Early-life risperidone administration alters maternal-offspring interactions and juvenile play fighting

Sex difference alters the behavioral and cognitive performance in a rat model of schizophrenia induced by sub-chronic ketamine

Schizophrenia is a complex neuropsychiatric disorder with positive, negative, and cognitive symptoms. In rats, sub-chronic administration of ketamine is used for the induction of schizophrenia model. Increased locomotor activity is one of the most important features of psychotic-like symptoms in rodents. On the other hand, risperidone is a potent antipsychotic medication that is approved for the treatment of schizophrenia and bipolar disorder. In the present research, we aimed to investigate the effect of sub-chronic treatment of ketamine on cognitive and behavioral functions, and brain-derived neurotrophic factor (BDNF) expression level in the prefrontal cortex. Also, we assessed the efficacy of risperidone on cognitive and behavioral impairments induced by ketamine. Possible sex differences were also measured. Ketamine was intraperitoneally injected at the dose of 30 mg/kg for five consecutive days. Risperidone was also intraperitoneally injected at the dose of 2 mg/kg. Novel object recognition memory, pain threshold, locomotor activity, rearing behavior, and BDNF level were evaluated. The results showed that ketamine injection for five consecutive days impaired the acquisition of long-term recognition memory and decreased BDNF level in the prefrontal cortex in both sexes. Also, it decreased pain threshold in females, increased rearing behavior in males, and induced hyperlocomotion with greater effect in females. On the other hand, risperidone restored or attenuated the effect of ketamine on all the behavioral effects and BDNF level. In conclusion, we suggested that there were sex differences in the effects of ketamine on pain perception, locomotion, and rearing behavior in a rat model of schizophrenia.

Early-life risperidone alters locomotor responses to apomorphine and quinpirole in adulthood

An escalating trend of antipsychotic drug use in children with ADHD, disruptive behavior disorder, or mood disorders has raised concerns about the impact of these drugs on brain development. Since antipsychotics chiefly target dopamine receptors, it is important to assay the function of these receptors after early-life antipsychotic administration. Using rats as a model, we examined the effects of early-life risperidone, the most prescribed antipsychotic drug in children, on locomotor responses to the dopamine D1/D2 receptor agonist, apomorphine, and the D2/D3 receptor agonist, quinpirole. Female and male Long-Evans rats received daily subcutaneous injections of risperidone (1.0 and 3.0 mg/kg) or vehicle from postnatal day 14-42. Locomotor responses to one of three doses (0.03, 0.1, and 0.3 mg/kg) of apomorphine or quinpirole were tested once a week for four weeks beginning on postnatal day 76 and 147 for each respective drug. The locomotor activity elicited by the two lower doses of apomorphine was significantly greater in adult rats, especially females, administered risperidone early in life. Adult rats administered risperidone early in life also showed more locomotor activity after the low dose of quinpirole. Overall, female rats were more sensitive to the locomotor effects of each agonist. In a separate group of rats administered risperidone early in life, autoradiography of forebrain D2 receptors at postnatal day 62 revealed a modest increase in D2 receptor density in the medial caudate. These results provide evidence that early-life risperidone administration can produce long-lasting changes in dopamine receptor function and density.

Risperidone impedes glutamate excitotoxicity in a valproic acid rat model of autism: Role of ADAR2 in AMPA GluA2 RNA editing

Several reports indicate a plausible role of calcium (Ca2+) permeable AMPA glutamate receptors (with RNA hypo-editing at the GluA2 Q/R site) and the subsequent excitotoxicity-mediated neuronal death in the pathogenesis of a wide array of neurological disorders including autism spectrum disorder (ASD). This study was designed to examine the effects of chronic risperidone treatment on the expression of adenosine deaminase acting on RNA 2 (Adar2), the status of AMPA glutamate receptor GluA2 editing, and its effects on oxidative/nitrosative stress and excitotoxicity-mediated neuronal death in the prenatal valproic acid (VPA) rat model of ASD. Prenatal VPA exposure was associated with autistic-like behaviors accompanied by an increase in the apoptotic marker "caspase-3" and a decrease in the antiapoptotic marker "BCL2" alongside a reduction in the Adar2 relative gene expression and an increase in GluA2 Q:R ratio in the hippocampus and the prefrontal cortex. Risperidone, at doses of 1 and 3 mg, improved the VPA-induced behavioral deficits and enhanced the Adar2 relative gene expression and the subsequent GluA2 subunit editing. This was reflected on the cellular level where risperidone impeded VPA-induced oxidative/nitrosative stress and neurodegenerative changes. In conclusion, the present study confirms a possible role for Adar2 downregulation and the subsequent hypo-editing of the GluA2 subunit in the pathophysiology of the prenatal VPA rat model of autism and highlights the favorable effect of risperidone on reversing the RNA editing machinery deficits, giving insights into a new possible mechanism of risperidone in autism.

