Pituitary Adenylate Cyclase-Activating Polypeptide Modulates Dendritic Spine Maturation and Morphogenesis via MicroRNA-132 Upregulation.

Alterations in pituitary adenylate cyclase-activating polypeptide (PACAP), a multifunctional neuropeptide, and its receptors have been identified as risk factors for certain psychiatric disorders, including schizophrenia. Increasing evidence from human genetic and animal model studies suggest an association between various psychiatric disorders and altered dendritic spine morphology. In the present study, we investigated the role of exogenous and endogenous PACAP in spine formation and maturation. PACAP modified the density and morphology of PSD-95-positive spines in primary cultured hippocampal neurons. Notably, PACAP increased the levels of microRNA (miR)-132 and decreased expression of corresponding miR-132 target genes and protein expression of p250GAP, a miR-132 effector known to be involved in spine morphology regulation. In corroboration, PSD-95-positive spines were reduced in PACAP-deficient (PACAP-/-) mice versus WT mice. Golgi staining of hippocampal CA1 neurons revealed a reduced spine densities and atypical morphologies in the male PACAP-/- mice. Furthermore, viral miR-132 overexpression reversed the reduction in hippocampal spinal density in the male PACAP-/- mice. These results indicate that PACAP signaling plays a critical role in spine morphogenesis possibly via miR-132. We suggest that dysfunction of PACAP signaling may contribute to the pathogenesis of neuropsychiatric disorders, at least partly through its effects on spine formation.SIGNIFICANCE STATEMENT Pituitary adenylate cyclase-activating polypeptide (PACAP) signaling dysfunction and dendritic spine morphology alterations have recently been suggested as important pathophysiological mechanisms underlying several psychiatric and neurological disorders. In this study, we investigated whether PACAP regulates dendritic spine morphogenesis. In a combination of pharmacological and viral gain- and loss-of-function approaches in vitro and in vivo experiments, we found PACAP to increase the size and density of dendritic spines via miR-132 upregulation. Together, our data suggest that a dysfunction of PACAP signaling may contribute to the pathogenesis of neuropsychiatric disorders, at least partly through abnormal spine formation.

Galantamine promotes adult hippocampal neurogenesis via M1 muscarinic and α7 nicotinic receptors in mice.

Galantamine, an inhibitor of acetylcholinesterase, promotes hippocampal neurogenesis, but the exact mechanism for this is not known. In the present study, we examined the mechanisms underlying the effects of acute galantamine on neurogenesis in the mouse hippocampus. Galantamine (3 mg/kg) increased the number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells in the subgranular zone of the dentate gyrus. This effect was blocked by the muscarinic receptor antagonist scopolamine and the preferential M1 muscarinic receptor antagonist telenzepine, but not by the nicotinic receptor antagonists mecamylamine and methyllycaconitine. Galantamine did not alter the ratio of neuronal nuclei (NeuN)- or glial fibrillary acidic protein (GFAP)-positive cells to BrdU-labeled cells in the subgranular zone and granule cell layer. Galantamine (1, 3 mg/kg) promoted the survival of 2-wk-old newly divided cells in mice in the granule cell layer of the dentate gyrus, whereas it did not affect the survival of newly divided cells at 1 and 4 wk. Galantamine-induced increases in cell survival were blocked by the α7 nicotinic receptor antagonist methyllycaconitine, but not by scopolamine. Bilateral injection of recombinant IGF2 into the dentate gyrus of the hippocampus mimicked the effects of galantamine. The effects of galantamine were blocked by direct injection of the IGF1 receptor antagonist JB1. These findings suggest that galantamine promotes neurogenesis via activation of the M1 muscarinic and α7 nicotinic acetylcholine receptors. The present study also suggests that IGF2 is involved in the effects of galantamine on the survival of 2-wk-old immature cells in the granule cell layer.

Atomoxetine-induced increases in monoamine release in the prefrontal cortex are similar in spontaneously hypertensive rats and Wistar-Kyoto rats.

