Prenatal exposure to ethanol affects postnatal neurogenesis in thalamus

The number of neurons in the ventrobasal thalamus (VB) in the adolescent rat is unaffected by prenatal exposure to ethanol. This is in sharp contrast to other parts of the trigeminal-somatosensory system, which exhibit 30–35% fewer neurons after prenatal ethanol exposure. The present study tested the hypothesis that prenatal ethanol exposure affects dynamic changes in the numbers of VB neurons; such changes reflect the sum of cell proliferation and death. Neuronal number in the VB was determined during the first postnatal month in the offspring of pregnant Long–Evans rats fed an ethanol-containing diet or pair-fed an isocaloric non-alcoholic liquid diet. Offspring were examined between postnatal day (P) 1 and P30. The size of the VB and neuronal number were determined stereologically. Prenatal exposure to ethanol did not significantly alter neuronal number on any individual day, nor was the prenatal generation of VB neurons affected. Interestingly, prenatal ethanol exposure did affect the pattern of the change in neuronal number over time; total neuronal number was stable in the ethanol-treated pups after P12, but it continued to rise in the controls until P21. In addition, the rate of cell proliferation during the postnatal period was greater in ethanol-treated animals. Thus, the rate of neuronal acquisition is altered by ethanol, and by deduction, there appears to be less ethanol-induced neuronal loss in the VB. A contributor to these changes is a latent effect of ethanol on postnatal neurogenesis in the VB and the apparent survival of new neurons.     

Impact of age and strain on ischemic brain injury and seizures after carotid ligation in immature mice

Stroke is an important cause of neurologic injury in the neonatal period and frequently results in lifelong neurologic impairments. We reported previously that unilateral carotid ligation on postnatal day (P)12 in CD1 mice causes acute behavioral seizures and unilateral brain injury and provides a model for neonatal stroke in human infants. In the present study we confirmed that behavioral seizures observed after ligation on P12 in the CD1 strain are associated with rhythmic ictal discharges that show temporal progression on electrocorticograms. We also examined the effects of carotid ligation performed at different ages in CD1 mice or performed in the C57Bl/6 strain. The right common carotid was ligated at P7, P10, P12 or P21 in CD1 mice or at P12 in C57Bl/6 mice. Littermate controls received sham surgery. Seizures were rated for 4 h after surgery; brain injury was scored one week later. In a separate group of P12 CD1 mice, electrocorticographic activity was recorded continuously for 4 h after carotid ligation or sham surgery. Brain injury and cumulative seizure score varied significantly with age (p < 0.001) and strain (p < 0.001). In CD1 mice, injury was greatest after ligation on P10 to P12 and seizure score was maximal at P12. Seizure scores were significantly correlated with injury after ligation on P10 or P12. C57Bl/6 mice, like C3Heb/FeJ mice examined previously, were much less vulnerable to seizures and injury than CD1 mice after ligation on P12. This study demonstrates that carotid ligation in the CD1 mouse on P12 causes acute electrographic rhythmic discharges that correlate with behavioral seizures. We also found that the age at which ligation is performed and genetic strain have a strong influence on the severity of injury.     

Role of plasminogen in macrophage accumulation during liver repair

Introduction

Although the involvement of plasminogen in liver repair has been reported, its roles are still poorly understood. Here, we investigated the role of plasminogen in accumulations of macrophages and neutrophils after liver injury in mice with gene deficient of plasminogen (Plg^−/−) or its wild type (Plg^+/+).

Materials and Methods

Mice received traumatic liver injury caused by stabbing on the lobe or hepatic ischemia-reperfusion, and the damaged sites were histologically analyzed.

Results

After the traumatic liver injury, both the stab wound and the damaged tissue were decreased until day 7 in the Plg^+/+ mice. In contrast, both the stab wound and the damaged tissue were still remained until day 7 in the Plg^−/− mice. On day 4 after traumatic liver injury, macrophages were abundant at the surrounding area of the damaged site in the Plg^+/+ mice. However, the macrophage accumulation was impaired in the Plg^−/− mice. After hepatic ischemia-reperfusion injury, macrophage accumulation and decrease in the damaged tissue were also observed in the Plg^+/+ mice until day 7. In contrast, these responses were also impaired in the Plg^−/− mice. Furthermore, neutrophil accumulation at the surrounding area of the damaged site was also impaired in the Plg^−/− mice on day 4 after both liver traumatic liver injury and hepatic ischemia-reperfusion injury.

