Restoration of neuronal plasticity by a phosphodiesterase type 1 inhibitor in a model of fetal alcohol exposure

Development of multisensory processing in ferret parietal cortex

It is well known that the nervous system adjusts itself to its environment during development. Although a great deal of effort has been directed towards understanding the developmental processes of the individual sensory systems (e.g., vision, hearing, etc.), only one major study has examined the maturation of multisensory processing in cortical neurons. Therefore, the present investigation sought to evaluate multisensory development in a different cortical region and species. Using multiple single-unit recordings in anaesthetised ferrets (n = 18) of different ages (from postnatal day 80 to 300), we studied the responses of neurons from the rostral posterior parietal (PPr) area to presentations of visual, tactile and combined visual-tactile stimulation. The results showed that multisensory neurons were infrequent at the youngest ages (pre-pubertal) and progressively increased through the later ages. Significant response changes that result from multisensory stimulation (defined as multisensory integration [MSI]) were observed in post-pubertal adolescent animals, and the magnitude of these integrated responses also increased across this age group. Furthermore, non-significant multisensory response changes were progressively increased in adolescent animals. Collectively, at the population level, MSI was observed to shift from primarily suppressive levels in infants to increasingly higher levels in later stages. These data indicate that, like the unisensory systems from which it is derived, multisensory processing shows developmental changes whose specific time course may be regionally and species-dependent.

Effects of developmental alcohol exposure on cortical multisensory integration

Fetal alcohol spectrum disorder (FASD) is one of the most common causes of mental disabilities in the world with a prevalence of 1%-6% of all births. Sensory processing deficits and cognitive problems are a major feature in this condition. Because developmental alcohol exposure can impair neuronal plasticity, and neuronal plasticity is crucial for the establishment of neuronal circuits in sensory areas, we predicted that exposure to alcohol during the third trimester equivalent of human gestation would disrupt the development of multisensory integration (MSI) in the rostral portion of the posterior parietal cortex (PPr), an integrative visual-tactile area. We conducted in vivo electrophysiology in 17 ferrets from four groups (saline/alcohol; infancy/adolescence). A total of 1157 neurons were recorded after visual, tactile and combined visual-tactile stimulation. A multisensory (MS) enhancement or suppression is characterized by a significantly increased or decreased number of elicited spikes after combined visual-tactile stimulation compared to the strongest unimodal (visual or tactile) response. At the neuronal level, those in infant animals were more prone to show MS suppression whereas adolescents were more prone to show MS enhancement. Although alcohol-treated animals showed similar developmental changes between infancy and adolescence, they always 'lagged behind' controls showing more MS suppression and less enhancement. Our findings suggest that alcohol exposure during the last months of human gestation would stunt the development of MSI, which could underlie sensory problems seen in FASD.

Corticostriatal Circuit Models of Cognitive Impairments Induced by Fetal Exposure to Alcohol

The term fetal alcohol spectrum disorder includes a group of diseases caused by fetal alcohol exposure (FAE). Patients with fetal alcohol spectrum disorder display heterogeneous socioemotional and cognitive deficits, particularly in the domain of executive function, that share symptoms with other neuropsychiatric disorders. Despite the availability of several preclinical models, the developmental brain defects causally linked to behavioral deficits induced by FAE remain poorly understood. Here, we first review the effects of FAE on corticostriatal development and its impact on both corticostriatal pathway function and cognitive abilities. We propose three non-mutually exclusive circuit models of corticostriatal dysfunctions to account for some of the FAE-induced cognitive deficits. One model posits that associative-sensorimotor imbalance causes hyper goal-directed behavior, and a second model implies that alteration of prefrontal-striatal behavioral suppression circuits results in loss of behavioral inhibition. A third model suggests that local striatal circuit deficits affect striatal neuronal ensemble function to impair action selection and performance. Finally, we discuss how preclinical approaches applied to these circuit models could offer potential rescue strategies for executive function deficits in patients with fetal alcohol spectrum disorder.

Vinpocetine, cognition, and epilepsy

OBJECTIVE

Vinpocetine has been shown to enhance memory in animal models, with possible cognitive benefit in humans. The present study sought to demonstrate if vinpocetine can enhance cognition in healthy volunteers or patients with epilepsy. In addition, we compare blood levels of vinpocetine and its active metabolite (apovincaminic acid; AVA) in humans and animals to further characterize factors related to possible therapeutic benefit.

METHODS

The cognitive effects of vinpocetine were assessed in healthy adult volunteers (n = 8) using a double-blind, randomized, crossover design at single doses (placebo, 10, 20, and 60 mg oral). Cognitive effects of vinpocetine in patients with focal epilepsy (n = 8) were tested using a double-blind, randomized, crossover design at single doses (placebo, 20 mg oral) followed by one-month open label at 20 mg oral three times a day. The neuropsychological battery included both computerized and non-computerized tests. Levels of vinpocetine and AVA in the human studies were compared to levels in 45 mice across time dosed at 5-20 mg/kg intraperitoneal of vinpocetine.

RESULTS

No significant cognitive benefits were seen in healthy volunteers or patients with epilepsy. No appreciable side effects occurred. Vinpocetine and AVA levels were lower in humans than animals.

CONCLUSIONS

Vinpocetine was well tolerated, but was not associated with positive cognitive effects. However, blood levels obtained in humans were substantially less than levels in animals obtained from dosages known to be effective in one model. This suggests that higher dosages are needed in humans to assess vinpocetine's cognitive efficacy.

Role of phosphodiesterase 1 in the pathophysiology of diseases and potential therapeutic opportunities

Cyclic nucleotide phosphodiesterases (PDEs) are superfamily of enzymes that regulate the spatial and temporal relationship of second messenger signaling in the cellular system. Among the 11 different families of PDEs, phosphodiesterase 1 (PDE1) sub-family of enzymes hydrolyze both 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP) in a mutually competitive manner. The catalytic activity of PDE1 is stimulated by their binding to Ca²⁺/calmodulin (CaM), resulting in the integration of Ca²⁺ and cyclic nucleotide-mediated signaling in various diseases. The PDE1 family includes three subtypes, PDE1A, PDE1B and PDE1C, which differ for their relative affinities for cAMP and cGMP. These isoforms are differentially expressed throughout the body, including the cardiovascular, central nervous system and other organs. Thus, PDE1 enzymes play a critical role in the pathophysiology of diseases through the fundamental regulation of cAMP and cGMP signaling. This comprehensive review provides the current research on PDE1 and its potential utility as a therapeutic target in diseases including the cardiovascular, pulmonary, metabolic, neurocognitive, renal, cancers and possibly others.

