Pharmacologic fibroblast reprogramming into photoreceptors restores vision.

Photoreceptor loss is the final common endpoint in most retinopathies that lead to irreversible blindness, and there are no effective treatments to restore vision1,2. Chemical reprogramming of fibroblasts offers an opportunity to reverse vision loss; however, the generation of sensory neuronal subtypes such as photoreceptors remains a challenge. Here we report that the administration of a set of five small molecules can chemically induce the transformation of fibroblasts into rod photoreceptor-like cells. The transplantation of these chemically induced photoreceptor-like cells (CiPCs) into the subretinal space of rod degeneration mice (homozygous for rd1, also known as Pde6b) leads to partial restoration of the pupil reflex and visual function. We show that mitonuclear communication is a key determining factor for the reprogramming of fibroblasts into CiPCs. Specifically, treatment with these five compounds leads to the translocation of AXIN2 to the mitochondria, which results in the production of reactive oxygen species, the activation of NF-κB and the upregulation of Ascl1. We anticipate that CiPCs could have therapeutic potential for restoring vision.

Temporal and region-specific tau hyperphosphorylation in the medulla and forebrain coincides with development of functional changes in male obese Zucker rats.

Metabolic syndrome (MetS) is associated with development of tauopathies that contribute to cognitive decline. Without functional leptin receptors, male obese Zucker rats (OZRs) develop MetS, and they have increased phosphorylated tau (ptau) with impaired cognitive function. In addition to regulating energy balance, leptin enhances activation of the hippocampus, which is essential for spatial learning and memory. Whether spatial learning and memory are always impaired in OZRs or develop with MetS is unknown. We hypothesized that male OZRs develop MetS traits that promote regional increases in ptau and functional deficits associated with those brain regions. In the medulla and cortex, tau-pSer199,202 and tau-pSer396 were comparable in juvenile (7-8 wk old) lean Zucker rats (LZRs) and OZRs but increased in 18- to 19-wk-old OZRs. Elevated tau-pSer396 was concentrated in the dorsal vagal complex of the medulla, and by this age OZRs had hypertension with increased arterial pressure variability. In the hippocampus, tau-pSer199,202 and tau-pSer396 were still comparable in 18- to 19-wk-old OZRs and LZRs but elevated in 28- to 29-wk-old OZRs, with emergence of deficits in Morris water maze performance. Comparable escape latencies observed during acquisition in 18- to 19-wk-old OZRs and LZRs were increased in 28- to 29-wk-old OZRs, with greater use of nonspatial search strategies. Increased ptau developed with changes in the insulin/phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway in the hippocampus and cortex but not medulla, suggesting different underlying mechanisms. These data demonstrate that leptin is not required for spatial learning and memory in male OZRs. Furthermore, early development of MetS-associated autonomic dysfunction by the medulla may be predictive of later hippocampal dysfunction and cognitive impairment.NEW & NOTEWORTHY Male obese Zucker rats (OZRs) lack functional leptin receptors and develop metabolic syndrome (MetS). At 16-19 wk, OZRs are insulin resistant, with increased ptau in dorsal medulla and impaired autonomic regulation of AP. At 28-29 wk OZRs develop increased ptau in hippocampus with deficits in spatial learning and memory. Juvenile OZRs lack elevated ptau and these deficits, demonstrating that leptin is not essential for normal function. Elevated ptau and deficits emerge before the onset of diabetes in insulin-resistant OZRs.

Long-term hypogonadism diminishes the neuroprotective effects of dietary genistein in young adult ovariectomized rats after transient focal ischemia.