Conclusions

Our data indicate that plasminogen plays a crucial role in macrophage accumulation together with the neutrophil accumulation after liver injury in both models, which may be essential for triggering the subsequent healing responses including decrease in the damaged tissue.     

Adolescent neuregulin 1 heterozygous mice display enhanced behavioural sensitivity to methamphetamine

Methamphetamine use triggers psychosis in genetically vulnerable individuals, however the exact nature of this genetic predisposition requires elucidation. In addition, adolescence may be a particular period of neurodevelopmental vulnerability to the actions of methamphetamine; interestingly, this period coincides with a higher likelihood of onset of schizophrenia and drug experimentation. In the current study we investigated whether adolescent mice heterozygous for the schizophrenia susceptibility gene neuregulin 1 (Nrg1 HET mice) exhibit altered behavioural responses to methamphetamine (0.6 or 2.4 mg/kg) in schizophrenia-relevant paradigms. The responses measured were locomotor activity in the open field test and sensorimotor gating function in the prepulse inhibition of startle paradigm (PPI). Adolescent Nrg1 HET mice displayed a subtle, transient, novelty-induced baseline locomotor hyperactivity over days, and a selective PPI deficit at the prepulse intensity-interstimulus interval (ISI) combination of 82 dB–64 ms. Adolescent Nrg1 HET mice were more sensitive to the locomotor stimulatory effects of an acute, low-dose of methamphetamine (0.6 mg/kg) relative to wild-type (WT) controls. The augmented response to acute methamphetamine observed in Nrg1 HET mice disappeared with repeated, daily dosing over 7 days. Methamphetamine did not affect average PPI (total or across different prepulse intensities), however 0.6 mg/kg methamphetamine triggered a PPI deficit selectively in Nrg1 HET mice but not WT mice at 82 dB–256 ms. Our results show that locomotor hyperactivity in Nrg1 HET mice, albeit subtle, can manifest much earlier than previously reported and that Nrg1 may confer vulnerability to the acute actions of methamphetamine, a drug known to trigger psychotic reactions in humans.     

The n-butanolic extract of Opuntia ficus-indica var. saboten enhances long-term memory in the passive avoidance task in mice

Opuntia ficus-indica var. saboten Makino (Cactaceae) is used to treat burns, edema, dyspepsia, and asthma in traditional medicine. The present study investigated the beneficial effects of the n-butanolic extract of O. ficus-indica var. saboten (BOF) on memory performance in mice and attempts to uncover the mechanisms underlying its action. Memory performance was assessed with the passive avoidance task, and western blotting and immunohistochemistry were used to measure changes in protein expression and cell survival. After the oral administration of BOF for 7 days, the latency time in the passive avoidance task was significantly increased relative to vehicle-treated controls (P < 0.05). Western blotting revealed that the expression levels of brain-derived neurotrophic factor (BDNF), phosphorylated cAMP response element binding-protein (pCREB), and phosphorylated extracellular signal-regulated kinase (pERK) 1/2 were significantly increased in hippocampal tissue after 7 days of BOF administration (P < 0.05). Doublecortin and 5-bromo-2-deoxyuridine immunostaining also revealed that BOF significantly enhanced the survival of immature neurons, but did not affect neuronal cell proliferation in the subgranular zone of the hippocampal dentate gyrus. These results suggest that the subchronic administration of BOF enhances long-term memory, and that this effect is partially mediated by ERK-CREB-BDNF signaling and the survival of immature neurons.     

