Home-based physiology labs in the time of COVID-19 prove popular with medical students

The COVID-19 pandemic and the resulting "lockdown" have forced many medical schools to shift from traditional "face-to-face" teaching methodologies and embrace full online delivery. Although lectures and tutorials are readily communicated by this approach, the execution of laboratory exercises is much more difficult. To overcome these challenges, face-to-face laboratory sessions were replaced by a blended learning approach in which students were provided instructional material online and then required to conduct the laboratory exercises at home. These laboratory exercises made use of easily accessible household materials and mobile applications. A self-report survey was designed to assess students' perception of their learning experience and attitudes to the home-based laboratory exercises. The survey consisted of 16 questions that students had to respond to using a 5-point Likert scale. Students were also allowed to provide open responses to select questions. Overall, the 80% of students that completed the survey expressed strong satisfaction with their learning experience and were enthusiastic toward home-based laboratory exercises. However, concerns about not being able to complete particular face-to-face exercises that required specialized equipment were expressed. Several students proposed a combined approach going forward. Our results show that home-based laboratory exercises offer a multimodal option that enriches the learning curriculum by engaging students in "hands-on" bespoke practicals using inexpensive household materials.

A cross-sectional study of neuromyths among teachers in a Caribbean nation

BACKGROUND

The current COVID-19 pandemic and proliferation of misinformation regarding science highlights the importance of improving general science literacy. The continued preponderance of neuromyths among educators is of concern, especially in lower- and middle-income countries.

METHOD

Using an adapted questionnaire, a cross-sectional survey was conducted among teachers in a small island developing state in the Caribbean.

RESULTS

Two-thirds of the sample were unable to recognise at least 50% of the myths. Regression analysis demonstrated that higher scores in brain knowledge and exposure to prior teacher-training increased belief in neuromyths. On the other hand, specific in-service training pertaining to educational neuroscience improved scores.

CONCLUSION

Neuromyths are prevalent among teachers and appear to inform their teaching practice. Further research needs to be conducted to explore not just the prevalence of these myths but in what ways they may be impacting teaching and learning outcomes in the classroom.

The Relationship Between Self-Esteem, Emotional Intelligence, and Empathy Among Students From Six Health Professional Programs

Theory: Psychosocial skills such as communication, empathy, and emotional intelligence are now considered key attributes of health professionals. Self-esteem is another important construct that is less well studied. Self-esteem is important because low levels have been linked to depression, suicide, and eating disorders. Given that health professional students experience high levels of stress and are at increased risk for similar psychopathology, self-esteem may be an important variable in student well-being and performance after graduation. Hypotheses: This study sought to explore self-esteem during students' 1st year of training hypothesizing that several would demonstrate low self-esteem. It is also hypothesized that emotional intelligence and empathy would be associated with self-esteem. Method: A cross-sectional survey was conducted, and data were gathered from dental, medical, nursing, optometry, pharmacy and veterinary students. Self-report questionnaires assessing self-esteem, emotional intelligence, and empathy were completed and demographic information was collected. Scores were calculated and differences between groups analyzed with analysis of variance and chi-square testing. Pearson's correlation was used to assess associations between the constructs. Results: The mean self-esteem score was 26.2 ± 2.3 but 21% of the sample evidenced low self-esteem. There was no difference in the proportion of students demonstrating low self-esteem among programs. Gender did not have a significant effect on self-esteem scores, though ethnicity did. Emotional intelligence scores were higher among male individuals than among female. Emotional intelligence and empathy showed a small association with self-esteem. Conclusions: A significant proportion of health professional students suffer from low self-esteem during their 1st year of study. Such students may be more susceptible to the stresses associated with study and the development of psychopathology. More research needs to be conducted to explore the relationships between self-esteem, emotional intelligence, and empathy with a view to strengthening training in these areas and managing the challenges faced by health professional students.

