. The animals were tested for anxiety-like behavior in the EPM and motor activity in the open-field test. Plasma corticosterone levels were measured at the end of the avoidance test. Cytokine levels of IL-6, IL-1beta, NGF-beta, TNF-alpha, and CINC-1 were measured in the plasma of the Wistar rats. Sixty-six percent of the Wistar rats and 35% of the SD rats exhibited a poor performance. This feature was associated with a decrease in anxiety-like behavior in the EPM. The poor and good performers exhibited lower levels of corticosterone compared with the control animals, which suggests that training alters corticosterone levels, thereby leading to hypocortisolism, independent of the performance. The CINC-1 levels were increased in the poor performers, which reinforces the role of immunologic system activation in learning deficits. Our study provides a better understanding of the complex interactions that underlie neuroimmune consequences and their implications for performance.

Exercise reduces diet-induced cognitive decline and increases hippocampal brain-derived neurotrophic factor in CA3 neurons

BackgroundPrevious studies have shown that a western diet impairs, whereas physical exercise enhances hippocampus-dependent learning and memory. Both diet and exercise influence expression of hippocampal brain-derived neurotrophic factor (BDNF), which is associated with improved cognition. We hypothesized that exercise reverses diet-induced cognitive decline while increasing hippocampal BDNF. MethodsTo test the effects of exercise on hippocampal-dependent memory, we compared cognitive scores of Sprague–Dawley rats exercised by voluntary running wheel (RW) access or forced treadmill (TM) to sedentary (Sed) animals. Memory was tested by two-way active avoidance test (TWAA), in which animals are exposed to a brief shock in a specific chamber area. When an animal avoids, escapes or has reduced latency to do either, this is considered a measure of memory. In a second experiment, rats were fed either a high-fat diet or control diet for 16weeks, then randomly assigned to running wheel access or sedentary condition, and TWAA memory was tested once a week for 7weeks of exercise intervention. ResultsBoth groups of exercised animals had improved memory as indicated by reduced latency to avoid and escape shock, and increased avoid and escape episodes (p<0.05). Exposure to a high-fat diet resulted in poor performance during both the acquisition and retrieval phases of the memory test as compared to controls. Exercise reversed high-fat diet-induced memory impairment, and increased brain-derived neurotrophic factor (BDNF) in neurons of the hippocampal CA3 region. ConclusionsThese data suggest that exercise improves memory retrieval, particularly with respect to avoiding aversive stimuli, and may be beneficial in protecting against diet induced cognitive decline, likely via elevated BDNF in neurons of the CA3 region.

Chronic exposure to WIN55,212-2 affects more potently spatial learning and memory in adolescents than in adult rats via a negative action on dorsal hippocampal neurogenesis

Several epidemiological studies show an increase in cannabis use among adolescents, especially in Morocco for being one of the major producers in the world. The neurobiological consequences of chronic cannabis use are still poorly understood. In addition, brain plasticity linked to ontogeny portrays adolescence as a period of vulnerability to the deleterious effects of drugs. The aim of this study was to investigate the behavioral neurogenic effects of chronic exposure to the cannabinoid agonist WIN55,212-2 during adolescence, by evaluating the emotional and cognitive performances, and the consequences on neurogenesis along the dorso-ventral axis of the hippocampus in adult rats. WIN55,212 was administered intraperitoneally (i.p.) once daily for 20days to adolescent (27–30PND) and adult Wistar rats (54–57PND) at the dose of 1mg/kg. Following a 20day washout period, emotional and cognitive functions were assessed by the Morris water maze test and the two-way active avoidance test. Twelve hours after, brains were removed and hippocampal neurogenesis was assessed using the doublecortin (DCX) as a marker for cell proliferation. Our results showed that chronic WIN55,212-2 treatment significantly increased thigmotaxis early in the training process whatever the age of treatment, induced spatial learning and memory deficits in adolescent but not adult rats in the Morris water maze test, while it had no significant effect in the active avoidance test during multitrial training in the shuttle box. In addition, the cognitive deficits assessed in adolescent rats were positively correlated to a decrease in the number of newly generated neurons in dorsal hippocampus. These data suggest that long term exposure to cannabinoids may affect more potently spatial learning and memory in adolescent compared to adult rats via a negative action on hippocampal plasticity.