Postnatal iron-induced motor behaviour alterations following chronic neuroleptic administration in mice

Summary. C57/BL6 mice were administered either 7.5 mg Fe²⁺/kg or vehicle (saline) postnatally on days 10–12 after birth. From 61 days of age onwards for 21 days, groups of mice were administered either clozapine (1 or 5 mg/kg, s.c.) or haloperidol (1 mg/kg, s.c.) or vehicle (Tween-80). Twenty-four hours after the final injection of either neuroleptic compound or vehicle, spontaneous motor activity was measured over a 60-min interval. Following this, each animal was removed, injected apomorphine (1 mg/kg, s.c.) and replaced in the same test chamber. It was found that postnatal administration of Fe²⁺ at the 7.5 mg/kg dose level reduced activity during the initial 20-min periods (0–20 and 20–40 min) and then induced hyperactivity during the final 20-min period over all three parameters of activity. Subchronic treatment with the higher, 5 mg/kg, dose of clozapine abolished or attenuated the hypoactivity in by postnatal Fe²⁺ during the 1^st two 20-min periods over all three parameters of activity. Subchronic treatment with the higher, 5 mg/kg, dose of clozapine abolished or attenuated the hyperactivity in by postnatal Fe²⁺ during the 3^rd and final 20-min period. Subchronic administration of haloperidol, without postnatal iron, increased the level of both locomotion (1^st 20 min) and rearing (2^nd 20 min) activity. Postnatal administration of Fe²⁺ at the 7.5 mg/kg dose increased the levels of both locomotion and rearing, but not total activity, following administration of apomorphine (1 mg/kg). Subchronic administration of clozapine, at both the 1 and 5 mg/kg doses, reduced the increased locomotor activity caused by postnatal Fe²⁺, whereas clozapine, 5 mg/kg, elevated further the postnatal Fe²⁺-induced increased in rearing. Subchronic administration of clozapine, at both the 1 and 5 mg/kg doses, and haloperidol, 1 mg/kg, increased the level of locomotor following administration of apomorphine (1 mg/kg) in mice treated postnatally with vehicle, whereas only clozapine increased the level of rearing. Correlational analyses indicated that both apomorphine-induced locomotion and rearing were highly correlated with the total iron content in the basal ganglia, thereby offering direct evidence of the linear relationship between iron content in the basal ganglia and the behavioural expression of DA D₂-receptor supersensitivity in mice.     

Prenatal stress alters the behavior and dendritic morphology of the medial orbitofrontal cortex in mouse offspring during lactation

Several preclinical and clinical studies have shown that prenatal stress alters neuronal dendritic development in the prefrontal cortex, together with behavioral disturbances (anxiety). Nevertheless, neither whether these alterations are present during the lactation period, nor whether such findings may reflect the onset of anxiety disorders observed in childhood and adulthood has been studied. The central aim of the present study was to determine the effects of prenatal stress on the neuronal development and behavior of mice offspring during lactation (postnatal days 14 and 21). We studied 24 CF-1 male mice, grouped as follows: (i) control P14 (n = 6), (ii) stressed P14 (n = 6), (iii) control P21 (n = 6) and (iv) stressed P21 (n = 6). On the corresponding days, animals were evaluated with the open field test and sacrificed. Their brains were then stained in Golgi-Cox solution for 30 days. The morphological analysis dealt with the study of 96 pyramidal neurons. The results showed, first, that prenatal stress resulted in a significant (i) decrease in the apical dendritic length of pyramidal neurons in the orbitofrontal cortex at postnatal day 14, (ii) increase in the apical dendritic length of pyramidal neurons in the orbitofrontal cortex at postnatal day 21, and (iii) reduction in exploratory behavior at postnatal day 14 and 21.     

Postnatal growth hormone deficiency in growing rats causes marked decline in the activity of spinal cord acetylcholinesterase but not butyrylcholinesterase

