The likelihood of cognitive enhancement

PWZ-029, an inverse agonist selective for α₅ GABAA receptors, improves object recognition, but not water-maze memory in normal and scopolamine-treated rats

Inverse agonism at the benzodiazepine site of α(5) subunit-containing GABA(A) receptors is an attractive approach for the development of putative cognition-enhancing compounds, which are still far from clinical application. Several ligands with binding and/or functional selectivity for α(5) GABA(A) receptors have been synthesized and tested in a few animal models. PWZ-029 is an α(5) GABA(A) selective inverse agonist whose memory enhancing effects were demonstrated in the passive avoidance task in rats and in Pavlovian fear conditioning in mice. In the present study we investigated the effects of PWZ-029 administration in novel object recognition test and Morris water maze, in normal and scopolamine-treated rats. All the three doses of PWZ-029 (2, 5 and 10 mg/kg) improved object recognition after the 24-h delay period, as shown by significant differences between the exploration times of the novel and old object, and the respective discrimination indices. PWZ-029 (2 mg/kg) also successfully reversed the 0.3 mg/kg scopolamine-induced deficit in recognition memory after the 1-h delay. In the Morris water maze test, PWZ-029 (5, 10 and 15 mg/kg) did not significantly influence swim patterns, either during five acquisition days or during the treatment-free probe trial. PWZ-029 (2, 5 and 10 mg/kg) also proved to be ineffective in the reversal of the 1mg/kg scopolamine-induced memory impairment in the water maze. The present mixed results encourage use of a variety of tests and experimental conditions in order to increase the predictability of preclinical testing of selective α(5) GABA(A) inverse agonists.

The NMDA receptor as a target for cognitive enhancement

NMDA receptors (NMDARs) play an important role in neural plasticity including long-term potentiation and long-term depression, which are likely to explain their importance for learning and memory. Cognitive decline is a major problem facing an ageing human population, so much so that its reversal has become an important goal for scientific research and pharmaceutical development. Enhancement of NMDAR function is a core strategy toward this goal. In this review we indicate some of the major ways of potentiating NMDAR function by both direct and indirect modulation. There is good evidence that both positive and negative modulation can enhance function suggesting that a subtle approach correcting imbalances in particular clinical situations will be required. Excessive activation and the resultant deleterious effects will need to be carefully avoided. Finally we describe some novel positive allosteric modulators of NMDARs, with some subunit selectivity, and show initial evidence of their ability to affect NMDAR mediated events. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Functional analysis of a novel positive allosteric modulator of AMPA receptors derived from a structure-based drug design strategy

Positive allosteric modulators of α-amino-3-hydroxy-5-methyl-isoxazole-propionic acid (AMPA) receptors facilitate synaptic plasticity and can improve various forms of learning and memory. These modulators show promise as therapeutic agents for the treatment of neurological disorders such as schizophrenia, ADHD, and mental depression. Three classes of positive modulator, the benzamides, the thiadiazides, and the biarylsulfonamides differentially occupy a solvent accessible binding pocket at the interface between the two subunits that form the AMPA receptor ligand-binding pocket. Here, we describe the electrophysiological properties of a new chemotype derived from a structure-based drug design strategy (SBDD), which makes similar receptor interactions compared to previously reported classes of modulator. This pyrazole amide derivative, JAMI1001A, with a promising developability profile, efficaciously modulates AMPA receptor deactivation and desensitization of both flip and flop receptor isoforms. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Cognitive-enhancing substance use at German universities: frequency, reasons and gender differences

BACKGROUND

The purpose of this study was to give an overview whether German students regularly use stimulants for enhancing their academic performance. Reasons associated with the use of these substances were explored. Moreover, gender differences were analyzed.

METHODS

A cross-sectional survey study was performed analyzing a random sample of 1,053 students of different fields of study in Germany. Students were asked to complete an anonymous self-administered web-based survey containing questions on cognitive performance-enhancing substance use. We used statistical analyses, e.g. non-parametric tests to evaluate the data of our questionnaire.

RESULTS

Among 1,053 students, 61 % responded to our questionnaire. The average age was M = 24.58; 635 participants were female and 418 were male students. Total 1-13 % of the participating students have taken prescription stimulants (e.g. modafinil) or illicit drugs (e.g. cannabis) at least once in their lifetime. The most common reasons for taking stimulants were to support concentration, to relax and to increase alertness. We found significant gender differences with regard to frequency and reason for using performance-enhancing substances.

CONCLUSIONS

Our study results give an overview about the actual situation on frequency and reasons for taking performance-enhancing substances. Departments of Public Health should address this issue in national health debates and discussions. Based on our study findings health education programmes should be developed.

Memory enhancement: consolidation, reconsolidation and insulin-like growth factor 2

Life and societies would change significantly if memory capacity or persistence in health and disease could be enhanced. It has been known for many years that memory can be improved and strengthened. Substances known to enhance memory include hormones, neurotransmitters, neuropeptides and metabolic substrates. Recently, attention has been given to identifying the molecular mechanisms and targets whereby memory enhancement can be achieved. One approach would be to target the physiological changes that are induced by learning and naturally required for memory strengthening via consolidation and reconsolidation. Here, we review approaches that boost memories by targeting the cAMP response element binding protein-CCAAT enhancer binding protein (CREB-C/EBP) pathway and/or its recently identified target gene insulin-like growth factor 2 (IGF2).