Spontaneously hypertensive rats (SHRs) are used as a model for attention-deficit/hyperactivity disorder (ADHD), since SHRs are hyperactive and show defective sustained attention in behavioral tasks. The psychostimulants amphetamine and methylphenidate and the selective norepinephrine reuptake inhibitor atomoxetine are used as ADHD medications. The effects of high K(+) stimulation or psychostimulants on brain norepinephrine or dopamine release in SHRs have been previously studied both in vitro and in vivo, but the effects of atomoxetine on these neurotransmitters have not. The present study examined the effects of administration of atomoxetine on extracellular norepinephrine, dopamine, and serotonin levels in the prefrontal cortex of juvenile SHRs and Wistar-Kyoto (WKY) rats. Baseline levels of prefrontal norepinephrine, dopamine, and serotonin were similar in SHRs and WKY rats. Systemic administration of atomoxetine (3 mg/kg) induced similar increases in prefrontal norepinephrine and dopamine, but not serotonin, levels in both strains. Furthermore, there was no difference in high K(+)-induced increases in extracellular norepinephrine, dopamine, and serotonin levels in the prefrontal cortex between SHRs and WKY rats. These findings indicate that monoamine systems in the prefrontal cortex are similar between SHRs and WKY rats.

Inhibition of apelin expression switches endothelial cells from proliferative to mature state in pathological retinal angiogenesis.

The recruitment of mural cells such as pericytes to patent vessels with an endothelial lumen is a key factor for the maturation of blood vessels and the prevention of hemorrhage in pathological angiogenesis. To date, our understanding of the specific trigger underlying the transition from cell growth to the maturation phase remains incomplete. Since rapid endothelial cell growth causes pericyte loss, we hypothesized that suppression of endothelial growth factors would both promote pericyte recruitment, in addition to inhibiting pathological angiogenesis. Here, we demonstrate that targeted knockdown of apelin in endothelial cells using siRNA induced the expression of monocyte chemoattractant protein-1 (MCP-1) through activation of Smad3, via suppression of the PI3K/Akt pathway. The conditioned medium of endothelial cells treated with apelin siRNA enhanced the migration of vascular smooth muscle cells, through MCP-1 and its receptor pathway. Moreover, in vivo delivery of siRNA targeting apelin, which causes exuberant endothelial cell proliferation and pathological angiogenesis through its receptor APJ, led to increased pericyte coverage and suppressed pathological angiogenesis in an oxygen-induced retinopathy model. These data demonstrate that apelin is not only a potent endothelial growth factor, but also restricts pericyte recruitment, establishing a new connection between endothelial cell proliferation signaling and a trigger of mural recruitment.

Direct visualization of an antidepressant analog using surface-enhanced Raman scattering in the brain.

Detailed spatial information of low-molecular weight compound distribution, especially in the brain, is crucial to understanding their mechanism of actions. Imaging techniques that can directly visualize drugs in the brain at a high resolution will complement existing tools for drug distribution analysis. Here, we performed surface-enhanced Raman scattering (SERS) imaging using a bioorthogonal alkyne tag to visualize drugs directly in situ at a high resolution. Focusing on the selective serotonin reuptake inhibitor S-citalopram (S-Cit), which possesses a nitrile group, we substituted an alkynyl group into its structure and synthesized alkynylated S-Cit (Alk-S-Cit). The brain transitivity and the serotonin reuptake inhibition of Alk-S-Cit were not significantly different as compared with S-Cit. Alk-S-Cit was visualized in the coronal mouse brain section using SERS imaging with silver nanoparticles. Furthermore, SERS imaging combined with fluorescence microscopy allowed Alk-S-Cit to be visualized in the adjacent neuronal membranes, as well as in the brain vessel and parenchyma. Therefore, our multimodal imaging technique is an effective method for detecting low-molecular weight compounds in their original tissue environment and can potentially offer additional information regarding the precise spatial distribution of such drugs.

Rivastigmine improves isolation rearing-induced prepulse inhibition deficits via muscarinic acetylcholine receptors in mice.