Inhibition of PDE1-B by Vinpocetine Regulates Microglial Exosomes and Polarization Through Enhancing Autophagic Flux for Neuroprotection Against Ischemic Stroke

Exosomes contribute to cell–cell communications. Emerging evidence has shown that microglial exosomes may play crucial role in regulation of neuronal functions under ischemic conditions. However, the underlying mechanisms of microglia-derived exosome biosynthesis are largely unknown. Herein, we reported that the microglial PDE1-B expression was progressively elevated in the peri-infarct region after focal middle cerebral artery occlusion. By an oxygen-glucose-deprivation (OGD) ischemic model in cells, we found that inhibition of PDE1-B by vinpocetine in the microglial cells promoted M2 and inhibited M1 phenotype. In addition, knockdown or inhibition of PDE1-B significantly enhanced the autophagic flux in BV2 cells, and vinpocetine-mediated suppression of M1 phenotype was dependent on autophagy in ischemic conditions. Co-culture of BV2 cells and neurons revealed that vinpocetine-treated BV2 cells alleviated OGD-induced neuronal damage, and treatment of BV2 cells with 3-MA abolished the observed effects of vinpocetine. We further demonstrated that ischemia and vinpocetine treatment significantly altered microglial exosome biogenesis and release, which could be taken up by recipient neurons and regulated neuronal damage. Finally, we showed that the isolated exosome per se from conditioned BV2 cells is sufficient to regulate cortical neuronal survival in vivo. Taken together, these results revealed a novel microglia-neuron interaction mediated by microglia-derived exosomes under ischemic conditions. Our findings further suggest that PDE1-B regulates autophagic flux and exosome biogenesis in microglia which plays a crucial role in neuronal survival under cerebral ischemic conditions.

Therapeutic Potential of Phosphodiesterase Inhibitors against Neurodegeneration: The Perspective of the Medicinal Chemist

Increasing human life expectancy prompts the development of novel remedies for cognitive decline: 44 million people worldwide are affected by dementia, and this number is predicted to triple by 2050. Acetylcholinesterase and N-methyl-d-aspartate receptors represent the targets of currently available drugs for Alzheimer’s disease, which are characterized by limited efficacy. Thus, the search for therapeutic agents with alternative or combined mechanisms of action is wide open. Since variations in 3′,5′-cyclic adenosine monophosphate, 3′,5′-cyclic guanosine monophosphate, and/or nitric oxide levels interfere with downstream pathways involved in memory processes, evidence supporting the potential of phosphodiesterase (PDE) inhibitors in contrasting neurodegeneration should be critically considered. For the preparation of this Review, more than 140 scientific papers were retrieved by searching PubMed and Scopus databases. A systematic approach was adopted when overviewing the different PDE isoforms, taking into account details on brain localization, downstream molecular mechanisms, and inhibitors currently under study, according to available in vitro and in vivo data. In the context of drug repurposing, a section focusing on PDE5 was introduced. Original computational studies were performed to rationalize the emerging evidence that suggests the role of PDE5 inhibitors as multi-target agents against neurodegeneration. Moreover, since such compounds must cross the blood–brain barrier and reach inhibitory concentrations in the central nervous system to exert their therapeutic activity, physicochemical parameters were analyzed and discussed. Taken together, literature and computational data suggest that some PDE5 inhibitors, such as tadalafil, represent promising candidates.

Updates of Recent Vinpocetine Research in Treating Cardiovascular Diseases

Vinpocetine is a derivative of vincamine. It has been used to prevent and treat cerebrovascular disorders such as stoke and dementia, and remains widely available in dietary supplements that often marketed as nootropics. Due to its excellent safety profile at therapeutic dose regimen, vinpocetine has raised research interest in its new applications in various experimental disease models. Here we review recent studies that uncovered novel functions of vinpocetine in cardiovascular diseases, including atherosclerosis, obesity, neointimal hyperplasia, vasoconstriction, pathological cardiac remodeling and ischemia stroke. Molecular mechanisms underlined the protective effects of vinpocetine are also discussed. These novel findings may suggest a broadened usage of vinpocetine against relevant cardiovascular diseases in human.

Phosphodiesterase inhibitors say NO to Alzheimer's disease

Phosphodiesterases (PDEs) consisted of 11 subtypes (PDE1 to PDE11) and over 40 isoforms that regulate levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP), the second messengers in cell functions. PDE inhibitors (PDEIs) have been attractive therapeutic targets due to their involvement in diverse medical conditions, e.g. cardiovascular diseases, autoimmune diseases, Alzheimer's disease (AD), etc. Among them; AD with a complex pathology is a progressive neurodegenerative disorder which affect mostly senile people in the world and only symptomatic treatment particularly using cholinesterase inhibitors in clinic is available at the moment for AD. Consequently, novel treatment strategies towards AD are still searched extensively. Since PDEs are broadly expressed in the brain, PDEIs are considered to modulate neurodegenerative conditions through regulating cAMP and cGMP in the brain. In this sense, several synthetic or natural molecules inhibiting various PDE subtypes such as rolipram and roflumilast (PDE4 inhibitors), vinpocetine (PDE1 inhibitor), cilostazol and milrinone (PDE3 inhibitors), sildenafil and tadalafil (PDE5 inhibitors), etc have been reported showing encouraging results for the treatment of AD. In this review, PDE superfamily will be scrutinized from the view point of structural features, isoforms, functions and pharmacology particularly attributed to PDEs as target for AD therapy.

Decreased glucose-6-phosphate dehydrogenase activity along with oxidative stress affects visual contrast sensitivity in alcoholics

OBJECTIVE

To evaluate oxidative stress and glucose-6-phosphate dehydrogenase (G6PD) status of alcoholics and discern their association, if any, with visual contrast sensitivity function.

METHODS

Forty male alcoholic subjects and 36 male non-alcoholic subjects with the same age and nutritional status were enrolled in this study. Serum malondialdehyde (MDA) level and glucose-6-phosphate dehydrogenase (G6PD) activity of erythrocytes were determined by spectrophotometric assay. Contrast sensitivity (CS) function of study subjects was measured using the Rabin Contrast Sensitivity Test (Precision Vision^®, La Salle, Illinois, United States).

RESULTS

Serum MDA levels were significantly higher (p < 0.0001) and erythrocyte G6PD activity was significantly lower (p = 0.0026) in alcoholic subjects compared to the controls. CS scores of both eyes were also found to be decreased significantly in alcoholic subjects (both at p < 0.0001) compared to control subjects. On the other hand, CS scores of the alcoholic subjects were inversely correlated with the serum MDA level (r = -0.746, p < 0.0001) and directly correlated with erythrocyte G6PD activity (r = 0.78, p < 0.0001). A strong inverse correlation (r = -0.84, p < 0.0001) was also observed between serum MDA level and erythrocyte G6PD activity of alcoholic subjects.

CONCLUSION

Reduced G6PD activity and increased serum MDA level might be the key cause of the early visual abnormalities, such as reduced CS function of the alcoholic subjects.