Increasing age disproportionately increases the risk of stroke among women compared to men of similar age, especially after menopause. One of the reasons for this observation is a sharp drop in circulating estrogens. However, the timing of initiation of estrogen replacement after menopause is associated with mixed beneficial and detrimental effects, hence contributing to widespread mistrust of estrogen use. Agents including soy isoflavones are being assessed as viable alternatives to estrogen therapy. In this study, we hypothesized that the neuroprotective effects of genistein, a soy isoflavone are less sensitive to the length of hypogonadism in young adult ovariectomized rats following cerebral ischemia. We expected that long-term hypogonadism will worsen motor and cognitive function, increase post-stroke inflammation with no effect on the neuroprotection of genistein. We compared the effect of treatment with dietary genistein (GEN) on short-term (2 weeks) and long-term hypogonadism (12 weeks) in young adult ovariectomized Sprague-Dawley rats on sensorimotor function, cognition and inflammation after focal ischemia. Dorsal Silastic implant of 17ß-estradiol (E2) was used as a control for hormone therapy. Long-term hypogonadism stroked rats performed worse than the short-term hypogonadism stroked rats on the motor and cognitive function tests. GEN did not improve neurological assessment and motor learning after either short-term or long-term hypogonadism. GEN improved cognitive flexibility after short-term hypogonadism but not after the long-term. Both GEN and E2 reduced tissue loss after short-term hypogonadism and reduced GFAP expression at the contralateral side of ischemia after long-term hypogonadism. The length of hypogonadism may differentially influence the neuroprotective effects of both GEN and E2 on the motor and cognitive functions in young adult rats.

Dietary genistein and 17ß-estradiol implants differentially influence locomotor and cognitive functions following transient focal ischemia in middle-aged ovariectomized rats at different lengths of estrogen deprivation.

Genistein possesses estrogenic activity and has been considered a potential replacement for estrogen replacement therapy after menopause. In the current study, we investigated the neuroprotective effects of dietary genistein at varied lengths of estrogen deprivation in middle-aged ovariectomized Sprague-Dawley rats under ischemic conditions. Two weeks of treatment with dietary genistein at 42 mg/kg but not 17ß-estradiol implants improved cognitive flexibility (Morris water maze test) after short-term estrogen deprivation (2 weeks) but not long-term estrogen deprivation (12 weeks). 17ß-estradiol implants but not dietary genistein improved locomotor asymmetry (cylinder test) after long-term but not short-term estrogen deprivation. Dietary genistein but not 17ß-estradiol implant improved early phase motor learning (rotarod test) after long-term estrogen deprivation. Neither 17ß-estradiol implant nor dietary genistein reduced infarct size after either short-term or long-term estrogen deprivation. Genistein, however, reduced ionized calcium-binding adaptor molecule-1 (Iba1) expression, a marker of brain inflammation, at the ipsilateral side of stroke injury after short-term but not long-term estrogen deprivation. This study suggests that the neuroprotective effects of dietary genistein on motor and cognitive functions are distinctly influenced by the length of estrogen deprivation following focal ischemia. SIGNIFICANCE: There is an increasing postmenopausal population opting for homeopathic medicines for the management of menopausal symptoms due to the perceived distrust in estrogen use as hormone replacement. Basic and clinical studies support the notion that early, but not delayed, hormone replacement after menopause is beneficial. Furthermore, evidence suggests that delaying hormone replacement augments the detrimental, rather than the beneficial effects of estrogens. Because of the active consideration of soy isoflavones including genistein as alternatives to estrogen replacement, it is necessary to understand the ramifications of soy isoflavones use when their administration is begun at various times after menopause.

Behavioral effects of four novel synthetic cathinone analogs in rodents.

A new generation of novel cathinone compounds has been developed as stimulant substitutes to avoid drug control laws and detection of use by blood tests. Dipentylone, N-ethylhexedrone, 4-chloroethcathinone (4-CEC), and 4'-methyl-α-pyrrolidinohexiophenone (MPHP) were tested for in vivo psychostimulant-like effects to assess their abuse liability. Locomotor activity was assessed in an open-field assay using Swiss-Webster mice to screen for locomotor stimulant effects and to identify behaviorally-active dose ranges, times of peak effect, and durations of action. Discriminative stimulus effects were assessed in separate groups of Sprague-Dawley rats trained to discriminate cocaine or methamphetamine from vehicle. Dipentylone, N-ethylhexedrone, 4-CEC, and MPHP dose-dependently increased locomotor activity. Dipentylone, N-ethylhexedrone, and MPHP produced maximal stimulant effects similar to cocaine and methamphetamine. 4-CEC was less efficacious, producing peak stimulant effects of about 74% of that of methamphetamine. The compounds were less potent than methamphetamine and approximately equipotent with cocaine. The doses of cocaine, methamphetamine, dipentylone, and 4-CEC that produced peak effects lasted 2 to 3 h, the peak dose of N-ethylhexedrone lasted 4 h, and the peak dose of MPHP lasted 6 h. All four compounds fully substituted for the discriminative stimulus effects of methamphetamine and cocaine, although full substitution by 4-CEC occurred at doses that substantially decreased response rate. Only 4-CEC fully substituted for MDMA. These data provide evidence that the novel cathinone compounds dipentylone, N-ethylhexedrone, 4-CEC, and MPHP demonstrate potential for abuse as psychostimulants, given their ability to stimulate locomotor activity and their substitution for the discriminative stimulus effects of methamphetamine and cocaine.

