Transesophageal Ultrasound-Guided Normothermic Regional Perfusion in Controlled Donors After Cardiocirculatory Determination of Death

Programs of donation after cardiocirculatory determination of death (DCD) are increasingly established in many countries to increase the availability of organs for transplantation. The use of abdominal normothermic regional reperfusion (A-NRP), shortening total warm ischemia time (tWIT), has been recently recommended by the European Society for Organ Transplantation (ESOT) to decrease the risk potentially associated with transplantation of grafts from DCD donors. We aimed to describe our transesophageal ultrasound (TEU)-guided technique to implement A-NRP in controlled DCD (cDCD) donors through femorofemoral venoarterial extracorporeal support, preventing coronary and cerebral reperfusion occluding the aorta with a balloon. After assessment of the central vascular structures, the use of TEU in real time guides the insertion of the guidewires and the balloon. Moreover, TEU allows us to verify the proper positioning of a venous cannula and aortic balloon. The entire procedure may be performed without the need for fluoroscopic or radiographic evaluation, or limiting the need for fluoroscopic or radiology assistance to a selected scenario of difficult or expected difficult cannulation and/or balloon insertion. The distribution of interventions as antemortem and postmortem reflects the scenario imposed by Italian laws regulating organ procurement in DCD donors.

Drug-Drug Interactions between Direct Oral Anticoagulants and Hepatitis C Direct-Acting Antiviral Agents: Looking for Evidence Through a Systematic Review

Background

Direct oral anticoagulants (DOACs), as substrates of cytochrome P450 (CYP) 3A4 and/or P-glycoprotein, are susceptible to drug–drug interactions (DDIs). Hepatitis C direct-acting antiviral agents (DAAs), via P-glycoprotein or CYP3A4 inhibition, may increase DOAC exposure with relevant bleeding risk. We performed a systematic review on DDIs between DOACs and DAAs.

Methods

Two reviewers independently identified studies through electronic databases, until 7 July 2020, supplementing the search by reviewing conference abstracts and the ClinicalTrials.gov website.

Results

Of 1386 identified references, four articles were finally included after applying the exclusion criteria. Three phase I clinical studies in healthy volunteers assessed interactions between dabigatran and glecaprevir/pibrentasvir, odalasvir/simeprevir, or sofosbuvir/velpatasvir/voxilaprevir, showing an increase in the dabigatran area under the concentration–time curve (AUC) by 138%, 103%, and 161%, respectively.

Conclusions

DOACs and DAAs are under-investigated for DDI risk. Real-world studies are needed to assess the clinical relevance of the pharmacokinetic interactions with dabigatran and describe the actual spectrum of possible DDIs between DAAs and other DOACs.

Assessing the association between fluoroquinolones and emerging adverse drug reactions raised by regulatory agencies: An umbrella review

BACKGROUND

Regulatory agencies warned against fluoroquinolones for the management of minor infections because of the risk of emerging adverse events (collagen-associated adverse events, neuropsychiatric toxicity and long-term disability). We aimed to assess quality and credibility of evidence as well as causality regarding these putative associations.

METHODS

MEDLINE, Scopus, Web of Science and PROSPERO were searched, from inception to August 2019, for systematic reviews with meta-analyses investigating emerging adverse events. Two investigators extracted data to grade quality (through validated AMSTAR-2 tool), rank credibility of the evidence (convincing, highly suggestive, suggestive, weak) through adapted criteria including E-value calculation, and assess causality (Hill's criteria).

RESULTS

Seven systematic reviews of observational studies providing 16 risk estimates [seven, five and four, respectively, for aortic aneurysm/dissection (AAD), retinal detachment (RD) and any tendon disorders (ATD)] met inclusion criteria. No systematic reviews with meta-analysis investigating the risk of neuropsychiatric toxicity or long-term disability were found. The associations between fluoroquinolones and AAD/ATD showed highly suggestive credibility and were supported by strong evidence of causality (double increased risk, especially within first 2 months of treatment). Conflicting data concerning the emergence of RD were retrieved, resulting in weak evidence of causality. Quality of the evidence ranged from high to low for AAD, from moderate to critically low for RD, and it was moderate for ATD.

CONCLUSION

Our analysis supports credible, plausible and highly suggestive associations with AAD (rare occurrence but strong causality) and ATD. Limitations of both umbrella reviews and observational evidence should be considered.

Evolving cardiovascular uses of direct-acting oral anticoagulants: a paradigm shift on the horizon?

Direct-acting oral anticoagulants (DOACs), by virtue of pharmacological properties perceived as innovative, are changing the therapeutic scenario of patients requiring short- and long-term anticoagulation. The evidence gathered so far (from pre-approval pivotal trials to real-world post-marketing observational data) consistently confirms that DOACs are overall comparable to vitamin-K antagonists (VKAs) in terms of safety, efficacy, effectiveness and unequivocally documents a clinically relevant reduced risk of intracranial bleeding in the settings of non-valvular atrial fibrillation (AF) and venous thromboembolism. The following issues are attracting considerable clinical interest: (a) identifying specific subpopulations of patients with AF most likely to benefit from one of these agents (the so-called tailored therapy), and (b) expanding therapeutic indications in emerging diseases characterized by arterial and venous thromboembolic risk. In these scenarios, the risk-benefit profile of DOACs, as compared to VKAs or heparins, is still incompletely characterized. In cardiology, the challenging task of selecting a suitable or even the most appropriate DOAC for patients with AF and a particular phenotype prompted experts to provide suggestions based on careful review of subgroups of patients from pivotal RCTs. However, in the past few months, variegated multicenter trials have been published (RE-CIRCUIT, PIONEER-AF-PCI, GEMINI-ACS-1), with potential influence on clinical practice. Therefore, this review aims to update the latest evidence on the evolving therapeutic uses of DOACs in the cardiovascular area, addressing potential impact for clinicians.