Cyclic nucleotide phosphodiesterases: potential therapeutic targets for alcohol use disorder

Alcohol use disorder (AUD), which combines the criteria of both alcohol abuse and dependence, contributes as an important causal factor to multiple health and social problems. Given the limitation of current treatments, novel medications for AUD are needed to better control alcohol consumption and maintain abstinence. It has been well established that the intracellular signal transduction mediated by the second messengers cyclic AMP (cAMP) and cyclic GMP (cGMP) crucially underlies the genetic predisposition, rewarding properties, relapsing features, and systemic toxicity of compulsive alcohol consumption. On this basis, the upstream modulators phosphodiesterases (PDEs), which critically control intracellular levels of cyclic nucleotides by catalyzing their degradation, are proposed to play a role in modulating alcohol abuse and dependent process. Here, we highlight existing evidence that correlates cAMP and cGMP signal cascades with the regulation of alcohol-drinking behavior and discuss the possibility that PDEs may become a novel class of therapeutic targets for AUD.

Hyperactivity and memory/learning deficits evoked by developmental exposure to nicotine and/or ethanol are mitigated by cAMP and cGMP signaling cascades activation

Pregnant smoking women are frequently episodic drinkers. Here, we investigated whether ethanol exposure restricted to the brain growth spurt period when combined with chronic developmental exposure to nicotine aggravates memory/learning deficits and hyperactivity, and associated cAMP and cGMP signaling disruption. To further investigate the role of these signaling cascades, we verified whether vinpocetine (a phosphodiesterase inhibitor) ameliorates the neurochemical and behavioral outcomes. Swiss mice had free access to nicotine (NIC, 50 μg/ml) or water to drink during gestation and until the 8th postnatal day (PN8). Ethanol (ETOH, 5 g/kg, i.p.) or saline were injected in the pups every other day from PN2 to PN8. At PN30, animals either received vinpocetine (20 mg/kg, i.p.) or vehicle before being tested in the step-down passive avoidance or open field. Memory/learning was impaired in NIC, ETOH and NIC + ETOH mice, and vinpocetine mitigated ETOH- and NIC + ETOH-induced deficits. Locomotor hyperactivity identified in ETOH and NIC + ETOH mice was ameliorated by vinpocetine. While cyclic nucleotides levels in cerebral cortex and hippocampus were reduced by NIC, ETOH and NIC + ETOH, this outcome was more consistent in the latter group. As observed for behavior, vinpocetine normalized NIC + ETOH nucleotides levels. pCREB levels were also increased in response to vinpocetine, with stronger effects in the NIC + ETOH group. Exposure to both drugs of abuse worsens behavioral and neurochemical disruption. These findings and the amelioration of deleterious effects by vinpocetine support the idea that cAMP and cGMP signaling contribute to nicotine- and ethanol-induced hyperactivity and memory/learning deficits.

Quantitative Determination of Vinpocetine in Dietary Supplements

Current United States regulatory policies allow for the addition of pharmacologically active substances in dietary supplements if derived from a botanical source. The inclusion of certain nootropic drugs, such as vinpocetine, in dietary supplements has recently come under scrutiny due to the lack of defined dosage parameters and yet unproven short- and long-term benefits and risks to human health. This study quantified the concentration of vinpocetine in several commercially available dietary supplements and found that a highly variable range of 0.6-5.1 mg/serving was present across the tested products, with most products providing no specification of vinpocetine concentrations.

Quantitative Determination of Vinpocetine in Dietary Supplements

Current United States regulatory policies allow for the addition of pharmacologically active substances in dietary supplements if derived from a botanical source. The inclusion of certain nootropic drugs, such as vinpocetine, in dietary supplements has recently come under scrutiny due to the lack of defined dosage parameters and yet unproven short- and long-term benefits and risks to human health. This study quantified the concentration of vinpocetine in several commercially available dietary supplements and found that a highly variable range of 0.6–5.1 mg/serving was present across the tested products, with most products providing no specification of vinpocetine concentrations.

Phosphodiesterase regulation of alcohol drinking in rodents

Alcohol use disorders are chronically relapsing conditions characterized by persistent drinking despite the negative impact on one's life. The difficulty of achieving and maintaining sobriety suggests that current treatments fail to fully address the underlying causes of alcohol use disorders. Identifying additional pathways controlling alcohol consumption may uncover novel targets for medication development to improve treatment options. One family of proteins recently implicated in the regulation of alcohol consumption is the cyclic nucleotide phosphodiesterases (PDEs). As an integral component in the regulation of the second messengers cyclic AMP and cyclic GMP, and thus their cognate signaling pathways, PDEs present intriguing targets for pharmacotherapies to combat alcohol use disorders. As activation of cAMP/cGMP-dependent signaling cascades can dampen alcohol intake, PDE inhibitors may provide a novel target for reducing excessive alcohol consumption, as has been proposed for PDE4 and PDE10A. This review highlights preclinical literature demonstrating the involvement of cyclic nucleotide-dependent signaling in neuronal and behavioral responses to alcohol, as well as detailing the capacity of various PDE inhibitors to modulate alcohol intake. Together these data provide a framework for evaluating the potential utility of PDE inhibitors as novel treatments for alcohol use disorders.

Developmental effects of antiepileptic drugs and the need for improved regulations

Antiepileptic drugs (AEDs) are among the most common teratogenic drugs prescribed to women of childbearing age. AEDs can induce both anatomical (malformations) and behavioral (cognitive/behavioral deficits) teratogenicity. Only in the last decade have we begun to truly discriminate differential AED developmental effects. Fetal valproate exposure carries a special risk for both anatomical and behavioral teratogenic abnormalities, but the mechanisms and reasons for individual variability are unknown. Intermediate anatomical risks exist for phenobarbital and topiramate. Several AEDs (e.g., lamotrigine and levetiracetam) appear to possess low risks for both anatomical and behavioral teratogenesis. Despite advances in the past decade, our knowledge of the teratogenic risks for most AEDs and the underlying mechanisms remain inadequate. Further, the long-term effects of AEDs in neonates and older children remain uncertain. The pace of progress is slow given the lifelong consequences of diminished developmental outcomes, exposing children unnecessarily to potential adverse effects. It is imperative that new approaches be employed to determine risks more expediently. Our recommendations include a national reporting system for congenital malformations, federal funding of the North American AED Pregnancy Registry, routine meta-analyses of cohort studies to detect teratogenic signals, monitoring of AED prescription practices for women, routine preclinical testing of all new AEDs for neurodevelopmental effects, more specific Food and Drug Administration requirements to establish differential AED cognitive effects in children, and improved funding of basic and clinical research to fully delineate risks and underlying mechanisms for AED-induced anatomical and behavioral teratogenesis.

Overexpression of Serum Response Factor in Neurons Restores Ocular Dominance Plasticity in a Model of Fetal Alcohol Spectrum Disorders

BACKGROUND

Deficits in neuronal plasticity underlie many neurobehavioral and cognitive problems presented in fetal alcohol spectrum disorder (FASD). Our laboratory has developed a ferret model showing that early alcohol exposure leads to a persistent disruption in ocular dominance plasticity (ODP). For instance, a few days of monocular deprivation results in a robust reduction of visual cortex neurons' responsiveness to stimulation of the deprived eye in normal animals, but not in ferrets with early alcohol exposure. Previously our laboratory demonstrated that overexpression of serum response factor (SRF) exclusively in astrocytes can improve neuronal plasticity in FASD. Here, we test whether neuronal overexpression of SRF can achieve similar effects.

