Inactivation of hippocampus or caudate nucleus with lidocaine differentially affects expression of place and response learning

Involvement of the hippocampus and caudate nucleus in place and response learning was examined by functionally inactivating these brain regions bilaterally with infusions of lidocaine. Rats were trained to approach a consistently baited arm in a cross-maze from the same start box (four trials/day/14 total days). On Days 8 and 16 a single probe trial was given, in which rats were placed in the start box opposite that used in training and allowed to approach a maze arm. Three minutes prior to the probe trial, rats received bilateral injections of either saline or a 2% lidocaine solution (in order to produce neural inactivation) into either the dorsal hippocampus or dorsolateral caudate nucleus. On the probe trials, rats which entered the baited maze arm (i.e., approached the place where food was located during training) were designated place learners, and rats which entered the unbaited maze arm (i.e., made the same turning response as during training) were designated response learners. Saline-treated rats displayed place learning on the Day 8 probe trial and response learning on the Day 16 probe trial, indicating that with extended training there is a shift in learning mechanisms controlling behavior. Rats given lidocaine injections into the hippocampus showed no preference for place or response learning on the Day 8 probe trial, but displayed response learning on the Day 16 probe trial, indicating a blockade of place learning following inactivation of the hippocampus. Rats given lidocaine injections into the caudate nucleus displayed place learning on both the Day 8 and the Day 16 probe trials, indicating a blockade of response learning following inactivation of the caudate nucleus. The findings indicate: (1) the hippocampus and caudate nucleus selectively mediate expression of place and response learning, respectively (2), in a visually cued extramaze environment, hippocampal-dependent place learning is acquired faster than caudate-dependent response learning, and (3) when animals shift to caudate-dependent response learning with extended training, the hippocampal-based place representation remains intact.

Hippocampal BDNF mediates the efficacy of exercise on synaptic plasticity and cognition

We found that a short exercise period enhanced cognitive function on the Morris water maze (MWM), such that exercised animals were significantly better than sedentary controls at learning and recalling the location of the platform. The finding that exercise increased brain-derived neurotrophic factor (BDNF), a molecule important for synaptic plasticity and learning and memory, impelled us to examine whether a BDNF-mediated mechanism subserves the capacity of exercise to improve hippocampal-dependent learning. A specific immunoadhesin chimera (TrkB-IgG), that mimics the BDNF receptor, TrkB, to selectively bind BDNF molecules, was used to block BDNF in the hippocampus during a 1-week voluntary exercise period. After this, a 2-trial-per-day MWM was performed for 5 consecutive days, succeeded by a probe trial 2 days later. By inhibiting BDNF action we blocked the benefit of exercise on cognitive function, such that the learning and recall abilities of exercising animals receiving the BDNF blocker were reduced to sedentary control levels. Inhibiting BDNF action also blocked the effect of exercise on downstream systems regulated by BDNF and important for synaptic plasticity, cAMP response-element-binding protein (CREB) and synapsin I. Specific to exercise, we found an association between CREB and BDNF expression and cognitive function, such that animals who were the fastest learners and had the best recall showed the highest expression of BDNF and associated CREB mRNA levels. These findings suggest a functional role for CREB under the control of BDNF in mediating the exercise-induced enhancement in learning and memory. Our results indicate that synapsin I might also contribute to this BDNF-mediated mechanism.

Spatial learning with a minislab in the dorsal hippocampus

We have determined the volume and location of hippocampal tissue required for normal acquisition of a spatial memory task. Ibotenic acid was used to make bilateral symmetric lesions of 20-100% of hippocampal volume. Even a small transverse block (minislab) of the hippocampus (down to 26% of the total) could support spatial learning in a water maze, provided it was at the septal (dorsal) pole of the hippocampus. Lesions of the septal pole, leaving 60% of the hippocampi intact, caused a learning deficit, although normal electrophysiological responses, synaptic plasticity, and preserved acetylcholinesterase staining argue for adequate function of the remaining tissue. Thus, with an otherwise normal brain, hippocampal-dependent spatial learning only requires a minislab of dorsal hippocampal tissue.