Emerging therapeutic uses of direct-acting oral anticoagulants: An evidence-based perspective

Direct-acting oral anticoagulants (DOACs) were claimed to cause a potential paradigm shift in the therapeutic scenario of patients requiring short- and long-term anticoagulation, by virtue of their pharmacological properties, perceived as innovative. The evidence gathered so far (from pre-approval pivotal trials to real-world post-marketing observational data) consistently confirmed that DOACs are overall comparable to vitamin-K antagonists (VKAs) in terms of safety, efficacy and effectiveness and unequivocally documented a consistent and clinically relevant reduced risk of intracranial bleeding in the settings of non-valvular atrial fibrillation (NVAF) and venous thromboembolism (VTE). Interestingly, two parallel paths can be identified in the current research scenario: A) in the aforementioned consolidated therapeutic indications, an innovative approach is directed towards tailored treatment strategies, to identify patients most likely to benefit from one of the different anticoagulant drugs, in particular subpopulations at increased risk of adverse events (e.g., bleeding); B) in unconventional settings, DOACs are gaining interest for potential use in emerging diseases characterized by arterial and venous thromboembolic risk. In these scenarios, the risk-benefit profile of DOACs, as compared to VKAs or heparins, is less defined. The aim of this review is to critically assess the body of evidence underlying emerging therapeutic uses of DOACs (e.g., heparin-induced thrombocytopenia, anti-phospholipid antibody syndrome), including evolving issues in special populations (e.g., patients with VTE and cancer or cirrhosis). This will be achieved by analyzing the strength (i.e., systematic reviews, randomized clinical trials, observational studies, case report/series) and consistency (i.e., concordance) of both published and unpublished evidence registered in major public repositories.

Adverse events associated with the use of direct-acting oral anticoagulants in clinical practice: beyond bleeding complications

Non-vitamin K oral anticoagulants, also known as direct oral anticoagulants (DOACs), have entered the market in 2008 with the expected breakthrough potential of circumventing limitations related to treatment with vitamin K antagonists (eg, warfarin) by virtue of their pharmacological properties. Although data derived from premarketing randomized clinical trials have largely demonstrated the clinical benefit of DOACs, especially in terms of reduced risk of intracranial bleeding, it is important to monitor the safety in the postmarketing phase, which better reflects real-world patients with comorbidities and polypharmacotherapy, in order to assess the actual risk-benefit profile. In this critical review, we aimed to evaluate the evidence on the latest debated safety issues. In the first section, we will discuss: 1) the need for pharmacovigilance (ie, the science and activities relating to the detection, assessment, understanding, and prevention of adverse effects or any other drug-related problems in the real-world setting), and 2) the importance of properly interpreting postmarketing data to avoid unnecessary alarm. In the second section, emerging and debated safety issues potentially associated with the use of DOACs in the postmarketing setting will be assessed: 1) the potential coronary risk (which emerged during the preapproval period); 2) the occurrence of liver injury (a risk undetected in clinical trials and highlighted by case reports or series); and 3) the potential for renal damage (a still unclear safety issue). It is anticipated that hepatic and renal issues still require dedicated postauthorization safety studies to ultimately assess causality.

Freeze shoe sampler for the collection of hyporheic zone sediments and porewater

The Starr and Ingleton (1992) drive point piston sampler (DPPS) design was modified by fitting it with a Murphy and Herkelrath (1996) type sample-freezing drive shoe (SFDS), which uses liquid carbon dioxide as a cryogen. Liquid carbon dioxide was used to freeze sediments in the lower 0.1 m of the core and the drive-point piston sealed the core at the top preserving the reductive-oxidation (redox) sensitive sediments from the atmosphere and maintaining natural stratigraphy. The use of nitrogen gas to provide positive pressure on the gas system blocked the ingress of water which froze on contact with the cryogen thus blocking the gas lines with ice. With this adaptation to the gas system cores could be collected at greater depths beneath the static water level. This tool was used to collect intact saturated sediment cores from the hyporheic zone of the tidally influenced Fraser River in Vancouver, British Columbia, Canada where steep geochemical and microbial gradients develop within the interface between discharging anaerobic groundwater and recharging aerobic river water. In total, 25 cores driven through a 1.5 m sampling interval were collected from the river bed with a mean core recovery of 75%. The ability to deploy this method from a fishing vessel makes the tool more cost effective than traditional marine-based drilling operations which often use barges, tug boats, and drilling rigs.

Incidence and etiology of dementia in a large elderly Italian population

OBJECTIVE

To estimate age- and sex-specific incidence of dementia, Alzheimer disease (AD), and vascular dementia (VaD) in the Conselice Study of Brain Aging, an Italian prospective population-based study, and to assess whether poor education is a risk factor for dementia.

METHODS

In 1999 to 2000, the baseline study identified a dementia-free cohort of 937 subjects aged 65 years and older who were reexamined in 2003 to 2004 using a two-phase procedure.

RESULTS

Information was obtained for 91% of the subjects at risk; 115 incident cases of dementia were identified. Incidence rates per 1,000 person-years were 37.8 (95% CI = 30.0 to 47.7) for dementia, 23.8 (95% CI = 17.3 to 31.7) for AD, and 11.0 (95% CI = 7.2 to 16.9) for VaD. This translates into more than 400,000 new cases of dementia expected per year in Italy. Increasing age was an independent risk factor for both AD and VaD. Poor education was an independent risk factor for AD but not VaD. Sex did not affect dementia risk.

CONCLUSIONS

In this Italian population-based cohort, incidence of dementia increased with age, and Alzheimer disease (AD) was the most frequent type of dementia. Poor education was associated with a higher risk of AD. Our incidence rates are higher than previously reported in Italy, and provide new estimates for projection of future burden of disease in Italy.

Cortical malformations are associated with a rare polymorphism of cellular prion protein

Studies in animals lacking the cellular prion protein (PrP(c)) gene (Prnp) showed higher neuronal excitability in vitro and increased sensitivity to seizures in vivo. The authors previously reported a rare polymorphism at codon 171 (Asn-->Ser) of human Prnp to be associated with mesial temporal lobe epilepsy related to hippocampal sclerosis. They demonstrated that the same variant allele is also associated with symptomatic epilepsies related to different forms of malformations of cortical development.