Evaluation of Substituted N-Phenylpiperazine Analogs as D3 vs. D2 Dopamine Receptor Subtype Selective Ligands.

N-phenylpiperazine analogs can bind selectively to the D3 versus the D2 dopamine receptor subtype despite the fact that these two D2-like dopamine receptor subtypes exhibit substantial amino acid sequence homology. The binding for a number of these receptor subtype selective compounds was found to be consistent with their ability to bind at the D3 dopamine receptor subtype in a bitopic manner. In this study, a series of the 3-thiophenephenyl and 4-thiazolylphenyl fluoride substituted N-phenylpiperazine analogs were evaluated. Compound 6a was found to bind at the human D3 receptor with nanomolar affinity with substantial D3 vs. D2 binding selectivity (approximately 500-fold). Compound 6a was also tested for activity in two in-vivo assays: (1) a hallucinogenic-dependent head twitch response inhibition assay using DBA/2J mice and (2) an L-dopa-dependent abnormal involuntary movement (AIM) inhibition assay using unilateral 6-hydroxydopamine lesioned (hemiparkinsonian) rats. Compound 6a was found to be active in both assays. This compound could lead to a better understanding of how a bitopic D3 dopamine receptor selective ligand might lead to the development of pharmacotherapeutics for the treatment of levodopa-induced dyskinesia (LID) in patients with Parkinson's disease.

Chronic Testosterone Deprivation Sensitizes the Middle-Aged Rat Brain to Damaging Effects of Testosterone Replacement.

INTRODUCTION: An increasing number of middle-aged men are being screened for low testosterone levels and the number of prescriptions for various forms of testosterone replacement therapy (TRT) has increased dramatically over the last 10 years. However, the safety of TRT has come into question with some studies suggesting increased morbidity and mortality. OBJECTIVE: Because the benefits of estrogen replacement in postmenopausal women and ovariectomized rodents are lost if there is an extended delay between estrogen loss and replacement, we hypothesized that TRT may also be sensitive to delayed replacement. METHODS: We compared the effects of testosterone replacement after short-term (2 weeks) and long-term testosterone deprivation (LTTD; 10 weeks) in middle-aged male rats on cerebral ischemia, oxidative stress, and cognitive function. We hypothesized that LTTD would increase oxidative stress levels and abrogate the beneficial effects of TRT. RESULTS: Hypogonadism itself and TRT after short-term castration did not affect stroke outcome compared to intact rats. However, after long-term hypogonadism in middle-aged male Fischer 344 rats, TRT exacerbated the detrimental behavioral effects of experimental focal cerebral ischemia, whereas this detrimental effect was prevented by administration of the free-radical scavenger tempol, suggesting that TRT exacerbates oxidative stress. In contrast, TRT improved cognitive performance in non-stroked rats regardless of the length of hypogonadism. In the Morris water maze, peripheral oxidative stress was highly associated with decreased cognitive ability. CONCLUSIONS: Taken together, these data suggest that TRT after long-term hypogonadism can exacerbate functional recovery after focal cerebral ischemia, but in the absence of injury can enhance cognition. Both of these effects are modulated by oxidative stress levels.

Supplementation with N-Acetyl Cysteine Affects Motor and Cognitive Function in Young but Not Old Mice.

