Imipramine ameliorates pain-related negative emotion via induction of brain-derived neurotrophic factor.

Depression-like behavior is often complicated by chronic pain. Antidepressants including imipramine (IMI) are widely used to treat chronic pain, but the mechanisms are not fully understood. Brain-derived neurotrophic factor (BDNF) is a neuromodulator that reduces depression by regulating synaptic transmission. We aimed to characterize the antidepressant effects of IMI without analgesia based on BDNF (trkB)-mediated signaling and gene expression in chronic pain. A chronic constriction injury (CCI) model was constructed in Sprague-Dawley (SD) rats. IMI (5 mg/kg, i.p.) was administered from day 10 after CCI. The pain response was assessed using the paw withdrawal latency (PWL) and depression was judged from the immobility time in a forced swim test. Anti-BDNF antibody, K252a, or 5,7-dihydroxytryptamine (5,7-DHT) were used to examine the antidepressant effects of imipramine. Changes in pERK1/2 (immunohistochemistry), 5-HT and BDNF (ELISA), and BDNF mRNA (RT-PCR) were measured in the anterior cingulate cortex (ACC), rostral ventromedial medulla (RVM), and spinal cord. After CCI, rats showed decreased PWL and increased immobility time. A low dose of IMI reduced the immobility time without having analgesic effects. This antidepressant effect was reversed by anti-BDNF antibody, K252a, and 5,7-DHT. IMI reduced excessive activation of pERK1/2 associated with decreased pCREB and BDNF mRNA, and these changes were reversed by 5,7-DHT. These results show that IMI reduces pain-related negative emotion without influencing pain and that this effect is diminished by denervation of 5-HT neurons and by anti-BDNF treatment. IMI also normalizes derangement of ERK/CREB coupling, which leads to induction of BDNF. This suggests a possible interaction between 5-HT and BDNF.

Intracellular interaction of newly synthesized nerve growth factor and its receptors.

In autocrine cells, both a ligand and its receptors are synthesized in the same cell, but their intracellular interaction is not well known. We examined it using PC84 cells, a mutant PC12 cell line expressing nerve growth factor (NGF). We have already reported that the intracellular precursor of TrkA was phosphorylated and that MAP kinase was phosphorylated in PC84 cells. In this paper we found that the NGF receptors, TrkA and p75NTR, existed mainly as precursors, and most p75NTR localized inside PC84 cells. The phosphorylation of MAP kinase was also observed even when PC84 cells were incubated with anti-NGF antibody to block the extracellular interaction. These results suggest the possibility that newly synthesized NGF could interact intracellularly with the receptors in PC84 cells.

Neurite outgrowth of PC12 cells by 4'-O-ß-D-glucopyranosyl-3',4-dimethoxychalcone from Brassica rapa L. 'hidabeni' was enhanced by pretreatment with p38MAPK inhibitor.

The cellular effects of eleven compounds including chalcone glycosides isolated from Brassica rapa L. 'hidabeni' and their synthetic derivatives were studied in rat pheochromocytoma PC12 cells. Of the compounds tested, 4'-O-ß-D-glucopyranosyl-3',4-dimethoxychalcone (A2) significantly increased the levels of the phosphorylated forms of extracellular signal-regulated kinases 1/2 (ERK 1/2), p38 mitogen-activated protein kinase (p38MAPK), and stress-activated protein kinases/Jun amino-terminal kinases (JNK/SAPK), but it did not affect Akt. Nerve growth factor (NGF), a well-known neurotrophic factor, increased the levels of phosphorylated ERK1/2, JNK/SAPK, and Akt but not p38MAPK, which may mediate marked neurite outgrowth. Signals evoked by A2 shared common characteristics with those induced by NGF; therefore, we evaluated the neuritogenic activity of A2 and found it induced only weak neurite outgrowth. However, this effect was enhanced by pre-treatment with a p38MAPK inhibitor, suggesting that the phosphorylation of p38MAPK down-regulated neurite outgrowth. From the results of this study, it was found that A2 in combination with a p38MAPK inhibitor can induce NGF-like effects. Hence, a combination of chalcone glycosides containing A2 and a p38MAPK inhibitor increases the likelihood that chalcone glycosides could be put to practical use in the form of drugs or alternative medicines to maintain neural health.

Knockdown of pre-mRNA cleavage factor Im 25 kDa promotes neurite outgrowth.

