Viltolarsen: a treatment option for Duchenne muscular dystrophy patients who are amenable to exon 53 skipping therapy

INTRODUCTION

Duchenne muscular dystrophy (DMD) is a progressive genetic disease leading to muscular weakness. DMD is caused by mutations of the dystrophin gene on the X chromosome that is responsible for production of dystrophin protein. Dystrophin contributes to structural support in muscle cells and mutations result in dystrophin protein deficiency which causes muscle damage and the associated clinical presentation. Exon skipping medications, including the exon 53 targeting viltolarsen, are the first agents with the ability to partially restore dystrophin protein.

AREAS COVERED

Herein, the authors profile viltolarsen for the DMD patients who are amenable to exon 53 skipping therapy and provide their expert perspectives on this subject.

EXPERT OPINION

Current findings suggest that viltolarsen could play a role in the current and possible future treatment of DMD. Viltolarsen seems to be safe and restores dystrophin protein to around 6% of the normal level. Due to orphan drug status, after the completion of the phase 2 clinical trial, viltolarsen was granted accelerated approval in Japan and in the US. A phase 3 trial is currently in progress and needs to earn full approval. Although a multidisciplinary approach continues to be critical, the addition of exon skipping agents like viltolarsen may improve the quality of patients' lives. However, data on the long-term safety and efficacy of this medication are not yet available due to its recent accelerated approval.

Making a joint decision: Cannabis as a potential substitute for opioids in obstetrics and gynecology

There is a growing body of evidence that cannabis may be effective as an analgesic with potential to reduce opioid usage in chronic pain. This review synthesizes the available literature to elucidate the possible role that cannabis might play in reducing opioid use in gynecological disorders that may potentially lead to a recommendation of substituting opioids with cannabis. With reports of a decrease in opioid use after cannabis initiation, an opioid-sparing effect has been seen in gynecologic malignancies such as ovarian, uterine, endometrial, and cervical cancers, in addition to chronic pelvic pain (CPP). Though many studies have found an association between cannabis and various adverse maternal and neonatal outcomes, there is a lack of randomized controlled trials making it difficult to claim a directly causal relationship between cannabis and these adverse outcomes. Additionally, with increased use of cannabis during pregnancy, the evidence of possible benefits and risks to mothers and fetuses is examined.

Perspectives on the advances in the pharmacotherapeutic management of Duchenne muscular dystrophy

INTRODUCTION

: Duchenne muscular dystrophy (DMD) is a progressive genetic disease characterized by muscular weakness with a global prevalence of 7.1 cases per 100,000 males. DMD is caused by mutations of the dystrophin gene on the X chromosome which is responsible for dystrophin protein production. Dystrophin is a cytoskeletal protein that contributes to structural support in muscle cells. DMD mutations result in dystrophin protein deficiency which leads to muscle damage and the associated clinical presentation.

AREAS COVERED

: Corticosteroids such as prednisone and deflazacort are routinely given to patients to treat inflammation, but their use is limited by the occurrence of side effects and a lack of standardized prescribing. Exon-skipping medications are emerging as treatment options for a small portion of DMD patients even though efficacy is uncertain. Many new therapeutics are under development that target inflammation, fibrosis, and dystrophin replacement.

EXPERT OPINION

: Because of side effects associated with corticosteroid use, there is need for better alternatives to the standard of care. Excessive cost is a barrier to patients receiving medications that have yet to have established efficacy. Additional therapies have the potential to help patients with DMD, although most are several years away from approval for patient use.

A case for continuing statin medications in the intensive care unit: Reducing the risk for delirium

DISCLAIMER

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

The objective of this review is to detail the utility of statin medications in the prevention and treatment of intensive care unit (ICU) delirium.

SUMMARY

Delirium is a syndrome characterized by altered mental status, inattention, and disorganized thinking. It is particularly concerning in the ICU where specific risk factors are much more prevalent. Nonpharmacological therapy is the mainstay of treatment, aimed at increasing patient awareness; pharmacological therapies have also been explored with varying success. The utility of statin medications in this scenario has been investigated because of the numerous pleiotropic effects of these drugs. Although the benefits in terms of treating delirium are uncertain, statins may be good candidates for prevention. The peak anti-inflammatory effect of statins is delayed, so initiating a statin on admission will likely have little protective benefit, whereas continuation of a home regimen seems more likely to exert an effect.