BACKGROUND: N-acetyl cysteine (NAC) is a thiolic antioxidant that is thought to increase cellular glutathione (GSH) by augmenting the concentration of available cysteine, an essential precursor to GSH production. Manipulating redox status can affect brain function, and NAC intake has been associated with improving brain function in models of neurodegenerative diseases. OBJECTIVES: The objective of the study was to determine if short-term dietary supplementation with NAC could ameliorate functional impairment associated with aging. METHODS: C57BL/6J male mice aged 6, 12, or 24 mo were fed a control diet or the control diet supplemented with 0.3% NAC for a total of 12 wk. After 4 wk of dietary supplementation, mice began a series of behavioral tests to measure spontaneous activity (locomotor activity test), psychomotor performance (bridge-walking and coordinated running), and cognitive capacity (Morris water maze and discriminated active avoidance). The performance of the mice on these tests was analyzed through the use of analyses of variance with Age and Diet as factors. RESULTS: Supplementation of NAC improved peak motor performance in a coordinated running task by 14% (P < 0.05), and increased the time spent around the platform by 24% in a Morris water maze at age 6 mo. However, the supplementation had no to minimal effect on the motor and cognitive functions of 12- and 24-mo-old mice. CONCLUSIONS: The findings of this preclinical study support the claim that NAC has nootropic properties in 6-mo-old mice, but suggest that it may not be useful for improving motor and cognitive impairments in older mice.

Creatine, Creatine Kinase, and Aging.

With an ever aging population, identifying interventions that can alleviate age-related functional declines has become increasingly important. Dietary supplements have taken center stage based on various health claims and have become a multi-million dollar business. One such supplement is creatine, a major contributor to normal cellular physiology. Creatine, an energy source that can be endogenously synthesized or obtained through diet and supplement, is involved primarily in cellular metabolism via ATP replenishment. The goal of this chapter is to summarize how creatine and its associated enzyme, creatine kinase, act under normal physiological conditions, and how altered levels of either may lead to detrimental functional outcomes. Furthermore, we will focus on the effect of aging on the creatine system and how supplementation may affect the aging process and perhaps reverse it.

Caspase-3-Dependent Proteolytic Cleavage of Tau Causes Neurofibrillary Tangles and Results in Cognitive Impairment During Normal Aging.

Mouse models of neurodegenerative diseases such as Alzheimer's disease (AD) are important for understanding how pathological signaling cascades change neural circuitry and with time interrupt cognitive function. Here, we introduce a non-genetic preclinical model for aging and show that it exhibits cleaved tau protein, active caspases and neurofibrillary tangles, hallmarks of AD, causing behavioral deficits measuring cognitive impairment. To our knowledge this is the first report of a non-transgenic, non-interventional mouse model displaying structural, functional and molecular aging deficits associated with AD and other tauopathies in humans with potentially high impact on both new basic research into pathogenic mechanisms and new translational research efforts. Tau aggregation is a hallmark of tauopathies, including AD. Recent studies have indicated that cleavage of tau plays an important role in both tau aggregation and disease. In this study we use wild type mice as a model for normal aging and resulting age-related cognitive impairment. We provide evidence that aged mice have increased levels of activated caspases, which significantly correlates with increased levels of truncated tau and formation of neurofibrillary tangles. In addition, cognitive decline was significantly correlated with increased levels of caspase activity and tau truncated by caspase-3. Experimentally induced inhibition of caspases prevented this proteolytic cleavage of tau and the associated formation of neurofibrillary tangles. Our study shows the strength of using a non-transgenic model to study structure, function and molecular mechanisms in aging and age related diseases of the brain.

The Prodrug DHED Delivers 17ß-Estradiol into the Retina for Protection of Retinal Ganglion Cells and Preservation of Visual Function in an Animal Model of Glaucoma.