Brief Exposure to Pictures Depicting Poor Environments Leads to Increased Consumption of Beer in Adult Social Drinkers

Previous studies have suggested a trait-like association between neighborhood deprivation and alcohol consumption. However, it is not known whether temporarily manipulating poverty and affluence states by exposure to stimuli signifying resource-scarcity or resource-wealth would influence alcohol-seeking behavior. Here, we aimed to investigate whether implicit exposure to affluence and poverty-related pictures would influence beer consumption. Participants in a "poverty" group viewed pictures depicting impoverished environments, and participants in an "affluence" group viewed images of wealthy environments. After priming, participants were provided with nonalcoholic beer (which they were told was alcohol-containing beer) and orange juice under the guise of a bogus taste test, to measure their alcohol-seeking behavior. Results showed that priming participants with a resource-scarce environment led to an increase in beer consumption (as a percentage of total fluid consumed), compared to priming with a resource-rich environment. The same pattern of results was obtained in both a Western European sample (Experiment 1) and a West Indian sample (Experiment 2). In Experiment 2, we also tested whether risk-taking behavior, measured by the Balloon Analogue Risk Task, was influenced by the environmental priming; no differences between groups were observed. These results provide the first experimental evidence that manipulation of poverty-affluence state, by brief exposure to pictures of impoverished or wealthy neighborhoods, can influence alcohol-seeking behavior in adult social drinkers.

Sex differences in the effects of acute stress on behavior in the ultimatum game

Acute stress affects human decision making. It has been argued that there are systematic sex differences in behavioral responses to acute stress, with males showing a 'fight or flight' and females showing a 'tend and befriend' response. A 'tend and befriend' response would suggest that women become more cooperative under acute stress, while men do not. We investigated the effects of acute stress on social behavior. We induced stress via the Trier Social Stress Test (TSST) and then immediately after measured how participants reacted to offers made in the ultimatum game by a male proposer. We found that female participants were less likely to reject offers under stress (n = 25) vs. no stress (n = 37), p = 0.009, independent of how fair these offers were, cooperative behavior consistent with the 'tend and befriend' hypothesis. Male participants when stressed (n = 30) did not show differences in rejections rates compared to the control condition (n = 26), p = 0.41. Our results provide support for a qualitatively different behavioral response to acute stress among men and women.

Attitudes toward mental illness among Caribbean medical students

BACKGROUND

There are limited empirical data on all matters pertaining to mental illness in the Caribbean but what little there is suggests significant levels of stigmatization exist. In this context, health professionals reveal at least equal to or only slightly improved attitudes to mental illness as compared to the general population. In addition, while there is evidence of improved attitudes among the population at large over the past decade this trend has not been observed among health professionals. This study, therefore, sought to assess medical students' knowledge about and attitudes toward mental illness as they traversed medical school.

METHODS

Preclinical medical students were surveyed and then retested in their final year of training. Students completed a knowledge scale, and the medical conditions regard scale comparing attitudes to four mental illness and three physical illness.

RESULTS

Knowledge about and attitudes toward mental illness showed significant improvement over the 5-year period. However, both preclinical and clinical students revealed significant levels of stigmatization toward mental illness despite improvements in knowledge. Students recognized the need to prioritize treatment for persons with mental illness but did not want to be personally involved in the treatment process.

DISCUSSION

Results highlight that significant negative attitudes still exist among medical students toward mental illness and these persist up until graduation. There is a need for further research into innovations and interventions to address this matter.

Effects of Jasminum multiflorum leaf extract on rodent models of epilepsy, motor coordination and anxiety

Jasmine flowers and leaves are used extensively in folk medicine in different parts of the world to treat a variety of diseases. However, there are very few published reports on the neuropsychiatric effects of Jasmine extracts. Hence, the objectives of the present study were to examine the effects of an alcohol extract of Jasminum multiflorum leaves on topically-applied bicuculline (a model of acute simple partial epilepsy) and maximal electroshock (MES, a model of generalized tonic-clonic seizure) in male Sprague-Dawley rats. The objectives also included an examination of the anxiolytic properties of the extract using an elevated plus maze and the effect of the extract on motor coordination using a rotarod treadmill. Phytochemical analysis of the extract showed the presence of three flavonoids and four additional compounds belonging to the steroid, terpenoid, phenol or sugar classes of compounds. The Jasmine alcohol extract, diluted with water and given orally or intraperitoneally, reduced the number of bicuculline-induced epileptiform discharges in a dose-dependent manner. The extract did not cause a significant increase in the current needed to induce hind limb extension in MES experiments. The extract significantly affected motor coordination when injected at 500mg/kg but not at 200mg/kg. At the latter dose, the extract increased open-arm entries and duration in the elevated plus maze to a level comparable to that of diazepam at 2mg/kg. We conclude that Jasmine leaf extract has a beneficial effect against an animal model of acute partial complex epilepsy, and significant anxiolytic effect at a dose that does not affect motor co-ordination.