CONCLUSION

Statin medications are very commonly used, and, while their role in treating delirium is unclear, continuation of these medications from a home regimen is reasonable to decrease the odds of delirium in the intensive care population.

Melatonin Use in Pediatrics: Evaluating the Discrepancy in Evidence Based on Country and Regulations Regarding Production

Melatonin manufacturers in the United States have begun producing melatonin products specifically targeted for use in the pediatric population. This paper aims to critically evaluate the evidence available regarding the use of melatonin in children based on where the clinical trials are performed and the regulations regarding the production of melatonin in that country. Melatonin is regulated differently around the world with the least amount of regulation placed on OTC supplements in the United States. The majority of studies evaluating melatonin use in the pediatric population are conducted with children who have comorbidities, such as autism spectrum disorder or attention-deficit/hyperactivity disorder. Evidence supporting the use of US formulations of melatonin in the otherwise healthy pediatric population is non-existent. Based on the lack of safety regulations in place in the United States and the lack of evidence regarding US melatonin products, they should be used sparingly in the otherwise healthy pediatric population, if they are used at all.

Perspectives on cannabis as a substitute for opioid analgesics

With the opioid epidemic reaching new heights in the USA, it has become critical to find suitable alternatives to opioids. Cannabis, an antinociceptive, is a strong contender to help patients reduce their opioid usage. A growing literature has been examining the complex effects cannabis has on pain relief and on opioid usage; whether it is a substitute for opioids or increases their use. This review explores the studies that compare cannabis-opioid interactions and presents some challenges of cannabis research and usage. The practical clinical pharmacology of cannabis as an analgesic, including the route of administration, safety and pharmacokinetics, are discussed to address the concerns, as well as possible solutions, of cannabis as a pain reliever.

White noise as a possible therapeutic option for children with ADHD

Attention deficit/hyperactivity disorder (ADHD) is a condition that affects many children and adults throughout the world. ADHD symptoms have been associated with changes in catecholamine release. Current therapies for ADHD have a variety of limitations that invite additional therapeutic options. White noise therapy has previously been utilized to improve sleep and aspects of cognition in a variety of patient populations. Through a proposed phenomenon called stochastic resonance, white noise may have the ability to improve symptoms in children with ADHD. Empirically, white noise therapy has been able to improve certain tasks affected by ADHD symptoms, including speech recognition and reading and writing speed. Not all tasks affected by ADHD are improved, however, and significant logistical challenges remain before this therapy could be realistically implemented. In this review, there appears to be evidence that white noise therapy could be beneficial for patients with ADHD, and therefore further research is encouraged to establish parameters for maximum therapeutic benefit.

The role of statins in both cognitive impairment and protection against dementia: a tale of two mechanisms

Nearly 30% of adults 40 years and older in the United States are on a statin. Their widespread use heightens the importance of careful consideration of their varied effects on the body. Although randomized controlled trials have not confirmed cognitive impairing effects with statins, continuing evidence suggests statins have the ability to cause reversible cognitive impairment in some patients. Paradoxically, statins have also been shown to decrease the risk of dementia, Alzheimer's disease, and improve cognitive impairment in some cases. However, randomized controlled trials have similarly failed to find the beneficial effect. Supporting evidence for both claims is compelling whereas known limitations of the clinical trials may explain the lack of findings. This narrative review aims to explain why there is still controversy and how both effects can, and may, be possible. The mechanisms that have been hypothesized for each effect are seemingly independent from one another and may explain the contradicting results. Being mindful of the complex effects of statins, health care providers need to be able to identify patients who are at risk for or already experiencing cognitive impairment from statin use while also identifying those who could potentially decrease their risk of dementia with statins.

Translational obstacles with off-label drug use in acute traumatic brain injury

Traumatic brain injury results in significant morbidity and mortality, and there is an urgent need for neuroprotective medications that can prevent the persisting symptoms and disabilities following injury. Several existing pharmacotherapies have been targeted for off-label benefit in traumatic brain injury, as these agents are well characterized and commercially available, easing the process of clinical trial development. Despite promising results in animal models, clinical trials have demonstrated minimal benefit. One possible reason for these failed translations could be that drug selection, characterization and dosing are not routinely established in the appropriate early phase trials before larger scale testing. Examining how recent trials may have bypassed these steps may help future trials to more definitively determine the efficacy of potential therapeutics.