We report a three-pronged phenotypic evaluation of the bioprecursor prodrug 10ß,17ß-dihydroxyestra-1,4-dien-3-one (DHED) that selectively produces 17ß-estradiol (E2) in the retina after topical administration and halts glaucomatous neurodegeneration in a male rat model of the disease. Ocular hypertension (OHT) was induced by hyperosmotic saline injection into an episcleral vein of the eye. Animals received daily DHED eye drops for 12 weeks. Deterioration of visual acuity and contrast sensitivity by OHT in these animals were markedly prevented by the DHED-derived E2 with concomitant preservation of retinal ganglion cells and their axons. In addition, we utilized targeted retina proteomics and a previously established panel of proteins as preclinical biomarkers in the context of OHT-induced neurodegeneration as a characteristic process of the disease. The prodrug treatment provided retina-targeted remediation against the glaucomatous dysregulations of these surrogate endpoints without increasing circulating E2 levels. Collectively, the demonstrated significant neuroprotective effect by the DHED-derived E2 in the selected animal model of glaucoma supports the translational potential of our presented ocular neuroprotective approach owing to its inherent therapeutic safety and efficacy.

Hyperbaric oxygen alleviates selective domains of cognitive and motor deficits in female 5xFAD mice.

Treatment of Alzheimer's disease (AD) has been limited to managing of symptoms or anti-amyloid therapy with limited results and uncertainty. Seeking out new therapies that can reverse the effects of this devastating disease is important. Hyperbaric oxygen (HBO) therapy could be such a candidate as it has been shown to improve brain function in certain neurological conditions. Furthermore, the role sex plays in the vulnerability/resilience to AD remains equivocal. An understanding of what makes one sex more vulnerable to AD could unveil new pathways for therapy development. In this study, we investigated the effects of HBO on cognitive, motor, and affective function in a mouse model of AD (5xFAD) and assessed protein oxidation in peripheral tissues as a safety indicator. The motor and cognitive abilities of 5xFAD mice were significantly impaired. HBO therapy improved cognitive flexibility and associative learning of 5xFAD females but not males, but HBO had no effect other aspects of cognition. HBO also reversed AD-related declines in balance but had no impact on gait and anxiety-like behavior. HBO did not affect body weights or oxidative stress in peripheral tissues. Our study provides further support for HBO therapy as a potential treatment for AD and emphasizes the importance of considering sex as a biological variable in therapeutic development. Further investigations into the underlying mechanisms of HBO's sex-specific responses are warranted, as well as optimizing treatment protocols for maximum benefits.

Experimental Ischemic Stroke Induces Secondary Bihemispheric White Matter Degeneration and Long-Term Cognitive Impairment.

Clinical studies have identified widespread white matter degeneration in ischemic stroke patients. However, contemporary research in stroke has predominately focused on the infarct and periinfarct penumbra regions. The involvement of white matter degeneration after ischemic stroke and its contribution to post-stroke cognitive impairment and dementia (PSCID) has remained less explored in experimental models. In this study, we examined the progression of locomotor and cognitive function up to 4 months after inducing ischemic stroke by middle cerebral artery occlusion in young adult rats. Despite evident ongoing locomotor recovery, long-term cognitive and affective impairments persisted after ischemic stroke, as indicated by Morris water maze, elevated plus maze, and open field performance. At 4 months after stroke, multimodal MRI was conducted to assess white matter degeneration. T2-weighted MRI (T2WI) unveiled bilateral cerebroventricular enlargement after ischemic stroke. Fluid Attenuated Inversion Recovery MRI (FLAIR) revealed white matter hyperintensities in the corpus callosum and fornix across bilateral hemispheres. A positive association between the volume of white matter hyperintensities and total cerebroventricular volume was noted in stroke rats. Further evidence of bilateral white matter degeneration was indicated by the reduction of fractional anisotropy and quantitative anisotropy at bilateral corpus callosum in diffusion-weighted MRI (DWI) analysis. Additionally, microglia and astrocyte activation were identified in the bilateral corpus callosum after stroke. Our study suggests that experimental ischemic stroke induced by MCAO in young rat replicate long-term cognitive impairment and bihemispheric white matter degeneration observed in ischemic stroke patients. This model provides an invaluable tool for unraveling the mechanisms underlying post-stroke secondary white matter degeneration and its contribution to PSCID.

Transient focal cerebral ischemia induces long-term cognitive function deficit in an experimental ischemic stroke model.