Effect of acute administration of Mitragyna speciosa Korth. standardized methanol extract in animal model of learning and memory

Mitragyna speciosa Korth. or ketum is classified under medicinal plants, used by locals in Thailand and Malaysia to treat various types of diseases. Due to lack of information present on the effect of M. speciosa in learning and memory function, therefore this study is conducted to understand its effect on cognitive functions (learning and long-term memory). The aim of this study is to evaluate cognitive functions of rats after acute exposure of M. speciosa standardized methanol extract using avoidance tasks. Sprague-Dawley rats were treated with three different concentrations of M. speciosa standardized methanol extract (100, 500 and 1000 mg/kg). Morphine was given to positive control group and carboxyl-methyl-cellulose (CMC) and piracetam were given to negative control group. Learning and memory were evaluated using one-way passive avoidance test and two-way active avoidance test. This study showed significant improvement in learning acquisition in the M. speciosa standardized methanol extract treated group compared to controls, however no benefit was observed on memory consolidation, in both passive and active avoidance tests. In conclusion, acute administration of M. speciosa standardized methanol extract facilitated learning, but there was no benefit on long-term memory consolidation.

P.1.014 Time-dependent alterations of the endocannabinoid system and synaptic markers following adolescent delta-9-tetrahydrocannabinol (THC) administration in female rats

Several epidemiological studies show an increase in cannabis use among adolescents, especially in Morocco for being one of the major producers in the world. The neurobiological consequences of chronic cannabis use are still poorly understood. In addition, brain plasticity linked to ontogeny portrays adolescence as a period of vulnerability to the deleterious effects of drugs. The aim of this study was to investigate the behavioral neurogenic effects of chronic exposure to the cannabinoid agonist WIN55,212-2 during adolescence, by evaluating the emotional and cognitive performances, and the consequences on neurogenesis along the dorso-ventral axis of the hippocampus in adult rats. WIN55,212 was administered intraperitoneally (i.p.) once daily for 20 days to adolescent (27–30 PND) and adult Wistar rats (54–57 PND) at the dose of 1 mg/kg. Following a 20 day washout period, emotional and cognitive functions were assessed by the Morris water maze test and the two-way active avoidance test. Twelve hours after, brains were removed and hippocampal neurogenesis was assessed using the doublecortin (DCX) as a marker for cell proliferation. Our results showed that chronic WIN55,212-2 treatment significantly increased thigmotaxis early in the training process whatever the age of treatment, induced spatial learning and memory deficits in adolescent but not adult rats in the Morris water maze test, while it had no significant effect in the active avoidance test during multitrial training in the shuttle box. In addition, the cognitive deficits assessed in adolescent rats were positively correlated to a decrease in the number of newly generated neurons in dorsal hippocampus. These data suggest that long term exposure to cannabinoids may affect more potently spatial learning and memory in adolescent compared to adult rats via a negative action on hippocampal plasticity.

S.04.05 Effects of early exposure to ethanol and/or a cannabinoid receptor agonist on alcohol preference at adult age in mice