"It's All About How You Carry Yourself About": How Medical Students Conceptualize Professionalism in Trinidad & Tobago

Phenomenon: This paper concerns itself with the value system that informs and motivates medical students of the twenty-first century as distinct from earlier cohorts. It notes a shift from an era of altruism within which the medical professional was a 'pillar of society' always 'on duty' and always concerned foremost for the patient to an era in which he/she is just another member of the work force, subject to public scrutiny and criticism, to patient autonomy and to a self-serving ethos which characterizes the present age. Whilst concerns have been raised for a continuing and separate morality of medicine, young professionals in other studies have cited a range of characteristics including honesty, trustworthiness and respect alongside competence and medical skill. However, the notion of 'performance' has made a strong thrust into the literature, with students citing the putting on and taking off of dual personae as part of their complex identity in this present time. They are entitled to their own lives, to drop the act and just be themselves when off duty, picking it back up again with the duty call.

APPROACH

The present study then investigated the views on this subject of two groups of medical students in Trinidad & Tobago in the Caribbean, one made up entirely of nationals and one including students from other parts of the Caribbean and the USA. They discussed the topic in focus groups of eight; their responses were then analysed thematically and subject to discourse analysis.

FINDINGS

The study revealed diverse attitudes with some embracing the ethical standards of a high calling that whilst others were concerned that too much was expected, that they had a right to break free and be themselves as long as they did not transgress too far from their expected roles. There were two distinct groups both concerned with 'how' they 'carried themselves about' but this meant different things to each dependent on which of the two perspectives they embraced. As a whole, the study revealed an ongoing conflict of value systems with concern for patient welfare just remaining uppermost. Insights: As The University of the West Indies has now stepped into the field of medical professionalism actively it would hope to support students in resolving their conflicts more consciously in response to the range of philosophical stances which currently present themselves.

Medical Student Stress, Burnout and Depression in Trinidad and Tobago

OBJECTIVE

Health-care workers in developed nations are well known to experience high levels of burnout and psychiatric morbidity, but little information is available from the Caribbean and other less well-developed regions. This study sought to explore the prevalence of stress, burnout, and depressive symptoms and associated risk factors among medical students in Trinidad and Tobago, the southernmost Caribbean island.

METHODS

A cross-sectional survey design was used to sample students. Data was collected utilizing standardized questionnaires that assess stress, burnout, and depressive symptoms. Demographic data and information pertaining to potential risk factors was also gathered. Overall, 450 questionnaires were distributed and analysis was performed upon 381 completed surveys (response rate 85%).

RESULTS

Students demonstrated high levels of stress and a significant prevalence of burnout (52%) and depressive symptoms (40%). Final year students demonstrated higher levels of burnout and depressive symptoms. Students who (i) felt they lacked emotional support, (ii) had little opportunity for relaxation and exercise, and (iii) did not feel they had control of their daily schedule all demonstrated higher levels of burnout and depressive symptoms. However, students who practiced from a faith base and considered their religion important demonstrated lower levels of both.

CONCLUSIONS

Medical students in Trinidad and Tobago are experiencing high levels of stress with a large proportion suffering from burnout and depressive symptoms. These data suggest that immediate interventions are necessary to help students cope with the challenges faced during medical school. Additionally, more research is needed to explore the potential causal links between burnout and depression during medical school and the effectiveness of tailored interventions especially within the context of developing nations.