Vascular dementia ranks as the second leading cause of dementia in the United States. However, its underlying pathophysiological mechanism is not fully understood and no effective treatment is available. The purpose of the current study was to evaluate long-term cognitive deficits induced by transient middle cerebral artery occlusion (tMCAO) in rats and to investigate the underlying mechanism. Sprague-Dawley rats were subjected to tMCAO or sham surgery. Behavior tests for locomotor activity and cognitive function were conducted at 7 or 30days after stroke. Hippocampal long term potentiation (LTP) and involvement of GABAergic neurotransmission were evaluated at 30days after sham surgery or stroke. Immunohistochemistry and Western blot analyses were conducted to determine the effect of tMCAO on cell signaling in the hippocampus. Transient MCAO induced a progressive deficiency in spatial performance. At 30days after stroke, no neuron loss or synaptic marker change in the hippocampus were observed. LTP in both hippocampi was reduced at 30days after stroke. This LTP impairment was prevented by blocking GABAA receptors. In addition, ERK activity was significantly reduced in both hippocampi. In summary, we identified a progressive decline in spatial learning and memory after ischemic stroke that correlates with suppression of hippocampal LTP, elevation of GABAergic neurotransmission, and inhibition of ERK activation. Our results indicate that the attenuation of GABAergic activity or enhancement of ERK/MAPK activation in the hippocampus might be potential therapeutic approaches to prevent or attenuate cognitive impairment after ischemic stroke.

The potential of hyperbaric oxygen as a therapy for neurodegenerative diseases.

The World Health Organization estimates that by the year 2040, neurodegenerative diseases will be the second leading cause of death in developed countries, overtaking cancer-related deaths and exceeded only by cardiovascular disease-related death. The search for interventions has therefore become paramount to alleviate some of this burden. Based on pathways affected in neurodegenerative diseases, hyperbaric oxygen treatment (HBOT) could be a good candidate. This therapy has been used for the past 50 years for conditions such as decompression sickness and wound healing and has been shown to have promising effects in conditions associated with neurodegeneration and functional impairments. The goal of this review was to explore the history of hyperbaric oxygen therapy, its uses, and benefits, and to evaluate its effectiveness as an intervention in treating neurodegenerative diseases. Additionally, we examined common mechanisms underlying the effects of HBOT in different neurodegenerative diseases, with a special emphasis on epigenetics.

Clinical evaluation of fall risk in older adults who use lower-limb prostheses: A scoping review.

BACKGROUND: No reviews or evidence-based clinical protocols exist to evaluate fall risk in older adults who use lower-limb prostheses, despite falls being prevalent and costly in this population. This scoping review sought to determine assessments, defined as clinical outcome measures and gait parameters, associated with fall risk in this population to determine if a systematic review is warranted and help inform an evidence-based clinical protocol. METHODS: Google Scholar, PubMed, and Scopus were searched on April 19th, 2022 to include peer-reviewed original research. Included articles reported relationships between falls and clinical outcome measures or gait parameters in older adults who use transtibial or transfemoral prostheses. Clinical outcome measures included self-reported questionnaires and functional mobility tests. Gait parameters included spatiotemporal, kinematic, and kinetic data during walking and stair negotiation. RESULTS: Nineteen articles were included. Clinical outcome measure scores, gait parameter data, and cutoff scores by fall status (nonfallers, single fallers, recurrent fallers) were summarized. Six articles determined clinical outcome measures that had statistically significant associations with falls, and two articles determined gait parameters that had statistically significant associations with falls. CONCLUSIONS: The majority of articles found no clinical outcome measure or gait parameter alone was effective at identifying fall risks in this population. Future research should evaluate a combination of assessments and collect prospective fall data to move towards establishing an evidence-based protocol to evaluate fall risk in older adults using lower-limb prostheses.

Comparison of locomotor stimulant and drug discrimination effects of four synthetic cathinones to commonly abused psychostimulants.