The time of prenatal immune challenge determines the specificity of inflammation-mediated brain and behavioral pathology

Disturbance to early brain development is implicated in several neuropsychiatric disorders including autism, schizophrenia, and mental retardation. Epidemiological studies have indicated that the risk of developing these disorders is enhanced by prenatal maternal infection, presumably as a result of neurodevelopmental defects triggered by cytokine-related inflammatory events. Here, we demonstrate that the effects of maternal immune challenge between middle and late gestation periods in mice are dissociable in terms of fetal brain cytokine responses to maternal inflammation and the pathological consequences in brain and behavior. Specifically, the relative expression of pro- and anti-inflammatory cytokines in the fetal brains in response to maternal immune challenge may be an important determinant among other developmental factors for the precise pathological profile emerging in later life. Thus, the middle and late gestation periods correspond to two windows with differing vulnerability to adult behavioral dysfunction, brain neuropathology in early adolescence, and of the acute cytokine responses in the fetal brain.

The olfactory bulbectomised rat as a model of depression

Bilateral olfactory bulbectomy results in changes in behavior, and in the endocrine, immune and neurotransmitter systems, that simulates many of those seen in patients with major depression. The olfactory system in the rat forms a part of the limbic region in which the amygdala and hippocampus contribute to the emotional and memory components of behavior. However, the loss of olfaction alone, which results from bulbectomy, is not the major factor that contributes to the behavioral abnormalities as peripherally induced anosmia does not cause the same behavioral changes. Thus it would appear that bulbectomy causes a major dysfunction of the cortical-hippocampal-amygdala circuit that underlies the behavioral and other changes. These neuroanatomical areas also seem to be dysfunctional in the patient with major depression. Chronic, but not acute, administration of antidepressants largely corrects most the behavioral, endocrine, immune and neurotransmitter changes that occur following bulbectomy. Thus the olfactory bulbectomized rat is not only a model for detecting antidepressant activity but also one for exploring the inter-relationships between these systems that are also dysfunctional in patients with major depression.

Anxiolytic effects of nicotine in zebrafish

Anxiolytic effects of nicotine have been documented in studies with rodents and humans. Understanding the neural basis of nicotine-induced anxiolysis can help both with developing better aids for smoking cessation as well as with the potential development of novel nicotinic ligands for treating anxiety. Complementary non-mammalian models may be useful for determining the molecular bases of nicotine effects on neurobehavioral function. The current project examined whether a zebrafish model of anxiety would be sensitive to nicotine. When zebrafish are placed in a novel environment, they dive to the bottom of the tank. In the wild, diving could help to escape predation. We tested the anxiolytic effect of nicotine on the novelty-elicited diving response and subsequent habituation. Zebrafish placed in a novel tank spent the majority of time at the bottom third of the tank during the first minute of a 5-min session and then show a gradual decrease in time spent at the tank bottom. Nicotine treatment at 100 mg/l for 3 min by immersion before testing caused a significant decrease in diving throughout the session, while 50 mg/l was effective during the first minute when the greatest bottom dwelling was seen in controls. Nicotine effects were reversed by the nicotinic antagonist mecamylamine given together with nicotine, but not when administered shortly before the test session after prior nicotine dosing. This implies that the effect of nicotine on diving was due to net stimulation at nicotinic receptors, an effect that is blocked by mecamylamine; and that once invoked, this effect is no longer dependent on continuing activation of nicotinic receptors. The effect of nicotine on diving did not seem to be the result of a general disorientation of the fish. The 100 mg/ml nicotine dose was shown in our earlier study to significantly improve spatial-discrimination learning in zebrafish. Nicotine-induced anxiolytic effects can be modeled in the zebrafish. This preparation will help in the investigation of the molecular bases of this effect.