Public trust in the healthcare system in a developing country

Broadly defined, trust in the healthcare system is concerned with how the public perceives the system and the actors therein as it pertains to their ability to both deliver services and seek the best interests of their clientele. Trust is important because it impacts upon a range of health behaviors including compliance and ultimately affects the ability of the healthcare system to meet its goals. While several studies exist on public trust within the developed world, few studies have explored this issue in developing countries. This paper therefore assesses public trust in the healthcare system of a developing small island nation, Trinidad and Tobago. A cross-sectional survey of adults was conducted using a questionnaire that has been successfully used across Europe. We report that trust levels in the healthcare system in Trinidad and Tobago are relatively low with less than 50% of persons indicating fair trust in the healthcare system. In addition, individual health professionals also did not score highly with lowest scores found for nurses and complementary therapists. Results on four out of five dimensions of trust also demonstrated scores significantly lower than those reported in more developed nations. Open-ended comments supported these findings with the majority of persons indicating a lack of confidence in the healthcare system. These results may reflect the reality in the wider developing world, and we suggest that bolstering trust is a needed area of focus in the delivery of healthcare services throughout the nation. Copyright © 2014 John Wiley & Sons, Ltd.

An exploration of changes in cognitive and emotional empathy among medical students in the Caribbean

OBJECTIVE

This study explored the empathy profile of students across five years of medical training. In addition the study examined whether the Jefferson Scale for Physician Empathy correlated with a measure of cognitive empathy, the Reading the Mind in the Eyes Test and a measure of affective empathy, the Toronto Empathy Questionnaire.

METHODS

The study was a comparative cross-sectional design at one Caribbean medical school. Students were contacted in class, participation was voluntary and empathy was assessed using all three instruments Descriptive statistics were calculated and differences between groups evaluated using non-parametric tests.

RESULTS

Overall 669 students participated (response rate, 67%). There was a significant correlation between the Jefferson Scale of Physician Empathy and the Toronto Empathy Questionnaire (ρ = 0.48), both scales indicating a decline in medical student empathy scores over time. There was, however, little correlation between scores from the Reading the Mind in the Eyes Test and the Jefferson Scale of Physician Empathy. Female students demonstrated significantly higher scores on all three measures.

CONCLUSIONS

Medical students' lower empathy scores during their final years of training appear to be due to a change in the affective component of empathy. These findings may reflect an adaptive neurobiological response to the stressors associated with encountering new clinical situations. Attention should be paid not only to providing empathy training for students but also to teaching strategies for improved cognitive processing capacity when they are encountering new and challenging circumstances.

Ketone bodies attenuate excitotoxic cell injury in the rat hippocampal slice under conditions of reduced glucose availability

Calorie restriction and the ketogenic diet have been successfully used in models of neuroprotection. However, there are limitations in clinical application of these diets and attention has turned to understanding their mechanism of action. Ketone bodies are produced in both diets and maybe involved in their ability to attenuate neuronal injury. This study seeks to assess the effects of ketone bodies on neuronal transmission and their efficacy in reducing the impact of known excitotoxins. We made use of extracellular recordings from rat hippocampal slices and demonstrate that ketone bodies had no effect on neuronal transmission or induction of long-term potentiation (LTP). Perfusion of slices with N-methyl-d-aspartate (NMDA, 15 μM) produced neuronal depression suggestive of cell injury (antidromic recording also demonstrated similar depression), such that recovery of population spike potentials after 60 minutes was 27% in normal (10 mM) glucose but only 7% during reduced (2·5 mM) glucose availability. Experiments in ketone bodies demonstrated improved recovery (31%) but only under conditions of low glucose. Similarly, there was enhanced recovery of slices treated with kainic acid (KA, 30 μM) in reduced glucose media (13-27%), but no difference in normal glucose. These findings suggest that ketone bodies do not alter neuronal function but can alter the response to excitotoxins when energy supplies are impaired, probably by acting as an alternative energy substrate.

Knowledge and attitudes towards mental illness among college students: insights into the wider English-speaking Caribbean population

BACKGROUND

Mental illness is a significant contributor to global disease burden and this is expected to increase over the coming decades. Traditionally mental illness has not been well understood by the general public, resulting in poor attitudes towards persons with mental illness and stigmatization. Such conditions are common in the Caribbean where less than 5% of the health budget is allocated to mental illness.

AIMS

To assess knowledge and attitudes towards mental illness among college students within the English-speaking Caribbean.