Several epidemiological studies show an increase in cannabis use among adolescents, especially in Morocco for being one of the major producers in the world. The neurobiological consequences of chronic cannabis use are still poorly understood. In addition, brain plasticity linked to ontogeny portrays adolescence as a period of vulnerability to the deleterious effects of drugs. The aim of this study was to investigate the behavioral neurogenic effects of chronic exposure to the cannabinoid agonist WIN55,212-2 during adolescence, by evaluating the emotional and cognitive performances, and the consequences on neurogenesis along the dorso-ventral axis of the hippocampus in adult rats. WIN55,212 was administered intraperitoneally (i.p.) once daily for 20 days to adolescent (27–30 PND) and adult Wistar rats (54–57 PND) at the dose of 1 mg/kg. Following a 20 day washout period, emotional and cognitive functions were assessed by the Morris water maze test and the two-way active avoidance test. Twelve hours after, brains were removed and hippocampal neurogenesis was assessed using the doublecortin (DCX) as a marker for cell proliferation. Our results showed that chronic WIN55,212-2 treatment significantly increased thigmotaxis early in the training process whatever the age of treatment, induced spatial learning and memory deficits in adolescent but not adult rats in the Morris water maze test, while it had no significant effect in the active avoidance test during multitrial training in the shuttle box. In addition, the cognitive deficits assessed in adolescent rats were positively correlated to a decrease in the number of newly generated neurons in dorsal hippocampus. These data suggest that long term exposure to cannabinoids may affect more potently spatial learning and memory in adolescent compared to adult rats via a negative action on hippocampal plasticity.

Preventive Action of Kai Xin San Aqueous Extract on Depressive-Like Symptoms and Cognition Deficit Induced by Chronic Mild Stress

Kai Xin San (KXS), a traditional Chinese herbal medicine, has been used clinically for the treatment of depressive disorders and cognitive impairment for centuries. However, the effects of KXS on cognitive dysfunction induced by depression have not been evaluated scientifically. The present study aimed to explore the antidepressant-like and nootropic effects of an aqueous extract of KXS (at doses of 0.3, 0.9, and 2.7 g/kg/day) using chronic mild stress (CMS) as a model of depression. Depressive symptoms were analyzed using the sucrose-preference and novelty-induced inhibition of feeding tests. Cognitive function was evaluated using a two-way active avoidance task. Serum corticosterone and adrenocorticotropic hormone (ACTH) levels, acetylcholinesterase (AChE) protein expression in the hippocampus, and monoamine neurotransmitter concentrations in the prefrontal cortex and hippocampus were also determined to elucidate the neurochemical mechanisms. Experimental results showed that KXS aqueous extract significantly ameliorated the CMS-induced depressive symptoms, including the reduced preference index and prolonged latency to novelty-suppressed feeding. Simultaneously, KXS significantly reversed the CMS-induced decrease in the numbers of active avoidance and active movement distances and increase in the numbers of the passive avoidance and passive movement distances, thereby producing nootropic effects in the two-way active avoidance test. KXS also inhibited the increased AChE expression in the hippocampus, up-regulated the decreased monoamine neurotransmitter concentrations of both brain areas and reduced the elevated ACTH concentrations in the serum induced by CMS. Taken together, these results indicate that KXS exerts its antidepressant-like and nootropic effects in the CMS model by modulating the HPA axis, monoamine neurotransmitter and cholinergic systems.

A comparative study on the effects of the benzodiazepine midazolam and the dopamine agents, apomorphine and sulpiride, on rat behavior in the two-way avoidance test

In recent years, studies in behavioral pharmacology have shown the involvement of dopaminergic mechanisms in avoidance behavior as assessed by the two-way active avoidance test (CAR). Changes in dopaminergic transmission also occur in response to particularly threatening challenges. However, studies on the effects of benzodiazepine (BZD) drugs in this test are still unclear. Given the interplay of dopamine and other neurotransmitters in the neurobiology of anxiety and schizophrenia the aim of this work was to evaluate the effects of systemic administration of midazolam, the dopaminergic agonist apomorphine, and the D 2 receptor antagonist sulpiride using the CAR, a test that shows good sensitivity to typical neuroleptic drugs. Whereas midazolam did not alter the avoidance response, apomorphine increased and sulpiride reduced them in this test. Escape was not affected by any drug treatments. Heightened avoidance was not associated with the increased motor activity caused by apomorphine. In contrast with the benzodiazepine midazolam, activation of post-synaptic D 2 receptors with apomorphine facilitates, whereas the D 2 receptor antagonism with sulpiride inhibited the acquisition of the avoidance behavior. Together, these results bring additional evidence for a role of D 2 mechanisms in the acquisition of the active avoidance.