Novel role of peroxisome proliferator activated receptor-α in valproic acid rat model of autism: Mechanistic study of risperidone and metformin monotherapy versus combination

Autism spectrum disorder (ASD) is a neurodevelopmental disorder of heterogenous etiology exhibiting a challenge in understanding its exact neuro-pathophysiology. Recently, peroxisome proliferator activated receptor (PPAR)-α activation was found to play a fundamental role in neuroprotection and improving autistic-like-behaviors in experimental animal models of ASD through alleviating neuroinflammation, oxidative-stress, astrocyte reactivity, tauopathy in addition to its favorable role in metabolic regulation, thus attracting attention as a possible target in treatment of ASD. This study aimed to investigate the role of PPAR-α, astrocytic dysfunction and tauopathy in ASD and detect the possible neuroprotective effects of metformin (MET), through PPAR-α activation, and risperidone (RIS) either monotherapy or in combination in alleviating autistic-like-changes at behavioral and neurobiological levels in male Wistar rats. Pregnant female Wistar rats received valproic-acid (VPA) to induce autistic-like-behavioral and neurobiological alterations in their offspring. Chronic intra-peritoneal MET (100 mg/kg/day) and RIS (1 mg/kg/day) either monotherapy or in combination started from postnatal day (PND) 24 till PND61 (38 days). Prenatal VPA exposure simulated the autistic core behaviors associated with neurochemical and histopathological neurodevelopmental degenerative changes. Both MET and RIS either monotherapy or in combination were able to reverse these changes. The effect of MET was comparable to RIS. Moreover, MET was able to alleviate the RIS induced weight gain and improve cognitive functions highlighting its promising adjunctive role in alleviating ASD pathophysiology. Our study highlighted the favorable effects of MET and RIS both in monotherapy and in combination in alleviating the autistic-like-changes and proposed PPAR-α activation along with restoring astrocytes homeostasis as promising targets in novel therapeutic strategies in ASD.

Antipsychotic Medications for Low-Income Preschoolers: Long Duration and Psychotropic Medication Polypharmacy

OBJECTIVE

This study aimed to evaluate prescribing patterns of antipsychotic medication and factors that predict duration of use among low-income, preschool-age children.

METHODS

State Medicaid claims from 2012 to 2017 were used to identify antipsychotic medication use for children <6 years old. ICD-9 and ICD-10 codes were used to describe child diagnoses. Descriptive and multivariable analyses were used to determine patterns of antipsychotic medication use and factors that predicted duration of use.

RESULTS

In 2012, 316 children <6 years of age started an antipsychotic medication in a southeastern state. Most were non-Hispanic White (N=202, 64%) and boys (N=231, 73%). Diagnoses included attention-deficit hyperactivity disorder (N=288, 91%), neurodevelopmental disorders (N=208, 66%), anxiety and trauma-related diagnoses (N=202, 64%), and autism spectrum disorders (ASDs) (N=137, 43%). The mean±SD duration of exposure to antipsychotic medication for children in the cohort was 2.6±1.7 years, but 86 children (27%) had >4 years of exposure. Almost one-third (N=97, 31%) received polypharmacy of four or more medication classes, and 42% (N=131) received metabolic screening. Being male, being in foster care, and having a diagnosis of ASD or disruptive mood dysregulation disorder were significantly associated with duration of use of antipsychotic medications; race-ethnicity was not significantly associated with duration of use. Emergency department visits (N=277, 88%) and inpatient hospitalizations (N=107, 34%) were observed during the study period.

CONCLUSIONS

Many preschoolers received antipsychotic medications for substantial periods. Further research is needed to identify evidence-based practices to reduce medication use and improve outcomes.

Chronic risperidone administration leads to greater amphetamine-induced conditioned place preference

Risperidone is an atypical antipsychotic drug used increasingly in children to manage symptoms of ADHD and conduct disorder. In rats, developmental risperidone administration is accompanied by increased locomotor activity during adulthood, as well as heightened sensitivity to the locomotor stimulating effects of amphetamine. This study compared sensitivity to the rewarding effects of amphetamine, as measured by conditioned place preference (CPP), between groups of rats administered chronic risperidone (3.0 mg/kg, s.c.) during development (postnatal days 14-42) or adulthood (postnatal days 77-105). Locomotor activity in a novel test cage and amphetamine-induced CPP were measured beginning three and four weeks, respectively, after the final risperidone injection. Female rats administered risperidone early in life were more active than any other group tested. Previous risperidone administration enhanced amphetamine CPP regardless of sex, and this effect appeared more prominent in the developmentally treated group. The density of forebrain dopamine transporters, a primary target of amphetamine, was also quantified in rats administered risperidone early in life and found to be reduced in the medial anterior, posterior, and ventral caudate nucleus. These results suggest that chronic risperidone treatment modifies later locomotor activity and sensitivity to the reinforcing effects of amphetamine, perhaps via a mechanism related to decreased forebrain dopamine transporter density.