METHODS

A self-report questionnaire was adapted from previous studies designed to measure knowledge and attitudes of mental illness. Students were sampled from the University of the West Indies campuses in Jamaica, Barbados and Trinidad & Tobago.

RESULTS

Responses were collected from 673 persons with a response rate of 84%. While participants were agreed that particular diseases were mental illnesses, overall knowledge scores were low. Knowledge was higher among those persons who knew someone with a mental illness. Attitude scores were suggestive of stigmatization, with drug abuse and schizophrenia seen in a particularly poor light.

CONCLUSIONS

These results suggest that widespread educational campaigns need to be implemented across the region, designed to both increase knowledge about mental illness and reduce discrimination towards persons suffering with mental illness.

Substance use among university students at the St Augustine campus of the University of the West Indies

OBJECTIVE

Substance use and abuse is a well known public health risk that peaks in persons between 18 and 25 years of age and is prevalent among university students. While this has been repeatedly documented in developed nations, there have been limited studies in the English-speaking Caribbean. This study therefore sought to assess the prevalence of alcohol, tobacco and marijuana use among university students in the English-speaking Caribbean and any associated risk factors.

METHODS

The study was designed as a descriptive, cross-sectional study to assess substance use in full-time, undergraduate students of The University of the West Indies (UWI), Trinidad and Tobago, over a six-month period. Questionnaires were distributed and students asked to self-report on their use of alcohol, tobacco and marijuana during the preceding six months.

RESULTS

The six-month prevalence rate for alcohol was 70% and 28% of students were identified as regular users. Binge drinking was estimated at 31%. Muslims were least likely to have used alcohol when compared to other religious groupings. The prevalence rate for tobacco and marijuana was 17% and 13%, respectively Ten per cent used all three substances. The use of all three substances was associated with multiple problems.

CONCLUSION

We conclude that substance use is common among many students of the UWI but generally lower than reports from other regions of the world. Despite this, substance use is associated with a number of problems and immediate educational interventions may be necessary to assist students in making informed and responsible choices.

Effect of acute changes in glucose concentration on neuronal activity and plasticity in the rat hippocampus

OBJECTIVES

Diabetes mellitus is a major public health concern in many regions of the world, including the Caribbean. Diabetes is associated with multi-system pathology and central nervous system complications have been receiving increasing attention (dementia, cognitive decline and memory loss). While such pathology has been shown to be associated with long term derangement in glucose metabolism, less is known about the effects of acute changes in glucose concentration on neuronal function. This study assesses the effects of acute changes in glucose concentration upon neuronal transmission and neuronal plasticity.

METHODS

We made use of extracellular recordings from hippocampal slices of young adult rats and exposed them to changes in glucose concentration for 60 minutes before assessing synaptic plasticity. Experiments were carried out at both 30 degrees C and 35 degrees C.

RESULTS

At 30 degrees C, glucose concentrations of 30 mM and 4 mM had little effect upon population spike potentials (PSP). However reducing glucose concentration to 2 mM, 1 mM and 0 mM respectively resulted in a progressive decrease in the size of PSP until they were completely abolished. Similar results were observed at 35 degrees C except that 30 mM caused a significant increase in PSP size. Changes in glucose concentration had no effect upon synaptic plasticity at either 30 degrees C or 35 degrees C except below 2 mM glucose.

CONCLUSION

Acute changes in glucose concentration have a limited impact on neuronal transmission unless concentrations drop below 2 mM. However there seems to be little impairment of synaptic plasticity even at very low concentrations of glucose. We suggest that short term acute changes in glucose concentrations may not contribute directly to the cognitive decline associated with diabetes unless extremely severe.

Neurophobia and its implications: evidence from a Caribbean medical school

BACKGROUND

Neurology is regarded as a difficult component of the medical curriculum. This has been so marked that the term neurophobia and its effects are being investigated. Given the impact of neurological disorders worldwide, neurophobia has the potential to affect the diagnosis and management of such cases.