Neocortical β-amyloid area is associated with dementia and APOE in the oldest-old

OBJECTIVE

Apolipoprotein E (APOE) ε2 carriers may be protected from dementia because of reduced levels of cortical β-amyloid. In the oldest-old, however, APOE ε2 carriers have high β-amyloid plaque scores and preserved cognition. We compared different measures of β-amyloid pathology across APOE genotypes in the oldest-old, and their relationship with dementia.

METHODS

The study included 96 participants from The 90+ Study. Using all information, dementia diagnoses were made. Neuropathological examination included staging for amyloid plaques and β-amyloid cortical percent area stained by NAB228 antibody.

RESULTS

Both APOE ε2 and APOE ε4 carriers had high Consortium to Establish a Registry for Alzheimer's Disease plaque scores. However, APOE ε2 carriers had low cortical β-amyloid percent areas. β-amyloid percent area was associated with dementia across APOE genotypes.

CONCLUSIONS

Lower levels of percent area in APOE ε2 carriers may reflect lower total β-amyloid and may contribute to APOE ε2 carriers' decreased risk of dementia, despite high β-amyloid plaque scores. The relationship between β-amyloid plaques and dementia in the oldest-old may vary by APOE genotype.

A population-based clinicopathological study in the oldest-old: the 90+ study

Population-based longitudinal clinicopathological studies provide an ideal opportunity to study a variety of risk and protective factors in relation to pathology associated with dementia in individuals who are representative of the general population. The 90+ Study is a population-based study designed specifically to study aging and dementia as well as its neuropathological correlates in participants 90 years of age and older. We present demographic and pathological data on the first 104 participants to come to autopsy from the brain donation component of the study, The 90+ Autopsy Study. Cognitive diagnosis was assigned according to diagnostic and statistical manual 4th edition criteria for dementia and neuropathological diagnoses were made according to the Consortium to Establish a Registry for Alzheimer's Disease protocol. Dementia was present in 61% of autopsied participants, the majority of whom were diagnosed with Alzheimer's disease (85%). Many different types of pathology typically associated with dementia were common in the oldest-old, and included neurofibrillary tangles, neuritic plaques, diffuse plaques, Lewy bodies, hippocampal sclerosis, and cerebral infarctions. Most types of pathology were more frequently found in participants suffering from dementia but there was extensive overlap in pathology among those with and without dementia. In addition, 22% of demented participants did not have sufficient pathology to account for their cognitive loss. Our results highlight the poor associations between these common pathological lesions and dementia in the oldest-old and the importance of considering many different types of pathology, possibly including some yet to be identified, in order to account for all dementias in the oldest-old.

Apolipoprotein E genotype, dementia, and mortality in the oldest old: the 90+ Study

BACKGROUND

Although the apolipoprotein E (APOE) ε4 allele is a major genetic risk factor for Alzheimer's disease (AD), it is not clear whether this relationship persists among the oldest old. Several European studies suggest that the effect of the APOE ε4 allele on dementia and mortality disappears in very old age. We describe the APOE allele and genotype frequencies and examine whether the presence of the APOE ε4 or APOE ε2 alleles is related to prevalent dementia, incident dementia, and mortality in a population-based cohort of oldest-old participants in the United States.

METHODS

We studied 904 participants aged 90 years and older from The 90+ Study. Eight hundred two (89%) participants were genotyped and included in the prevalent dementia and mortality analyses. The 520 initially nondemented participants were included in the incident dementia analyses and were evaluated for dementia every 6 months.

RESULTS

The APOE ε4 allele was significantly associated with prevalent dementia (odds ratio = 2.06) and AD (odds ratio = 2.37) in women but not in men. The APOE ε2 allele was not related to prevalent dementia in either sex. After an average follow-up of 2.4 years, 188 incident dementia cases were identified. Neither the APOE ε4 nor the APOE ε2 allele was related to incident dementia or AD. Five hundred ten (64%) participants died after an average follow-up of 2.3 years, and their mortality was not related to the presence of either the APOE ε2 or APOE ε4 allele.