Mammalian precursor mRNA (pre-mRNA) cleavage factor I (CFIm) plays important roles in the selection of poly(A) sites in a 3'-untranslated region (3'-UTR), producing mRNAs with variable 3' ends. Because 3'-UTRs often contain cis elements that impact stability or localization of mRNA or translation, alternative polyadenylation diversifies utilization of primary transcripts in mammalian cells. However, the physiological role of CFIm remains unclear. CFIm acts as a heterodimer comprising a 25kDa subunit (CFIm25) and one of the three large subunits-CFIm59, CFIm68, or CFIm72. CFIm25 binds directly to RNA and introduces and anchors the larger subunit. To examine the physiological roles of CFIm, we knocked down the CFIm25 gene in neuronal cells using RNA interference. Knockdown of CFIm25 increased the number of primary dendrites of developing hippocampal neurons and promoted nerve growth factor (NGF)-induced neurite extension from rat pheochromocytoma PC12 cells without affecting the morphology of proliferating PC12 cells. On the other hand, CFIm25 knockdown did not influence constitutively active or dominantly negative RhoA suppression or promotion of NGF-induced neurite extension from PC12 cells, respectively. Taken together, our results indicate that endogenous CFIm may promote neuritogenesis in developing neurons by coordinating events upstream of NGF-induced RhoA inactivation.

Antidepressant-like activity of 10-hydroxy-trans-2-decenoic Acid, a unique unsaturated Fatty Acid of royal jelly, in stress-inducible depression-like mouse model.

Symptoms of depression and anxiety appeared in mice after they had been subjected to a combination of forced swimming for 15 min followed by being kept in cages that were sequentially subjected to leaning, drenching, and rotation within 1-2 days for a total of 3 weeks. The animals were then evaluated by the tail-suspension test, elevated plus-maze test, and open-field test at 1 day after the end of stress exposure. Using these experimental systems, we found that 10-hydroxy-trans-2-decenoic acid (HDEA), an unsaturated fatty acid unique to royal jelly (RJ), protected against the depression and anxiety when intraperitoneally administered once a day for 3 weeks simultaneously with the stress loading. Intraperitoneally administered RJ, a rich source of HDEA, was also protective against the depression, but RJ given by the oral route was less effective. Our present results demonstrate that HDEA and RJ, a natural source of it, were effective in ameliorating the stress-inducible symptoms of depression and anxiety.

Injury-induced accumulation of glial cell line-derived neurotrophic factor in the rostral part of the injured rat spinal cord.

The spinal cord of a 7-week-old female Wistar rat was hemi-transected at thoracic position 10 with a razor blade, and changes in glial cell line-derived neurotrophic factor (GDNF) protein and mRNA expression levels in the spinal cord were examined. GDNF protein and mRNA expression levels were evaluated by enzyme immunoassay and reverse transcription polymerase chain reaction, respectively. Although GDNF is distributed in the healthy spinal cord from 150 to 400 pg/g tissue in a regionally dependent manner, hemi-transection (left side) of the spinal cord caused a rapid increase in GDNF content in the ipsilateral rostral but not in the caudal part of the spinal cord. On the other hand, injury-induced GDNF mRNA was distributed limitedly in both rostral and caudal stumps. These observations suggest the possibility that increased GDNF in the rostral part is responsible for the accumulation of GDNF that may be constitutively transported from the rostral to caudal side within the spinal cord. Although such local increase of endogenous GDNF protein may not be sufficient for nerve regeneration and locomotor improvement, it may play a physiological role in supporting spinal neurons including motoneurons.

2-decenoic acid ethyl ester, a compound that elicits neurotrophin-like intracellular signals, facilitating functional recovery from cerebral infarction in mice.

In our previous study, we found that trans-2-decenoic acid ethyl ester (DAEE), a derivative of a medium-chain fatty acid, elicits neurotrophin-like signals including the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in cultured mouse cortical neurons. Here, we examined the efficacy of intraperitoneal administration of DAEE on the treatment of a mouse model of the cerebral infarction caused by unilateral permanent middle cerebral artery occlusion (PMCAO). DAEE-treatment (100 µg/kg body weight injected at 0.5, 24, 48, 72 h after PMCAO) significantly restored the mice from PMCAO-induced neurological deficits including motor paralysis when evaluated 48, 72, and 96 h after the PMCAO. Furthermore, DAEE facilitated the phosphorylation of ERK1/2 on the infarction side of the brain when analyzed by Western immunoblot analysis, and it enhanced the number of phosphorylated ERK1/2-positive cells in the border areas between the infarction and non-infarction regions of the cerebral cortex, as estimated immunohistochemically. As the infarct volume remained unchanged after DAEE-treatment, it is more likely that DAEE improved the neurological condition through enhanced neuronal functions of the remaining neurons in the damaged areas rather than by maintaining neuronal survival. These results suggest that DAEE has a neuro-protective effect on cerebral infarction.