Modulation of fronto-cortical activity by modafinil: a functional imaging and fos study in the rat

Modafinil (MOD) is a wake-promoting drug with pro-cognitive properties. Despite its increasing use, the neuronal substrates of MOD action remain elusive. In particular, animal studies have highlighted a putative role of diencephalic areas as primary neuronal substrate of MOD action, with inconsistent evidence of recruitment of fronto-cortical areas despite the established pro-cognitive effects of the drug. Moreover, most animal studies have employed doses of MOD of limited clinical relevance. We used pharmacological magnetic resonance imaging (phMRI) in the anesthetized rat to map the circuitry activated by a MOD dose producing clinically relevant plasma exposure, as here ascertained by pharmacokinetic measurements. We observed prominent and sustained activation of the prefrontal and cingulate cortex, together with weaker but significant activation of the somatosensory cortex, medial thalamic domains, hippocampus, ventral striatum and dorsal raphe. Correlation analysis of phMRI data highlighted enhanced connectivity within a neural network including dopamine projections from the ventral tegmental area to the nucleus accumbens. The pro-arousing effect of MOD was assessed using electroencephalographic recording under anesthetic conditions comparable to those used for phMRI, together with the corresponding Fos immunoreactivity distribution. MOD produced electroencephalogram desynchronization, resulting in reduced delta and increased theta frequency bands, and a pattern of Fos induction largely consistent with the phMRI study. Altogether, these findings show that clinically relevant MOD doses can robustly activate fronto-cortical areas involved in higher cognitive functions and a network of pro-arousing areas, which provide a plausible substrate for the wake-promoting and pro-cognitive effects of the drug.

Factors affecting cognitive function of opiate-dependent patients

BACKGROUND

A wide range of studies found that opiate-dependent patients suffer from cognitive impairment due to a number of different factors. However, this issue has never been examined systematically. Thus, the aim of the present study is to provide a comprehensive analysis of factors that might contribute to cognitive impairment of opiate-dependent patients and specifically differentiates between various cognitive abilities as these might be impacted differently.

METHODS

Based on a comprehensive review of the literature with regard to previous findings and suggestions about which factors might affect cognitive functioning, we assessed a wide variety of variables related to substance use and opiate-dependence as well as demographic and socioeconomic variables. Cognitive functioning was assessed through a neuropsychological test-battery.

RESULTS

We found that the duration of opiate dependence and maintenance treatment, as well as additional substance consumption (alcohol, amphetamines, and cocaine) are the main variables contributing to cognitive impairment in the domains of attention and executive function. Comorbid depressive symptoms negatively affected reaction times. There was no evidence for the role of demographic variables like age and education on cognitive functioning.

CONCLUSIONS

Our findings suggest that it might be important in the treatment of opiate dependence to address the consumption of additional substances and to closely monitor the negative effects of maintenance treatment on cognitive functioning.

α7 nicotinic ACh receptors as a ligand-gated source of Ca(2+) ions: the search for a Ca(2+) optimum

The spatiotemporal distribution of cytosolic Ca(2+) ions is a key determinant of neuronal behavior and survival. Distinct sources of Ca(2+) ions including ligand- and voltage-gated Ca(2+) channels contribute to intracellular Ca(2+) homeostasis. Many normal physiological and therapeutic neuronal functions are Ca(2+)-dependent, however an excess of cytosolic Ca(2+) or a lack of the appropriate balance between Ca(2+) entry and clearance may destroy cellular integrity and cause cellular death. Therefore, the existence of optimal spatiotemporal patterns of cytosolic Ca(2+) elevations and thus, optimal activation of ligand- and voltage-gated Ca(2+) ion channels are postulated to benefit neuronal function and survival. Alpha7 nicotinic -acetylcholine receptors (nAChRs) are highly permeable to Ca(2+) ions and play an important role in modulation of neurotransmitter release, gene expression and neuroprotection in a variety of neuronal and non-neuronal cells. In this review, the focus is placed on α7 nAChR-mediated currents and Ca(2+) influx and how this source of Ca(2+) entry compares to NMDA receptors in supporting cytosolic Ca(2+) homeostasis, neuronal function and survival.

Alzheimer's disease and age-related memory decline (preclinical)

An unfortunate result of the rapid rise in geriatric populations worldwide is the increasing prevalence of age-related cognitive disorders such as Alzheimer's disease (AD). AD is a devastating neurodegenerative illness that is characterized by a profound impairment of cognitive function, marked physical disability, and an enormous economic burden on the afflicted individual, caregivers, and society in general. The rise in elderly populations is also resulting in an increase in individuals with related (potentially treatable) conditions such as "Mild Cognitive Impairment" (MCI) which is characterized by a less severe (but abnormal) level of cognitive impairment and a high-risk for developing dementia. Even in the absence of a diagnosable disorder of cognition (e.g., AD and MCI), the perception of increased forgetfulness and declining mental function is a clear source of apprehension in the elderly. This is a valid concern given that even a modest impairment of cognitive function is likely to be associated with significant disability in a rapidly evolving, technology-based society. Unfortunately, the currently available therapies designed to improve cognition (i.e., for AD and other forms of dementia) are limited by modest efficacy and adverse side effects, and their effects on cognitive function are not sustained over time. Accordingly, it is incumbent on the scientific community to develop safer and more effective therapies that improve and/or sustain cognitive function in the elderly allowing them to remain mentally active and productive for as long as possible. As diagnostic criteria for memory disorders evolve, the demand for pro-cognitive therapeutic agents is likely to surpass AD and dementia to include MCI and potentially even less severe forms of memory decline. The purpose of this review is to provide an overview of the contemporary therapeutic targets and preclinical pharmacologic approaches (with representative drug examples) designed to enhance memory function.