The effects of growth hormone (GH) deficiency on the developmental changes in the abundance and activity of cholinesterase enzymes were studied in the developing spinal cord (SC) of postnatal rats by measuring the specific activity of acetylcholinesterase (AChE), a marker for cholinergic neurons and their synaptic compartments, and butyrylcholinesterase (BuChE), a marker for glial cells and neurovascular cells. Specific activities of these two enzymes were measured in SC tissue of 21- and 90 day-old (P21, weaning age; P90, young adulthood) GH deficient spontaneous dwarf (SpDwf) mutant rats which lack anterior pituitary and circulating plasma GH, and were compared with SC tissue of normal age-matched control animals. Assays were carried out for AChE and BuChE activity in the presence of their specific chemical inhibitors, BW284C51 and iso-OMPA, respectively. Results revealed that mean AChE activity was markedly and significantly reduced [28% at P21, 49% at P90, (p < 0.01)] in the SC of GH deficient rats compared to age-matched controls. GH deficiency had a higher and more significant effect on AChE activity of the older (P90) rats than the younger ones (P21) ones. In contrast, BuChE activity in SC showed no significant changes in GH deficient rats at either of the two ages studied. Results imply that, in the absence of pituitary GH, the postnatal proliferation of cholinergic synapses in the rat SC, a CNS structure, where AChE activity is abundant, is markedly reduced during both the pre- and postweaning periods; more so in the postweaning than preweaning ages. In contrast, the absence of any effects on BuChE activity implies that GH does not affect the development of non-neuronal elements, e.g., glia, as much as the neuronal and synaptic compartments of the developing rat SC.     

Parent–child DRD4 genotype as a potential biomarker for oppositional,anxiety, and repetitive behaviors in children with autism spectrum disorder

The primary objective of the present study was to examine whether a combination of parent-child DRD4 genotypes results in more informative biomarkers of oppositional, separation anxiety, and repetitive behaviors in children with autism spectrum disorder (ASD). Based on prior research indicating the 7-repeat allele as a potential risk variant, participants were sorted into one of four combinations of parent–child genotypes. Owing to the possibility of parent-of-origin effects, analyses were conducted separately for mother–child (MC) and father–child (FC) dyads. Mothers completed a validated DSM-IV-referenced rating scale. Partial eta-squared (ηp²) was used to determine the magnitude of group differences: 0.01–0.06 = small, 0.06–0.14 = moderate, and > 0.14 = large. Analyses indicated that children in MC dyads with matched genotypes had the least (7−/7−) and most (7+/7+) severe mother-rated oppositional-defiant (ηp² = 0.11) and separation anxiety (ηp² = 0.19) symptoms. Conversely, youths in FC dyads with matched genotypes had the least (7−/7−) and most (7+/7+) severe obsessive-compulsive behaviors (ηp² = 0.19) and tics (ηp² = 0.18). Youths whose parents were both noncarriers had less severe tics than peers with at least one parental carrier, and the effect size was large (ηp² = 0.16). There was little evidence that noncarrier children were rated more severely by mothers who were carriers versus noncarriers. Transmission Disequilibrium Test analyses provided preliminary evidence for undertransmission of the 2-repeat allele in youths with more severe tics (p = 0.02). Parent genotype may be helpful in constructing prognostic biomarkers for behavioral disturbances in ASD; however, findings are tentative pending replication with larger, independent samples.     

Effects of prenatal stress and exercise on dentate granule cells maturation and spatial memory in adolescent mice

Exposure to prenatal stress (PS) increases the risk of developing neurobehavioral disturbances later in life. Previous work has shown that exercise can exert beneficial effects on brain damage; however, it is unknown whether voluntary wheel running (VWR) can ameliorate the neurobehavioral impairments induced by PS in adolescent offspring. Pregnant CF-1 mice were randomly assigned to control (n = 5) or stressed (n = 5) groups. Pregnant dams were subjected to restraint stress between gestational days 14 and 21 (G14–21), whereas controls remained undisturbed in their home cages. On postnatal day 21 (P21), male pups were randomly assigned to the following experimental groups: control (n = 5), stressed (n = 5), and stressed mice + daily submitted to VWR (n = 4). At P52, all groups were behaviorally evaluated in the Morris water maze. Animals were then sacrificed, and Golgi-impregnated granule cells were morphometrically analyzed. The results indicate that PS produced significant behavioral and neuronal impairments in adolescent offspring and that VWR significantly offset these deleterious effects.     