A behavioural analysis of spatial localization following electrolytic, kainate- or colchicine-induced damage to the hippocampal formation in the rat

This experiment examines the notion that in the rat the hippocampal formation is an essential structure in the neurological representation of spatial abilities. Spatial localization by rats with different types of hippocampal damage, including bilateral electrolytic lesions, unilateral and bilateral kainic acid-induced CA3-CA4 lesions, and unilateral and bilateral colchicine-induced dentate gyrus lesions, was compared with vehicle-injected and normal control groups in the Morris water task. The task required the rats to escape from cold water by finding a submerged and hidden platform located at a fixed place within the room. The start point was varied randomly from trial to trial and there were no local cues available to indicate the position of the hidden platform. After training, the platform was moved. Escape latencies and the initial swimming headings revealed that all lesion groups, except the unilateral CA3-damaged group, were impaired at finding the platform: the dentate-damaged rats exhibited the greatest deficit. When the platform was moved the control rats swam mainly in the part of the pool that had previously contained the platform and, on finding it in the new location, they showed a marked dishabituation of rearing. None of the bilateral lesion groups showed these effects.

Dopamine-dependent facilitation of LTP induction in hippocampal CA1 by exposure to spatial novelty

In addition to its role in memory formation, the hippocampus may act as a novelty detector. Here we investigated whether attention to novel events can promote the associative synaptic plasticity mechanisms believed to be necessary for storing those events in memory. We therefore examined whether exposure to a novel spatial environment promoted the induction of activity-dependent persistent increases in glutamatergic transmission (long-term potentiation, LTP) at CA1 synapses in the rat hippocampus. We found that brief exposure to a novel environment lowered the threshold for the induction of LTP. This facilitatory effect was present for a short period following novelty exposure but was absent in animals that explored a familiar environment. Furthermore, the facilitation was dependent on activation of D1/D5 receptors. These findings support an important role for dopamine-regulated synaptic plasticity in the storage of unpredicted information in the CA1 area.

Lactate produced by glycogenolysis in astrocytes regulates memory processing

When administered either systemically or centrally, glucose is a potent enhancer of memory processes. Measures of glucose levels in extracellular fluid in the rat hippocampus during memory tests reveal that these levels are dynamic, decreasing in response to memory tasks and loads; exogenous glucose blocks these decreases and enhances memory. The present experiments test the hypothesis that glucose enhancement of memory is mediated by glycogen storage and then metabolism to lactate in astrocytes, which provide lactate to neurons as an energy substrate. Sensitive bioprobes were used to measure brain glucose and lactate levels in 1-sec samples. Extracellular glucose decreased and lactate increased while rats performed a spatial working memory task. Intrahippocampal infusions of lactate enhanced memory in this task. In addition, pharmacological inhibition of astrocytic glycogenolysis impaired memory and this impairment was reversed by administration of lactate or glucose, both of which can provide lactate to neurons in the absence of glycogenolysis. Pharmacological block of the monocarboxylate transporter responsible for lactate uptake into neurons also impaired memory and this impairment was not reversed by either glucose or lactate. These findings support the view that astrocytes regulate memory formation by controlling the provision of lactate to support neuronal functions.

The influence of substance use on adolescent brain development

Adolescence is a unique period in neurodevelopment. Alcohol and marijuana use are common. Recent research has indicated that adolescent substance users show abnormalities on measures of brain functioning, which is linked to changes in neurocognition over time. Abnormalities have been seen in brain structure volume, white matter quality, and activation to cognitive tasks, even in youth with as little as 1-2 years of heavy drinking and consumption levels of 20 drinks per month, especially if > 4-5 drinks are consumed on a single occasion. Heavy marijuana users show some subtle anomalies too, but generally not the same degree of divergence from demographically similar non-using adolescents. This article reviews the extant literature on neurocognition, brain structure, and brain function in adolescent substance users with an emphasis on the most commonly used substances, and in the context of ongoing neuromaturational processes. Methodological and treatment implications are provided.