COMMON POLYMORPHISMS IN METHYLENETETRAHYDROFOLATE REDUCTASE (MTHFR): RELATIONSHIPS WITH PLASMA HOMOCYSTEINE CONCENTRATIONS AND COGNITIVE STATUS IN ELDERLY NORTHERN ITALIAN SUBJECTS

Hyperhomocysteinemia may be a risk factor for cognitive impairment. Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in homocysteine (Hcy) metabolism. Both the MTHFR 677C-->T and the 1298A-->C polymorphisms are associated with mild hyperhomocysteinemia, particularly in conditions of low folate status. The prevalence of these MTHFR polymorphisms and their relationships with plasma total Hcy (tHcy), serum folate and cognitive function was evaluated in 194 elderly Italian individuals: 122 healthy controls (73.8 +/- 7.1 years of age), 24 cognitively- impaired- not-demented individuals (78.6 +/- 9.3 years), and 48 subjects with Alzheimer dementia (AD = 26), vascular dementia (VD =22; 85.5 +/- 7.0 years). Twenty-one percent of all subjects were homozygous for 677C-->T and 7 % for 1298A-->C polymorphism. No significant relationship was found betweenMTHFR polymorphisms and age, cognitive status and type of dementia. Plasma tHcy did not differ significantly by MTHFR genotypes, but, subjects of all genotypes with low serum folate (<12 nmole/l) had higher plasma tHcy (p < 0.001), than subjects with high serum folate (>= 12 nmole/l). The study suggests that 677C-->T and 1298A-->C polymorphisms are common in the Northern Italian population, but do not significantly affect plasma tHcy levels of elderly individuals, even under conditions of low folate status. The lack of association of age and cognitive function with MTHFR genotypes argues against a negative selection for these polymorphisms.

HOMOCYSTEINE AND COGNITIVE PERFORMANCE IN HEALTHY ELDERLY SUBJECTS

Hyperhomocysteinemia is a risk factor for dementia but only scanty data exist about its relationship to specific cognitive abilities during normal aging. We recruited 62 healthy and cognitively normal subjects of age 65-91 years from the Conselice Study of brain aging. The following neuropsychological tests were applied (i) The mental deterioration battery(MDB) consisting of 7 parts: the Rey's 15 words immediate and delayed recall, word fluency, sentence construction, Raven's progressive matrices '47, immediate visual memory, freehand copying of drawings and copying drawings with landmarks. (ii) The Prose memory test. (iii) The Corsi block-tapping task. (iv) The mini mental state examination(MMSE) scores. We measured plasma total homocysteine (tHcy), serum folate, vitamin B12 and plasma vitamin B6. Multivariate-adjusted linear regression analysis showed statistically significant negative association of plasma tHcy with scores at MMSE (b= -0.01 2,p < 0.001) and word fluency (b = -0.009, p = 0.021). A non-significant trend towards a negative association was also found for sentence construction (b = -0.006, p = 0.076). One can conclude that in healthy elderly subjects, increased plasma tHcy is correlated to poorer performance at a specific measure of language abilities being compromised in both vascular and Alzheimer's dementia. The study suggests that plasma tHcy could be an early marker of cognitive impairment.

Interictal serum S100B levels in chronic neurocysticercosis and idiopathic epilepsy

OBJECTIVE

To assess whether serum S100B levels could reflect a glial response in patients with epilepsy secondary to neurocysticercosis (NCC) and with idiopathic epilepsy.

SUBJECTS AND METHODS

Serum S100B levels were measured using an immunoluminometric assay in 20 patients with focal epilepsy related to chronic NCC (NCC group), and 19 patients with focal epilepsy (EPI group), matched by epidemiological and clinical data. Epileptic patients were compared with 20 healthy controls (CON group) matched by age and sex.

RESULTS

No difference was observed in S100B levels among NCC, EPI and CON groups (P>0.39). Serum S100B levels were not affected by antiepileptic drugs, frequency and type of seizures. Preliminarily, significantly higher levels of S100B were observed in patients with bilateral electroencephalographic (EEG) findings than in patients with unilateral and normal EEG findings (P<0.05).

CONCLUSION

Serum S100B is normal in patients with focal epilepsy related or not to chronic NCC.

Cognitive Performance of Patients with Epilepsy and Calcified Neurocysticercotic Lesions: A Case-Control Study

Neuropsychological tests were applied to 20 patients with focal epilepsy related to calcified neurocysticercosis (NCC) (mean: three lesions/patient; NCC group), 22 patients with focal epilepsy without NCC (EPI group), and 29 healthy controls matched for age, sex, and educational level. The EPI and NCC groups were matched for age at onset of epilepsy, epilepsy duration, frequency of attacks, seizure semiology, interictal EEG findings, and antiepileptic drugs used. There were no differences in the digit span, word span, calculus, and Mini-Mental State examination among the three groups studied. The NCC and EPI groups showed lower scores than controls in immediate and delayed verbal memory, famous faces test, spatial recognition span, abstractions and judgment, and visuoconstructional abilities. The EPI group, but not the NCC group, also had lower scores in a praxis tests. There were no differences between the NCC and EPI groups in any of the tests applied (P > 15), except for the spatial recognition span, which was lower in the former. Cognitive impairment is a prevalent neuropsychological feature of patients with epilepsy and NCC.