CONCLUSIONS

Our findings suggest that the associations between APOE ε4, dementia, and mortality are age dependent, and that APOE ε4 no longer plays a role in dementia and mortality at very old ages.

Neocortical and hippocampal amyloid-β and tau measures associate with dementia in the oldest-old

The emergence of longevity in the modern world has brought a sense of urgency to understanding age-related neurodegenerative diseases such as Alzheimer's disease. Unfortunately, there is a lack of consensus regarding the correlation between the pathological substrates of neurodegeneration and dementia status, particularly in the oldest-old. To better understand the pathological correlates of dementia in the oldest-old, we characterized the topographical spread and severity of amyloid-β, tau, TDP-43 and α-synuclein pathologies in the 90+ Study, a prospective longitudinal population-based study of ageing and dementia. Neuropathological analysis with immunohistochemically labelled sections was carried out blind to clinical diagnosis on the first 108 participants of the 90+ Study who came to autopsy including participants with dementia (n = 66) and without dementia (n = 42). We used quantitative and/or semi-quantitative measures to assess the burden of amyloid-β, tau, TDP-43 and α-synuclein pathologies as well as hippocampal sclerosis. Amyloid-β and tau were the predominant pathologies in the 90+ Study cohort and both amyloid-β area and tau area occupied measures were strongly associated with the presence of dementia, as was Braak staging but semi-quantitative plaque scores were not. Notably, TDP-43 pathology also correlated with dementia, while α-synuclein distribution did not. In addition, hippocampal sclerosis was specific to participants with dementia and correlated with the presence of limbic TDP-43. In contrast to previous reports, we found that tau and amyloid-β continue to be robust pathological correlates of dementia, even in the oldest-old. While individuals with no dementia had limited hippocampal tau and neocortical amyloid-β pathology, dementia associated with an expansion in pathology, including increased neocortical tau and hippocampal amyloid-β plaques, more abundant neocortical amyloid-β deposition and hippocampal sclerosis with its attendant TDP-43 pathology.

Incidence of dementia in oldest-old with amnestic MCI and other cognitive impairments

OBJECTIVE

To examine the incidence of dementia among the oldest-old people with normal cognition and different types of cognitive impairment.

METHODS

This study included 395 participants without dementia (mean age 93.3 years) from The 90+ Study, a prospective, population-based study of aging and dementia in people aged 90 years and older. The participants had evaluations for dementia every 6 months, and their average follow-up was 2.5 years. We examined the incidence of all-cause dementia in participants stratified into 4 cognitive groups: normal, amnestic mild cognitive impairment (aMCI), nonamnestic mild cognitive impairment (naMCI), and other cognitive impairment (OCI).

RESULTS

Dementia incidence was highest for participants with aMCI (31.4% per year) and OCI (39.9% per year). Participants with naMCI had an incidence of 14.1% per year, and participants with normal cognition had an incidence of 8.4% per year. Dementia incidence was associated with increasing age in both normal and cognitively impaired participants; however, an APOE4 allele was associated with a higher dementia incidence only in participants with baseline cognitive impairment.

CONCLUSIONS

The risk of developing dementia in the oldest-old is high and increases to higher rates when cognitive impairment is present. Similar to results of studies in younger elderly individuals, cognitive impairment and increasing age were related to increased dementia incidence. High dementia incidence rates in the oldest-old individuals, particularly when cognitively impaired, emphasize the need to further study cognitive impairment and dementia in this rapidly expanding age group.

Cognitive impairment in nondemented oldest-old: prevalence and relationship to cardiovascular risk factors

OBJECTIVE

To determine the prevalence and types of cognitive impairment in a sample of nondemented participants aged ≥90 (the oldest-old) and to examine the relationships between cognitive impairment and cardiovascular risk factors.

PARTICIPANTS

The participants were 420 nondemented individuals from The 90+ Study, a study of aging and dementia in the oldest-old. These participants were categorized into four nonoverlapping groups: normal cognition, amnestic mild cognitive impairment (aMCI), nonamnestic MCI (naMCI), and other cognitive impairment (OCI). History of cardiovascular risk factors was assessed through self-report.