METHODS

Ferrets received 3.5 g/kg alcohol intraperitoneally (25% in saline) or saline as control every other day between postnatal day 10 to 30, which is roughly equivalent to the third trimester of human gestation. Animals were given intracortical injections of a Herpes Simplex Virus-based vector to express either green fluorescent protein or a constitutively active form of SRF in infected neurons. They were then monocularly deprived by eyelid suture for 4 to 5 days after which single-unit recordings were conducted to determine whether changes in ocular dominance had occurred.

RESULTS

Overexpression of a constitutively active form of SRF by neurons restored ODP in alcohol-treated animals. This effect was observed only in areas near the site of viral infection.

CONCLUSIONS

Overexpression of SRF in neurons can restore plasticity in the ferret model of FASD, but only in areas near the site of infection. This contrasts with SRF overexpression in astrocytes which restored plasticity throughout the visual cortex.

Cognitive outcomes of prenatal antiepileptic drug exposure

Antiepileptic drugs (AEDs) have been known to have teratogenic effects for a little over 50 years. While early reports focused on fetal malformations, there has been an increasing amount of data over the last few decades exploring the cognitive outcomes of offspring exposed to AEDs in utero. Although the challenges of confounding factors and varied methodologies have led to inconsistent results, the negative impact of some of the agents, such as valproate, have become clear. Further studies are needed to evaluate the cognitive effects of prenatal exposure to many AEDs which have not been tested, to clarify the effects of existing AEDs which have yielded mixed results, and to better understand the effects of polytherapy. Research in animal models is warranted to screen AEDs for their effects on cognition in exposed offspring and to further our understanding of the underlying mechanisms by which AEDs exert their harmful effects on the developing brain. And finally, new AEDs without these harmful effects and agents which can prevent or reverse the negative consequences imparted by AED therapy on cognition should be sought.

Developmental consequences of fetal exposure to drugs: what we know and what we still must learn

Most drugs of abuse easily cross the placenta and can affect fetal brain development. In utero exposures to drugs thus can have long-lasting implications for brain structure and function. These effects on the developing nervous system, before homeostatic regulatory mechanisms are properly calibrated, often differ from their effects on mature systems. In this review, we describe current knowledge on how alcohol, nicotine, cocaine, amphetamine, Ecstasy, and opiates (among other drugs) produce alterations in neurodevelopmental trajectory. We focus both on animal models and available clinical and imaging data from cross-sectional and longitudinal human studies. Early studies of fetal exposures focused on classic teratological methods that are insufficient for revealing more subtle effects that are nevertheless very behaviorally relevant. Modern mechanistic approaches have informed us greatly as to how to potentially ameliorate the induced deficits in brain formation and function, but conclude that better delineation of sensitive periods, dose-response relationships, and long-term longitudinal studies assessing future risk of offspring to exhibit learning disabilities, mental health disorders, and limited neural adaptations are crucial to limit the societal impact of these exposures.

Selective inhibitors of phosphodiesterases: therapeutic promise for neurodegenerative disorders

PDE inhibitors: significant contributors to the treatment of neurodegenerative diseases.

Neurological and psychiatric sequelae of developmental exposure to antiepileptic drugs

The neurons in the developing mammalian brain are susceptible to antiepileptic drug (AED) effects. It is known that later in life deficits in cognitive performance as well as psychiatric deficits can manifest after early AED exposure. The extent of these deficits will be addressed. This review will attempt to draw parallels between the existent animal models and human studies. Through analysis of these studies, important future research will be elucidated and possible new and emerging therapies will be discussed.

Phosphodiesterases as therapeutic targets for Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia among the elderly. In AD patients, memory loss is accompanied by the formation of beta-amyloid plaques and the appearance of tau in a pathological form. Given the lack of effective treatments for AD, the development of new management strategies for these patients is critical. The continued failure to find effective therapies using molecules aimed at addressing the anti-beta amyloid pathology has led researchers to focus on other non-amyloid-based approaches to restore memory function. Promising non-amyloid related candidate targets include phosphosdiesterases (PDEs), and indeed, Rolipram, a specific PDE4 inhibitor, was the first compound found to effectively restore cognitive deficits in animal models of AD. More recently, PDE5 inhibitors have also been shown to effectively restore memory function. Accordingly, inhibitors of other members of the PDE family may also improve memory performance in AD and non-AD animal models. Hence, in this review, we will summarize the data supporting the use of PDE inhibitors as cognitive enhancers and we will discuss the possible mechanisms of action underlying these effects. We shall also adopt a medicinal chemistry perspective that leads us to propose the most promising PDE candidates on the basis of inhibitor selectivity, brain distribution, and mechanism of action.

PDE5 Inhibitors as Potential Tools in the Treatment of Cystic Fibrosis

Despite great advances in the understanding of the genetics and pathophysiology of cystic fibrosis (CF), there is still no cure for the disease. Using phosphodiesterase type 5 (PDE5) inhibitors, we and others have provided evidence of rescued F508del-CFTR trafficking and corrected deficient chloride transport activity. Studies using PDE5 inhibitors in mice homozygous for the clinically relevant F508del mutation have been conducted with the aim of restoring F508del-CFTR protein function. We demonstrated, by measuring transepithelial nasal potential difference in F508del mice following intraperitoneal injection of sildenafil, vardenafil, or taladafil at clinical doses are able to restore the decreased CFTR-dependent chloride transport across the nasal mucosa. Moreover, vardenafil, but not sildenafil, stimulates chloride transport through the normal CFTR protein. We developed a specific nebulizer setup for mice, with which we demonstrated, through a single inhalation of PDE5 inhibitors, local activation of CFTR protein in CF. Significant potential advantages of inhalation drug therapy over oral or intravenous routes include rapid onset of pharmacological action, reduced systemic secondary effects, and reduced effective drug doses compared to the drug delivered orally; this underlines the relevance and impact of our work for translational science. More recently, we analyzed the bronchoalveolar lavage of CF and wild-type mice for cell infiltrates and expression of pro-inflammatory cytokines and chemokines; we found that the CFTR activating effect of vardenafil, selected as a representative long-lasting PDE5 inhibitor, breaks the vicious circle of lung inflammation which plays a major role in morbi-mortality in CF. Our data highlight the potential use of PDE5 inhibitors in CF. Therapeutic approaches using clinically approved PDE5 inhibitors to address F508del-CFTR defects could speed up the development of new therapies for CF.

