Increasing dietary choline attenuates spatial memory deficits resulting from exposure to the chemotherapeutic agents cyclophosphamide and doxorubicin.

BACKGROUND: Choline supplementation (+Ch) improves cognitive function in impaired animals and humans. Chemotherapy-related cognitive deficits (CRCDs) occur in cancer patients, and these deficits persist following treatment, adversely impacting quality of life. To date, there are no approved treatments for this condition. AIM: Because +Ch improves impaired memory, it was of interest to determine whether +Ch can attenuate spatial memory deficits induced by the chemotherapeutic agents doxorubicin (DOX) and cyclophosphamide (CYP). METHODS: Female BALB/C mice, 64 days of age, were trained in the Morris water maze and baseline performance determined on day 15. Following baseline assessment, mice were placed on +Ch diet (2.0% Ch) or remained on standard diet (0.12% Ch). Mice received intravenous injections of DOX (2.5 mg/kg) and CYP (25 mg/kg), or equivalent volumes of saline (0.9% NaCl), on days 16, 23, 30, and 37, and spatial memory was assessed weekly from day 22 to 71. RESULTS: DOX and CYP produced a prolonged impairment in spatial memory as indicated by an increased latency to the correct zone (p < 0.05), and a decrease in time in the correct zone (p < 0.05), % of total swim distance in the correct zone (p < 0.05) and % entries to the correct zone (p < 0.05). These effects were attenuated by +Ch. CONCLUSION: Although it remains to be determined whether this effect extends to other cognitive domains and whether +Ch is prophylactic or therapeutic, these findings suggest that +Ch may be an effective intervention for CRCDs.

The ASPET Mentoring Network: Enhancing Diversity and Inclusion through Career Coaching Groups within a Scientific Society.

Over the past decades, two persisting priorities in science, technology, engineering, and mathematics (STEM) training have been: 1) increasing the knowledge of and access to careers beyond academic scientist; and 2) increasing the diversity of the STEM workforce. Previous studies show that a uniquely constructed career coaching group provides strong support and progress for both priorities. This report extends this design into a more sustainable model that is positioned within the professional context of rising young scientists. This new model is based in the American Society for Pharmacology and Experimental Therapeutics (ASPET)-the ASPET Mentoring Network. Groups of PhD students and postdocs were assigned to an ASPET professional (academic or other career) member (the coach) with an initial meeting held the day before the society's annual meeting. The coaching groups interacted during the meeting and then virtually for a year. Extensive survey and interview evaluation data gathered from the first three cohorts (12 coaching groups) in 2016- 2018 provided strong evidence of the perceived and real benefits of the network. This new version of career coaching groups is both feasible and linked to career success due to its close association with a scientific society, peers, and coaches who share scientific identities and aspirations.

Longitudinal gait and balance decline in Friedreich's Ataxia: A pilot study.

INTRODUCTION: Friedreich's Ataxia (FA) is a devastating, progressive, neurodegenerative disease. Objective measures that detect changes in neurological function in FA patients are needed to facilitate therapeutic clinical trials. The purpose of this pilot study was to analyze longitudinal changes in gait and balance in subjects with FA using the GAITRite Walkway System® and Biodex Balance System™, respectively, and to test the ability of these measures to detect change over time compared to the Friedreich's Ataxia Rating Scale (FARS). METHODS: This was a 24-month longitudinal study comparing ambulatory FA subjects with age- and gender-matched, healthy controls. Eight FA subjects and 8 controls were tested at regular intervals using the GAITRite and Biodex Balance systems and the FARS. RESULTS: In the FA group, comfortable and fast gait velocity declined 8.0% and 13.9% after 12 months and 24.1% and 30.3% after 24 months, respectively. Postural stability indices increased in FA subjects an average of 41% from baseline to 24 months, representing a decline in balance. Subjects with FA also demonstrated a 17.7% increase in FARS neurological exam scores over 24 months. There were no changes in gait or balance variables in controls. In the FA group, multiple gait and balance measures correlated significantly with FARS neurological exam scores. CONCLUSIONS: The GAITRite and Biodex Balance systems provided objective and clinically relevant measures of functional decline in subjects with FA that correlated significantly with performance measures in the FARS. Gait velocity may be an important objective measure to identify disease progression in adults with FA.