RESULTS

The overall prevalence of cognitive impairment in nondemented participants was 34.0% (95% CI: 29.5-38.5). The prevalence of OCI was highest (17.4%; 95% CI: 13.9-21.4), followed by aMCI (8.3%; 95% CI: 5.9-11.4) and naMCI (8.3%; 95% CI: 5.9-11.4). Normal cognition was present in 66.0% (95% CI: 61.2-70.5) of participants. History of hypertension and stroke were the only risk factors that varied between the groups, occurring more frequently in participants with naMCI (χ(2) = 3.82; P < .05) and OCI (χ(2) = 5.51; P < .05).

CONCLUSIONS

This study found a high prevalence of cognitive impairment in a sample of nondemented oldest-old. We did not find a strong relationship between cardiovascular risk factors and the cognitive impairment groups, other than between hypertension and naMCI and stroke and OCI. Future studies comparing the incidence of dementia in these groups will ultimately determine their predictive utility in the oldest-old.

The prevalence of disability in the oldest-old is high and continues to increase with age: findings from The 90+ Study

OBJECTIVES

To examine the prevalence and type of disability in the oldest-old (90+), the fastest growing age group in the United States.

METHODS

The current study included functional data on 697 participants from The 90+ Study, a population-based longitudinal study of aging and dementia in people aged 90 and older. Data were obtained by participant's informants via a written questionnaire. The prevalence of disability was calculated for two definitions using activities of daily living (ADLs). ADL difficulty was defined as difficulty with one or more ADLs whereas ADL dependency was defined as needing help on one or more ADLs.

RESULTS

ADL difficulty was present in 71% in 90-94 year olds, 89% in 95-99 year olds, and 97% in centenarians. ADL dependency was present in 44% of 90-94 year olds, 66% of 95-99 year olds, and 92% of centenarians. The ADL most commonly causing difficulty was walking (70%) whereas the ADL most commonly causing dependency was bathing (51%). Age, gender, and institutionalization were significantly associated with both ADL difficulty and ADL dependency.

CONCLUSIONS

Similar to studies in younger individuals, the current study suggests that the prevalence of disability continues to increase rapidly in people aged 90 and older. With the rapid growth in the number of people in this age group, disability in the oldest-old has major public health implications.

APOE epsilon2 is associated with intact cognition but increased Alzheimer pathology in the oldest old

BACKGROUND

Many studies have examined the role of APOE genotype in the development of dementia, specifically Alzheimer disease (AD). The APOE epsilon4 allele (APOE4) is a risk factor for both clinical and neuropathologic AD whereas the APOE epsilon2 allele (APOE2) seems to be protective. This would predict, even with advanced age, that APOE2 carriers would be less likely to have dementia and less likely to meet pathologic criteria for AD.

METHODS

The first 85 genotyped participants from The 90+ Study to come to autopsy were included. All-cause dementia (using DSM-IV criteria) and AD (using National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria) diagnoses were made by consensus conference using all available information including neuropsychological testing, neurologic examination, and medical records. Neuropathologic examination included Braak and Braak staging for plaques and tangles and diagnosis of neuropathologic AD using National Institute on Aging-Reagan criteria.

RESULTS

Across all genotypes, 58.5% of subjects were diagnosed with clinical dementia (81% of dementia was AD) and 50.0% met neuropathologic criteria for AD. Compared to those with an APOE epsilon3/epsilon3 genotype (APOE3/3), APOE4 carriers were more likely to be diagnosed with dementia (odds ratio [OR] = 12.2, 95% confidence interval [CI] = 1.5-102.0), whereas APOE2 carriers were not (OR = 0.3, 95% CI = 0.1-1.3). Surprisingly, both APOE4 (OR = 4.6, 95% CI = 1.3-16.5) and APOE2 (OR = 7.8, 95% CI = 1.5-40.2) carriers were more likely to meet neuropathologic criteria for AD than those with APOE3/3 genotype.

CONCLUSIONS

In the oldest old, the presence of the APOE epsilon2 allele (APOE2) was associated with a somewhat reduced risk of dementia, but paradoxically was associated with increased Alzheimer disease (AD) neuropathology. Therefore, oldest old APOE2 carriers may have some mechanism that contributes to the maintenance of cognition independently of the formation of AD pathology.

