Effects of chronic haloperidol treatment on the expression of fear memory and fear memory extinction in the cued fear-conditioned rats.

AIM: Impairments in emotional memory are frequently observed in several mental disorders, highlighting their significance as potential therapeutic targets. Recent research on the cued fear conditioning model has elucidated the neural circuits involved in fear memory processing. However, contradictory findings have been reported concerning the role of dopamine and the impact of dopamine D2 receptor (D2R) antagonists. There is notably limited knowledge regarding the clinical utility of chronic D2R antagonist treatments. This study aimed to uncover how such treatments affect fear memory processing. METHODS: We utilized a cued fear conditioning rat model and conducted chronic haloperidol treatment for 14 days. Subsequently, to investigate the effect of chronic haloperidol treatment on fear-conditioned memory expression and extinction, we observed freezing behavior under exposure to a conditioned stimulus for 14 days. RESULTS: Chronic haloperidol treatment suppressed freezing time on the fear memory expression. In contrast, a single haloperidol administration enhanced the freezing time on fear memory expression and delayed extinction. CONCLUSION: The results of this study suggest that chronic administration of antipsychotic drugs affects fear memory processing differently from single-dose administration. This indicates that the effects of chronic D2R antagonist treatment are distinct from the nonspecific effects of the drugs. This study provides fundamental insights that may contribute to our understanding of therapeutic mechanisms for fear memory disorders related to D2R in the future.

Effect of intermittent subchronic MK-801 administration on dopamine synthesis capacity and responsiveness in the prefrontal cortex.

AIM: The therapeutic potential of N-methyl-D-aspartate glutamate receptor (NMDAR) antagonists, particularly ketamine, in mood disorders, is linked to their modulation of dopamine dynamics in the medial prefrontal cortex (mPFC). However, conflicting effects of distinct NMDAR antagonists, like ketamine and phencyclidine, on mPFC dopamine levels stem from variances in their receptor affinity profiles. This study investigates the impact of intermittent subchronic administration of an NMDAR antagonist on dopamine synthesis capacity and responsiveness within the mPFC, focusing on Dizocilpine (MK-801), a highly selective NMDAR antagonist. METHODS: In vivo microdialysis and high-performance liquid chromatography assessed extracellular dopamine levels in the mPFC following subchronic MK-801 treatment. Locomotor activity was measured using a computed video tracking system. RESULTS: Intermittent subchronic MK-801 administration, followed by a 24-h withdrawal, preserved both dopamine synthesis capacity and responsiveness to MK-801 challenge in the mPFC. However, altered locomotor activity was observed, deviating from previous findings indicating impaired dopamine synthesis and responsiveness in the mPFC with twice-daily subchronic NMDAR antagonist treatment. CONCLUSION: These findings offer crucial biochemical insights into the diverse impacts of NMDAR antagonists on dopamine dynamics and the distinct therapeutic mechanisms associated with ketamine in depression treatment. However, further investigation is imperative to pinpoint potential inconsistencies stemming from variances in drug type, dosage, or administration frequency.

A case study of the utilization of clozapine treatment for treatment-resistant schizophrenia associated with 22q11.2 deletion syndrome.

BACKGROUND: The optimal treatment strategy for patients with treatment-resistant schizophrenia (TRS) associated with 22q11.2 deletion syndrome (DS) remains a subject of debate. CASE PRESENTATION: We present the case of a 40-year-old female patient diagnosed with TRS and 22q11.2DS who was effectively treated with clozapine. She was diagnosed with schizophrenia and mild intellectual disability during her adolescence; despite being hospitalized for a period of 10 years beginning in her 30s, she continued to exhibit symptoms of impulsivity, and explosive behavior, requiring periods of isolation. We ultimately decided to switch her medication to clozapine, which was administered with caution and gradually titrated upward, with no discernable adverse effects, resulting in a marked improvement in her symptoms and obviated the need for isolation. Subsequently, the patient's history of congenital heart disease and facial abnormalities prompted initial suspicions of a 22q11.2DS diagnosis, which was subsequently confirmed through genetic testing. CONCLUSION: Clozapine may serve as an efficacious pharmacological intervention for TRS patients with 22q11.2DS, including those of Asian descent.

Guidelines for diagnosis and treatment of depression in older adults: A report from the Japanese Society of mood disorders.