Effect of repeated restraint stress on memory in different tasks.

The present study investigated the effect of repeated stress applied to female rats on memory evaluated by three behavioral tasks: two-way shuttle avoidance, inhibitory avoidance and habituation to an open field. Repeated stress had different effects on rat behavior when different tasks were considered. In the two-way active avoidance test the stressed animals presented memory of the task, but their memory scores were impaired when compared to all other groups. In the habituation to the open field, only the control group showed a significant difference in the number of rearings between training and testing sessions, which is interpreted as an adequate memory of the task. In the handled and chronically stressed animals, on the other hand, no memory was observed, suggesting that even a very mild repeated stress would be enough to alter habituation to this task. The performance in the inhibitory avoidance task presented no significant differences between groups. The findings suggest that repeated restraint stress might induce cognitive impairments that are dependent on the task and on stress intensity.

The modulatory effects of high affinity GABA(B) receptor antagonists in an active avoidance learning paradigm in rats.

It has been reported that selective GABA(B) receptor antagonists can enhance cognitive performance in a variety of learning paradigms. This prompted us to examine the effects of some more potent and newly synthesised GABAB antagonists CGP 71982, CGP 62349 and CGP 55845A in an active avoidance test in rats. A two-way active avoidance test with negative reinforcement was performed for the first 5 of 12 days of antagonist administration. CGP 71982 and CGP 55845A at all doses applied (0.01-1.0 mg/kg) had an improving effect on learning, and memory retention on day 12; the rats made more avoidances in both sessions compared to controls. CGP 62349 was only active at the lowest dose tested (0.01 mg/kg). The present study confirms that GABA(B) receptor antagonists can enhance cognitive performance but provides no insight into the mechanism of action of these novel antagonists.

Fetal Alcohol Effects in Rats Exposed Pre‐ and Postnatally to a Low Dose of Ethanol

Wistar rats were exposed pre- and/or postnatally to a low dose of ethanol (1 g/kg of body weight of dams/day) via maternal peroral intubation. This dose significantly increased the mortality rate (23 to 32% vs. 7% in controls) in offspring exposed to ethanol during pregnancy, with a continued postnatal exposure having no additional effect. However, offspring cross-fostered to dams that had been exposed to ethanol only during gestation (the offspring themselves never being directly exposed to ethanol) displayed an even greater (59%) mortality. Growth of the offspring was initially delayed, but 9 weeks after birth their body weight reached that of the controls. The two-way active avoidance test showed an impairment, compared with the controls, of learning and memory in both male and female adolescent (9-week-old) rats, as well as in male (but not in female) 5-month-old rats born of dams exposed to ethanol during gestation and lactation. In the group of male rats treated prenatally and postnatally with ethanol, 60% were "poor learners," compared with 33% in the control group. Results suggest that ethanol at a dose of 1 g/kg/day administered to dams during gestation and lactation produced growth and behavioral changes in the offspring.

Fetal Alcohol Effects in Rats Exposed Pre- and Postnatally to a Low Dose of Ethanol

Wistar rats were exposed pre- and/or postnatally to a low dose of ethanol (1 g/kg of body weight of dams/day) via maternal peroral intubation. This dose significantly increased the mortality rate (23 to 32% vs. 7% in controls) in offspring exposed to ethanol during pregnancy, with a continued postnatal exposure having no additional effect. However, offspring cross-fostered to dams that had been exposed to ethanol only during gestation (the offspring themselves never being directly exposed to ethanol) displayed an even greater (59%) mortality. Growth of the offspring was initially delayed, but 9 weeks after birth their body weight reached that of the controls. The two-way active avoidance test showed an impairment, compared with the controls, of learning and memory in both male and female adolescent (9-week-old) rats, as well as in male (but not in female) 5-month-old rats born of dams exposed to ethanol during gestation and lactation. In the group of male rats treated prenatally and postnatally with ethanol, 60% were “poor learners,” compared with 33% in the control group. Results suggest that ethanol at a dose of 1 g/kg/day administered to dams during gestation and lactation produced growth and behavioral changes in the offspring.

