Risperidone and aripiprazole alleviate prenatal valproic acid-induced abnormalities in behaviors and dendritic spine density in mice.

RATIONALE: Rodents exposed prenatally to valproic acid (VPA) exhibit autism spectrum disorder (ASD)-like behavioral abnormalities. We recently found that prenatal VPA exposure causes hypofunction of the prefrontal dopaminergic system in mice. This suggests that the dopaminergic system may be a potential pharmacological target for treatment of behavioral abnormalities in ASD patients. OBJECTIVES: In the present study, we examined the effects of antipsychotic drugs, which affect the dopaminergic system, on the social interaction deficits, recognition memory impairment, and reduction in dendritic spine density in the VPA mouse model of ASD. RESULTS: Both acute and chronic administrations of the atypical antipsychotic drugs risperidone and aripiprazole increased prefrontal dopamine (DA) release, while the typical antipsychotic drug haloperidol did not. Chronic risperidone and aripiprazole, but not haloperidol, increased the expression of c-Fos in the prefrontal cortex, although they all increased c-Fos expression in the striatum. Chronic, but not acute, administrations of risperidone and aripiprazole improved the VPA-induced social interaction deficits and recognition memory impairment, as well as the reduction in dendritic spine density in the prefrontal cortex and hippocampus. In contrast, chronic administration of haloperidol did not ameliorate VPA-induced abnormalities in behaviors and dendritic spine density. CONCLUSIONS: These findings indicate that chronic risperidone and aripiprazole treatments improve VPA-induced abnormalities in behaviors and prefrontal dendritic spine density, which may be mediated by repeated elevation of extracellular DA in the prefrontal cortex. Our results also imply that loss of prefrontal dendritic spines may be involved in the abnormal behaviors in the VPA mouse model of ASD.

Prenatal Exposure to Histone Deacetylase Inhibitors Affects Gene Expression of Autism-Related Molecules and Delays Neuronal Maturation.

Valproic acid (VPA) is a multi-target drug and an inhibitor of histone deacetylase (HDAC). We have previously demonstrated that prenatal exposure to VPA at embryonic day 12.5 (E12.5), but not at E14.5, causes autism-like behavioral abnormalities in male mouse offspring. We have also found that prenatal VPA exposure causes transient histone hyperacetylation in the embryonic brain, followed by decreased neuronal cell numbers in the prefrontal and somatosensory cortices after birth. In the present study, we examined whether prenatal HDAC inhibition affects neuronal maturation in primary mouse cortical neurons. Pregnant mice were injected intraperitoneally with VPA (500 mg/kg) and the more selective HDAC inhibitor trichostatin A (TSA; 500 µg/kg) at E12.5 or E14.5, and primary neuronal cultures were prepared from the cerebral cortices of their embryos. Prenatal exposure to VPA at E12.5, but not at E14.5, decreased total number, total length, and complexity of neuronal dendrites at 14 days in vitro (DIV). The effects of VPA weakened at 21 DIV. Exposure to TSA at E12.5, but not at E14.5, also delayed maturation of cortical neurons. In addition, real-time quantitative PCR revealed that the prenatal exposure to TSA decreased neuroligin-1 (Nlgn1), Shank2, and Shank3 mRNA levels and increased contactin-associated protein-like 2 mRNA level. The delay in neuronal maturation was also observed in Nlgn1-knockdown cells, which were transfected with Nlgn1 siRNA. These findings suggest that prenatal HDAC inhibition causes changes in gene expression of autism-related molecules linked to a delay of neuronal maturation.

Improvement by methylphenidate and atomoxetine of social interaction deficits and recognition memory impairment in a mouse model of valproic acid-induced autism.

Rodents exposed prenatally to valproic acid (VPA) show autism-related behavioral abnormalities. We recently found that prenatal VPA exposure causes a reduction of dopaminergic activity in the prefrontal cortex of male, but not female, mice. This suggests that reduced prefrontal dopaminergic activity is associated with behavioral abnormalities in VPA-treated mice. In the present study, we examined whether the attention deficit/hyperactivity disorder drugs methylphenidate and atomoxetine (which increase dopamine release in the prefrontal cortex, but not striatum, in mice) could alleviate the behavioral abnormalities and changes in dendritic spine morphology induced by prenatal VPA exposure. We found that methylphenidate and atomoxetine increased prefrontal dopamine and noradrenaline release in VPA-treated mice. Acute treatment with methylphenidate or atomoxetine did not alleviate the social interaction deficits or recognition memory impairment in VPA-treated mice, while chronic treatment for 2 weeks did. Methylphenidate or atomoxetine for 2 weeks also improved the prenatal VPA-induced decrease in dendritic spine density in the prefrontal cortex. The effects of these drugs on behaviors and dendritic spine morphology were antagonized by concomitant treatment with the dopamine-D1 receptor antagonist SCH39166 or the dopamine-D2 receptor antagonist raclopride, but not by the α2 -adrenoceptor antagonist idazoxan. These findings suggest that chronic treatment with methylphenidate or atomoxetine improves abnormal behaviors and diminishes the reduction in spine density in VPA-treated mice via a prefrontal dopaminergic system-dependent mechanism. Autism Res 2016, 9: 926-939. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.

Decreased expression of hippocampal Na⁺/Ca²âº exchanger isoform-1 by pentylenetetrazole kindling in mice.

Previous studies have shown that inhibitors of the Na(+)/Ca(2+) exchanger (NCX) attenuate seizure activity in drug-induced epilepsy models, but the role of NCX in epilepsy is not fully understood. The present study examined the effects of pentylenetetrazole (PTZ)-induced kindling on the mRNA expression of NCX isoforms (NCX1, NCX2 and NCX3) in mouse brain. Chronic administration of PTZ at 40mg/kg resulted in kindling seizure development. It caused decreases in the mRNA levels of NCX1 and NCX2, but not NCX3, in the hippocampus. Changes in NCX isoform expression levels were not observed in the prefrontal cortex or striatum. Acute PTZ at 40mg/kg, which caused little seizure activity, also decreased NCX2, but not NCX1 mRNA levels in the hippocampus. These results suggest that down-regulation of hippocampal NCX1 expression is associated with PTZ-induced kindling seizure development.

Reduced prefrontal dopaminergic activity in valproic acid-treated mouse autism model.

Previous studies suggest that dysfunction of neurotransmitter systems is associated with the pathology of autism in humans and the disease model rodents, but the precise mechanism is not known. Rodent offspring exposed prenatally to VPA shows autism-related behavioral abnormalities. The present study examined the effect of prenatal VPA exposure on brain monoamine neurotransmitter systems in male and female mice. The prenatal VPA exposure did not affect the levels of dopamine (DA), noradrenaline (NA), serotonin (5-HT) and their metabolites in the prefrontal cortex and striatum, while it significantly reduced methamphetamine (METH) (1.0 mg/kg)-induced hyperlocomotion in male offspring. In vivo microdialysis study demonstrated that prenatal VPA exposure attenuated METH-induced increases in extracellular DA levels in the prefrontal cortex, while it did not affect those in extracellular NA and 5-HT levels. Prenatal VPA exposure also decreased METH-induced c-Fos expression in the prefrontal cortex and the mRNA levels of DA D1 and D2 receptors in the prefrontal cortex. These effects of VPA were not observed in the striatum. In contrast to male offspring, prenatal VPA exposure did not affect METH-induced increases in locomotor activity and prefrontal DA levels and the D1 and D2 receptor mRNA levels in the prefrontal cortex in female offspring. These findings suggest that prenatal VPA exposure causes hypofunction of prefrontal DA system in a sex-dependent way.