Effect of acute stress on NTPDase and 5′-nucleotidase activities in brain synaptosomes in different stages of development

The aim of the present study was to examine the effect of acute restraint stress on rat brain synaptosomal plasma membrane (SPM) ecto-nucleotidase activities at specific stages of postnatal development (15-, 30-, 60- and 90-day-old rats) by measuring the rates of ATP, ADP and AMP hydrolysis 1, 24 and 72 h post-stress. At 1 h after stress NTPDase and ecto-5′-nucleotidase activities were decreased in rats aged up to 60 days old. In adult rats elevated enzyme activities were detected, which indicated the existence of different short-term stress responses during development. A similar pattern of ATP and ADP hydrolysis changes as well as the ATP/ADP ratio in all developmental stages indicated that NTPDase3 was acutely affected after stress. The long-term effect of acute stress on NTPDase activity differed during postnatal development. In juvenile animals (15 days old) NTPDase activity was not altered. However, in later developmental stages (30 and 60 days old rats) NTPDase activity decreased and persisted for 72 h post-stress. In adult rats only ATP hydrolysis was decreased after 24 h, indicating that ecto-ATPase was affected by stress. Ecto-5′-nucleotidase hydrolysing activity was decreased within 24 h in adult rats, while in 15- and 30-day old rats it decreased 72 h post-stress. At equivalent times in pubertal rats (60 days old) a slight activation of ecto-5′-nucleotidase was detected. Our results highlight the developmental-dependence of brain ecto-nucleotidase susceptibility to acute stress and the likely existence of different mechanisms involved in time-dependent ecto-nucleotidase activity modulation following stress exposure. Clearly there are differences in the response of the purinergic system to acute restraint stress between young and adult rats.     

Genetic determinants of acenocoumarol and warfarin maintenance dose requirements in Slavic population: A potential role of CYP4F2 and GGCX polymorphisms

Introduction

VKORC1 and cytochrome CYP2C9 genetic variants contribute largely to inter-individual variations in vitamin K antagonists (VKAs) dose requirements. Cytochrome P450 4 F2 isoform (CYP4F2), gamma-glutamyl carboxylase (GGCX) and apolipoprotein E (APOE) polymorphisms have been suggested to be of minor significance.

Materials and Methods

We sought to assess the impact of those polymorphisms on dose requirements in Central-Eastern European cohort of 479 patients receiving acenocoumarol (n = 260) or warfarin (n = 219).

Results

There were no differences between the acenocoumarol and warfarin groups with regard to the gender, age, body mass index and international normalized ratio. The VKORC1 c.-1639A allele carriers required a lower dose of acenocoumarol and warfarin than the non-carriers (28.0 [21.0–35.0] vs. 42.0 [28.0–56.0] mg/week, p < 0.0001; 35.0 [28.0–52.0] vs. 52.0 [35.0–70.0] mg/week, p = 0.0001, respectively). Carriers of *2 and/or *3 variant alleles for CYP2C9 also required a lower dose of warfarin as compared with *1*1 carriers (35.0 [31.5–52.5] vs. 43.8 [35.0–60.2] mg/week, p = 0.02; 35.0 [23.5–35.0] vs. 43.8 [35.0-60.2] mg/week, p < 0.0001, respectively). Similarly, possession of G allele of GGCX c.2084 + 45 polymorphism was associated with lower warfarin dose (35.0 [26.3–39.2] vs. 45.5 [35.0–65.1] mg/week, p = 0.03). No effect of CYP2C9*2,-*3 and GGCX c.2084 + 45G > C polymorphisms on acenocoumarol dosage was observed. Interestingly, carriers of CYP4F2 c.1297A variant required a higher dose of acenocoumarol and warfarin than non-carriers (43.8 [35.0–60.2] vs. 35.0 [35.0–52.5] mg/week, p = 0.01; 35.0 [28.0–52.5] vs. 28.0 [28.0–42.0] mg/week, p = 0.05).

Conclusions

We have shown for the first time, that besides VKORC1 and CYP2C9 genetic variants, the CYP4F2 c.1297A and GGCX c.2084 + 45G have a moderate effect on VKAs dose requirements in Slavic population from Central-Eastern Europe.     