The Committee for Treatment Guidelines of Mood Disorders, Japanese Society of Mood Disorders, published a Japanese guideline for the treatment of late-life depression in 2020. Based on that guideline, the present guideline was developed and revised to incorporate the suggestions of global experts and the latest published evidence. In the diagnosis of late-life depression, it is important to carefully differentiate it from bipolar disorders, depressive states caused by physical and organic brain disease, drug effects, and dementia, and to determine the comorbidity between late-life depression and dementia. It is necessary to fully understand the clinical characteristics and psychosocial background of late-life depression, evaluate the patient's condition, and provide basic interventions based on these factors. Problem-solving therapy, reminiscence therapy/life review therapy, and behavioral activation therapy, and other forms of psychotherapy can reduce depressive symptoms. In terms of pharmacotherapy, newer antidepressants or non-tricyclic antidepressants are recommended for late-life depression, and it is recommended that the efficacy of least the minimal effective dosage should first be determined. Switching antidepressants and aripiprazole augmentation can be used to treatment-resistant therapy. Electroconvulsive therapy and repetitive transcranial magnetic stimulation have demonstrated usefulness for late-life depression. Exercise therapy, high-intensity light therapy, and diet therapy also show some effectiveness and are useful for late-life depression. Continuation therapy should be maintained for at least 1 year after remission.

Clinical Factors Associated with New-Onset Glucose Intolerance among Patients with Schizophrenia during Clozapine Treatment: All-Case Surveillance in Japan.

Clozapine (CLZ), an antipsychotic with a unique mechanism of action, is known to be superior to any other antipsychotic for schizophrenia. However, CLZ is also known to be associated with the development of lethal side effects, which include agranulocytosis and glucose intolerance (GI). Regular measurement and registration of blood test results have been mandatory for all CLZ users; however, these risks may still prevent therapists from prescribing CLZ. While CLZ-induced agranulocytosis has been well documented, CLZ-induced GI in the real world has not been fully investigated. Therefore, in this study, we used data registered in monitoring systems to investigate background factors associated with new-onset GI after CLZ administration and changes in HbA1c levels during CLZ treatment. Data of all patients with schizophrenia who were using CLZ from July 29, 2009 to January 20, 2016 were used for the analysis. Of the 3,746 patients enrolled in the study, 92 (2.5%) had GI at baseline; of the remaining 3,654 patients, 428 (11.7%) developed new-onset GI. Multivariate logistic regression analysis revealed that the development of new-onset GI was significantly associated with older age, higher baseline HbA1c levels, and longer treatment duration. In patients with GI at baseline, HbA1c levels were maintained or improved over 18 months, while in the other patients, CLZ administration gradually elevated HbA1c levels. The findings of this study suggest that, although adequate monitoring and intervention is required, CLZ induction and maintenance therapy may be safe, even for patients with impaired glucose tolerance.

Clozapine-induced agranulocytosis in Japan: Changes in leukocyte/neutrophil counts before and after discontinuation of clozapine.

OBJECTIVE: To determine the prevalence, background factors, and progression of and recovery from clozapine-induced agranulocytosis in Japan. METHODS: Data on treatment-resistant schizophrenia patients registered with the Clozaril Patient Monitoring Service (CPMS) between July 29, 2009 and January 20, 2016 were extracted. Patients with a neutrophil count <500/mm3 were defined as having agranulocytosis, and those with a leukocyte count <3,000/mm3 or a neutrophil count <1,500/mm3 but not meeting the criteria for agranulocytosis were defined as having leukopenia/neutropenia. RESULTS: Of 3,746 patients, agranulocytosis and leukopenia/neutropenia were observed in 38 (1.0%) and 182 (4.9%) patients, respectively. Age was significantly higher in the agranulocytosis group (p < .001). Decreased leukocyte counts 1 week prior to discontinuation were observed only in the agranulocytosis group. The median number of days to recovery from agranulocytosis and leukopenia/neutropenia was 10 and 4, respectively, with more variation in the latter. CONCLUSIONS: Although some patients with leukopenia/neutropenia might carry less pathologic significance, the results of this study reconfirmed the importance of regular blood monitoring for preventing agranulocytosis.

Escitalopram attenuates fear stress-induced increase in amygdalar dopamine following methamphetamine-induced sensitisation: Implications of fine-tuning action of selective serotonin reuptake inhibitors on emotional processing.