Dissociation of neuropathologic findings and cognition: case report of an apolipoprotein E epsilon2/epsilon2 genotype

BACKGROUND

The apolipoprotein E (APOE) epsilon2 allele has been suggested as having a protective effect and delaying the age at onset of Alzheimer disease.

OBJECTIVE

To describe a dissociation between neuropathologic findings with normal cognition in a woman with severe Alzheimer disease with the APOE epsilon2/epsilon2 genotype.

DESIGN

Case report from a community-based prospective study of persons 90 years or older (The 90+ Study).

PARTICIPANT

A 92-year-old woman without dementia with the APOE epsilon2/epsilon2 genotype who lived independently without significant cognitive or functional loss and was a participant in The 90+ Study. She died in December 2004, and postmortem examination of her brain was performed.

INTERVENTION

Neurologic examination and a battery of neuropsychological tests were performed 6 months and 1 month before death. Neuropathologic examination included Braak and Braak staging for senile plaques and neurofibrillary tangles.

RESULTS

Neuropathologic examination of the brain revealed advanced senile plaque and neurofibrillary tangle disease consistent with a high likelihood of Alzheimer disease. At clinical evaluation, the participant demonstrated no dementia and only mild cognitive deficits.

CONCLUSIONS

The APOE genotype may have contributed to maintenance of cognition despite advanced neuropathologic findings of Alzheimer disease. This case suggests that the APOE epsilon2 isoform may have a protective effect against cognitive decline in Alzheimer disease that may be independent from senile plaques and neurofibrillary tangles.

Basolateral amygdala noradrenergic activity mediates corticosterone-induced enhancement of auditory fear conditioning

The present experiment examined whether posttraining noradrenergic activity within the basolateral complex of the amygdala (BLA) is required for mediating the facilitating effects of acutely administered glucocorticoids on memory for auditory-cue classical fear conditioning. Male Sprague-Dawley rats received five pairings of a single-frequency auditory stimulus and footshock, followed immediately by bilateral infusions of the beta1-adrenoceptor antagonist atenolol (0.5 microg in 0.2 microl) or saline into the BLA together with a subcutaneous injection of either corticosterone (3.0 mg/kg) or vehicle. Retention was tested 24 h later in a novel test chamber and suppression of ongoing motor behavior served as the measure of conditioned fear. Corticosterone facilitated memory as assessed by suppression of motor activity during the 10-s presentation of the auditory stimulus and intra-BLA administration of atenolol selectively blocked this corticosterone-induced memory enhancement. These findings provide evidence that, as found with other emotionally arousing tasks, the enhancing effects of corticosterone on memory consolidation of auditory-cue fear conditioning require posttraining noradrenergic activity within the BLA.

Enhancement of extinction memory consolidation: the role of the noradrenergic and GABAergic systems within the basolateral amygdala

Evidence from previous studies indicates that the noradrenergic and GABAergic influences within the basolateral amygdala (BLA) modulate the consolidation of memory for fear conditioning. The present experiments investigated whether the same modulatory influences are involved in regulating the extinction of fear-based learning. To investigate this issue, male Sprague Dawley rats implanted with unilateral or bilateral cannula aimed at the BLA were trained on a contextual fear conditioning (CFC) task and 24 and 48 h later were given extinction training. Immediately following each extinction session they received intra-BLA infusions of the GABAergic antagonist bicuculline (50 ng), the beta-adrenocepter antagonist propranolol (500 ng), bicuculline with propranolol, norepinephrine (NE) (0.3, 1.0, and 3.0 microg), the GABAergic agonist muscimol (125 ng), NE with muscimol or a control solution. To investigate the involvement of the dorsal hippocampus (DH) as a possible target of BLA activation during extinction, other animals were given infusions of muscimol (500 ng) via an ipsilateral cannula implanted in the DH. Bilateral BLA infusions of bicuculline significantly enhanced extinction, as did infusions into the right, but not left BLA. Propranolol infused into the right BLA together with bicuculline blocked the bicuculline-induced memory enhancement. Norepinephrine infused into the right BLA also enhanced extinction, and this effect was not blocked by co-infusions of muscimol. Additionally, muscimol infused into the DH did not attenuate the memory enhancing effects of norepinephrine infused into the BLA. These findings provide evidence that, as with original CFC learning, noradrenergic activation within the BLA modulates the consolidation of CFC extinction. The findings also suggest that the BLA influence on extinction is not mediated by an interaction with the dorsal hippocampus.