Overexpression of serum response factor in astrocytes improves neuronal plasticity in a model of early alcohol exposure

Neuronal plasticity deficits underlie many of the cognitive problems seen in fetal alcohol spectrum disorders (FASD). We have developed a ferret model showing that early alcohol exposure leads to a persistent disruption in ocular dominance (OD) plasticity. Recently, we showed that this deficit could be reversed by overexpression of serum response factor (SRF) in the primary visual cortex during the period of monocular deprivation (MD). Surprisingly, this restoration was observed throughout the extent of visual cortex and most of the cells transfected by the virus were positive for the astrocytic marker GFAP rather than the neuronal marker NeuN. Here we test whether overexpression of SRF exclusively in astrocytes is sufficient to restore OD plasticity in alcohol-exposed ferrets. To accomplish that, first we exposed cultured astrocytes to Sindbis viruses carrying either a constitutively active form of SRF (SRF+), a dominant negative (SRF-) or control Green Fluorescent Protein (GFP). After 24h, these astrocytes were implanted in the visual cortex of alcohol-exposed animals or saline controls one day before MD. Optical imaging of intrinsic signals showed that alcohol-exposed animals that were implanted with astrocytes expressing SRF, but not SRF- or GFP, showed robust restoration of OD plasticity in all visual cortex. These findings suggest that overexpression of SRF exclusively in astrocytes can improve neuronal plasticity in FASD.

Early alcohol exposure disrupts visual cortex plasticity in mice

There is growing evidence that deficits in neuronal plasticity underlie the cognitive problems seen in fetal alcohol spectrum disorders (FASD). However, the mechanisms behind these deficits are not clear. Here we test the effects of early alcohol exposure on ocular dominance plasticity (ODP) in mice and the reversibility of these effects by phosphodiesterase (PDE) inhibitors. Mouse pups were exposed to 5 g/kg of 25% ethanol i.p. on postnatal days (P) 5, 7 and 9. This type of alcohol exposure mimics binge drinking during the third trimester equivalent of human gestation. To assess ocular dominance plasticity animals were monocularly deprived at P21 for 10 days, and tested using optical imaging of intrinsic signals. During the period of monocular deprivation animals were treated with vinpocetine (20mg/kg; PDE1 inhibitor), rolipram (1.25mg/kg; PDE4 inhibitor), vardenafil (3mg/kg; PDE5 inhibitor) or vehicle solution. Monocular deprivation resulted in the expected shift in ocular dominance of the binocular zone in saline controls but not in the ethanol group. While vinpocetine successfully restored ODP in the ethanol group, rolipram and vardenafil did not. However, when rolipram and vardenafil were given simultaneously ODP was restored. PDE4 and PDE5 are specific to cAMP and cGMP respectively, while PDE1 acts on both of these nucleotides. Our findings suggest that the combined activation of the cAMP and cGMP cascades may be a good approach to improve neuronal plasticity in FASD models.

Acute administration of vinpocetine, a phosphodiesterase type 1 inhibitor, ameliorates hyperactivity in a mice model of fetal alcohol spectrum disorder

BACKGROUND

Maternal alcohol use during pregnancy causes a continuum of long-lasting disabilities in the offspring, commonly referred to as fetal alcohol spectrum disorder (FASD). Attention-deficit/hyperactivity disorder (ADHD) is possibly the most common behavioral problem in children with FASD and devising strategies that ameliorate this condition has great clinical relevance. Studies in rodent models of ADHD and FASD suggest that impairments in the cAMP signaling cascade contribute to the hyperactivity phenotype. In this work, we investigated whether the cAMP levels are affected in a long-lasting manner by ethanol exposure during the third trimester equivalent period of human gestation and whether the acute administration of the PDE1 inhibitor vinpocetine ameliorates the ethanol-induced hyperactivity.

METHODS

From postnatal day (P) 2 to P8, Swiss mice either received ethanol (5g/kg i.p.) or saline every other day. At P30, the animals either received vinpocetine (20mg/kg or 10mg/kg i.p.) or vehicle 4h before being tested in the open field. After the test, frontal cerebral cortices and hippocampi were dissected and collected for assessment of cAMP levels.

RESULTS

Early alcohol exposure significantly increased locomotor activity in the open field and reduced cAMP levels in the hippocampus. The acute treatment of ethanol-exposed animals with 20mg/kg of vinpocetine restored both their locomotor activity and cAMP levels to control levels.

CONCLUSIONS

These data lend support to the idea that cAMP signaling system contribute to the hyperactivity induced by developmental alcohol exposure and provide evidence for the potential therapeutic use of vinpocetine in FASD.

Molecular and behavioral aspects of the actions of alcohol on the adult and developing brain

The brain is one of the major target organs of alcohol actions. Alcohol abuse can lead to alterations in brain structure and functions and, in some cases, to neurodegeneration. Cognitive deficits and alcohol dependence are highly damaging consequences of alcohol abuse. Clinical and experimental studies have demonstrated that the developing brain is particularly vulnerable to alcohol, and that drinking during gestation can lead to a range of physical, learning and behavioral defects (fetal alcohol spectrum disorders), with the most dramatic presentation corresponding to fetal alcohol syndrome. Recent findings also indicate that adolescence is a stage of brain maturation and that heavy drinking at this stage can have a negative impact on brain structure and functions causing important short- and long-term cognitive and behavioral consequences. The effects of alcohol on the brain are not uniform; some brain areas or cell populations are more vulnerable than others. The prefrontal cortex, the hippocampus, the cerebellum, the white matter and glial cells are particularly susceptible to the effects of ethanol. The molecular actions of alcohol on the brain are complex and involve numerous mechanisms and signaling pathways. Some of the mechanisms involved are common for the adult brain and for the developing brain, while others depend on the developmental stage. During brain ontogeny, alcohol causes irreversible alterations to the brain structure. It also impairs several molecular, neurochemical and cellular events taking place during normal brain development, including alterations in both gene expression regulation and the molecules involved in cell-cell interactions, interference with the mitogenic and growth factor response, enhancement of free radical formation and derangements of glial cell functions. However, in both adult and adolescent brains, alcohol damages specific brain areas through mechanisms involving excitotoxicity, free radical formation and neuroinflammatory damage resulting from activation of the innate immune system mediated by TLR4 receptors. Alcohol also acts on specific membrane proteins, such as neurotransmitter receptors (e.g. NMDA, GABA-A), ion channels (e.g. L-type Ca²⁺ channels, GIRKs), and signaling pathways (e.g. PKA and PKC signaling). These effects might underlie the wide variety of behavioral effects induced by ethanol drinking. The neuroadaptive changes affecting neurotransmission systems which are more sensitive to the acute effects of alcohol occur after long-term alcohol consumption. Alcohol-induced maladaptations in the dopaminergic mesolimbic system, abnormal plastic changes in the reward-related brain areas and genetic and epigenetic factors may all contribute to alcohol reinforcement and alcohol addiction. This manuscript reviews the mechanisms by which ethanol impacts the adult and the developing brain, and causes both neural impairments and cognitive and behavioral dysfunctions. The identification and the understanding of the cellular and molecular mechanisms involved in ethanol toxicity might contribute to the development of treatments and/or therapeutic agents that could reduce or eliminate the deleterious effects of alcohol on the brain.