Doxorubicin and cyclophosphamide lead to long-lasting impairment of spatial memory in female, but not male mice.

Self-reports of chemotherapy-related cognitive deficits (CRCDs) are more prevalent among women than men, suggesting that women may be more vulnerable to the cognitive-impairing effects of chemotherapy. However, there have been no direct comparisons of females and males using objective measures of cognitive function either during or following exposure to the same chemotherapeutic regimen. The present study used an animal model, and a prospective longitudinal design, to assess sex differences in the manifestation and persistence of spatial memory deficits resulting from exposure to doxorubicin (DOX) and cyclophosphamide (CYP), commonly used anticancer drugs. The spatial memory of female and male BALB/C mice was assessed using the Morris water maze prior to, during and following 4 weekly intravenous injections of DOX (2.5mg/kg) and CYP (25mg/kg) or vehicle. Females receiving DOX+CYP experienced significant deficits in spatial memory during and following injections when compared to baseline or females receiving vehicle. These deficits persisted for at least 34 days following the final injection. In contrast, males receiving DOX+CYP injections did not exhibit alterations in spatial memory relative to baseline or males receiving vehicle. These findings indicate that females may be more vulnerable than males to the cognitive-impairing effects of DOX+CYP and demonstrate that deficits in females persist for at least several weeks following drug exposure. Preclinical studies of CRCDs should parallel clinical work by including females and examine sex specific factors as potential mechanisms.

Regulation of Gait and Balance: The Underappreciated Role of Neuronal Nicotinic Receptor Agonists.

Alterations in gait and balance are manifest in numerous neurological disorders such as the ataxias and Parkinson's disease, and may occur as a consequence of stroke, traumatic brain injury and chemical insults to the brain. Although the underlying etiology of these disorders differs, disturbances in gait and balance appear to reflect deficits in cholinergic pathways within the brain. During the past 40 years, both clinical case studies and preclinical data have provided evidence that nicotinic cholinergic activation is beneficial for alleviating gait and balance deficits in many disorders. Further, studies indicate that activation of neuronal nicotinic receptors leads to neuroprotective and neurotrophic actions. And yet, despite these findings, there hsas been no concerted effort to develop neuronal nicotinic agonists for the treatment of abnormal gait and balance. The goal of this review is to shed light on the therapeutic benefit of the cholinergic nicotinic system for the treatment of ataxia, and discuss the challenges and limitations associated with developing drugs to treat disorders involving deficits in gait and balance.

Obstacles and Opportunities for Cholinergic Drug Development in the Treatment of Cognitive Disorders.

The frequency of neuropsychiatric disorders is greater than that of cancer, cardiovascular disease, and diabetes combined, and is growing at a faster rate than any other ailments in the United States or Europe. Despite a considerable need for the development of treatments for central nervous system disorders, pharmaceutical companies continue to reduce investment in this area of research. Of particular concern is the treatment of diseases and disorders that affect cognitive function, which are often given a lower priority for research investment than life threatening conditions or those with overt physical symptoms. Several reasons exist for this reduced investment, including a poor understanding of the mechanisms underlying impaired cognitive function, costly and long periods of development for these medications, disproportionately lower success rates, and a stigma associated with the medical treatment of mental illness. This paper will discuss these issues, review some of the successes resulting from research investment and discuss opportunities that should encourage increased research investment in cognitive disorders and their treatment.

Gait and balance in adults with Friedreich's ataxia.