The effect of oxcarbazepine on behavioural despair and learned helplessness.

The effect of oxcarbazepine was evaluated in two tests of depression (forced swimming and learned helplessness) and in the open-field test. Acute (three times over 24 h) oxcarbazepine 80 mg/kg (but not 40 mg/kg) decreased immobility time in the forced swimming test. In the learned helplessness test, 4 days of treatment with oxcarbazepine 80 mg/kg reversed the deficits induced by foot-shock in rats submitted to the two-way active avoidance test. Oxcarbazepine 80 mg/kg did not modify the behaviour of rats in the open-field test, an indication that, at this dose, oxcarbazepine did not show a locomotor stimulatory effect. Thus, the data of the present study suggest that oxcarbazepine has a potential antidepressive effect.

Effects of GABA B receptor antagonists on learning and memory retention in a rat model of absence epilepsy

A variety of animal models of absence epilepsy have been described and among these exists a genetically susceptible strain of rat (genetic absence epilepsy rats of Strasbourg (GAERS)). These rats produce periods of behavioural arrest with simultaneous production of cortical spike and wave discharges (SWD). GABA B receptor antagonists suppress completely the production of these spike and wave discharges. GABA B receptor ligands have also been reported to affect cognitive performance in rodents. The present study examined the cognitive performance of GAERS and the influence of GABA B receptor antagonists on this activity. Rats were injected intraperitoneally once per day with saline or a GABA B receptor antagonist (CGP 36742 (3-amino-propyl- n-butyl-phosphinic acid) 100 mg/kg; CGP 56433 ([3-{1-( S)-[{3-(cyclohexylmethyl)hydroxy phosphinyl]-2-( S) hydroxy propyl] amino]ethyl]benzoic acid) ([3-{1-( S)-[{3-(cyclohexylmethyl)hydroxy phosphinyl]-2-( S) hydroxy propyl] amino]ethyl]benzoic acid) 1 mg/kg or CGP 61334 ([3-{[3-[(diethoxymethyl)hydroxy phosphinyl]propyl] amino}methyl]-benzoic acid (1 mg/kg). A two-way active avoidance test paradigm with negative reinforcement was used. Untreated GAERS performed significantly better than non-epileptic rats ( P<0.05) and this enhancement in cognitive performance was sustained in rats treated with the GABA B receptor antagonists.

Neuroprotective effect of chronic verapamil treatment on cognitive and noncognitive deficits in an experimental alzheimer's disease in rats

It is well known that disturbance of calcium homeostasis has a significant role in the development of neurodegenerative disorders, such as Alzheimer's disease (AD). Our recent data suggest that acute treatment with the calcium antagonist verapamil can improve some behavioral deficits in an experimental model of AD. Therefore, the present study was done to establish the effect of chronically administered verapamil on cognitive and noncognitive behavior of rats with bilateral electrolitical lesions of nucleus basalis manocellularis (NBM)—an animal model of AD. The NBM lesions produce a deficit in performance of diverse behavior tests: active avoidance (AA), low level of fear (the open field test) as well as aggressive (the test of foot-shock induced aggression) and depressive (the learned helplesness test) behavior. Verapamil (1.0, 2.5, 5.0 and 10.0 mg/kg i.p.) or saline solution (1 ml/kg i.p.) were injected 24 hr after the lesion of NBM and then repeatedly administered during the next 8 days (twice a day). Performance of the two-way active avoidance test, the open field test, the foot shock-induced aggression test and the learned helplessness test were done on day 4 after the last verapamil or saline treatment (day 13 after the lesion). Verapamil in doses of 2.5 and 5.0 mg/kg significantly ameliorated the deficit in the performance of AA, the open field behavior, and the depression, but not the aggressive behavior. The obtained beneficial effect of chronic administered verapamil suggests that the regulation of calcium homeostasis during the early period after NBM lesions might be a reasonable way to prevent the behavioral deficits in an experimental model of AD.