PDE1 isozymes, key regulators of pathological vascular remodeling

Pathological vascular remodeling is a hallmark of most vascular disorders such as atherosclerosis, postangioplasty restenosis, allograft vasculopathy, and pulmonary hypertension. Pathological vascular remodeling is a multi-cell-dependent process leading to detrimental changes of vessel structure and eventual vessel occlusion. Cyclic nucleotide signaling regulates a variety of vascular functions ranging from cell contractility to cell growth. Cyclic nucleotide phosphodiesterases (PDEs), a large family of structurally and functionally distinct isozymes, regulate cyclic nucleotide levels and compartmentalization through catalyzing their degradation reaction. Increasing evidence has suggested that one of the important mechanisms for specific cyclic nucleotide regulation is exerted through selective activation or inhibition of distinct PDE isozymes. This review summarizes the work done to characterize the role and therapeutic potential of PDE1 isozymes in pathological vascular remodeling.

From research to practice: an integrative framework for the development of interventions for children with fetal alcohol spectrum disorders

Since fetal alcohol syndrome was first described over 35 years ago, considerable progress has been made in the delineation of the neurocognitive profile in children with prenatal alcohol exposure. Preclinical investigators have made impressive strides in elucidating the mechanisms of alcohol teratogenesis and in testing the effectiveness of pharmacological agents and dietary supplementation in the amelioration of alcohol-induced deficits. Despite these advances, only limited progress has been made in the development of evidence-based comprehensive interventions for functional impairment in alcohol-exposed children. Having performed a search in PubMed and PsycINFO using key words, interventions, treatment, fetal alcohol syndrome, prenatal alcohol exposure, and fetal alcohol spectrum disorders, we found only 12 papers on empirically-based interventions. Only two of these interventions had been replicated and none met the criteria of "well-established," as defined by Chambless and Hollon (Journal of Consulting and Clinical Psychology 66(1):7-18, 1998). There has been only limited cross-fertilization of ideas between preclinical and clinical research with regard to the development of interventions. Therefore, we propose a framework that allows integrating data from preclinical and clinical investigations to develop comprehensive intervention programs for children with fetal alcohol spectrum disorders. This framework underscores the importance of multi-level evaluations and interventions.

Fetal alcohol spectrum disorders and abnormal neuronal plasticity

The ingestion of alcohol during pregnancy can result in a group of neurobehavioral abnormalities collectively known as fetal alcohol spectrum disorders (FASD). During the past decade, studies using animal models indicated that early alcohol exposure can dramatically affect neuronal plasticity, an essential property of the central nervous system responsible for the normal wiring of the brain and involved in processes such as learning and memory. The abnormalities in neuronal plasticity caused by alcohol can explain many of the neurobehavioral deficits observed in FASD. Conversely, improving neuronal plasticity may have important therapeutic benefits. In this review, the author discuss the mechanisms that lead to these abnormalities and comment on recent pharmacological approaches that have been showing promising results in improving neuronal plasticity in FASD.

Therapeutic utility of phosphodiesterase type I inhibitors in neurological conditions

Neuronal plasticity is an essential property of the brain that is impaired in different neurological conditions. Phosphodiesterase type 1 (PDE1) inhibitors can enhance levels of the second messengers cAMP/cGMP leading to the expression of neuronal plasticity-related genes, neurotrophic factors, and neuroprotective molecules. These neuronal plasticity enhancement properties make PDE1 inhibitors good candidates as therapeutic agents in many neurological conditions. However, the lack of specificity of the drugs currently available poses a challenge to the systematic evaluation of the beneficial effect of these agents. The development of more specific drugs may pave the way for the use of PDE1 inhibitors as therapeutic agents in cases of neurodevelopmental conditions such as fetal alcohol spectrum disorders and in degenerative disorders such as Alzheimer's and Parkinson's.

Early valproic acid exposure alters functional organization in the primary visual cortex

Epilepsy is one of the most common neurologic disorders and affects 0.5 to 1% of pregnant women. The use of antiepileptic drugs, which is usually continued throughout pregnancy, can cause in offspring mild to severe sensory deficits. Neuronal selectivity to stimulus orientation is a basic functional property of the visual cortex that is crucial for perception of shapes and borders. Here we investigate the effects of early exposure to valproic acid (Val) and levetiracetam (Lev), commonly used antiepileptic drugs, on the development of cortical neuron orientation selectivity and organization of cortical orientation columns. Ferrets pups were exposed to Val (200mg/kg), Lev (100mg/kg) or saline every other day between postnatal day (P) 10 and P30, a period roughly equivalent to the third trimester of human gestation. Optical imaging of intrinsic signals or single-unit recordings were examined at P42-P84, when orientation selectivity in the ferret cortex has reached a mature state. Optical imaging of intrinsic signals revealed decreased contrast of orientation maps in Val- but not Lev- or saline-treated animals. Moreover, single-unit recordings revealed that early Val treatment also reduced orientation selectivity at the cellular level. These findings indicate that Val exposure during a brief period of development disrupts cortical processing of sensory information at a later age and suggest a neurobiological substrate for some types of sensory deficits in fetal anticonvulsant syndrome.

Fetal alcohol spectrum disorders: experimental treatments and strategies for intervention

Despite the known damaging effects of prenatal alcohol exposure, women continue to drink during pregnancy, creating a need for effective interventions and treatments for fetal alcohol spectrum disorders (FASD). Experimental models can be useful in identifying potential treatments, and this article describes the spectrum of experimental therapeutics that currently are being investigated, including pharmacological, nutritional, and environmental/behavioral interventions. Some treatments target the underlying mechanisms that contribute to alcohol-induced damage, protecting against alcohol's teratogenic effects, whereas other treatments may enhance central nervous system plasticity either during alcohol exposure or long after alcohol exposure has ceased. The insights gained to date from experimental models offer several candidates for attenuating the deficits associated with FASD.

Focus on: the use of animal models for the study of fetal alcohol spectrum disorders

Considerable efforts to educate women not to abuse alcohol during pregnancy have failed to reduce the incidence of fetal alcohol syndrome. Therefore, other approaches to limit the effects of prenatal alcohol exposure are under consideration, including the development of prevention programs and interventions. For these strategies to be as successful as possible, it also is important to improve methods for identifying affected children. The use of animal models in prenatal alcohol exposure research is critical because of the practical and ethical limitations of using human subjects for such studies. This article reviews the use of animal models in three areas of research: addressing basic questions about alcohol exposure during development; improving the identification of affected individuals; and developing approaches to reduce the impact of prenatal alcohol exposure. The various animal-model systems that have been used to study fetal alcohol spectrum disorders, each with their own specific strengths, have provided new findings that have been successfully extrapolated to human subjects, resulting in advancement of the research field and our understanding of fetal alcohol spectrum disorders.