Friedreich's ataxia (FA) is an autosomal recessive, neurodegenerative disease characterized by progressive muscle weakness and sensory loss, balance deficits, and gait ataxia. Gait and balance impairments become worse as the disease progresses, but limited research has quantitatively assessed these deficits in adults with FA. The purpose of this study was to analyze gait and balance in this population and investigate the relationship between these variables. Eight subjects with genetically confirmed FA (29.4±9.0 years) and eight healthy, matched control subjects (29.6±9.1 years) participated in this study. Spatiotemporal gait parameters were examined using the GAITRite Walkway System while balance was examined utilizing the Biodex Balance System SD and the Berg Balance Scale (BBS). The FA group exhibited approximately 50% slower gait velocity and 32% shorter step and stride lengths compared to the control group for both comfortable and fast walking (p<0.001). Further, stride length variability in the FA group was 3.4 and 2.7 times that of controls for comfortable and fast walking, respectively (p<0.01). Subjects with FA took 72% longer to complete the limits of stability (LOS) test and attained an overall directional control score that was 50% that of controls (p<0.05). Lastly, age at FA symptom onset correlated with stride length variability during fast walking (p<0.05), and BBS and LOS test scores correlated with stride length variability during both comfortable and fast walking (p<0.05). Results demonstrate that adults with FA have significantly impaired gait and balance and several measures of these impairments are correlated.

Postpartum depression in rats: differences in swim test immobility, sucrose preference and nurturing behaviors.

Postpartum depression (PPD) is a common disorder affecting both mothers and their offspring. Studies of PPD in laboratory animals have typically assessed either immobility on forced swim testing or sucrose preference in ovariectomized rats following hormone supplementation and withdrawal or in stress models. To date, few studies have related these measures to maternal behaviors, a potential indicator of depressive-like activity postpartum. Because a single measure may be insufficient to characterize depression, the present study determined the distribution of depressive-like behaviors in Sprague-Dawley rats postpartum. Nurturing and non-nurturing behaviors exhibited by undisturbed dams were recorded during the first 12 days postpartum, and immobility in the forced swim test and sucrose preference were determined thereafter. A median-split analysis indicated that 19% of dams exhibited high sucrose preference and low immobility, 30% exhibited either only high immobility or only low sucrose preference, and 21% exhibited both high immobility and low preference. Dams exhibiting depressive-like activity on either or both tests displayed increased self-directed behaviors and decreased active nurturing during the dark phase of the diurnal cycle. This is the first study to characterize undisturbed nurturing and non-nurturing behaviors, and use both sucrose preference and immobility in the forced swim test, to classify PPD endophenotypes exhibited by rat dams following parturition. The present study underscores the idea that multiple tests should be used to characterize depressive-like behavior, which is highly heterogeneous in both the human and laboratory animal populations.

Ethanol conditioned place preference and alterations in ΔFosB following adolescent nicotine administration differ in rats exhibiting high or low behavioral reactivity to a novel environment.

This study determined the effects of adolescent nicotine administration on adult alcohol preference in rats exhibiting high or low behavioral reactivity to a novel environment, and ascertained whether nicotine altered ΔFosB in the ventral striatum (vStr) and prefrontal cortex (PFC) immediately after drug administration or after rats matured to adulthood. Animals were characterized as exhibiting high (HLA) or low (LLA) locomotor activity in the novel open field on postnatal day (PND) 31 and received injections of saline (0.9%) or nicotine (0.56 mg free base/kg) from PND 35 to 42. Ethanol-induced conditioned place preference (CPP) was assessed on PND 68 following 8 days conditioning in a biased paradigm; ΔFosB was measured on PND 43 or PND 68. Following adolescent nicotine exposure, HLA animals demonstrated a CPP when conditioned with ethanol; LLA animals were unaffected. Further, adolescent nicotine exposure for 8 days increased levels of ΔFosB in limbic regions in both HLA and LLA rats, but this increase persisted into adulthood only in LLA animals. Results indicate that adolescent nicotine exposure facilitates the establishment of an ethanol CPP in HLA rats, and that sustained elevations in ΔFosB are not necessary or sufficient for the establishment of an ethanol CPP in adulthood. These studies underscore the importance of assessing behavioral phenotype when determining the behavioral and cellular effects of adolescent nicotine exposure.

The role of estrogen receptor ß and nicotinic cholinergic receptors in postpartum depression.

Postpartum depression (PPD) is a devastating disease occurring in approximately 20% of women. Women who suffer from PPD appear to be more sensitive to postpartum hormonal changes than women who do not experience this form of depression. Furthermore, women who quit smoking prior to or during pregnancy, and who develop PPD, are at an increased risk of smoking relapse. Unfortunately, the mechanistic relationship between the pathophysiology of PPD and smoking relapse is unknown. Here we review the roles of both estrogen receptor beta (ERß) and cholinergic nicotinic receptors (nAChRs) in the pathogenesis of depression and propose a mechanistic rationale to explain the high rate of smoking relapse exhibited by women who develop PPD.