Infusions of AP5 into the basolateral amygdala impair the formation, but not the expression, of step-down inhibitory avoidance

We evaluated the effects of infusions of the NMDA receptor antagonist D,L-2-amino-5-phosphonopentanoic acid (AP5) into the basolateral nucleus of the amygdala (BLA) on the formation and expression of memory for inhibitory avoidance. Adult male Wistar rats (215-300 g) were implanted under thionembutal anesthesia (30 mg/kg, ip) with 9.0-mm guide cannulae aimed 1.0 mm above the BLA. Bilateral infusions of AP5 (5.0 microg) were given 10 min prior to training, immediately after training, or 10 min prior to testing in a step-down inhibitory avoidance task (0.3 mA footshock, 24-h interval between training and the retention test session). Both pre- and post-training infusions of AP5 blocked retention test performance. When given prior to the test, AP5 did not affect retention. AP5 did not affect training performance, and a control experiment showed that the impairing effects were not due to alterations in footshock sensitivity. The results suggest that NMDA receptor activation in the BLA is involved in the formation, but not the expression, of memory for inhibitory avoidance in rats. However, the results do not necessarily imply that the role of NMDA receptors in the BLA is to mediate long-term storage of fear-motivated memory within the amygdala.

6-Chloro-3'-nitroflavone is a potent ligand for the benzodiazepine binding site of the GABA(A) receptor devoid of intrinsic activity

6-Chloro-3'-nitroflavone integrates a list of nearly 70 flavone derivatives synthesized in our laboratories. The effects of 6-chloro-3'-nitroflavone on the benzodiazepine binding sites (BDZ-BSs) of the GABA(A) receptor were examined in vitro and in vivo. 6-Chloro-3'-nitroflavone inhibited the [3H]flunitrazepam ([3H]FNZ) binding to rat cerebral cortex membranes with a Ki of 6.68 nM and the addition of GABA to extensively washed membranes did not modify its affinity for the BDZ-BSs (GABA-shift = 1.16+/-0.12). The binding assays performed in rat striatal and cerebellar brain membranes showed that this compound has similar affinity to different populations of BDZ-BSs. Electrophysiological experiments revealed that 6-chloro-3'-nitroflavone did not affect GABA(A)-receptors (GABA(A)-Rs) responses recorded in Xenopus oocytes expressing alpha1beta2gamma2s subunits, but blocked the potentiation exerted by diazepam (DZ) on GABA-activated chloride currents. In vivo experiments showed that 6-chloro-3'-nitroflavone did not possess anxiolytic, anticonvulsant, sedative, myorelaxant actions in mice or amnestic effects in rats; however, 6-chloro-3'-nitroflavone antagonized diazepam-induced antianxiety action, anticonvulsion, short-term, and long-term amnesia and motor incoordination. These biochemical, electrophysiological, and pharmacological results suggest that 6-chloro-3'-nitroflavone behaves as an antagonist of the BDZ-BSs.

Benzene in blood as a biomarker of low level occupational exposure

The occupational airborne exposure to benzene of 150 workers employed in petrol stations and a refinery plant was assessed using personal sampling pumps. All workers provided blood samples after the end of work and on the following morning before resuming work. Benzene concentrations in the blood of 243 non-occupationally-exposed subjects were also measured. The median occupational benzene exposure for all 150 workers studied was 80 micrograms/m3. Overall median blood benzene of all workers was 251 ng/l at the end of the shift, and 174 ng/l the following morning. The benzene concentrations measured in blood collected the following morning proved to be significantly lower than those measured at the end of the shift. Median blood benzene for the 243 'normal' subjects was 128 ng/l, which was significantly lower than that measured in the workers before a new work shift. The median blood benzene concentration was significantly higher in smokers than in non-smokers, both in the general population (210 ng/l vs. 110 ng/l) and in the exposed workers at the end of the shift (476 ng/l vs. 132 ng/l) and the following morning (360 ng/l vs. 99 ng/l). End-of-shift blood benzene correlated significantly with environmental exposure; this correlation was better in the 83 non-smokers than in the 67 smokers. In non-smokers with the median benzene occupational exposure of 50 micrograms/m3, no difference was found in blood benzene concentration in exposed and non-exposed subjects.

The amygdala is involved in the modulation of long-term memory, but not in working or short-term memory

Rats with cannulae implanted in the junction between the central and the basolateral nuclei of the amygdala were trained in one-trial step-down inhibitory avoidance and tested at 3 s for working memory (WM) or 1.5 or 24 h later for short-term memory (STM) and long-term memory (LTM), respectively. Several drugs were infused 6 min prior to training in the animals in which WM was measured or 0 min posttraining in those in which STM and LTM were measured: the glutamate receptor antagonists CNQX (0.5 microg) and AP5 (5.0 microg), the indirect GABA A receptor antagonist picrotoxin (0.08 microg), the cholinergic muscarinic receptor blocker scopolamine (2. 0 microg), norepinephrine (0.3 microg), the protein kinase C inhibitor staurosporin (1.0 microg), or the calcium/calmodulin dependent protein kinase II inhibitor Kn-62 (3.5 ng). None of the drugs had any effect on either WM or STM. All had, as previously shown, strong effects on LTM: picrotoxin and norepinephrine enhanced it, and CNQX, AP5, scopolamine, Kn-62, and staurosporin inhibited it. The results do not support the idea that memory of this task is formed in the amygdala; they indicate that the amygdala is not involved in WM or STM processing and support the idea that the amygdala modulates LTM storage processes carried out elsewhere.

Benzene in environmental air and human blood

OBJECTIVE

To study the blood benzene levels resulting from environmental and occupational benzene exposure.

METHODS

Benzene in venous blood was measured in 243 nonoccupationally exposed subjects ("normal" people) and in 167 workers occupationally exposed to benzene. All exposed workers gave blood samples at the end of the work shift and on the following morning before resuming work. Blood benzene was assayed by gas chromatography (GC)-mass spectrometry. Occupational benzene exposure was monitored by environmental personal samplers and measured by GC analysis.