Long-term treatment with estrogen and progesterone enhances acquisition of a spatial memory task by ovariectomized aged rats

Female Sprague-Dawley rats were ovariectomized at 13 months of age. Four groups received different regimens of estrogen or estrogen plus progesterone replacement beginning either immediately, 3 months, or 10 months after ovariectomy and were compared with non-hormone-treated controls. Eight to twelve months after ovariectomy, animals were trained on a delayed matching-to-position (DMP) spatial memory task. Long-term treatment with estrogen or estrogen plus progesterone significantly enhanced acquisition of the DMP task by aged animals after long-term loss of ovarian function. Weekly administration of estrogen and progesterone was at least as effective as, if not more effective than, continuous treatment with estrogen alone. In addition, treatment initiated 3 months, but not 10 months, after ovariectomy was as effective at enhancing DMP acquisition as continuous estrogen treatment initiated immediately after ovariectomy, suggesting a window of opportunity after the loss of ovarian function during which hormone replacement can effectively prevent the effects of aging and hormone deprivation on cognitive function. These findings suggest that repeated treatment with estrogen and progesterone initiated within a specific period of time after the loss of ovarian function may be effective at preventing specific negative effects of hormone deprivation on brain aging and cognitive decline.

M1 Receptors Play a Central Role in Modulating AD-like Pathology in Transgenic Mice

We investigated the therapeutic efficacy of the selective M1 muscarinic agonist AF267B in the 3xTg-AD model of Alzheimer disease. AF267B administration rescued the cognitive deficits in a spatial task but not contextual fear conditioning. The effect of AF267B on cognition predicted the neuropathological outcome, as both the Abeta and tau pathologies were reduced in the hippocampus and cortex, but not in the amygdala. The mechanism underlying the effect on the Abeta pathology was caused by the selective activation of ADAM17, thereby shifting APP processing toward the nonamyloidogenic pathway, whereas the reduction in tau pathology is mediated by decreased GSK3beta activity. We further demonstrate that administration of dicyclomine, an M1 antagonist, exacerbates the Abeta and tau pathologies. In conclusion, AF267B represents a peripherally administered low molecular weight compound to attenuate the major hallmarks of AD and to reverse deficits in cognition. Therefore, selective M1 agonists may be efficacious for the treatment of AD.

Targeting BACE1 with siRNAs ameliorates Alzheimer disease neuropathology in a transgenic model

In Alzheimer disease, increased beta-secretase (BACE1) activity has been associated with neurodegeneration and accumulation of amyloid precursor protein (APP) products. Thus, inactivation of BACE1 could be important in the treatment of Alzheimer disease. In this study, we found that lowering BACE1 levels using lentiviral vectors expressing siRNAs targeting BACE1 reduced amyloid production and the neurodegenerative and behavioral deficits in APP transgenic mice, a model of Alzheimer disease. Our results suggest that lentiviral vector delivery of BACE1 siRNA can specifically reduce the cleavage of APP and neurodegeneration in vivo and indicate that this approach could have potential therapeutic value for treatment of Alzheimer disease.

Air pollution impairs cognition, provokes depressive-like behaviors and alters hippocampal cytokine expression and morphology

Particulate matter air pollution is a pervasive global risk factor implicated in the genesis of pulmonary and cardiovascular disease. Although the effects of prolonged exposure to air pollution are well characterized with respect to pulmonary and cardiovascular function, comparatively little is known about the impact of particulate matter on affective and cognitive processes. The central nervous system may be adversely affected by activation of reactive oxygen species and pro-inflammatory pathways that accompany particulate matter pollution. Thus, we investigated whether long-term exposure to ambient fine airborne particulate matter (<2.5 μm (PM(2.5))) affects cognition, affective responses, hippocampal inflammatory cytokines and neuronal morphology. Male mice were exposed to either PM(2.5) or filtered air (FA) for 10 months. PM(2.5) mice displayed more depressive-like responses and impairments in spatial learning and memory as compared with mice exposed to FA. Hippocampal pro-inflammatory cytokine expression was elevated among PM(2.5) mice. Apical dendritic spine density and dendritic branching were decreased in the hippocampal CA1 and CA3 regions, respectively, of PM(2.5) mice. Taken together, these data suggest that long-term exposure to particulate air pollution levels typical of exposure in major cities around the globe can alter affective responses and impair cognition.