Effects of nicotine exposure on locomotor activity and pCREB levels in the ventral striatum of adolescent rats.

Behavioral reactivity to novel stimuli, which is greater in the adolescent than young adult population, is associated with drug abuse liability, suggesting that the increased addiction vulnerability of adolescents may be related to heightened novel stimulus reactivity and underlying cellular processes. We examined the hypothesis that adolescent animals who exhibit higher novel stimulus reactivity, exhibit greater locomotor activity in response to nicotine than adolescents who exhibit lower novel stimulus reactivity, and that this difference is associated with alterations in CREB expression and activity in the ventral striatum (vStr) and prefrontal cortex (PFC). Adolescents exhibiting high locomotor activity (HLA) in the novel open field developed tolerance to the locomotor depressant effects of nicotine with fewer exposures and at lower doses than adolescents with low locomotor activity (LLA). Further, HLA adolescents exhibited lower CREB activity in the vStr than LLA adolescents and this difference was attenuated by repeated exposure to high, but not low doses of nicotine. Thus, inherent differences in the reactivity to novel stimulation during the adolescent period appear to predict sensitivity to the behavioral and cellular effects of nicotine and may underlie differences in progression to addiction.

Activation and inhibition of mouse muscle and neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes.

Transgenic mouse models with nicotinic acetylcholine receptor (nAChR) knockouts and knockins have provided important insights into the molecular substrates of addiction and disease. However, most studies of heterologously expressed neuronal nAChR have used clones obtained from other species, usually human or rat. In this work, we use mouse clones expressed in Xenopus oocytes to provide a relatively comprehensive characterization of the three primary classes of nAChR: muscle-type receptors, heteromeric neuronal receptors, and homomeric alpha7-type receptors. We evaluated the activation of these receptor subtypes with acetylcholine and cytisine-related compounds, including varenicline. We also characterized the activity of classic nAChR antagonists, confirming the utility of mecamylamine and dihydro-beta-erythroidine as selective antagonists in mouse models of alpha3beta4 and alpha4beta2 receptors, respectively. We also conducted an in-depth analysis of decamethonium and hexamethonium on muscle and neuronal receptor subtypes. Our data indicate that, as with receptors cloned from other species, pairwise expression of neuronal alpha and beta subunits in oocytes generates heterogeneous populations of receptors, most likely caused by variations in subunit stoichiometry. Coexpression of the mouse alpha5 subunit had varying effects, depending on the other subunits expressed. The properties of cytisine-related compounds are similar for mouse, rat, and human nAChR, except that varenicline produced greater residual inhibition of mouse alpha4beta2 receptors than with human receptors. We confirm that decamethonium is a partial agonist, selective for muscle-type receptors, but also note that it is a nondepolarizing antagonist for neuronal-type receptors. Hexamethonium was a relatively nonselective antagonist with mixed competitive and noncompetitive activity.

Repeated ethanol exposure during adolescence alters the developmental trajectory of dopaminergic output from the nucleus accumbens septi.

Individuals who begin using alcohol prior to 14 years of age are 4 times more likely to progress to addiction than those who do not initiate use until 21 years of age. The nucleus accumbens septi undergoes dramatic developmental transitions during the adolescent period, and dopaminergic activity within this region has been identified as a central neurochemical mediator of drug reward, addiction and dependence. Thus, alcohol-induced neurochemical alterations in dopaminergic activity within this brain region likely mediate the heightened vulnerability to addiction observed in adolescent alcohol users. To investigate this idea, Sprague-Dawley rats were exposed to intraperitoneal injections of either saline or ethanol (0.5, 1.0 or 2.0 g/kg) twice daily over four days beginning on postnatal day 21, 31, 41 or 56. Cannulas were implanted toward the nucleus accumbens septi, subsequent in vivo microdialysis was used to collect samples, and both basal and ethanol-stimulated dopamine overflow was measured using high performance liquid chromatography with electrochemical detection. A developmental transition in basal levels of dopamine in the nucleus accumbens septi was apparent with peak levels at postnatal day 45. An ethanol challenge produced unique responses across ages, with greater peak effects relative to baseline in younger animals (postnatal day 25 and 35). Following repeated exposure to ethanol, a significant increase in basal dopamine was apparent for all ages, and when these animals were challenged with ethanol, peak effects relative to baseline were decreased in younger animals, but unchanged in older animals (postnatal day 45 and 60). Results indicate that there is a key developmental transition in the ability of rats to adapt to the effects of repeated ethanol exposure, which occurs between postnatal day 35 and 45. This alteration may explain the increased addiction vulnerability observed in individuals who initiate alcohol use during early adolescence.