RESULTS

The mean occupational benzene exposure for all 167 workers studied was 186 ng/l (58 ppb; range 5 1535 ng/l, 2-500 ppb). Overall, the mean blood benzene level of all workers was 420 ng/1 at the end of the shift and 287 ng/l on the morning thereafter. The blood benzene levels measured the morning after turned out to be significantly lower (t=3.6; P < 0.0001) than those measured at the end of the shift. The mean blood benzene level of the 243 "normal" subjects was 165 ng/l, which was significantly lower than that measured in the workers on the morning thereafter (t=5.8: P < 0.0000001). The mean blood benzene concentration was significantly higher in smokers than in nonsmokers in both the general population (264 versus 123 ng/l) and in the exposed workers. In the group of nonsmoking workers, whose workplace exposure to benzene was lower than 100 ng/l, blood benzene levels were similar (210-202 ng/l) to those measured in the nonsmoking general population (165 ng/l). End-of-shift blood benzene correlated significantly with environmental exposure (y=0.91x + 251; r=0.581; n=162; P < 0.00001). Finally, there was also a significant correlation between blood benzene measured at the end of the shift and that determined on the morning thereafter (y=0.45x + 109; r=0.572; n=156; P < 0.00001).

CONCLUSION

Nonsmoking workers occupationally exposed to benzene at environmental levels lower than 100 ng/l (mean 35 ng/l) and the nonsmoking general population exposed to ubiquitous benzene pollution have similar blood benzene concentrations. This suggests that it is impossible to distinguish between occupational and environmental exposure when the benzene level in the workplace is less than 100 ng/l.

Cerebral phaeohyphomycosis caused by Cladophialophora bantiana in a Brazilian drug abuser

We present a case of cerebral phaeohyphomycosis caused by Cladophialophora bantiana in an apparently immunocompetent patient with a history of intravenous drug use. The diagnosis was achieved in specimens obtained at necropsy by histological and mycological examination, with subsequent identification of the isolate in culture.

Drugs acting upon the cyclic adenosine monophosphate/protein kinase A signalling pathway modulate memory consolidation when given late after training into rat hippocampus but not amygdala

Rats implanted bilaterally with cannulae in the CA1 region of the dorsal hippocampus or in the amygdala were trained in one-trial step-down inhibitory (passive) avoidance using a 0.4 mA footshock. At various times after training (0, 1.5, 3, 6 or 9 h for animals implanted in the hippocampus; 0 or 3 h for those implanted in the amygdala), they received infusions of 8-Br-cAMP (cyclic adenosine monophosphate) (1.25 micrograms/side), SKF38393 (7.5 micrograms/side), SCH23390 (0.5 microgram/side), norepinephrine ClH (0.3 microgram/side), timolol ClH (0.3 microgram/side), 8-HO-DPAT (2.5 micrograms/side), NAN-190 (2.5 micrograms/side), forskolin (0.5 microgram/side) or KT5720 (0.5 microgram/side). Rats were tested for retention 24 h after training. SKF38393 is an agonist and SCH23390 an antagonist at dopamine D1 receptors, timolol is a beta-adrenoceptor antagonist, 8-HO-DPAT is an agonist and NAN-190 an antagonist at 5HT1A receptors, forskolin enhances adenylyl cyclase, and KT5720 inhibits protein kinase A. When given into the hippocampus 0 h post-training, norepinephrine enhanced memory and KT5720 was amnestic. When given 1.5 h after training, all treatments were ineffective. When given 3 or 6 h post-training, 8-Br-cAMP, forskolin, SKF 38393, noradrenaline and NAN-190 caused memory facilitation, and KT5720, SCH23390, timolol and 8-HO-DPAT caused retrograde amnesia. At 9 h from training, all treatments were again ineffective. When given into the amygdala 0 or 3 h post-training all treatments were ineffective, except for noradrenaline at 0 h, which caused retrograde facilitation. The data agree with the suggestion that in the hippocampus, but not the amygdala, a cAMP/protein kinase A pathway is involved in memory consolidation at 3 and 6 h from training, and that this is regulated by D1, beta, and 5HT1A receptors. This correlates with a previous report of increased cAMP levels, protein kinase A activity and P-CREB levels at 3-6 h from training in rat hippocampus in this task. This may be taken to suggest that the hippocampus, but not the amygdala, is involved in the long-term storage of step-down inhibitory avoidance in the rat.

Agents that affect cAMP levels or protein kinase A activity modulate memory consolidation when injected into rat hippocampus but not amygdala

Male Wistar rats were trained in one-trial step-down inhibitory avoidance using a 0.4-mA footshock. At various times after training (0, 1.5, 3, 6 and 9 h for the animals implanted into the CA1 region of the hippocampus; 0 and 3 h for those implanted into the amygdala), these animals received microinfusions of SKF38393 (7.5 micrograms/side), SCH23390 (0.5 microgram/side), norepinephrine (0.3 microgram/side), timolol (0.3 microgram/side), 8-OH-DPAT (2.5 micrograms/side), NAN-190 (2.5 micrograms/side), forskolin (0.5 microgram/side), KT5720 (0.5 microgram/side) or 8-Br-cAMP (1.25 micrograms/side). Rats were tested for retention 24 h after training. When given into the hippocampus 0 h post-training, norepinephrine enhanced memory whereas KT5720 was amnestic. When given 1.5 h after training, all treatments were ineffective. When given 3 or 6 h post-training, 8-Br-cAMP, forskolin, SKF38393, norepinephrine and NAN-190 caused memory facilitation, while KT5720, SCH23390, timolol and 8-OH-DPAT caused retrograde amnesia. Again, at 9 h after training, all treatments were ineffective. When given into the amygdala, norepinephrine caused retrograde facilitation at 0 h after training. The other drugs infused into the amygdala did not cause any significant effect. These data suggest that in the hippocampus, but not in the amygdala, a cAMP/protein kinase A pathway is involved in memory consolidation at 3 and 6 h after training, which is regulated by D1, beta, and 5HT1A receptors. This correlates with data on increased post-training cAMP levels and a dual peak of protein kinase A activity and CREB-P levels (at 0 and 3-6 h) in rat hippocampus after training in this task. These results suggest that the hippocampus, but not the amygdala, is involved in long-term storage of step-down inhibitory avoidance in the rat.

