Statistical and theoretical considerations for the platform re-location water maze

Effects of personality on assessments of anxiety and cognition

Individual variation in responses to commonly used tests of anxiety and spatial memory is often reported. While this variation is frequently considered to be 'noise', evidence suggests that it is, at least partially, related to consistent individual differences in behavioral responses (i.e., personality). The same tests used to assess anxiety are often used to profile personality traits, but personality differences are rarely considered when testing treatment differences in anxiety. Focusing on the rat literature, we describe fundamental principles involved in anxiety and spatial memory tests and we discuss how personality differences and housing conditions can influence behavioral responses in these tests. We propose that an opportunity exists to increase stress resiliency in environmentally sensitive individuals by providing environmental enrichment. We conclude by discussing different approaches to incorporating personality measures into the design and analysis of future studies; given the potential that variation masks research outcomes, we suggest that a strategy which considers the individual and its housing can contribute to improving research reproducibility.

A cellular approach to understanding and treating Gulf War Illness

Gulf War Illness (GWI), a disorder suffered by approximately 200,000 veterans of the first Gulf War, was caused by exposure to low-level organophosphate pesticides and nerve agents in combination with battlefield stress. To elucidate the mechanistic basis of the brain-related symptoms of GWI, human-induced pluripotent stem cells (hiPSCs) derived from veterans with or without GWI were differentiated into forebrain glutamatergic neurons and then exposed to a Gulf War (GW) relevant toxicant regimen consisting of a sarin analog and cortisol, a human stress hormone. Elevated levels of total and phosphorylated tau, reduced microtubule acetylation, altered mitochondrial dynamics/transport, and decreased neuronal activity were observed in neurons exposed to the toxicant regimen. Some of the data are consistent with the possibility that some veterans may have been predisposed to acquire GWI. Wistar rats exposed to a similar toxicant regimen showed a mild learning and memory deficit, as well as cell loss and tau pathology selectively in the CA3 region of the hippocampus. These cellular responses offer a mechanistic explanation for the memory loss suffered by veterans with GWI and provide a cell-based model for screening drugs and developing personalized therapies for these veterans.

BoDV-1 infection induces neuroinflammation by activating the TLR4/MyD88/IRF5 signaling pathway, leading to learning and memory impairment in rats

Borna disease virus (BoDV-1) can infect the hippocampus and limbic lobes of newborn rodents, causing cognitive deficits and abnormal behavior. Studies have found that neuroinflammation caused by viral infection in early life can affect brain development and impair learning and memory function, revealing the important role of neuroinflammation in cognitive impairment caused by viral infection. However, there is no research to explore the pathogenic mechanism of BoDV-1 in cognition from the direction of neuroinflammation. We established a BoDV-1 infection model in rats, and tested the learning and memory impairment by Morris water maze (MWM) experiment. RNAseq was introduced to detect changes in the gene expression profile of BoDV-1 infection, focusing on inflammation factors and related signaling pathways. BoDV-1 infection impairs the learning and memory of Sprague-Dawley rats in the MWM test and increases the expression of inflammatory cytokines in the hippocampus. RNAseq analysis found 986 differentially expressed genes (DEGs), of which 845 genes were upregulated and 141 genes were downregulated, and 28 genes were found to be enriched in the toll-like receptor (TLR) pathway. The expression of TLR4, MyD88, and IRF5 in the hippocampus was significantly changed in the BoDV-1 group. Our results indicate that BoDV-1 infection stimulates TLR4/MyD88/IRF5 pathway activation, causing the release of downstream inflammatory factors, which leads to neuroinflammation in rats. Neuroinflammation may play a significant role in learning and memory impairment caused by BoDV-1 infection.

Betaine Alleviates Cognitive Deficits in Diabetic Rats via PI3K/Akt Signaling Pathway Regulation

BACKGROUND

Diabetes mellitus is a metabolic disease which also causes cognitive deficits. Betaine (N,N,N-trimethylglycine), also known as trimethylglycine, has been shown to ameliorate diabetic symptoms in diabetic animals and improve cognitive ability in Alzheimer disease (AD) animals. However, the effects of betaine on cognitive deficits in diabetic animals have not been described yet. Therefore, in the current study, the effects of betaine on cognition in diabetic rats were evaluated.

METHODS

We established a diabetic rat model by injecting streptozotocin (STZ) into rats and administrated betaine to these diabetic rats. We monitored the metabolism index, and glucose and insulin levels in blood and cerebrospinal fluid. We measured inflammatory cytokine levels, including TNF-α, IL-1β, and IL-6, in serum and hippocampus. We also monitored oxidative stress in the hippocampus by measuring malondialdehyde (MDA) level and superoxide dismutase (SOD) activity. We measured the learning and memory ability of diabetic rats using the Morris water and Y maze tests and tested the phosphatidylinositol 3-kinase (PI3K)/Akt activation and p-mTOR level in the hippocampus.

RESULTS

Betaine improved glucose metabolism and suppressed the production of inflammatory cytokines, including TNF-α, IL-1β, and IL-6. Also, betaine decreased MDA concentration and increased SOD activity in the hippocampus of diabetic rats. Betaine ameliorated cognitive deficits in diabetic rats, and it promoted PI3K expression and Akt activation and decreased p-mTOR expression.

CONCLUSION

Betaine alleviates cognitive deficits in STZ-induced diabetic rats via regulating the PI3K/Akt signaling pathway.