Knockout of GAD65 has major impact on synaptic GABA synthesized from astrocyte-derived glutamine

γ-Aminobutyric acid (GABA) synthesis from glutamate is catalyzed by glutamate decarboxylase (GAD) of which two isoforms, GAD65 and GAD67, have been identified. The GAD65 has repeatedly been shown to be important during intensified synaptic activity. To specifically elucidate the significance of GAD65 for maintenance of the highly compartmentalized intracellular and intercellular GABA homeostasis, GAD65 knockout and corresponding wild-type mice were injected with [1-¹³C]glucose and the astrocyte-specific substrate [1,2-¹³C]acetate. Synthesis of GABA from glutamine in the GABAergic synapses was further investigated in GAD65 knockout and wild-type mice using [1,2-¹³C]acetate and in some cases γ-vinylGABA (GVG, Vigabatrin), an inhibitor of GABA degradation. A detailed metabolic mapping was obtained by nuclear magnetic resonance (NMR) spectroscopic analysis of tissue extracts of cerebral cortex and hippocampus. The GABA content in both brain regions was reduced by ∼20%. Moreover, it was revealed that GAD65 is crucial for maintenance of biosynthesis of synaptic GABA particularly by direct synthesis from astrocytic glutamine via glutamate. The GAD67 was found to be important for synthesis of GABA from glutamine both via direct synthesis and via a pathway involving mitochondrial metabolism. Furthermore, a severe neuronal hypometabolism, involving glycolysis and tricarboxylic acid (TCA) cycle activity, was observed in cerebral cortex of GAD65 knockout mice.     

TPH2 is not a susceptibility gene for suicide in Japanese population

Background

Serotonergic systems mediate a control of aggression and/or impulsivity in human and are suggested to be involved in suicidal behavior. The newly identified neuronal tryptophan hydroxylase isoform 2 (TPH2), the rate-limiting enzyme in serotonin synthesis, represents a prime candidate in numerous genetic association analyses of suicidal behavior; however, the results are still inconclusive. The discrepancy may result from the heterogeneity of pathogenesis of suicidal behavior and/or methodological mismatches. We, therefore, attempted to replicate the association of TPH2 gene with suicide using a case-control study of 234 completed suicides and 260 control subjects in Japanese population.

Methods

We genotyped 15 tagging-single nucleotide polymorphisms (SNPs) including 4 SNPs, which were previously reported to be associated with suicidal behavior, using the TaqMan probe assays and the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method.

Results

We found no significant differences in genotypic distributions (uncorrected p = 0.06–0.98) or allelic frequencies (uncorrected p = 0.09–0.95) of the fifteen SNPs between the completed suicides and control groups. Haplotypes constructed with these SNPs were also not associated with suicide (uncorrected p = 0.03–0.96 and corrected p = 0.20–1.00). Even when we took sex and suicidal methods (violent or non-violent) into account for the analyses, no significant differences in genotypic distributions, allelic/haplotypic frequencies were found in the two groups.

Conclusion

Our results suggest that the common SNPs and haplotypes of the TPH2 gene are unlikely to contribute to the genetic susceptibility to suicidal behavior in Japanese population.     

Early exposure of cultured hippocampal neurons to excitatory amino acids protects from later excitotoxicity

Status epilepticus occurring in early postnatal development protects CA1 hippocampal neurons, the region most sensitive to seizure-induced injury in the developing brain. Here, we developed a “two hit” model in dissociated cultures of the rat hippocampus to test whether pre-exposure of immature neurons to high concentrations of glutamate, N-methyl-d-aspartic acid (NMDA) or α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) during a relatively resistant period prevents neurons from dying following a second exposure to the same chemicals after neurons mature and become highly vulnerable to excitatory amino acids (EAAs). Cultures were exposed to varied doses of glutamate, NMDA, or AMPA for 48 h at 5 DIV and again at 14 DIV for 5, 15, or 30 min. NeuN immunohistochemistry showed early exposure to glutamate (500 μM) killed approximately half of the neurons (52 ± 8.6%) compared to the marked depletion that occurs after one exposure at 14 DIV (98 ± 0.79%). When cultures were first challenged with moderate doses of glutamate (200 μM) followed by the high dose 7 days later, a significant population of neurons was spared (35.3 ± 1.2%). Similarly, pre-exposure to maximal doses of NMDA (100 μM) increased the proportion of surviving cells following the second challenge. In contrast, AMPA (100 μM) was equally toxic after early or late applications and did not protect from the second exposure. GluR1 subunit expression was markedly decreased at 48 h after one or two exposures to 200 μM glutamate (by 44.57 ± 3.6%, 45.07 ± 3.69%) whereas GluR2 subunit expression was reduced by a lesser amount (25.7 57 ± 3.8%). Confocal microscopy showed that one or two exposures to NMDA caused GluR2 protein to downregulate even further whereas parvalbumin (PV) was dramatically increased in the same neurons by over four-fold. On the other hand, calbindin (CB) immunoreactivity was nearly absent after the first exposure to 500 μM glutamate. These data indicate that early, transient exposure to certain EAAs at high doses can induce long-lasting neuroprotection. Alterations in the GluR1/GluR2 ratio as well as differential expression of specific calcium binding proteins may contribute to this neuroprotection.     