Involvement of hippocampal cAMP/cAMP-dependent protein kinase signaling pathways in a late memory consolidation phase of aversively motivated learning in rats

cAMP/cAMP-dependent protein kinase (PKA) signaling pathway has been recently proposed to participate in both the late phase of long term potentiation in the hippocampus and in the late, protein synthesis-dependent phase of memory formation. Here we report that a late memory consolidation phase of an inhibitory avoidance learning is regulated by an hippocampal cAMP signaling pathway that is activated, at least in part, by D1/D5 receptors. Bilateral infusion of SKF 38393 (7.5 microg/side), a D1/D5 receptor agonist, into the CA1 region of the dorsal hippocampus, enhanced retention of a step-down inhibitory avoidance when given 3 or 6 h, but not immediately (0 h) or 9 h, after training. In contrast, full retrograde amnesia was obtained when SCH 23390 (0.5 microg/side), a D1/D5 receptor antagonist, was infused into the hippocampus 3 or 6 h after training. Intrahippocampal infusion of 8Br-cAMP (1.25 microg/side), or forskolin (0.5 microg/side), an activator of adenylyl cyclase, enhanced memory when given 3 or 6 h after training. KT5720 (0.5 microg/side), a specific inhibitor of PKA, hindered memory consolidation when given immediately or 3 or 6 h posttraining. Rats submitted to the avoidance task showed learning-specific increases in hippocampal 3H-SCH 23390 binding and in the endogenous levels of cAMP 3 and 6 h after training. In addition, PKA activity and P-CREB (phosphorylated form of cAMP responsive element binding protein) immunoreactivity increased in the hippocampus immediately and 3 and 6 h after training. Together, these findings suggest that the late phase of memory consolidation of an inhibitory avoidance is modulated cAMP/PKA signaling pathways in the hippocampus.

The effects of intra-amygdala infusion of the AMPA receptor antagonist CNQX on retention performance following aversive training

The aim of these experiments was to determine whether impaired retention performance in aversively motivated tasks, induced by blockade of amygdala AMPA receptors, is due to influences on mechanisms underlying memory retrieval or to other influences on performance. Rats received either footshock escape training (1 or 10 trials), or no foot shock, in a two-compartment straight alley and bilateral intra-amygdala infusions of the AMPA receptor antagonist CNQX (0.5 microgram) were subsequently administered prior to inhibitory avoidance retention testing 8 days later. The CNQX impaired, but did not block, inhibitory avoidance retention performance as indicated by the initial latencies to enter the shock compartment. The animals were then retained in the alley until they remained in the starting compartment for 100 consecutive s and entries into the shock compartment were recorded as errors. In both the controls and CNQX-treated groups, increases in amount of original training resulted in fewer errors, indicating memory for the escape training. Furthermore, regardless of the amount of original training (i.e., 0, 1, or 10 trials), CNQX-treated groups made more errors. Other experiments examined intra-amygdala CNQX effects on reactivity to footshock, locomotor activity, and anxiety. CNQX decreased reactivity to footshock, blocked shock-induced decreases in locomotor activity, and had an anxiolytic effect in an elevated plus maze comparable to that induced by midazolam (0.5 microgram). These findings suggest that intra-amygdala infusions of CNQX prior to retention testing affect inhibitory avoidance retention performance following aversive training by altering locomotor activity, reducing sensitivity to footshock, and reducing anxiety. The implications of these findings for hypotheses concerning amygdala function in aversively motivated learning and memory is discussed.

Experiments suggesting a role for nitric oxide in the hippocampus in memory processes

Nitric oxide (NO) has been proposed to be involved in the induction of long-term potentiation (LTP) and in other processes. When coupled with weak tetanic stimulation, NO produces a long-term synaptic enhancement on its own. N-Nitroarginine (NO-Arg) inhibits NO-synthase, the enzyme that produces NO, and blocks LTP in hippocampal slices. We investigated the effect on memory of the pre- or post-training infusion of NO-Arg and of the post-training infusion of the No donor, S-nitroso-N-acetylpenicillamine (SNAP) into the hippocampus. Male Wistar rats were implanted bilaterally with cannulae in the dorsal hippocampus. After recovery from surgery, the animals were trained in step-down inhibitory avoidance using a 0.4-mA footshock and tested for retention 24 h later. NO-Arg (2.0 microgram) hindered retention test performance when infused either before or immediately after training, but not 30 or 60 min later. SNAP (5.0 microgram) enhanced retention test performance when given 0, 60, or 150 min, but not 300 min, after training. The results suggest that memory storage depends on NO-sensitive processes in the hippocampus, perhaps, as suggested in previous papers, LTP generated at the time of training.

Memory of inhibitory avoidance in the rat is regulated by glutamate metabotropic receptors in the hippocampus

This experiment investigated the effect on memory, in rats, of the bilateral intrahippocampal post-training infusion of the glutamate metabotropic receptor (mGLUR) agonist, ACPD (1S, 2R-aminocyclopentane dicarboxylate) and of the mGLUR antagonist, MCPG ([RS]-alpha-methyl-4-carboxyphenyl glycine). Male Wistar rats were implanted bilaterally with cannulae in the CA1 region of the dorsal hippocampus. After recovery from surgery they were trained in a step-down inhibitory avoidance task and tested for retention 24h later. Immediately or 180min after training they received a bilateral intrahippocampal infusion of saline (0.5µl), ACPD (1.0 or 2.5µg/side), MCPG (2.5µg/side) or ACPD plus MCPG, in 0.5µl saline. Upon immediate post-training infusion, ACPD caused a dose-dependent enhancement of memory and MCPG was amnestic. The effect of MCPG was antagonized by the simultaneous administration of ACPD. When given 180min after training, the drugs had no effect on memory. The results indicate that the early phase of memory is regulated by mGLURs in the hippocampus, and support the suggestion that memory involves long-term potentiation initiated at the time of training in the hippocampus.