Liquid-diet with alcohol alters maternal, fetal and placental weights and the expression of molecules involved in integrin signaling in the fetal cerebral cortex

Maternal alcohol consumption during pregnancy causes wide range of behavioral and structural deficits in children, commonly known as Fetal Alcohol Syndrome (FAS). Children with FAS may suffer behavioral deficits in the absence of obvious malformations. In rodents, the exposure to alcohol during gestation changes brain structures and weights of offspring. The mechanism of FAS is not completely understood. In the present study, an established rat (Long-Evans) model of FAS was used. The litter size and the weights of mothers, fetuses and placentas were examined on gestation days 18 or 20. On gestation day 18, the effects of chronic alcohol on the expression levels of integrin receptor subunits, phospholipase-Cγ and N-cadherin were examined in the fetal cerebral cortices. Presence of alcohol in the liquid-diet reduced the consumption and decreased weights of mothers and fetuses but increased the placental weights. Expression levels of β₁ and α₃ integrin subunits and phospholipase-Cγ₂ were significantly altered in the fetal cerebral cortices of mothers on alcohol containing diet. Results show that alcohol consumption during pregnancy even with protein, mineral and vitamin enriched diet may affect maternal and fetal health, and alter integrin receptor signaling pathways in the fetal cerebral cortex disturbing the development of fetal brains.

A neurodevelopmental framework for the development of interventions for children with fetal alcohol spectrum disorders

Despite considerable data published on cognitive and behavioral disabilities in children with fetal alcohol spectrum disorders (FASD), relatively little information is available on behavioral or pharmacological interventions for alcohol-affected children. The main goals of this article, therefore, are to summarize published intervention studies of FASD and to present a neurodevelopmental framework, based on recent findings from a number of disciplines, for designing new therapies for alcohol-affected children. This framework assumes a neuroconstructionist view, which posits that reciprocal interactions between neural activity and the brain's hardware lead to the progressive formation of intra- and interregional neural connections. In this view, behavioral interventions can be conceptualized as a series of guided experiences that are designed to produce neural activation. Based on evidence from cognitive neuroscience, it is hypothesized that specific interventions targeting executive attention and self-regulation may produce greater generalizable results than those aimed at domain-specific skills in children with FASD. In view of reciprocal interactions between environmental effects and neural structures, the proposed framework suggests that the maximum effects of interventions can eventually be achieved by optimally combining behavioral methods and cognition-enhancing drugs.

Effects of a novel cognition-enhancing agent on fetal ethanol-induced learning deficits

BACKGROUND

Drinking during pregnancy has been associated with learning disabilities in affected offspring. At present, there are no clinically effective pharmacotherapeutic interventions for these learning deficits. Here, we examined the effects of ABT-239, a histamine H₃ receptor antagonist, on fetal ethanol-induced fear conditioning and spatial memory deficits.

METHODS AND RESULTS

Long-Evans rat dams stably consumed a mean of 2.82 g ethanol/kg during a 4-hour period each day during pregnancy. This voluntary drinking pattern produced a mean peak serum ethanol level of 84 mg/dl. Maternal weight gain, litter size and birth weights were not different between the ethanol-consuming and control groups. Female adult offspring from the control and fetal alcohol-exposed (FAE) groups received saline or 1 mg ABT-239/kg 30 minutes prior to fear conditioning training. Three days later, freezing time to the context was significantly reduced in saline-treated FAE rats compared to control. Freezing time in ABT-239-treated FAE rats was not different than that in controls. In the spatial navigation study, adult male offspring received a single injection of saline or ABT-239 30 minutes prior to 12 training trials on a fixed platform version of the Morris Water Task. All rats reached the same performance asymptote on Trials 9 to 12 on Day 1. However, 4 days later, first-trial retention of platform location was significantly worse in the saline-treated FAE rats compared control offspring. Retention by ABT-239-treated FAE rats was similar to that by controls. ABT-239's effect on spatial memory retention in FAE rats was dose dependent.

CONCLUSIONS

These results suggest that ABT-239 administered prior to training can improve retention of acquired information by FAE offspring on more challenging versions of hippocampal-sensitive learning tasks. Further, the differential effects of ABT-239 in FAE offspring compared to controls raises questions about the impact of fetal ethanol exposure on histaminergic neurotransmission in affected offspring.

Overexpression of serum response factor restores ocular dominance plasticity in a model of fetal alcohol spectrum disorders

Neuronal plasticity deficits underlie many of the neurobehavioral problems seen in fetal alcohol spectrum disorders (FASD). Recently, we showed that third trimester alcohol exposure leads to a persistent disruption in ocular dominance (OD) plasticity. For instance, a few days of monocular deprivation results in a robust reduction of cortical regions responsive to the deprived eye in normal animals, but not in ferrets exposed early to alcohol. This plasticity deficit can be reversed if alcohol-exposed animals are treated with a phosphodiesterase type 1 (PDE1) inhibitor during the period of monocular deprivation. PDE1 inhibition can increase cAMP and cGMP levels, activating transcription factors such as the cAMP response element binding protein (CREB) and the serum response factor (SRF). SRF is important for many plasticity processes such as LTP, LTD, spine motility, and axonal pathfinding. Here we attempt to rescue OD plasticity in alcohol-treated ferrets using a Sindbis viral vector to express a constitutively active form of SRF during the period of monocular deprivation. Using optical imaging of intrinsic signals and single-unit recordings, we observed that overexpression of a constitutively active form of SRF, but neither its dominant-negative nor GFP, restored OD plasticity in alcohol-treated animals. Surprisingly, this restoration was observed throughout the extent of the primary visual cortex and most cells infected by the virus were positive for GFAP rather than NeuN. This finding suggests that overexpression of SRF in astrocytes may reduce the deficits in neuronal plasticity seen in models of FASD.

Phosphodiesterase type 1 inhibition improves learning in rats exposed to alcohol during the third trimester equivalent of human gestation

Deficits in learning and memory have been extensively observed in animal models of fetal alcohol spectrum disorders (FASD). Here we use the Morris maze to test whether vinpocetine, a phosphodiesterase type 1 inhibitor, restores learning performance in rats exposed to alcohol during the third trimester equivalent of human gestation. Long Evans rats received ethanol (5g/kg i.p.) or saline on alternate days from postnatal day (P) 4 to P10. Two weeks later (P25), the latency to find a hidden platform was evaluated (2 trials per day spaced at 40-min inter-trial intervals) during 4 consecutive days. Vinpocetine treatment started on the first day of behavioral testing: animals received vinpocetine (20mg/kg i.p.) or vehicle solution every other day until the end of behavioral procedures. Early alcohol exposure significantly affected the performance to find the hidden platform. The average latency of ethanol-exposed animals was significantly higher than that observed for the control group. Treatment of alcohol-exposed animals with vinpocetine restored their performance to control levels. Our results show that inhibition of PDE1 improves learning and memory deficits in rats early exposed to alcohol and provide evidence for the potential therapeutic use of vinpocetine in FASD.