Genetic variants of D2 but not D3 or D4 dopamine receptor gene are associated with rapid onset and poor prognosis of methamphetamine psychosis

D2-like receptors are key targets for methamphetamine in the CNS, and their activation is an initial and indispensable effect in the induction of dependence and psychosis. It is possible that genetic variants of D2-like receptors may affect individual susceptibility to methamphetamine dependence and psychosis. To test this hypothesis, 6 putatively functional polymorphisms of D2-like receptors, −141C Ins/Del, Ser311Cys and TaqIA of the DRD2 gene, Ser9Gly of the DRD3 gene, and −521C>T and a variable number of tandem repeats in exon 3 of the DRD4 gene, were analyzed in 202 patients with methamphetamine dependence and/or psychosis and 243 healthy controls in a Japanese population. No polymorphism examined showed significant association with methamphetamine dependence, but two polymorphisms of DRD2 were associated with the clinical course and prognosis of methamphetamine psychosis. The A1/A1 homozygote of DRD2 was a negative risk factor for a poorer prognosis of psychosis that continues for more than 1 month after the discontinuance of methamphetamine abuse and the beginning of treatment with neuroleptics (p = 0.04, odds ratio (OR) = 0.42, 95% CI; 0.27–0.65) and the complication of spontaneous relapse of methamphetamine psychosis after remission (p = 0.014, OR = 0.34, 95% CI; 0.22–0.54). The genotype of −141C Del positive (Del/Del and Del/Ins) was at risk for rapid onset of methamphetamine psychosis that develops into a psychotic state within 3 years after initiation of methamphetamine abuse (p = 0.00037, OR = 3.62, 95% CI 2.48–5.28). These findings revealed that genetic variants of DRD2, but not DRD3 or DRD4, confer individual risks for rapid onset, prolonged duration, and spontaneous relapse of methamphetamine psychosis.     

Dysfunction of mouse cerebral arteries during early aging

Aging leads to a gradual decline in the fidelity of cerebral blood flow (CBF) responses to neuronal activation, resulting in an increased risk for stroke and dementia. However, it is currently unknown when age-related cerebrovascular dysfunction starts or which vascular components and functions are first affected. The aim of this study was to examine the function of microcirculation throughout aging in mice. Microcirculation was challenged by inhalation of 5% and 10% CO₂ or by forepaw stimulation in 6-week, 8-month, and 12-month-old FVB/N mice. The resulting dilation of pial vessels and increase in CBF was measured by intravital fluorescence microscopy and laser Doppler fluxmetry, respectively. Neurovascular coupling and astrocytic endfoot Ca²⁺ were measured in acute brain slices from 18-month-old mice. We did not reveal any changes in CBF after CO₂ reactivity up to an age of 12 months. However, direct visualization of pial vessels by in vivo microscopy showed a significant, age-dependent loss of CO₂ reactivity starting at 8 months of age. At the same age neurovascular coupling was also significantly affected. These results suggest that aging does not affect cerebral vessel function simultaneously, but starts in pial microvessels months before global changes in CBF are detectable.     