CNQX infused into entorhinal cortex blocks memory expression, and AMPA reverses the effect

Rats were trained in a step-down inhibitory avoidance task using a 0.8-mA foot shock and tested for retention 26 days later. Three to five days prior to the retention test they were bilaterally implanted with cannulae aimed at the entorhinal cortex. Ten minutes before testing they received an infusion, into the entorhinal cortex, of vehicle, ciano-nitro-quinoxaline-dione (CNQX; 0.5 micrograms), amino-hydroxy-methyl-isoxalone-propionate (AMPA; 1.0 or 2.5 micrograms), or AMPA (1.0 micrograms) plus CNQX (0.5 micrograms). CNQX blocked memory expression; the effect lasted less than 90 min. AMPA had no effect of its own, but at the lower dose level it counteracted the depressant influence of CNQX. It is not likely that the effect of CNQX could have been due to an influence on performance: In separate sets of experiments the bilateral intraentorhinal infusion of CNQX (0.5 micrograms) 10 min before training did not affect either acquisition or retention of the avoidance task or general activity during 3 min of free exploration in the training box. The results indicate that the integrity of AMPA receptors in the entorhinal cortex is necessary for memory expression.

Intrahippocampal or intraamygdala infusion of KN62, a specific inhibitor of calcium/calmodulin-dependent protein kinase II, causes retrograde amnesia in the rat

We investigated the effect of a bilateral post-training intracerebral infusion of KN62, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaM-II), on memory. This enzyme plays a crucial role in the early phases of long-term potentiation. Male Wistar rats were implanted bilaterally with cannulae aimed at the CA1 region of the dorsal hippocampus or at the junction between the central and the basolateral nuclei of the amygdala. After recovery, rats were trained in step-down inhibitory avoidance using a 0.5-mA footshock and tested for retention 24 h later. At various times after training (0, 30, 120, or 240 min for the animals implanted into the hippocampus; 0 or 240 min for the animals implanted in the amygdala) they received, through the cannulae, an infusion of vehicle (0.1% dimethylsulfoxide in water) or KN62 (100 mumol/side). KN62 caused full retrograde amnesia when given 0 min after training into either the amygdala or the hippocampus. When given into the hippocampus 30 min post-training it had a partial amnestic effect. When given 120 min after training into the hippocampus, or 240 min after training into either structure, KN62 had no effect. The data suggest that the early phase of memory requires intact CaM-II activity in the amygdala and hippocampus and support the hypothesis that memory involves long-term potentiation initiated at the time of training in both structures.

Effect of the infusion of the GABA-A receptor agonist, muscimol, on the role of the entorhinal cortex, amygdala, and hippocampus in memory processes

Rats were bilaterally implanted with cannulae in the entorhinal cortex, amygdala, and hippocampus; after recovery, they were trained in a step-down inhibitory avoidance task and tested for retention 24 h later. Muscimol (0.03 microgram) or D-amino-5-phosphonovalerate (5.0 micrograms) infused in the entorhinal cortex 20 min prior to training inhibited the amnestic effect of the same dose of muscimol infused into this area 100 min after training. Thus, memory-relevant information must be processed by the entorhinal cortex at the time of training in order that this cortex may play a late post-training role in memory processing. Pretraining intraentorhinal muscimol administration did not affect the amnestic effect of the post-training infusion of muscimol into the amygdala and hippocampus, or the inhibition of memory expression induced by a pretest infusion of CNQX into the amygdala and hippocampus or into the entorhinal cortex. Pretest intraentorhinal muscimol also did not influence the effect of pretest intra-amygdala and intrahippocampal CNQX administration. These data indicate that the cells of the entorhinal cortex that are sensitive to pretraining muscimol are not part of the inputs that lead to post-training processing by the amygdala and hippocampus, or to the intervention of the amygdala, hippocampus, and entorhinal cortex in memory expression. The present findings are compatible with the possibility that, instead, the entorhinal cortex may be an output of the amygdala and hippocampus at the time of memory expression.

Memory processing by the limbic system: role of specific neurotransmitter systems

Experiments using localized infusions into selected brain structures of agonists and antagonists of various synaptic receptors, given before or after behavioral training, have led to the following conclusions: (1) Memory is processed shortly after training in the amygdala, medial septum and hippocampus by glutamatergic NMDA and AMPA receptors activated in that sequence. Cholinergic muscarinic receptors are activated concurrently with the former. GABAA receptors modulated by brain benzodiazepines and by beta-noradrenergic receptors inhibit the process. (2) The sequential involvement of NMDA and AMPA receptors suggests that long-term potentiation (LTP) of the synapses activated by the learning experiences in the hippocampus and/or amygdala and medial septum is the crucial event. Expression of this LTP at the time of testing is necessary for retrieval: AMPA receptor blockade in the hippocampus and amygdala at the time of testing hinders retrieval. This suggests that the LTP underlies the memory process itself. (3) The amygdala, medial septum and hippocampus mediate different types of memory and/or different components of memories. The entorhinal cortex, through mechanisms that require intact NMDA receptors and are inhibited by GABAA receptors, intervenes in post-training memory processing 90-180 min after the other limbic regions. The entorhinal cortex integrates consecutively acquired memories; this role could be maintained by the LTP that is generated after training in the amygdala, hippocampus and medial septum. Post-training intervention of the entorhinal cortex does not occur if this region is inhibited at the time of training.

Chronic use of benzodiazepines and cognitive deficit complaints: a risk factor study

Benzodiazepines produce an anterograde amnesia after acute administration but whether their chronic use is hazardous to memory processes remains unclear. The present study analyses the risk of increasing cognitive complaints with chronic benzodiazepine use. Subjects seeking medical assistance at the General Internal Medicine Outpatient Clinic of Hospital de Clinicas de Porto Alegre, were interviewed before seeing physicians. They were asked about use of benzodiazepines, history of neurological and psychiatric diseases, use of alcohol, and deficits in remembering and learning as well as age, sex and level of education. Age (over 51 years), low level of education, a history of neurological and psychiatric diseases and use of benzodiazepines showed significant associations with cognitive complaints. After a conditional logistic regression analysis, benzodiazepine use lost its association with memory complaints. These data support the hypothesis that the chronic use of benzodiazepines does not carry a risk for cognitive deficits complaints.