METHODS

A cross-sectional survey was done among clinical fourth and fifth year students at the Faculty of Medical Sciences, University of the West Indies, St. Augustine, Trinidad & Tobago. A survey tool successfully used in other schools was adapted to assess perceived level of difficulty, knowledge and interest in various medical sub-specialties including, neurology, cardiology, psychiatry, geriatrics, endocrinology, respiratory medicine, gastroenterology and pediatrics. Questions asked included: "What is your current level of interest in the following medical specialties?"; "What is your current level of knowledge in the given medical specialties?"; "Do you think the subject is easy or difficult?" and "Why do you think neurology is difficult?" Students were required to answer using a Likert scale and results were tabulated into mean scores and standard errors.

RESULTS

The response rate was 65% (167/255). Neurology was identified as the subject which students found most difficult (score 3.89 +/- 0.068) and had least knowledge of (2.32 +/- 0.075). These scores were significantly different from those observed for the other disciplines (p < 0.001). The need to know basic neuroscience was identified as the biggest contributor to the difficulty associated with neurology (3.89 +/- 0.072) followed closely by the complex clinical examination associated with neurology (3.69 +/- 0.072). Greater clinical and practical exposure, more time being spent on the subject, and improved teaching skills of lecturers were put forward as suggestions for improving the teaching of neurology.

CONCLUSION

This study provides empirical evidence that 'neurophobia' may indeed exist among the student population of the school. It suggests the need to re-visit the approach to neuroscience and neurology education and is consistent with similar trends worldwide.

Knowledge of, attitudes toward, and perceptions of epilepsy among college students in Trinidad and Tobago

Epilepsy is poorly understood by the public and has been associated with numerous myths. This, coupled with its sometimes dramatic clinical manifestations, has often resulted in stigmatization of persons with epilepsy. A questionnaire to measure knowledge of, attitudes toward, and perceptions of epilepsy (KAPE) was adapted from previous studies and administered to students of the University of the West Indies, St. Augustine, Trinidad and Tobago. The response rate was 91% (355 students). Knowledge was limited, especially with respect to epilepsy's cause, its incidence, and management of an acute emergency. Attitudes toward epilepsy were generally positive. Students who knew someone with epilepsy scored significantly higher on knowledge and attitude questions. A stigma score was calculated to assess perceived stigmatization. There were no differences between the genders, but persons from rural areas and persons of mixed ethnicity perceived less stigmatization. Hindus perceived greater stigmatization than people of other religions. Overall, students still feel persons with epilepsy are discriminated against and experience stigmatization.

Adult-onset calorie restriction attenuates kainic acid excitotoxicity in the rat hippocampal slice

Lifelong calorie restriction is the only known intervention that has been shown to consistently increase life span and reduce the effects of aging on the brain. Given the difficulties of replicating lifelong calorie restriction within human populations, we have sought to assess the effects of short-term adult-onset calorie restriction upon acute excitotoxic insults in the rat hippocampus. Adult animals (approximately 6 months of age) underwent calorie restriction (alternate day feeding) for 7-10 weeks. Utilizing both electrophysiological and immunocytochemical techniques, we report that calorie restriction had no effect upon long-term potentiation (LTP), a measure of neuronal function. In control animals, application of kainic acid (20 microM) resulted in only 35% recovery of CA1 population spikes post-insult. However calorie-restricted animals showed significantly improved recovery after kainic acid treatment (64%). This data was supported by immunocytochemical studies which noted widespread loss of microtubule-associated protein (MAP 2) immunoreactivity in control slices following treatment with kainic acid; however MAP 2 staining was preserved in the CA1 and CA3 regions of calorie-restricted animals. Interestingly there was no significant difference in the recovery of population spikes between groups when slices were treated with N-methyl-d-aspartate (15 microM). We conclude that short-term adult-onset calorie restriction does not alter normal neuronal function and serves to protect the hippocampus from acute kainic acid excitotoxicity.