Decreases in rat extracellular hippocampal glucose concentration associated with cognitive demand during a spatial task

Using in vivo microdialysis, we measured hippocampal extracellular glucose concentrations in rats while they performed spontaneous alternation tests of spatial working memory in one of two mazes. Extracellular glucose levels in the hippocampus decreased by 32% below baseline during the test period on the more complex maze, but by a maximum of 11% on the less complex maze. Comparable decreases were not observed in samples taken from rats tested on the more complex maze but with probes located near but outside of the hippocampus. Systemic glucose fully blocked any decrease in extracellular glucose and enhanced alternation on the more complex maze. These findings suggest that cognitive activity can deplete extracellular glucose in the hippocampus and that exogenous glucose administration reverses the depletion while enhancing task performance.

The role of the dorsal hippocampus in the acquisition and retrieval of context memory representations

It is argued that the hippocampus contributes to contextual fear conditioning by supporting the acquisition of a conjunctive memory representation of context, which associates with shock. This function was examined by studying the context pre-exposure facilitation effect (CPFE). A rat that is shocked immediately after being placed into a context subsequently displays almost no fear of that context. However, if it is pre-exposed to the context the day before immediate shock, it displays significant freezing to that context. By using 5-aminomethyl-3-hydroxysoxazole to temporarily inactivate the dorsal hippocampus (DH) at three different phases of the procedure, which produces the CPFE, we show that the hippocampus is necessary for the following: (1) acquisition of the context memory, (2) retrieval of this memory at the time of immediate shock, and (3) retrieval of the context-shock memory at the time of testing. In contrast, inactivating the DH before a standard contextual shock experience had no effect on contextual fear conditioning. These results support the view that two processes can support contextual fear conditioning: (1) conditioning to the conjunctive representation, which depends on the hippocampus, and (2) conditioning to the features that make up the context, which does not.

Knockdown of DISC1 by in utero gene transfer disturbs postnatal dopaminergic maturation in the frontal cortex and leads to adult behavioral deficits

Adult brain function and behavior are influenced by neuronal network formation during development. Genetic susceptibility factors for adult psychiatric illnesses, such as Neuregulin-1 and Disrupted-in-Schizophrenia-1 (DISC1), influence adult high brain functions, including cognition and information processing. These factors have roles during neurodevelopment and are likely to cooperate, forming pathways or "signalosomes." Here we report the potential to generate an animal model via in utero gene transfer in order to address an important question of how nonlethal deficits in early development may affect postnatal brain maturation and high brain functions in adulthood, which are impaired in various psychiatric illnesses such as schizophrenia. We show that transient knockdown of DISC1 in the pre- and perinatal stages, specifically in a lineage of pyramidal neurons mainly in the prefrontal cortex, leads to selective abnormalities in postnatal mesocortical dopaminergic maturation and behavioral abnormalities associated with disturbed cortical neurocircuitry after puberty.

Systemic or intrahippocampal cannabinoid administration impairs spatial memory in rats

The purpose of the present study was to investigate the disruptive effects of cannabinoids on working memory as assessed in the eight-arm radial-maze. Systemic administration of delta 9-THC, WIN-55,212-2, and CP-55,940 increased the number of errors committed in the radial-maze. CP-55,940 was the most potent cannabinoid in impairing memory (ED50 = 0.13 mg/kg). delta 9-THC and WIN-55,212-2 disrupted maze-choice accuracy at equipotent doses (ED50 values = 2.1 and 2.2 mg/kg, respectively). In addition, systemic administration of each of these agents retarded completion time. Whereas the doses of delta 9-THC and CP-55,940 required to retard maze performance were higher than those needed to increase error numbers, WIN-55,212-2 was equipotent in both of these measures. On the other hand, neither anandamide, the putative endogenous cannabinoid ligand, nor cannabidiol, an inactive naturally occurring cannabinoid, had any apparent effects on memory. A second aim of this study was to elucidate the neuroanatomical substrates mediating the disruptive effects of cannabinoids on memory. Intrahippocampal injections of CP-55,940 impaired maze performance in a dose-dependent manner (ED50 = 8 micrograms/rat), but did not retard the amount of time required to complete the maze. The effects of intrahippocampal CP-55,940 were apparently specific to cognition because no other cannabinoid pharmacological effects (e.g., antinociception, hypothermia, and catalepsy) were detected. This dissociation between choice accuracy in the radial-maze and other cannabinoid pharmacological effects suggests that the working memory deficits produced by cannabinoids may be mediated by cannabinoid receptors in the hippocampus.