A peptide muscarinic toxin from the Green Mamba venom shows agonist-like action in an inhibitory avoidance learning task

A peptide, muscarinic toxin 2 (MTX2), isolated from Dendroaspis angusticeps venom was previously shown to displace the specific binding of [3H]pirenzepine, a muscarinic M1 receptor ligand, from rat brain synaptosomal membranes. We have tested MTX2 for muscarinic agonist or antagonist actions in an inhibitory avoidance task in rats. Infusion of the muscarinic receptor antagonist scopolamine into the hippocampus of rats immediately after the training period produced amnesia, whereas the muscarinic agonist oxotremorine increased retention. When MTX2 was injected into the hippocampus of rats after the inhibitory avoidance task, it caused memory facilitation, which could be suppressed by the concomitant infusion of scopolamine. Hence, in this test, MTX2 showed muscarinic receptor agonist-like actions, which are probably mediated by the M1 subtype of muscarinic acetylcholine receptors.

Muscimol infused into the entorhinal cortex prior to training blocks the involvement of this area in post-training memory processing

Muscimol infusions into the entorhinal cortex (ERC) have previously been reported to impair the retention of passive avoidance learning, but only when infusions were delayed until 90min after training. In the present study, three experiments were carried out to examine further the effects of muscimol infusions into the ERC prior to training. In Experiment 1, muscimol infusions prior to training had no effect on retention, confirming earlier findings, but blocked the amnestic effect of a second muscimol infusion 90min post-training. In Experiment 2, muscimol infusions prior to training blocked the improvement of retention normally seen following a second training trial 2h after the first. In Experiment 3, the technique of summation of performance across training trials was used to confirm that the direct effects of muscimol infusions lasted less than 2h. The results indicate that the GABA-ergic mechanism in the ERC is normally involved in the formation of memory for passive avoidance, but if the ERC is inactivated at the time of training, memory formation is diverted to other structures, which appear less capable of integrating consecutive memories across time.

Memory expression is blocked by the infusion of CNQX into the hippocampus and/or the amygdala up to 20 days after training

Bilateral infusion of CNQX (0.5 microgram) into the amygdala and the dorsal hippocampus prior to a retention test blocked the expression of step-down inhibitory avoidance in rats 6, 13, or 20 days after training. Retention test performance recovered 90 min after the infusions. Pretest intrahippocampal CNQX (0.5 microgram) blocked the expression of habituation to a novel environment measured 20 days after training. The data suggest that memory expression depends on non-NMDA receptor-mediated mechanisms, perhaps the expression of LTP, up to at least 20 days after acquisition. These mechanisms operate in the hippocampus in both tasks and in the amygdala in the avoidance task.

CNQX infused into rat hippocampus or amygdala disrupts the expression of memory of two different tasks

The bilateral infusion of CNQX (0.5 or 1.25 micrograms) into the amygdala or dorsal hippocampus 10 min prior to a retention test partially blocked the expression of stepdown inhibitory avoidance in rats 24 h after training. When infused into both the amygdala and the hippocampus at a dose of 0.5 microgram. CNQX caused a complete blockade of the expression of that task. Retention test performance recovered 2 h after the infusions. In rats trained for habituation to a novel environment and tested 24 h later, pretest intrahippocampal CNQX (0.5 microgram) blocked the expression of retention at a dose of 0.5 microgram, and intra-amygdala CNQX (0.5 or 1.25 micrograms) had no effect. The data suggest that, up to at least 1 day after training, memory of the avoidance task depends on glutamate acting on non-NMDA receptors in both the hippocampus and the amygdala, whereas memory of the habituation task depends on non-NMDA receptor activity in the hippocampus but not the amygdala.

Amnesia by post-training infusion of glutamate receptor antagonists into the amygdala, hippocampus, and entorhinal cortex

The blockers of glutamate receptors, aminophosphonovaleric acid (AP5) (5.0 micrograms) and cyano-nitroquinoxaline-dione (CNQX) (0.5 microgram), were infused bilaterally into the amygdala, dorsal hippocampus, or entorhinal cortex of rats through indwelling cannulae 0, 90, 180, or 360 min after step-down inhibitory avoidance training. Animals were tested for retention 24 h after training. In the amygdala or hippocampus, AP5 was amnestic when given 0 min after training and CNQX was amnestic when given 0, 90, or 180 min after training. In the entorhinal cortex, AP5 was amnestic when given 90 or 180 min after training and CNQX had no effect. The results suggest that a phenomenon sensitive first to AP5 and then to CNQX in the amygdala and hippocampus, probably long-term potentiation (LTP), is crucial to post-training memory processing. LTP in these two structures could underlie their role in memory consolidation and could explain the late involvement of the entorhinal cortex in post-training memory processing.

Memory facilitation by post-training intraperitoneal, intracerebroventricular and intra-amygdala injection of Ro 5-4864

Post-training i.p. (2.0 or 5.0 mg/kg), i.c.v. (2.5 micrograms/rat), or intra-amygdala (1.6-40 ng/amygdala) administration of Ro 5-4864 causes memory facilitation of step-down inhibitory avoidance in rats. The effect is expressed as an increased latency to step down in a retention test carried out 24 h after training. Ro 5-4864 is a blocker of the Cl(-)-channel associated with GABAA receptors, at a site sensitive to the antagonist, PK11195, and different from that sensitive to picrotoxin. PK11195, given i.c.v. (2.5 micrograms/rat) or into the amygdala (8 ng/amygdala), antagonized the effect of Ro 5-4864. Intra-amygdala picrotoxin administration (80 ng/amygdala) also caused retrograde memory facilitation, but its effect was not antagonized by PK11195. At a higher dose (40 ng/amygdala), PK11195 had an amnestic effect of its own, which suggests that it might be acting against an endogenous ligand of receptor to Ro 5-4864 in the Cl(-)-channel. These findings support the hypothesis that there is a GABAA mechanism in the amygdala normally involved in the modulation of the post-training memory processing of aversive learnings.