AMPA receptor activation reduces epileptiform activity in the rat neocortex

We have previously reported that topical application of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) to the rat neocortex prevents the effects of a subsequent application of N-methyl-d-aspartic acid (NMDA). Activation of NMDA receptors is involved in the pathogenesis of epileptic activity. Therefore, we examined if topically applied AMPA could affect changes in the somatosensory evoked potentials (SEPs) and electrocorticogram (ECoG) epileptic spikes caused by bicuculline. AMPA (50 microM) prevented the epileptiform activity to a level that was comparable to that caused by diazepam (3 mg/kg i.p.) or clomethiazole (100 mg/kg i.p.). Also, the epileptiform activity was suppressed by the AMPAR antagonist, CNQX, or the blocker of AMPAR desensitization, cyclothiazide. In the hippocampal slice, bicuculline-induced changes in the population spike potentials recorded from the CA1 cells were not affected by AMPA. We conclude that in the complex neuronal network of the rat neocortex, epileptiform activity can be suppressed in a variety of strategies that target the AMPA receptors: (1) blocking AMPA receptors, (2) promoting an apparent desensitization of AMPA receptors (possibly on the pyramidal neurons) or (3) reducing an apparent desensitization of AMPA receptors (possibly on the inhibitory GABA-ergic interneurons).

Cannabinoid modulation of neuronal function after oxygen/glucose deprivation in area CA1 of the rat hippocampus

Endocannabinoids released during cerebral ischemia have been implicated as neuroprotective agents. We assessed the role of cannabinoid receptors in modulating the response of neurons to oxygen/glucose deprivation (OGD), a model for in vitro ischemia, in rat hippocampal slices using extracellular recording techniques. Under control conditions, 15 min OGD resulted in only 50% recovery of CA1 field excitatory postsynaptic potentials (fEPSPs) 60 min post-insult. This post-OGD depression of function was primarily NMDA receptor-dependent as the NMDA receptor antagonist MK-801 (50 microM) promoted recovery of synaptic transmission to 76% of the baseline. Treatment with the CB1 receptor antagonist AM251 (1 microM), which prevented the depression of excitatory synaptic transmission caused by WIN55,212-2 (1 microM), also markedly enhanced recovery of function (71% of control). The enhanced recovery after OGD in the presence of AM251 was independent of both GABA(A) receptors and NMDA receptors since co-application of AM251 with either bicuculline (10 microM) or MK-801 (50 microM) did not alter recovery, or further improved recovery, respectively. These results suggest endocannabinoids released during OGD may modulate synaptic transmission and post-OGD neuronal outcome via activation of an AM251-sensitive cannabinoid receptor.

NMDA-induced preconditioning attenuates synaptic plasticity in the rat hippocampus

It was recently demonstrated that glutamate could precondition hippocampal slices against the damaging effects of hypoxia, and we have now extended this observation by investigating (i) the ability of glutamate receptor agonists to act as preconditioning agents and (ii) the effects of preconditioning on synaptic plasticity. Using rat hippocampal slices, 15 microM NMDA applied for 10 min (chemical insult) caused abolition of the population spike potentials (PS) followed by approximately 33% recovery at 60 min post-insult. In comparison, a 5 min preconditioning exposure of 10 microM NMDA given 30 min prior to the insult significantly improved the recovery to 69%. Preconditioning did not alter paired pulse facilitation; however, it significantly enhanced paired pulse depression and reduced population spike long-term potentiation (PS-LTP) and LTP in field recordings. This effect on PS-LTP appeared to be NMDA receptor dependent and was blocked by the nitric oxide synthase inhibitors nitro-L-arginine methyl ester (L-NAME) and 7-nitro indazole (7-NI) but not by the adenosine receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). We conclude that preconditioning by NMDA can improve recovery following acute insults but may have deleterious effects on neuronal plasticity.

LTP-induced depression of response to hypoxia in hippocampus: effects of adenosine receptor activation

Previous work has shown that long-term potentiation (LTP) can reduce the effects of hypoxia in depressing population spikes in rat hippocampal slices. We have now investigated the role of adenosine in this phenomenon. There is no mutual inhibition between the depressant effects of hypoxia and adenosine, but LTP reduces responses to both hypoxia and adenosine, as does application of an A1 receptor antagonist. The effect of LTP is not due to a change in the balance of activation of A1 and A2A adenosine receptors since a selective A2A receptor antagonist did not prevent the interaction. We suggest that LTP may reduce the response to hypoxia by attenuating neuronal sensitivity to adenosine A1 receptors.