Anisomycin infused into the hippocampus fails to block "reconsolidation" but impairs extinction: the role of re-exposure duration

Recent studies have reported new evidence consistent with the hypothesis that reactivating a memory by re-exposure to a training context destabilizes the memory and induces "reconsolidation." In the present experiments, rats' memory for inhibitory avoidance (IA) training was tested 6 h (Test 1), 2 d (Test 2), and 6 d (Test 3) after training. On Test 1 the rats were either removed from the shock compartment immediately after entry or retained in the shock context for 200 sec, and intrahippocampal infusions of the protein synthesis inhibitor anisomycin (75 microg/side) were administered immediately after the test. Anisomycin infusions administered after Test 1 impaired IA performance on Test 2 in animals given the brief re-exposure, but impaired extinction in animals exposed to the context for 200 sec. Rats with anisomycin-induced retention impairment on Test 2 demonstrated spontaneous recovery of retention performance on Test 3, whereas rats showing extinction on Test 2 showed further extinction on Test 3. The findings indicate that post-retrieval administration of anisomycin impairs subsequent retention performance only in the absence of extinction and that this impairment is temporary.

Basolateral amygdala lesions do not prevent memory of context-footshock training

The present studies examined the effects of basolateral amygdala (BLA) lesions induced prior to or after context-footshock training on 48-h memory, using several retention measures. In experiment 1, male Sprague-Dawley rats with bilateral BLA lesions (NMDA, 12.5 mg/mL, 0.2 microL) were given footshock training in one compartment of a two-compartment alley. Rats were habituated to the alley and 24 h later were given two footshocks in the shock compartment. Retention was tested 48 h later, using latency to enter the shock compartment and time spent freezing as measures of memory. Two days later, they were tested again and received a footshock on each re-entry of the shock compartment prior to remaining in the safe compartment for 200 consecutive seconds. The BLA lesions did not block retention as assessed by freezing or number of re-entries of the shock compartment. In experiment 2, no prior habituation was given, and only one footshock was used for the training. BLA lesions did not block retention, as indicated by latencies to enter the shock compartment on a 48-h test or by number of entries of the shock compartment. Experiment 3 examined the effects of the GABAA agonist muscimol infused into the BLA prior to the 48-h retention test. The muscimol infusions decreased retention test entrance latencies but did not block retention as assessed by the number of subsequent entries of the shock compartment. These findings provide additional evidence that an intact BLA is not required for the acquisition or retention of context-footshock training.

Comparative study of aging in the mouse olfactory bulb

Gene knockout technologies have been used to elevate the mouse as a model species. However, little work has examined age and strain differences in the mouse olfactory system. The present study compared the olfactory bulbs of mature (6 month) and aged (24 month) males of BALB/cBy, C57BL/6J, and DBA/2 strains. Volumes of the glomerular (GLM), external plexiform (EPL), and mitral/granule cell (MIG) layers varied little from strain to strain. Volume measurements increased with age even when corrected for body weight differences. Two nonoverlapping interneuron populations were examined with immunohistochemistry. Staining for the calcium binding protein calretinin varied little between strains, but age-related increases in staining were seen in EPL of C57BL/6J mice. Typical patterns of tyrosine hydroxylase immunoreactivity were observed in all subjects except for old DBA/2 mice, which evidenced considerable staining in submitral areas. Age-related increases were observed in BALB/cBy and DBA/2 mice but not in the C57BL/6J strain. Glial fibrillary acidic protein staining was similar in old BALB/cBy and DBA/2 mice, with astrocytes in all layers of the bulb, but more concentrated in the MIG. However, C57BL/6J tissue revealed very large astrocytes relatively evenly distributed in all layers. Cell proliferation dropped dramatically with age. Labeled cells could still be observed along the lateral ventricles, but very few were observed within the rostral migratory stream or subventricular zone. Although TUNEL labeling revealed many apoptotic figures in the granule cell layer of young subjects, almost no staining was seen in aged mice.