Decreased kainate receptors in the hippocampus of apolipoprotein D knockout mice

Apolipoprotein D (ApoD) has many actions critical to maintaining mammalian CNS function. It is therefore significant that levels of ApoD have been shown to be altered in the CNS of subjects with schizophrenia, suggesting a role for ApoD in the pathophysiology of the disorder. There is also a large body of evidence that cortical and hippocampal glutamatergic, serotonergic and cholinergic systems are affected by the pathophysiology of schizophrenia. Thus, we decided to use in vitro radioligand binding and autoradiography to measure levels of ionotropic glutamate, some muscarinic and serotonin 2A receptors in the CNS of ApoD^-/- and isogenic wild-type mice. These studies revealed a 20% decrease (mean ± SEM: 104 ± 10.2 vs. 130 ± 10.4 fmol/mg ETE) in the density of kainate receptors in the CA 2–3 of the ApoD^-/- mice. In addition there was a global decrease in AMPA receptors (F_1,214 = 4.67, p < 0.05) and a global increase in muscarinic M2/M4 receptors (F_1,208 = 22.77, p < 0.0001) in the ApoD^-/- mice that did not reach significance in any single cytoarchitectural region. We conclude that glutamatergic pathways seem to be particularly affected in ApoD^-/- mice and this may contribute to the changes in learning and memory, motor tasks and orientation-based tasks observed in these animals, all of which involve glutamatergic neurotransmission.     

Neuronal protective role of PBEF in a mouse model of cerebral ischemia

Pre-B-cell colony-enhancing factor (PBEF) (also known as nicotinamide phosphoribosyltransferase) is a rate-limiting enzyme in the salvage pathway for mammalian biosynthesis of nicotinamide adenine dinucleotide (NAD⁺). By synthesizing NAD⁺, PBEF functions to maintain an energy supply that has critical roles in cell survival. Cerebral ischemia is a major neural disorder with a high percentage of mortality and disability. Ischemia leads to energy depletion and eventually neuronal death and brain damage. This study investigated the role of PBEF in cerebral ischemia using a photothrombosis mouse model. Using immunostaining, we initially determined that PBEF is highly expressed in neurons, but not in glial cells in the mouse brain. To study the role of PBEF in ischemia in vivo, we used PBEF knockout heterozygous (Pbef+/−) mice. We showed that these mice have lower PBEF expression and NAD⁺ level than do wild-type (WT) mice. When subjected to photothrombosis, Pbef+/− mice have significantly larger infarct volume than do age-matched WT mice at 24 hours after ischemia. Higher density of degenerating neurons was detected in the penumbra of Pbef+/− mice than in WT mice using Fluoro-Jade B staining. Our study shows that PBEF has a neuronal protective role in cerebral ischemia presumably through enhanced energy metabolism.     

HDAC inhibitors dysregulate neural stem cell activity in the postnatal mouse brain

The mammalian central nervous system (CNS) undergoes significant expansion postnatally, producing astrocytes, oligodendrocytes and inhibitory neurons to modulate the activity of neural circuits. This is coincident in humans with the emergence of pediatric epilepsy, a condition commonly treated with valproate/valproic acid (VPA), a potent inhibitor of histone deacetylases (HDACs). The sequential activity of specific HDACs, however, may be essential for the differentiation of distinct subpopulations of neurons and glia. Here, we show that different subsets of CNS neural stem cells (NSCs) and progenitors switch expression of HDAC1 and HDAC2 as they commit to a neurogenic lineage in the subventricular zone (SVZ) and dentate gyrus (DG). The administration of VPA for only one week from P7–P14, combined with sequential injections of thymidine analogs reveals that VPA stimulates a significant and differential decrease in the production and differentiation of progeny of NSCs in the DG, rostral migratory stream (RMS), and olfactory bulb (OB). Cross-fostering VPA-treated mice revealed, however, that a postnatal failure to thrive induced by VPA treatment had a greater effect on DG neurogenesis than VPA action directly. By one month after VPA, OB interneuron genesis was significantly and differentially reduced in both periglomerular and granule neurons. Using neurosphere assays to test if VPA directly regulates NSC activity, we found that short term treatment with VPA in vivo reduced neurosphere numbers and size, a phenotype that was also obtained in neurospheres from control mice treated with VPA and an alternative HDAC inhibitor, Trichostatin A (TSA) at 0 and 3 days in vitro (DIV). Collectively, these data show that clinically used HDAC inhibitors like VPA and TSA can perturb postnatal neurogenesis; and their use should be carefully considered, especially in individuals whose brains are actively undergoing key postnatal time windows of development.