Erythropoietin prevents place navigation disability and cortical infarction in rats with permanent occlusion of the middle cerebral artery

Erythropoietin (EPO) prevents the ischemia-induced delayed neuronal death in the hippocampal CA1 field in gerbils. EPO receptor (EPOR) is also expressed in the cerebral cortex but its function is not known. To examine whether EPO has a neuroprotective action in the cortex, EPO was infused into the cerebroventricles of stroke-prone spontaneously hypertensive rats with permanent occlusion of the left middle cerebral artery. Morris water maze test indicated that EPO infusion alleviated the ischemia-induced place navigation disability. The left (ischemic)-to-right (contralateral nonischemic) (L/R) ratio of cerebrocortical area in the EPO-infused ischemic group was larger than that in the vehicle-infused ischemic group. The occlusion caused secondary thalamic degeneration but infusion of EPO prevented the decrease in the L/R ratio of thalamic area and supported neuron survival in the ventroposterior thalamic nucleus. In situ hybridization indicated that EPOR mRNA was upregulated in the periphery (ischemic penumbra) of a cerebrocortical infarct after occlusion of the middle cerebral artery, suggesting that an increased number of EPOR in neurons facilitates the EPO signal transmission, thereby preventing the damaged area from enlarging.

Effects of methylphenidate on spatial working memory and planning in healthy young adults

Previous studies of the effects of the psychomotor stimulant, methylphenidate, have concentrated on vigilance and reaction time tasks. In this study, the effects of methylphenidate on more complex aspects of cognition were studied using tasks from the CANTAB battery and related tests which have been shown to be sensitive to frontal lobe dysfunction. Twenty-eight young healthy men participated in a counterbalanced, double-blind, placebo-controlled study of the effects of methylphenidate. Cognitive assessment included tests of spatial working memory, planning, verbal fluency, attentional set-shifting and sustained attention. Methylphenidate had significant effects on performance of the tests of spatial working memory and planning but not on the attentional and fluency tests. When the drug was taken on the first test session, performance on the spatial tests was enhanced by the drug compared to placebo. However, when the drug was taken second, performance accuracy was impaired whereas response latencies were decreased. These results are consistent with a hypothesis that methylphenidate influences performance in two conflicting ways; enhancing executive aspects of spatial function on novel tasks but impairing previously established performance. This pattern of effects is discussed within the framework of dual, interacting arousal mechanisms.

Effects of extracellular matrix-degrading proteases matrix metalloproteinases 3 and 9 on spatial learning and synaptic plasticity

Rats learning the Morris water maze exhibit hippocampal changes in synaptic morphology and physiology that manifest as altered synaptic efficacy. Learning requires structural changes in the synapse, and multiple cell adhesion molecules appear to participate. The activity of these cell adhesion molecules is, in large part, dependent on their interaction with the extracellular matrix (ECM). Given that matrix metalloproteinases (MMPs) are responsible for transient alterations in the ECM, we predicted that MMP function is critical for hippocampal-dependent learning. In support of this, it was observed that hippocampal MMP-3 and -9 increased transiently during water maze acquisition as assessed by western blotting and mRNA analysis. The ability of the NMDA receptor channel blocker MK801 to attenuate these changes indicated that the transient MMP changes were in large part dependent upon NMDA receptor activation. Furthermore, inhibition of MMP activity with MMP-3 and -9 antisense oligonucleotides and/or MMP inhibitor FN-439 altered long-term potentiation and prevented acquisition in the Morris water maze. The learning-dependent MMP alterations were shown to modify the stability of the actin-binding protein cortactin, which plays an essential role in regulating the dendritic cytoskeleton and synaptic efficiency. Together these results indicate that changes in MMP function are critical to synaptic plasticity and hippocampal-dependent learning.