Cortical alpha7 nicotinic acetylcholine receptor and beta-amyloid levels in early Alzheimer disease.

OBJECTIVE: To examine alpha7 nicotinic acetylcholine receptor (nAChR) binding and beta-amyloid (Abeta) peptide load in superior frontal cortex (SFC) across clinical and neuropathological stages of Alzheimer disease (AD). DESIGN: Quantitative measures of alpha7 nAChR by [(3)H]methyllycaconitine binding and Abeta concentration by enzyme-linked immunosorbent assay in SFC were compared across subjects with antemortem clinical classification of no cognitive impairment, mild cognitive impairment, or mild to moderate AD, and with postmortem neuropathological diagnoses. SETTING: Academic medical center. Subjects Twenty-nine elderly retired clergy. MAIN OUTCOME MEASURES: Quantitative measures of alpha7 nAChR binding and Abeta peptide concentration in SFC. RESULTS: Higher concentrations of total Abeta peptide in SFC were associated with clinical diagnosis of mild to moderate AD (P = .02), lower Mini-Mental State Examination scores (P = .003), presence of cortical Abeta plaques (P = .02), and likelihood of AD diagnosis by the National Institute on Aging-Reagan criteria (P = .002). Increased alpha7 nAChR binding was associated with National Institute on Aging-Reagan diagnosis (P = .02) and, albeit weakly, the presence of cortical Abeta plaques (P = .08). There was no correlation between the 2 biochemical measures. CONCLUSIONS: These observations suggest that during the clinical progression from normal cognition to neurodegenerative disease state, total Abeta peptide concentration increases while alpha7 nAChRs remain relatively stable in SFC. Regardless of subjects' clinical status, however, elevated alpha7 nAChR binding is associated with increased Abeta plaque pathology, supporting the hypothesis that cellular expression of these receptors may be upregulated selectively in Abeta plaque-burdened brain areas.

Dependence of adolescent novelty-seeking behavior on response phenotype and effects of apparatus scaling.

Adult rats have been phenotyped as high (HRs) or low (LRs) responders to novelty, the former associated with high-risk behaviors. Data indicating that adolescent rodents exhibit increased novelty-seeking relative to adults are equivocal, and phenotypic variations in adolescent novel stimulus reactivity are unknown. To determine whether novelty-seeking differs between adolescent and adult rats, reflecting phenotypic variations within each age, activities in an inescapable novel environment and novel object exploration were measured. Adolescents moved further, faster, and more continuously than adults, and exhibited a greater variability and range of activity in the novel environment. Both adolescent and adult LRs habituated to the environment by the second trial, but HRs maintained increased activity throughout 8 trials. In the free-choice paradigm, adolescents approached the novel object more frequently and spent more time in proximity to the object than adults. Similar results were obtained using arenas and objects of the same size or scaled to animal size. Results confirm that novelty-seeking by adolescents is greater than by adults, a behavior attributed primarily to the response magnitude exhibited by adolescents with the HR phenotype.

Cyclic AMP-dependent protein kinase (PKA) phosphorylates Ser362 and 467 and protein kinase C phosphorylates Ser550 within the M3/M4 cytoplasmic domain of human nicotinic receptor alpha4 subunits.