Prenatal immune challenge compromises the normal course of neurogenesis during development of the mouse cerebral cortex.

Maternal infection during pregnancy is an environmental risk factor for the development of severe brain disorders in offspring, including schizophrenia and autism. However, little is known about the neurodevelopmental mechanisms underlying the association between prenatal exposure to infection and the emergence of cognitive and behavioral dysfunctions in later life. By injecting viral mimetic polyriboinosinic-polyribocytidylic acid (Poly I:C) into mice, we investigated the influence of maternal immune challenge during pregnancy on the development of the cerebral cortex of offspring. Our previous study showed that stimulation of the maternal immune system compromised the expression properties of transcription factors and the synaptogenesis of cortical neurons in upper layers but not those in deeper layers. The objective of the current study was to examine further whether maternal immune challenge has an influence on the cellular-biological features of the cortical progenitors that generate distinct cortical neuronal subtypes. We found the following abnormalities in the cortex of mice given the prenatal Poly I:C injection during later stages of cortical neurogenesis. First, proliferative activity and the expression of Pax6, which is a master regulator of the gene expression of transcription factors, were significantly decreased in the cortical progenitors. Second, the laminar allocation and gene expression were significantly altered in the daughter neurons generated at the same birth dates. These results demonstrate that specific abnormalities in the cortical progenitors preceded deficits in neuronal phenotypes. These changes may underlie the emergence of psychiatric brain and behavioral dysfunctions after in utero exposure to an infection.

Prenatal immune challenge compromises development of upper-layer but not deeper-layer neurons of the mouse cerebral cortex.

Maternal infection during pregnancy is an environmental risk factor for the offspring to develop severe brain disorders, including schizophrenia. However, little is known about the neurodevelopmental mechanisms underlying the association between prenatal exposure to infection and emergence of cognitive and behavioral dysfunctions later in life. By injecting the viral mimetic polyriboinosinic-polyribocytidylic acid (Poly I:C) into mice, we investigated the influence of maternal immune challenge during pregnancy on the development of the cerebral cortex, a responsive organ for cognition. Stimulation of the maternal immune system did not influence the cell number or density of the cortical neurons of postnatal 10-day-old and 8-week-old offspring, whereas gene expressions of upper-layer-specific transcription factors were significantly reduced, without affecting those of the deeper-layer ones. Moreover, the prenatal Poly I:C injection impaired synaptic development of the upper-layer neurons at a later stage, and there was a decrease in the synaptophysin- and glutamic acid decarboxylase-67-positive puncta surrounding the neuronal cell bodies and an increase in the dendritic spine density in postnatal 8-week-old offspring. Considering their importance for cognitive function, the specific abnormalities in the development of upper-layer neuronal phenotypes may underlie the development of psychiatric brain and behavioral dysfunctions emerging after in utero exposure to an infection.

A superoxide anion-scavenger, 1,3-selenazolidin-4-one suppresses serum deprivation-induced apoptosis in PC12 cells by activating MAP kinase.

Synthetic organic selenium compounds, such as ebselen, may show glutathione peroxidase-like antioxidant activity and have a neurotrophic effect. We synthesized 1,3-selenazolidin-4-ones, new types of synthetic organic selenium compounds (five-member ring compounds), to study their possible applications as antioxidants or neurotrophic-like molecules. Their superoxide radical scavenging effects were assessed using the quantitative, highly sensitive method of real-time kinetic chemiluminescence. At 166µM, the O(2)(-) scavenging activity of 1,3-selenazolidin-4-ones ranged from 0 to 66.2%. 2-[3-(4-Methoxyphenyl)-4-oxo-1,3-selenazolidin-2-ylidene]malononitrile (compound b) showed the strongest superoxide anion-scavenging activity among the 6 kinds of 2-methylene-1,3-selenazolidin-4-ones examined. Compound b had a 50% inhibitory concentration (IC(50)) at 92.4µM and acted as an effective and potentially useful O(2)(-) scavenger in vitro. The effect of compound b on rat pheochromocytome cell line PC12 cells was compared with that of ebselen or nerve growth factor (NGF) by use of the MTT [3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide] assay. When ebselen was added at 100µM or more, toxicity toward PC12 cells was evident. On the contrary, compound b suppressed serum deprivation-induced apoptosis in PC12 cells more effectively at a concentration of 100µM. The activity of compound b to phosphorylate mitogen-activated protein kinase/extracellular signal-regulated protein kinase (ERK) 1/2 (MAP kinase) in PC12 cells was higher than that of ebselen, and the former at 100µM induced the phosphorylation of MAP kinase to a degree similar to that induced by NGF. From these results, we conclude that this superoxide anion-scavenger, compound b, suppressed serum deprivation-induced apoptosis by promoting the phosphorylation of MAP kinase.