The effects of amphetamine on working memory and locomotor activity in adult rats administered risperidone early in life

Antipsychotic drugs are used to manage symptoms of pediatric psychiatric disorders despite the relative absence of research regarding the long-term effects of these drugs on brain development. Using rats as a model, research has demonstrated that administration of the antipsychotic drug, risperidone, during early postnatal development elevates locomotor activity and sensitivity to the locomotor effects of amphetamine during adulthood. Because risperidone targets neurotransmitter receptors and forebrain regions associated with working memory, the present study determined whether early-life risperidone altered working memory during adulthood and its sensitivity to amphetamine-induced impairment. Female and male rats received subcutaneous (sc) injections of risperidone daily on postnatal days 14-42. Early-life risperidone increased spontaneous locomotor activity and amphetamine-induced hyperactivity during adulthood, although the effects were significantly greater in females. Working memory was tested in an operant-based, delayed non-matching-to-sample task. Early-life risperidone did not affect the percentage of correct choices observed during sessions with 0-8 second delays but impaired performance during sessions with 0-24 second delays. In a subsequent set of tests using 0-24 second delays, amphetamine (0.75 and 1.25 mg/kg, sc) significantly reduced the percentage of correct choices at most delays, but risperidone did not exacerbate this effect. These data suggest that early-life risperidone leads to modest deficits in working memory during adulthood, but does not alter the perturbation of working memory by amphetamine.

Delayed yet persistent effects of daily risperidone on activity in developing rats

Early-life administration of risperidone, the most widely used antipsychotic drug in children, leads to persistently elevated locomotor activity in adult rats. This study determined whether and when elevated locomotor activity emerges during developmental risperidone administration. Developing and adult rats were administered daily injections of risperidone (1.0 and 3.0 mg/kg) or vehicle for 4 weeks beginning at postnatal days 14 and 74, respectively. Starting with the first injection and every 7 days thereafter, locomotor activity was measured immediately after the injection and 20 min before the next day's injection. Activity was also recorded 1 week after the final injection. Risperidone markedly decreased locomotor activity in developing and adult rats immediately after injection. Within 24 h after their first injection, adult rats administered risperidone showed greater activity levels. In contrast, developing rats did not show compensatory hyperactivity until the beginning of the fourth week of risperidone administration. One week after the final risperidone injection, there was no evidence of hyperactivity in the adult rats maintained on risperidone, but developing rats administered risperidone, especially females, showed greater activity levels relative to vehicle-administered controls. In comparison with adult rats, the emergence of compensatory hyperactivity during long-term antipsychotic drug administration is delayed in developing rats, but persists after treatment cessation.

Early-life risperidone enhances locomotor responses to amphetamine during adulthood

Antipsychotic drug prescriptions for pediatric populations have increased over the past 20 years, particularly the use of atypical antipsychotic drugs such as risperidone. Most antipsychotic drugs target forebrain dopamine systems, and early-life antipsychotic drug exposure could conceivably reset forebrain neurotransmitter function in a permanent manner that persists into adulthood. This study determined whether chronic risperidone administration during development modified locomotor responses to the dopamine/norepinephrine agonist, D-amphetamine, in adult rats. Thirty-five male Long-Evans rats received an injection of one of four doses of risperidone (vehicle, .3, 1.0, 3.0mg/kg) each day from postnatal day 14 through 42. Locomotor activity was measured for 1h on postnatal days 46 and 47, and then for 24h once a week over the next two weeks. Beginning on postnatal day 75, rats received one of four doses of amphetamine (saline, .3, 1.0, 3.0mg/kg) once a week for four weeks. Locomotor activity was measured for 27h after amphetamine injection. Rats administered risperidone early in life demonstrated increased activity during the 1 and 24h test sessions conducted prior to postnatal day 75. Taking into account baseline group differences, these same rats exhibited significantly more locomotor activity in response to the moderate dose of amphetamine relative to controls. These results suggest that early-life treatment with atypical antipsychotic drugs, like risperidone, permanently alters forebrain catecholamine function and increases sensitivity to drugs that target such function.