RATIONALE: The acetylcholinesterase inhibitors donepezil, galantamine, and rivastigmine are used for the treatment of Alzheimer's disease. We previously demonstrated that donepezil and galantamine differentially affect isolation rearing-induced prepulse inhibition (PPI) deficits and that this might be due to differential effects on brain muscarinic acetylcholine (mACh) receptor function in mice. OBJECTIVES: We examined the effects of rivastigmine on isolation rearing-induced PPI deficits, brain ACh levels, and mACh receptor function in mice. METHODS: Acoustic startle responses were measured in a startle chamber. Microdialysis was performed, and the levels of dopamine and ACh in the prefrontal cortex were measured. RESULTS: Rivastigmine (0.3 mg/kg) improved PPI deficits, and this improvement was antagonized by the mACh receptor antagonist telenzepine but not by the nicotinic ACh receptor antagonist mecamylamine. Rivastigmine increased extracellular ACh levels by approximately 2-3-fold, less than the increase produced by galantamine. Rivastigmine enhanced the effect of the mACh receptor agonist N-desmethylclozapine on prefrontal dopamine release, a marker of mACh receptor function, and this increase was blocked by telenzepine. In contrast, galantamine did not affect N-desmethylclozapine-induced dopamine release. Furthermore, rivastigmine did not affect cortical dopamine release induced by the serotonin1A receptor agonist osemozotan, suggesting that the effect of rivastigmine has specificity for mACh receptors. CONCLUSIONS: Taken together with our previous finding that marked increases in ACh levels are required for the PPI deficit improvement induced by galantamine, our present results suggest that rivastigmine improves isolation rearing-induced PPI deficits by increasing ACh levels and by concomitantly enhancing mACh receptor function.

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.

Effects of acute and chronic administration of venlafaxine and desipramine on extracellular monoamine levels in the mouse prefrontal cortex and striatum.

Prefrontal catecholamine neurotransmission plays a key role in the therapeutic actions of drugs for attention-deficit/hyperactivity disorder (ADHD). We have recently shown that serotonin/noradrenaline reuptake inhibitors and the noradrenaline reuptake inhibitor desipramine attenuated horizontal hyperactivity in spontaneously hypertensive rats, an animal model of ADHD, and that these drugs are potential pharmacotherapeutics for ADHD. In this study, we used in vivo microdialysis to study the effects of acute and chronic (once daily for 3 weeks) administration of the serotonin/noradrenaline reuptake inhibitor venlafaxine and the noradrenaline reuptake inhibitor desipramine on noradrenaline, dopamine, and serotonin levels, and the expression of the neuronal activity marker c-Fos in the mouse prefrontal cortex and striatum. Both acute and chronic venlafaxine administration increased prefrontal noradrenaline, dopamine, and serotonin levels and striatal noradrenaline and serotonin levels. Both acute and chronic desipramine administration increased prefrontal noradrenaline and dopamine levels and striatal noradrenaline levels, with chronic administration yielding stronger increase. Chronic desipramine did not affect striatal dopamine and serotonin levels. Both acute and chronic venlafaxine administration increased the expression of c-Fos in the prefrontal cortex, whereas chronic, but not acute, desipramine administration increased the expression of c-Fos in the prefrontal cortex. Both acute and chronic venlafaxine administration increased the striatal c-Fos expression to some degree, whereas desipramine administration did not. These results suggest that acute and chronic venlafaxine and chronic desipramine administration maximally activate the prefrontal adrenergic and dopaminergic systems without affecting striatal dopaminergic systems in mice.

Isolation rearing reduces mechanical allodynia in a mouse model of chronic inflammatory pain.

Social isolation rearing in mice after weaning reduces pain sensitivity to acute pain, and this hypoalgesia is mediated by the descending serotonergic pain inhibitory system in which the spinal serotonin (5-HT)1A receptor is involved. However, it is not known whether isolation rearing affects pain sensitivity to neuropathic or inflammatory chronic pain. In this study, we examined the effects of isolation rearing on chronic pain induced by Freund's complete adjuvant (FCA) and partial sciatic nerve ligation using the von Frey test (to assess mechanical allodynia) and the plantar test (to assess thermal hyperalgesia). In the FCA model, isolation rearing reduced mechanical allodynia, but not thermal hyperalgesia. In contrast, isolation rearing had no effect on allodynia or hyperalgesia in the sciatic nerve ligation model. The isolation rearing-induced inhibition of allodynia was alleviated by intrathecal injection of WAY100635, a selective 5-HT1A receptor antagonist. FCA increased 5-HT turnover and decreased 5-HT1A receptor expression in the spinal cord of group-reared mice, while it did not have these effects in isolation-reared mice. These results suggest that FCA suppresses the serotonergic pain inhibitory system selectively in group-reared mice. Moreover, systemic administration of osemozotan, a selective 5-HT1A receptor agonist, inhibited FCA-induced mechanical allodynia in group-reared mice, and this effect of the drug was suppressed by intrathecal injection of WAY100635. Collectively, these findings suggest that isolation rearing selectively reduces FCA-induced mechanical allodynia in mice and that this effect is mediated by the activation of spinal 5-HT1A receptors.