Ethanol extract of chinese propolis facilitates functional recovery of locomotor activity after spinal cord injury.

An ethanol extract of Chinese propolis (EECP) was given intraperitoneally to rats suffering from hemitransection of half of their spinal cord (left side) at the level of the 10th thoracic vertebra to examine the effects of the EECP on the functional recovery of locomotor activity and expression of mRNAs of inducible nitric oxide (NO) synthase (iNOS) and neurotrophic factors in the injury site. Daily administration of EECP after the spinal cord injury ameliorated the locomotor function, which effect was accompanied by a reduced lesion size. Furthermore, the EECP suppressed iNOS gene expression, thus reducing NO generation, and also increased the expression level of brain-derived neurotrophic factor and neurotrophin-3 mRNAs in the lesion site, suggesting that the EECP reduced the inflammatory and apoptotic circumstances through attenuation of iNOS mRNA expression and facilitation of mRNA expression of neurotrophins in the injured spinal cord. These results suggest that Chinese propolis may become a promising tool for wide use in the nervous system for reducing the secondary neuronal damage following primary physical injury.

Royal jelly facilitates restoration of the cognitive ability in trimethyltin-intoxicated mice.

Trimethyltin (TMT) is a toxic organotin compound that induces acute neuronal death selectively in the hippocampal dentate gyrus (DG) followed by cognition impairment; however the TMT-injured hippocampal DG itself is reported to regenerate the neuronal cell layer through rapid enhancement of neurogenesis. Neural stem/progenitor cells (NS/NPCs) are present in the adult hippocampal DG, and generate neurons that can function for the cognition ability. Therefore, we investigated whether royal jelly (RJ) stimulates the regenerating processes of the TMT-injured hippocampal DG, and found that orally administered RJ significantly increased the number of DG granule cells and simultaneously improved the cognitive impairment. Furthermore, we have already shown that RJ facilitates neurogenesis of cultured NS/NPCs. These present results, taken together with previous observations, suggest that the orally administered RJ may be a promising avenue for ameliorating neuronal function by regenerating hippocampal granule cells that function in the cognition process.

3-(2,6-dimethylphenyl)-2-selenoxo-1,3-thiazolidin-4-one suppresses hydrogen peroxide-induced cytotoxicity on PC12 cells via activation of MAPK.

We newly synthesized organic selenium compounds (5-membered ring compounds) including 2-selenoxo-1,3-thiazolidin-4-ones (compounds A) and 3-alkoxy-4,5-dihydro-5-selenoxo-1H-1,2,4-triazole-1-carboxylates (compounds B). To address whether these compounds show antioxidative effects, we also examined their superoxide radical (O(2) (-))-scavenging effects. Moreover, we examined the effects of compound Aa on the activation of mitogen-activated protein kinase/extracellular signal-regulated protein kinases (MAPK/ERK1/2) and suppression of hydrogen peroxide-induced cytotoxicity in rat pheochromocytoma cells (PC12 cells). We evaluated the O(2) (-)-scavenging activities of the compounds by a chemiluminescence method, and activation of ERK1/2 in PC12 cells was evaluated by Western blot analysis. At 166 µmol/L, the O(2) (-)-scavenging activities were markedly different among compounds A and B. 3-(2,6-Dimethylphenyl)-2-selenoxo-1,3-thiazolidin-4-one (compound Aa) exhibited the strongest superoxide anion-scavenging activity among compounds A and B. The concentration necessary for 50% inhibition of the activity (IC(50)) of compound Aa was 25.9 µmol/L. Compound Aa activated ERK1/2 of the PC12 cell, as did ebselen, and suppressed hydrogen peroxide-induced cytotoxicity more potently than ebselen. In addition, the toxicity of compound Aa was less than that of ebselen. From these results, it is assumed that compound Aa is a candidate drug to prevent oxidative stress-induced cell death.