BACKGROUND: The underground market is constantly flooded with newer synthetic as alternatives to the older cathinones. Drug Enforcement Administration (DEA) has identified four cathinone compounds of particular concern: 3,4-methylenedioxy-alpha-pyrrolidinohexanophenone (3,4-MD-α-PHP), 4-chloro-α-pyrrolidinopropiophenone (4-Cl-α-PPP), alpha-pyrrolidinoisohexiophenone (α-PiHP) and 4-chloro-pentedrone (4-Cl-pentedrone). AIMS: The current study aimed to evaluate the behavioral pharmacology of four synthetic cathinones. METHODS: 3,4-MD-α-PHP, 4-Cl-α-PPP, α-PiHP, and 4-CPD were tested for locomotor activity in mice and in a drug discrimination assay with rats trained to discriminate either methamphetamine or cocaine. RESULTS: Locomotor stimulant effects of 3,4-MD-α-PHP ((effective dose) ED50 = 1.98 mg/kg), α-PiHP (ED50 = 2.46 mg/kg), and 4-Cl-α-PPP (ED50 = 7.18 mg/kg) were observed within 10 min following injection and lasted from 2 to 3.5 h. The stimulant action of 4-CPD (ED50 = 17.24 mg/kg) was delayed, occurring 40-70 min following injection. The maximal motor stimulant actions of 3,4-MD-α-PHP and α-PiHP 1 were equivalent to that of cocaine and methamphetamine, whereas 4-CPD (50% of cocaine) and 4-Cl-α-PPP (73% of cocaine) were less efficacious. All of the test compounds fully substituted for the discriminative stimulus effects of cocaine, 3,4-MD-α-PHP (ED50 = 2.28 mg/kg), α-PiHP (ED50 = 3.84 mg/kg), and 4-Cl-α-PPP (ED50 = 15.56 mg/kg). Only 3,4-MD-α-PHP (ED50 = 1.65 mg/kg), α-PiHP (ED50 = 1.87 mg/kg), and 4-Cl-α-PPP (ED50 = 9.79 mg/kg) fully substituted for the discriminative stimulus effects of methamphetamine. 4-Cl-pentedrone caused 55-70% methamphetamine-appropriate responding at doses that also suppressed responding and produced convulsions. CONCLUSIONS: These data indicate that 3,4-MD-α-PHP, α-PiHP, and 4-Cl-α-PPP have a potential for abuse similar to that of methamphetamine and cocaine. In contrast, 4-Cl-pentedrone may not be popular for recreational use due to its convulsant effects.

Locomotor and discriminative stimulus effects of three benzofuran compounds in comparison to abused psychostimulants.

Aims: Benzofurans are used recreationally, due their ability to cause psychostimulant and/or entactogenic effects, but unfortunately produce substantial adverse effects, including death. Three benzofurans 5-(2-aminopropyl)-2,3-dihydrobenzofuran (5-APDB), 5-(2-aminopropyl)-2,3-dihydrobenzofuran (5-MAPB) and 6-(2-aminopropyl) benzofuran (6-APB) were tested to determine their behavioral effects in comparison with 2,3-methylenedioxymethamphetamine (MDMA), cocaine, and methamphetamine. Methods: Locomotor activity was tested in groups of 8 male Swiss-Webster mice in an open-field task to screen for locomotor stimulant or depressant effects and to identify behaviorally active doses and times of peak effect. Discriminative stimulus effects were tested in groups of 6 male Sprague-Dawley rats trained to discriminate MDMA (1.5 mg/kg), cocaine (10 mg/kg), or methamphetamine (1 mg/kg) from saline using a FR 10 for food in a two-lever operant task. Results: In the locomotor activity test, MDMA (ED50 = 8.34 mg/kg) produced peak stimulant effects 60 to 80 min following injection. 5-MAPB (ED50 = 0.92 mg/kg) produced modest stimulant effects 50 to 80 min after injection, whereas 6-APB (ED50 = 1.96 mg/kg) produced a robust stimulant effect 20 to 50 min after injection. 5-APDB produced an early depressant phase (ED50 = 3.38 mg/kg) followed by a modest stimulant phase (ED50 = 2.57 mg/kg) 20 to 50 min after injection. In the drug discrimination tests, 5-APDB (ED50 = 1.02 mg/kg), 5-MAPB (ED50 = 1.00 mg/kg) and 6-APB (ED50 = 0.32 mg/kg) fully substituted in MDMA-trained rats, whereas only 5-MAPB fully substituted for cocaine, and no compounds fully substituted for methamphetamine. Conclusions: The synthetic benzofuran compound 5-APDB and 5-MAPB produced weak locomotor effects, whereas 6-APB produced robust locomotor stimulant effects. All compounds were more potent than MDMA. All three compounds fully substituted in MDMA-trained rats suggesting similar subjective effects. Taken together, these results suggest that these benzofuran compounds may have abuse liability as substitutes for MDMA.