Serotonin reuptake inhibitors modulate the serotonergic pathways of the nervous system and are widely used for treating psychiatric conditions such as anxiety and depression. The dopaminergic system is related to the development of these conditions. Previous studies on methamphetamine-sensitised rats (behavioural models of stress vulnerability) have shown increased release of dopamine in response to conditioned stress in the amygdala. This biochemical abnormality was proposed to underlie the pathophysiology of stress vulnerability. However, the effect of serotonin reuptake inhibitors on dopamine levels and its consequent impact on emotional processing is unclear. Here we examined the acute effect of escitalopram, a highly selective serotonin reuptake inhibitor, on fear-related behaviour, baseline dopamine release and dopamine release in response to conditioned fear stress in the amygdala of model rats. Male Sprague-Dawley rats received 2 mg/kg/day, s.c. of methamphetamine for 10 days to sensitise them to the drug, and a fear conditioning paradigm was instituted to model psychological stress. Dopamine changes in the amygdala in response to systemic administration of escitalopram followed by conditioned fear stress were measured using microdialysis and high-performance liquid chromatography. Baseline dopamine release in the amygdala was increased by escitalopram in non-sensitised rats but not in methamphetamine-sensitised rats. Escitalopram attenuated dopamine release in response to the fear-conditioned stimulus in both sensitised and non-sensitised rats. The extent of suppression in methamphetamine-sensitised rats (- 90%) was greater than that in non-sensitised rats (- 48%). These findings suggest that serotonin reuptake inhibitors indirectly stabilise the dopaminergic pathway and modulate emotional processing in the amygdala.

Diazepam suppresses the stress-induced dopaminergic release in the amygdala of methamphetamine-sensitized rat.

Although the benzodiazepine class of drugs has proven useful in treating anxiety symptoms, recent studies yield no consistent empirical support for their use in treating psychiatric disorders. However, animal studies using a fear conditioning paradigm have suggested that benzodiazepines facilitate fear memory extinction, dependent on treatment timing and subject conditions. However, we have no data on the effect of subject conditions. The purpose of this study was to investigate whether the effect of benzodiazepines depends on hypersensitivity to fear-memory processing. We examined the effect of diazepam, a benzodiazepine, on the extracellular dopamine level in the left amygdala of methamphetamine-sensitized, fear-conditioned model rats, using microdialysis and high-performance liquid chromatography. In this model, the dopamine level in the amygdala excessively increases in response to a fear-conditioned stimulus; the phenomenon has been proposed as a biological marker for hypersensitivity to fear-memory processing. Diazepam inhibited this excessive increase. The extent of the inhibitory effect was greater in the sensitized condition. Diazepam alone increased amygdalar dopamine levels under physiological conditions but not under sensitized conditions. Diazepam did not shorten freezing time in any group. These results suggest that diazepam modulates amygdala dopamine with state dependence and that amygdalar dopamine fine-tuning accounts for part of the therapeutic effect of benzodiazepines on fear memory processing. Further investigation is required to identify patients suitable for treatment with benzodiazepines. This is the first report on the pharmacodynamic effects of benzodiazepine on the amygdalar dopamine basal level and on fear memory processing.

Dopamine dynamics during emotional cognitive processing: Implications of the specific actions of clozapine compared with haloperidol.

Clozapine has improved efficacy relative to typical antipsychotics in schizophrenia treatment, particularly regarding emotional symptoms. However, the mechanisms underlying its therapeutic benefits remain unclear. Using a methamphetamine-sensitised rat model, we measured changes in dopamine levels in the amygdalae in response to a fear-conditioned cue, serving as a biochemical marker of emotional cognitive processing disruption in psychosis, for analysing the biochemical mechanisms associated with the clinical benefits of clozapine. We also compared how clozapine and haloperidol affected basal dopamine levels and phasic dopamine release in response to the fear-conditioned cue. Extracellular dopamine was collected from the amygdalae of freely moving rats via microdialysis and was analysed by high-performance liquid chromatography. Clozapine or haloperidol was injected during microdialysis, followed by exposure to the fear-conditioned cue. We analysed the ratio of change in dopamine levels from baseline. Haloperidol treatment increased the baseline dopamine levels in both non-sensitised and sensitised rats. Conversely, clozapine only increased the basal dopamine levels in the non-sensitised rats, but not in the sensitised rats. Although both antipsychotics attenuated phasic dopamine release in both the non-sensitised and sensitised rats, the attenuation extent was greater for clozapine than for haloperidol under both dopaminergic conditions. Our findings indicate that stabilized dopamine release in the amygdalae is a common therapeutic mechanism of antipsychotic action during emotional processing. However, the specific dopaminergic state-dependent action of clozapine on both basal dopamine levels and stress-induced dopamine release may be the underlying mechanism for its superior clinical effect on emotional cognitive processing in patients with schizophrenia.