AMP N(1)-oxide, a unique compound of royal jelly, induces neurite outgrowth from PC12 cells via signaling by protein kinase A independent of that by mitogen-activated protein kinase.

Earlier we identified adenosine monophosphate (AMP) N(1)-oxide as a unique compound of royal jelly (RJ) that induces neurite outgrowth (neuritegenesis) from cultured rat pheochromocytoma PC12 cells via the adenosine A(2A) receptor. Now, we found that AMP N(1)-oxide stimulated the phosphorylation of not only mitogen-activated protein kinase (MAPK) but also that of cAMP/calcium-response element-binding protein (CREB) in a dose-dependent manner. Inhibition of MAPK activation by a MEK inhibitor, PD98059, did not influence the AMP N(1)-oxide-induced neuritegenesis, whereas that of protein kinase A (PKA) by a selective inhibitor, KT5720, significantly reduced neurite outgrowth. AMP N(1)-oxide also had the activity of suppressing the growth of PC12 cells, which correlated well with the neurite outgrowth-promoting activity. KT5720 restored the growth of AMP N(1)-oxide-treated PC12 cells. It is well known that nerve growth factor suppresses proliferation of PC12 cells before causing stimulation of neuronal differentiation. Thus, AMP N(1)-oxide elicited neuronal differentiation of PC12 cells, as evidenced by generation of neurites, and inhibited cell growth through adenosine A(2A) receptor-mediated PKA signaling, which may be responsible for characteristic actions of RJ.

Estrogen stimulates proliferation and differentiation of neural stem/progenitor cells through different signal transduction pathways.

Our previous study indicated that both 17ß-estradiol (E2), known to be an endogenous estrogen, and bisphenol A (BPA), known to be a xenoestrogen, could positively influence the proliferation or differentiation of neural stem/progenitor cells (NS/PCs). The aim of the present study was to identify the signal transduction pathways for estrogenic activities promoting proliferation and differentiation of NS/PCs via well known nuclear estrogen receptors (ERs) or putative membrane-associated ERs. NS/PCs were cultured from the telencephalon of 15-day-old rat embryos. In order to confirm the involvement of nuclear ERs for estrogenic activities, their specific antagonist, ICI-182,780, was used. The presence of putative membrane-associated ER was functionally examined as to whether E2 can activate rapid intracellular signaling mechanism. In order to confirm the involvement of membrane-associated ERs for estrogenic activities, a cell-impermeable E2, bovine serum albumin-conjugated E2 (E2-BSA) was used. We showed that E2 could rapidly activate extracellular signal-regulated kinases 1/2 (ERK 1/2), which was not inhibited by ICI-182,780. ICI-182,780 abrogated the stimulatory effect of these estrogens (E2 and BPA) on the proliferation of NS/PCs, but not their effect on the differentiation of the NS/PCs into oligodendroglia. Furthermore, E2-BSA mimicked the activity of differentiation from NS/PCs into oligodendroglia, but not the activity of proliferation. Our study suggests that (1) the estrogen induced proliferation of NS/PCs is mediated via nuclear ERs; (2) the oligodendroglial generation from NS/PCs is likely to be stimulated via putative membrane-associated ERs.

Pyrroloquinoline quinone attenuates iNOS gene expression in the injured spinal cord.

Pyrroloquinoline quinone (PQQ) is a naturally occurring redox cofactor that acts as an essential nutrient, antioxidant, and redox modulator. PQQ has been demonstrated to oxidize the redox modulatory site of N-methyl-d-aspartic acid (NMDA) receptors. Such agents are known to be neuroprotective in experimental stroke models. Therefore, we examined the possible ameliorating effect of PQQ on spinal cord injury (SCI) in adult rats. Intraperitoneal administration of PQQ effectively promoted the functional recovery of SCI rats after hemi-transection, which was preceded by the attenuation of the expression of inducible nitric oxide (NO) synthase (iNOS) mRNA in the injury site. NO is involved in the secondary detrimental mechanisms and has been implicated in NMDA receptor-mediated neurotoxicity. In fact, administration of PQQ induced significantly decreased lesion size and increased axon density adjoining the lesion area. These observations suggest that PQQ protects against the secondary damage by reducing iNOS expression following primary physical injury to the spinal cord.

Neurotrophin-3 stimulates neurogenetic proliferation via the extracellular signal-regulated kinase pathway.