Neonatal cerebral hypoxia-ischemia impairs plasticity in rat visual cortex

Ocular dominance plasticity (ODP) following monocular deprivation (MD) is a model of activity-dependent neural plasticity that is restricted to an early critical period regulated by maturation of inhibition. Unique developmental plasticity mechanisms may improve outcomes following early brain injury. Our objective was to determine the effects of neonatal cerebral hypoxia-ischemia (HI) on ODP. The rationale extends from observations that neonatal HI results in death of subplate neurons, a transient population known to influence development of inhibition. In rodents subjected to neonatal HI and controls, maps of visual response were derived from optical imaging during the critical period for ODP and changes in the balance of eye-specific response following MD were measured. In controls, MD results in a shift of the ocular dominance index (ODI) from a baseline of 0.15 to -0.10 (p < 0.001). Neonatal HI with moderate cortical injury impairs this shift, ODI = 0.14 (p < 0.01). Plasticity was intact in animals with mild injury and in those exposed to hypoxia alone. Neonatal HI resulted in decreased parvalbumin expression in hemispheres receiving HI compared with hypoxia alone: 23.4 versus 35.0 cells/high-power field (p = 0.01), with no change in other markers of inhibitory or excitatory neurons. Despite abnormal inhibitory neuron phenotype, spontaneous activity of single units and development of orientation selective responses were intact following neonatal HI, while overall visual responses were reduced. Our data suggest that specific plasticity mechanisms are impaired following early brain injury and that the impairment is associated with altered inhibitory neuronal development and cortical activation.

Fetal alcohol spectrum disorders: from research to policy

Forty years ago, alcohol was not commonly recognized as a teratogen, an agent that can disrupt the development of a fetus. Today, we understand that prenatal alcohol exposure induces a variety of adverse effects on physical, neurological, and behavioral development. Research supported by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) has contributed to the identification of the range and prevalence of fetal alcohol spectrum disorders (FASD), as well as methods for prevention and treatment of FASD. The worldwide prevalence and high personal and societal costs of FASD speak to the importance of this research. This article briefly examines some of the ways that NIAAA has contributed to our understanding of FASD, the challenges that we still face, and how this research is translated into changes in public policy.

Phosphodiesterase type 4 inhibition does not restore ocular dominance plasticity in a ferret model of fetal alcohol spectrum disorders

BACKGROUND

There is growing evidence that deficits in neuronal plasticity account for some of the neurological problems observed in fetal alcohol spectrum disorders (FASD). Recently, we showed that early alcohol exposure results in a permanent impairment in visual cortex ocular dominance (OD) plasticity in a ferret model of FASD. This disruption can be reversed, however, by treating animals with a Phosphodiesterase (PDE) type 1 inhibitor long after the period of alcohol exposure.

AIM

Because the mammalian brain presents different types of PDE isoforms we tested here whether inhibition of PDE type 4 also ameliorates the effects of alcohol on OD plasticity.

MATERIAL AND METHODS

Ferrets received 3.5 g/Kg alcohol i.p. (25% in saline) or saline as control every other day between postnatal day (P) 10 to P30, which is roughly equivalent to the third trimester equivalent of human gestation. Following a prolonged alcohol-free period (10 to 15 days), ferrets had the lid of the right eye sutured closed for 4 days and were examined for ocular dominance changes at the end of the period of deprivation.

RESULTS

Using in vivo electrophysiology we show that inhibition of PDE4 by rolipram does not restore OD plasticity in alcohol-treated ferrets.

CONCLUSION

This result suggests that contrary to PDE1, PDE4 inhibition does not play a role in the restoration of OD plasticity in the ferret model of FASD.

Phosphodiesterase inhibition increases CREB phosphorylation and restores orientation selectivity in a model of fetal alcohol spectrum disorders

Background

Fetal alcohol spectrum disorders (FASD) are the leading cause of mental retardation in the western world and children with FASD present altered somatosensory, auditory and visual processing. There is growing evidence that some of these sensory processing problems may be related to altered cortical maps caused by impaired developmental neuronal plasticity.

Methodology/Principal Findings

Here we show that the primary visual cortex of ferrets exposed to alcohol during the third trimester equivalent of human gestation have decreased CREB phosphorylation and poor orientation selectivity revealed by western blotting, optical imaging of intrinsic signals and single-unit extracellular recording techniques. Treating animals several days after the period of alcohol exposure with a phosphodiesterase type 1 inhibitor (Vinpocetine) increased CREB phosphorylation and restored orientation selectivity columns and neuronal orientation tuning.

Conclusions/Significance

These findings suggest that CREB function is important for the maturation of orientation selectivity and that plasticity enhancement by vinpocetine may play a role in the treatment of sensory problems in FASD.

Neocortical plasticity deficits in fetal alcohol spectrum disorders: lessons from barrel and visual cortex

Fetal Alcohol Spectrum Disorder (FASD) is characterized by a constellation of behavioral and physiological abnormalities, including learning and sensory deficits. There is growing evidence that abnormalities of neuronal plasticity underlie these deficits. However, the cellular and molecular mechanisms by which prenatal alcohol exposure disrupts neuronal plasticity remain elusive. Recently, studies with the barrel and the visual cortex as models to study the effects of early alcohol exposure on neuronal plasticity shed light on this subject. In this Mini-Review, we discuss the effects of ethanol exposure during development on neuronal plasticity and suggest environmental and pharmacological approaches to ameliorate these problems.

Vinpocetine for acute ischaemic stroke

BACKGROUND

Vasoactive and neuroprotective drugs such as vinpocetine are used to treat stroke in some countries.

OBJECTIVES

To assess the effect of vinpocetine in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched February 2007), MEDLINE (1966 to February 2007) and Scopus (1960 to February 2007). We also searched the Internet Stroke Center Stroke Trials Registry, Google Scholar, the science-specific search engine Scirus and Wanfang Data, the leading information provider in China. We contacted researchers in the field and four pharmaceutical companies that manufacture vinpocetine. Searches were complete to February 2007.

SELECTION CRITERIA

Unconfounded randomised trials of vinpocetine compared with placebo, or any other reference treatment, in people with acute ischaemic stroke. We included trials if treatment started no later than 14 days after stroke onset.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria. One review author extracted the data, which was then checked by the second review author. We assessed trial quality. The primary outcome measure was death or dependency.

MAIN RESULTS

We included two trials, involving a total of 70 participants. Data for 63 participants were reported in the two trials combined. The rate of death or dependency did not differ between the treatment and placebo groups at one and three months. The 95% confidence intervals for the outcome measures were wide and included the possibility of both significant benefit and significant harm. No adverse effects were reported.

AUTHORS' CONCLUSIONS

There is not enough evidence to evaluate the effect of vinpocetine on survival or dependency in patients with acute ischaemic stroke.

Neural stem cell transplantation in a model of fetal alcohol effects

Neural stem cell (NSC) transplantation has been investigated and developed in areas such as brain injury, stroke and neurodegenerative diseases. Recently, emerging evidence suggest that many of clinical symptoms observed in psychiatric disease are likely related to neural network disruptions including neurogenesis dysfunction. In the present study, we transplanted NSCs into a model of fetal alchol effects (FAE) for the purpose of investigating the possibility of regenerative therapy for the FAE. We labeled NSCs with fluorescent dye and radioisotope which were transplanted into FAE rats by intravenous injection. The transplanted cells were detected in wide areas of brain and were greater in number in the brains of the FAE group compared to the control group. Furthermore NSC transplantation attenuated behavioral abnormalities in FAE animals. These results suggest NSC transplantation as a potental new therapy for human FAE.