Effects of chronic methamphetamine exposure on rewarding behavior and neurodegeneration markers in adult mice.

Recreational and medical use of stimulants among young adults have gained popularity in the United States over the last decade and their use may increase vulnerability to brain biochemical changes and addictive behaviors. The long-term effects of chronic stimulant exposure in later adulthood have not been fully elucidated.Our study investigated whether chronic exposure to methamphetamine (METH), at a dose designed to emulate human therapeutic dosing for ADHD, would promote biochemical alterations and affect sensitivity to the rewarding effects of subsequent METH dosing.Groups of 3.5-month-old male and female C57BL/6J mice were administered non-contingent intraperitoneal injections of either saline or METH (1.4 mg/kg) twice a day for 1 month (5 days/week). METH (0.5 mg/kg)-induced conditioned place preference (CPP) was tested in mice to determine the effects of previous METH exposure on reward-related behavior. Mice were randomly assigned to Experiment I (males and females) or Experiment II (females only) in which CPP testing was respectively performed either 0.5 or 5 months after the end of METH injections, at ~5 or 10 months old respectively. The midbrain and striatum, regions involved in reward circuit, were assessed for markers associated with neurotoxicity, dopaminergic function, neuroinflammation and epigenetic changes after behavioral testing.Previous exposure to chronic METH did not have significant short-term effects on CPP response but led to a decreased CPP response in 10-month-old females. Previous exposure to METH induced some short-term changes to biochemical markers measured in a brain region and sex-dependent manner, while long-term changes were only observed with GFAP and KDM5C.In conclusion, our data suggest sex- and post-exposure duration-dependent outcomes and warrant further exploration of the long-term neurobehavioral consequences of psychostimulant use in both sexes.

Sex differences in neurobehavioral consequences of methamphetamine exposure in adult mice.

RATIONALE: Recreational and medical use of stimulants is increasing, and their use may increase susceptibility to aging and promote neurobehavioral impairments. The long-term consequences of these psychostimulants and how they interact with age have not been fully studied. OBJECTIVES: Our study investigated whether chronic exposure to the prototypical psychostimulant, methamphetamine (METH), at doses designed to emulate human therapeutic dosing, would confer a pro-oxidizing redox shift promoting long-lasting neurobehavioral impairments. METHODS: Groups of 4-month-old male and female C57BL/6 J mice were administered non-contingent intraperitoneal injections of either saline or METH (1.4 mg/kg) twice a day for 4 weeks. Mice were randomly assigned to one experimental group: (i) short-term cognitive assessments (at 5 months), (ii) long-term cognitive assessments (at 9.5 months), and (ii) longitudinal motor assessments (at 5, 7, and 9 months). Brain regions were assessed for oxidative stress and markers of neurotoxicity after behavior testing. RESULTS: Chronic METH exposure induced short-term effects on associative memory, gait speed, dopamine (DA) signaling, astrogliosis in females, and spatial learning and memory, balance, DA signaling, and excitotoxicity in males. There were no long-term effects of chronic METH on cognition; however, it decreased markers of excitotoxicity in the striatum and exacerbated age-associated motor impairments in males. CONCLUSION: In conclusion, cognitive and motor functions were differentially and sex-dependently affected by METH exposure, and oxidative stress did not seem to play a role in the observed behavioral outcomes. Future studies are necessary to continue exploring the long-term neurobehavioral consequences of drug use in both sexes and the relationship between aging and drugs.