Studies have suggested that the expression, translocation, and function of alpha4beta2 nicotinic receptors may be modulated by alpha4 subunit phosphorylation, but little direct evidence exists to support this idea. The objective of these experiments was to identify specific serine/threonine residues on alpha4 subunits that are phosphorylated in vivo by cAMP-dependent protein kinase and protein kinase C (PKC). To accomplish this, DNAs coding for human alpha4 subunits containing alanines in place of serines/threonines predicted to represent phosphorylation sites were constructed, and transiently transfected with the DNA coding for wild-type beta2 subunits into SH-EP1 cells. Cells were pre-incubated with (32)Pi and incubated in the absence or presence of forskolin or phorbol 12,13-dibutyrate. Immunoprecipitated alpha4 subunits were subjected to immunoblot, autoradiographic and phosphoamino acid analyses, and two-dimensional phosphopeptide mapping. Results confirmed the presence of two alpha4 protein bands, a major band of 71/75 kDa and a minor band of 80/85 kDa. Phosphoamino acid analysis of the major band indicated that only serine residues were phosphorylated. Phosphopeptide maps demonstrated that Ser362 and 467 on the M3/M4 cytoplasmic domain of the alpha4 subunit represent major cAMP-dependent protein kinase phosphorylation sites, while Ser550 also contained within this major intracellular loop is a major site for protein kinase C phosphorylation.

The controversy concerning plasma homocysteine in Parkinson disease patients treated with levodopa alone or with entacapone: effects of vitamin status.

Levodopa treatment of Parkinson disease results in hyperhomocysteinemia (HHcy) as a consequence of levodopa methylation by catechol-O-methyltransferase (COMT). Although inhibition of COMT should theoretically prevent or reduce levodopa-induced HHcy, results from several prospective studies are conflicting. Our review of these studies suggests that the ability of COMT inhibition to reduce or prevent levodopa-induced HHcy in Parkinson disease patients may be attributed to differences in the vitamin status of the study participants. In patients with low or low-normal folate levels, levodopa administration is associated with a greater increase in homocysteine and concomitant entacapone administration is associated with a greater reduction in homocysteine.

The alpha7 nicotinic acetylcholine receptor subunit exists in two isoforms that contribute to functional ligand-gated ion channels.

Fast synaptic transmission in mammalian autonomic ganglia is mediated primarily by nicotinic receptors, and one of the most abundant nicotinic acetylcholine receptor subtypes in these neurons contains the alpha7 subunit (alpha7-nAChRs). Unlike alpha7-nAChRs expressed in other cells, the predominant alpha7-nAChR subtype found in rat intracardiac and superior cervical ganglion neurons exhibits a slow rate of desensitization and is reversibly blocked by alpha-bungarotoxin (alphaBgt). We report here the identification of an alpha7 subunit sequence variant in rat autonomic neurons that incorporates a novel 87-base pair cassette exon in the N terminus of the receptor and preserves the reading frame of the transcript. This alpha7 isoform was detected using reverse transcriptase-polymerase chain reaction techniques in neonatal rat brain and intracardiac and superior cervical ganglion neurons. Immunoblot experiments using a polyclonal antibody directed against the deduced amino acid sequence of the alpha7-2 insert showed a pattern of expression consistent with alpha7-2 subunit mRNA distribution. Moreover, the alpha7-2 subunit could be immunodepleted from protein extracts by solid-phase immunoprecipitation techniques using the anti-alpha7 monoclonal antibody 319. The alpha7-2 subunit was shown to form functional homomeric ion channels that were activated by acetylcholine and blocked by alpha-bungarotoxin when expressed in Xenopus laevis oocytes. This alpha7 isoform exhibited a slow rate of desensitization, and inhibition of these channels by alphaBgt reversed rapidly after washout. Taken together, these data indicate that the alpha7-2 subunit is capable of forming functional alphaBgt-sensitive acetylcholine receptors that resemble the alpha7-nAChRs previously identified in rat autonomic neurons. Furthermore, the distribution of the alpha7-2 isoform is not limited to peripheral neurons.

Developmental differences in nicotine place conditioning.

To understand the motivations and implications of the prevalence of smoking, studies have compared the behavioral effects of nicotine, the psychoactive drug in tobacco, in adolescent and adult animals. The present study used a biased three-chambered conditioned-place preference procedure without prior habituation to examine the potential rewarding and anxiolytic effects of nicotine across adolescence and adulthood to assess the presence of age-dependent differences in response to nicotine.