The effects of neurotrophin-3 (NT3) administered into the ventricular space of 13.5-day-old mouse embryos on neurogenesis in the developing cerebral cortex were examined. 5-Bromo-2'-deoxyuridine (BrdU) was injected into pregnant mice 3 hr after the NT3 administration to label the neural progenitor cells. NT3 increased the number of BrdU-positive cells without altering their distribution. The increment in BrdU-positive cells 24 hr after the BrdU injection was attributed to Pax6-/BrdU-positive cells (neural stem cells), which was followed by a significant elevation of the number of Tuj1-/BrdU-positive cells (neurons) 36 or 48 hr after the BrdU injection, suggesting that NT3 facilitated neurogenesis by acting in two sequential steps, i.e., causing proliferation of neural stem cells and generation of neurons from these progenitors. NT3 stimulated phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and ERK5 in the cortical progenitors, and the effects of NT3 on the increase in total BrdU-positive cells and Pax6-/BrdU-positive cells were diminished by an MEK inhibitor, suggesting the involvement of MEK-mediated ERK signal transduction in the NT3 actions.

Pyrroloquinoline quinone improves abnormal functional development of whisker-mediated tactile perception and social behaviors caused by neonatal whisker trimming.

Abnormalities in tactile perception and response, such as sensory defensiveness, are core features of autism spectrum disorder (ASD) and may be associated with impaired communication skills. However, the influences of tactile perception deficits on the development of social behaviors and neuronal circuits related to emotional regulation of social interactions remain unclear. Whiskers are the most important tactile apparatus in rodents. We previously reported that adult mice receiving bilateral whisker trimming for 10 days after birth (BWT10) exhibited deficits in whisker-mediated tactile discrimination, abnormal social behaviors, and hyperactivity of brain emotional systems under psychological stress. Pyrroloquinoline quinone (PQQ) is an essential nutrient with important roles in central nervous system development and function through modulation of glutamatergic N-methyl-d-aspartate receptor (NMDAR) activity. Here we examined the effect of neonatal PQQ administration on the behavioral abnormalities of BWT10 mice. PQQ treatment significantly reversed abnormal social behavior in adult BWT10 mice as detected by three-chamber social interaction and social dominance tube tests, and improved whisker perception as revealed by the gap-crossing test. In addition, PQQ reversed hyperactivity in emotional systems as evidenced by c-Fos expression pattern following elevated-platform stress. These data suggest that PQQ may be a promising candidate therapeutic drug for neurodevelopmental disorders such as ASD.

Exposure to valproic acid during middle to late-stage corticogenesis induces learning and social behavioral abnormalities with attention deficit/hyperactivity in adult mice.

Single prenatal exposure to valproic acid (VPA) in rodents is a widely used preclinical model of autism spectrum disorder (ASD). Continuous prenatal VPA exposure has been recently proposed as a new ASD model that closely captures the neuropathological features of ASD, including increases in cerebral cortex volume and the number of cortical upper layer neurons. We investigated the influence of prenatal VPA exposure on the behavior of adult offspring of pregnant dams that received intraperitoneal injections of VPA twice on one day during the genesis of cortical upper layer neurons. Mice exposed to VPA at E14 (E14-VPA) showed typical behavior abnormalities including reduced social interaction, hyperactivity, and poor maze learning due to attention deficit/impulsivity relative to healthy controls. Histological analysis revealed that E14-VPA mice had significantly increased neuronal density and impaired neural activity in the prefrontal cortex, but not the somatosensory area, which is likely linked to the observed abnormalities in social behavior. These results suggest that this VPA exposure method is a good model for gaining new insights into the underlying neuropathology of ASD.

PACAP decides neuronal laminar fate via PKA signaling in the developing cerebral cortex.

Laminar formation in the developing cerebral cortex requires the precisely regulated generation of phenotype-specified neurons. To test the possible involvement of pituitary adenylate cyclase-activating polypeptide (PACAP) in this formation, we investigated the effects of PACAP administered into the telencephalic ventricular space of 13.5-day-old mouse embryos. PACAP partially inhibited the proliferation of cortical progenitors and altered the position and gene-expression profiles of newly generated neurons otherwise expected for layer IV to those of neurons for the deeper layers, V and VI, of the cerebral cortex. The former and latter effects were seen only when the parent progenitor cells were exposed to PACAP in the later and in earlier G1 phase, respectively; and these effects were suppressed by co-treatment with a protein kinase A (PKA) inhibitor. These observations suggest that PACAP participates in the processes forming the neuronal laminas in the developing cortex via the intracellular PKA pathway.