Neuroprotective role of learning in dementia: a biological explanation

Several epidemiological studies have found an association between low educational level (or low cognitively demanding occupations) and dementia. Although other studies have not found evidence to support such an association, there has been a general trend toward a "use it or lose it" concept which attempts to promote a neuroprotective role of intellectual activity against the development of dementia. Formation of amyloid-beta peptide (Abeta) in the brain plays a key role in the development of Alzheimer's disease whilst glutamate has been implicated in the pathophysiology of a number of neurological disorders including Alzheimer's disease and vascular dementia. Abeta can mediate neurodegeneration by a complex interaction of neurodegenerative processes that involve increasing extracellular concentration of glutamate, increasing intracellular Ca2+ concentration, and apoptosis. Long-term potentiation (LTP, a biological correlate of learning and memory) increases the sensitivity of hippocampal neurons to synaptically released glutamate whilst decreasing responses of neurons to bath applied glutamate receptor agonists and to hypoxia/ischemia in vitro. The effects of LTP are likely to involve changes in intracellular Ca2+ concentration. Based on these findings we are proposing that the LTP-induced neuroprotection in vitro may help explain the epidemiological evidence of a possible neuroprotective role of high intellectual activity against dementia.

Learning may provide neuroprotection against dementia

A number of studies attempting to identify specific risk factors for dementia have noted an inverse relationship between educational background and the likelihood of developing dementia. This idea has been somewhat controversial as educational background can introduce a number of confounding factors that generally affect health and lifestyle. Despite these reservations, there is mounting evidence to support the concept of education (or increased mental activity) producing a functional reserve in the brain, a process that provides some protection against the clinical manifestation of dementia. Long-term potentiation (LTP) is a recognized neural correlate of learning and memory. We have shown recently that LTP reduces the sensitivity of hippocampal neurons to agonists of the neurotransmitter glutamate; additionally, we have reported that LTP protects the neurons from the effects of acute hypoxia. Given that the effect of hypoxia on neurons involves over-stimulation by glutamate, and hypoxia has been implicated in the aetio-pathology of some types of dementia, our observations suggest that LTP has a protective effect on neuronal tissue. Such an interaction offers a physiological basis for the epidemiological evidence that lifelong learning can protect a person from some types of dementia.

Long-term potentiation protects rat hippocampal slices from the effects of acute hypoxia

We have previously shown that long-term potentiation (LTP) decreases the sensitivity of glutamate receptors in the rat hippocampal CA1 region to exogenously applied glutamate agonists. Since the pathophysiology of hypoxia/ischemia involves increased concentration of endogenous glutamate, we tested the hypothesis that LTP could reduce the effects of hypoxia in the hippocampal slice. The effects of LTP on hypoxia were measured by the changes in population spike potentials (PS) or field excitatory post-synaptic potentials (fepsps). Hypoxia was induced by perfusing the slice with (i) artificial CSF which had been pre-gassed with 95%N2/5% CO2; (ii) artificial CSF which had not been pre-gassed with 95% O2/5% CO2; or (iii) an oxygen-glucose deprived (OGD) medium which was similar to (ii) and in which the glucose had been replaced with sucrose. Exposure of a slice to a hypoxic medium for 1.5-3.0 min led to a decrease in the PS or fepsps; the potentials recovered to control levels within 3-5 min. Repeat exposure, 45 min later, of the same slice to the same hypoxic medium for the same duration as the first exposure caused a reduction in the potentials again; there were no significant differences between the degree of reduction caused by the first or second exposure for all three types of hypoxic media (P>0.05; paired t-test). In some of the slices, two episodes of LTP were induced 25 and 35 min after the first hypoxic exposure; this caused inhibition of reduction in potentials caused by the second hypoxic insult which was given at 45 min after the first; the differences in reduction in potentials were highly significant for all the hypoxic media used (P<0.01; paired t-test). The neuroprotective effects of LTP were not prevented by cyclothiazide or inhibitors of NO synthetase compounds that have been shown to be effective in blocking the effects of LTP on the actions of exogenously applied AMPA and NMDA, respectively. The neuroprotective effects of LTP were similar to those of propentofylline, a known neuroprotective compound. We conclude that LTP causes an appreciable protection of hippocampal slices to various models of acute hypoxia. This phenomenon does not appear to involve desensitisation of AMPA receptors or mediation by NO, but may account for the recognised inverse relationship between educational attainment and the development of dementia.