Neurochemical correlate of a spatial preference in rats

Spatial (left or right) preferences were determined for rats given foot shock in a T-maze. The animals were killed, and left and right striata were assayed separately for dopamine and left and right teldiencephalic regions were assayed for norepinephrine. Dopamine content was significantly higher (by 12 percent) in the striata contralateral to rats' side preferences than in the ipsilateral striata; there was no such difference for teldiencephalic norepinephrine. The small asymmetry in striatal dopamine content is not due to any learning- or stress-related change induced by the testing procedure but is probably inherent in normal rats. Some spatial behavior appears to be the manifestation of a normal and specific difference in the activity of left and right nigrostriatal systems.

Pomegranate juice decreases amyloid load and improves behavior in a mouse model of Alzheimer's disease

Although there are no proven ways to delay onset or slow progression of Alzheimer's disease (AD), studies suggest that diet can affect risk. Pomegranates contain very high levels of antioxidant polyphenolic substances as compared to other fruits and vegetables. Polyphenols have been shown to be neuroprotective in different model systems. We asked whether dietary supplementation with pomegranate juice (PJ) would influence behavior and AD-like pathology in a transgenic mouse model. Transgenic mice (APP(sw)/Tg2576) received either PJ or sugar water control from 6 to 12.5 months of age. PJ-treated mice learned water maze tasks more quickly and swam faster than controls. Mice treated with PJ had significantly less (approximately 50%) accumulation of soluble Abeta42 and amyloid deposition in the hippocampus as compared to control mice. These results suggest that further studies to validate and determine the mechanism of these effects, as well as whether substances in PJ may be useful in AD, should be considered.

Plant-derived flavanol (-)epicatechin enhances angiogenesis and retention of spatial memory in mice

Diet and exercise have a profound impact on brain function. In particular, natural nutrients found in plants may influence neuronal survival and plasticity. Here, we tested whether consumption of a plant-derived flavanol, (-)epicatechin, enhances cognition in sedentary or wheel-running female C57BL/6 mice. Retention of spatial memory in the water maze was enhanced by ingestion of (-)epicatechin, especially in combination with exercise. Improved spatial memory was associated with increased angiogenesis and neuronal spine density, but not newborn cell survival, in the dentate gyrus of the hippocampus. Moreover, microarray analysis showed upregulation of genes associated with learning and downregulation of markers of neurodegeneration in the hippocampus. Together, our data show that ingestion of a single flavanol improves spatial memory retention in adult mammals.

Estrus-associated decrements in a water maze task are limited to acquisition

To ascertain whether gonadal hormones have activational influences on spatial ability, the relationship between estrous cycle, sex differences and water maze performance was examined in two studies. In the first study, the performance of females at different cycle phases was compared within females and to that of males. All animals were naive to the task. Similar to other studies, females had longer latencies and distances to reach the water maze platform than males. This sex difference was statistically significant only in comparisons of estrous females and males, not in comparisons of diestrous females and males. To determine whether estrus-associated decrements in acquisition of the water maze task extended to postacquisition performance, a second study assesessed performance of ovariectomized rats--trained to criterion in the task--whose cycle phases were mimicked by exogenous hormones. In the initial trial, "estrous" animals had longer latencies to reach the platform than "diestrous" and ovariectomized animals. In subsequent trials, no hormone-dependent differences in performance were observed. Taken together, the results indicate a modest association between phase of estrous cycle, acquisition, and postacquisition performance when the task is novel. These findings suggest estrus-associated decrements in acquisition may account for previous discrepancies among studies of sex differences in spatial ability.