Anti-IL17 treatment ameliorates Down syndrome phenotypes in mice

Down syndrome (DS) is characterized by structural and functional anomalies that are present prenatally and that lead to intellectual disabilities. Later in life, the cognitive abilities of DS individuals progressively deteriorate due to the development of Alzheimer's disease (AD)-associated neuropathology (i.e., β-amyloid (Aβ) plaques, neurofibrillary tangles (NFTs), neurodegeneration, synaptic pathology, neuroinflammation and increased oxidative stress). Increasing evidence has shown that among these pathological processes, neuroinflammation plays a predominant role in AD etiopathology. In AD mouse models, increased neuroinflammation appears earlier than Aβ plaques and NFTs, and in DS and AD models, neuroinflammation exacerbates the levels of soluble and insoluble Aβ species, favoring neurodegeneration. The Ts65Dn (TS) mouse, the most commonly used murine model of DS, recapitulates many alterations present in both DS and AD individuals, including enhanced neuroinflammation. In this study, we observed an altered neuroinflammatory milieu in the hippocampus of the TS mouse model. Pro-inflammatory mediators that were elevated in the hippocampus of this model included pro-inflammatory cytokine IL17A, which has a fundamental role in mediating brain damage in neuroinflammatory processes. Here, we analyzed the ability of an anti-IL17A antibody to reduce the neuropathological alterations that are present in TS mice during early neurodevelopmental stages (i.e., hippocampal neurogenesis and hypocellularity) or that are aggravated in later-life stages (i.e., cognitive abilities, cholinergic neuronal loss and increased cellular senescence, APP expression, Aβ peptide expression and neuroinflammation). Administration of anti-IL17 for 5 months, starting at the age of 7 months, partially improved the cognitive abilities of the TS mice, reduced the expression of several pro-inflammatory cytokines and the density of activated microglia and normalized the APP and Aβ_1-42 levels in the hippocampi of the TS mice. These results suggest that IL17-mediated neuroinflammation is involved in several AD phenotypes in TS mice and provide a new therapeutic target to reduce these pathological characteristics.

Decreasing the Expression of GABAA α5 Subunit-Containing Receptors Partially Improves Cognitive, Electrophysiological, and Morphological Hippocampal Defects in the Ts65Dn Model of Down Syndrome

Trisomy 21 or Down syndrome (DS) is the most common cause of intellectual disability of a genetic origin. The Ts65Dn (TS) mouse, which is the most commonly used and best-characterized mouse model of DS, displays many of the cognitive, neuromorphological, and biochemical anomalies that are found in the human condition. One of the mechanisms that have been proposed to be responsible for the cognitive deficits in this mouse model is impaired GABA-mediated inhibition. Because of the well-known modulatory role of GABA_A α5 subunit-containing receptors in cognitive processes, these receptors are considered to be potential targets for improving the intellectual disability in DS. The chronic administration of GABA_A α5-negative allosteric modulators has been shown to be procognitive without anxiogenic or proconvulsant side effects. In the present study, we use a genetic approach to evaluate the contribution of GABA_A α5 subunit-containing receptors to the cognitive, electrophysiological, and neuromorphological deficits in TS mice. We show that reducing the expression of GABA_A α5 receptors by deleting one or two copies of the Gabra5 gene in TS mice partially ameliorated the cognitive impairments, improved long-term potentiation, enhanced neural differentiation and maturation, and normalized the density of the GABAergic synapse markers. Reducing the gene dosage of Gabra5 in TS mice did not induce motor alterations and anxiety or affect the viability of the mice. Our results provide further evidence of the role of GABA_A α5 receptor-mediated inhibition in cognitive impairment in the TS mouse model of DS.

A new coumarin derivative, IMM-H004, attenuates okadaic acid-induced spatial memory impairment in rats

AIM

A novel coumarin derivative 7-hydroxy-5-methoxy-4-methyl-3-(4-methylpiperazin-1-yl)-coumarin (IMM-H004) has shown anti-apoptotic, anti-inflammatory and neuroprotective activities. In this study we investigated the effects of IMM-H004 on spatial memory in rats treated with okadaic acid (OKA), which was used to imitate Alzheimer's disease (AD)-like symptoms.

METHODS

SD rats were administered IMM-H004 (8 mg·kg(-1)·d(-1), ig) or donepezil (positive control, 1 mg·kg(-1)·d(-1), ig) for 25 d. On d 8 and 9, OKA (200 ng) was microinjected into the right ventricle. Morris water maze test was used to evaluate the spatial memory impairments. Tau and β-amyloid (Aβ) pathology in the hippocampus was detected using Western blot and immunohistochemistry. TUNEL staining was used to detect cell apoptosis.

RESULTS

OKA-treated rats showed significant impairments of spatial memory in Morris water maze test, which were largely reversed by administration of IMM-H004 or donepezil. Furthermore, OKA-treated rats exhibited significantly increased phosphorylation of tau, deposits of Aβ protein and cell apoptosis in the hippocampus, which were also reversed by administration of IMM-H004 or donepezil.

CONCLUSION

Administration of IMM-H004 or donepezil protects rats against OKA-induced spatial memory impairments via attenuating tau or Aβ pathology. Thus, IMM-H004 may be developed as a therapeutic agent for the treatment of AD.

Cognitive Deficits in Calsyntenin-2-deficient Mice Associated with Reduced GABAergic Transmission

Calsyntenin-2 has an evolutionarily conserved role in cognition. In a human genome-wide screen, the CLSTN2 locus was associated with verbal episodic memory, and expression of human calsyntenin-2 rescues the associative learning defect in orthologous Caenorhabditis elegans mutants. Other calsyntenins promote synapse development, calsyntenin-1 selectively of excitatory synapses and calsyntenin-3 of excitatory and inhibitory synapses. We found that targeted deletion of calsyntenin-2 in mice results in a selective reduction in functional inhibitory synapses. Reduced inhibitory transmission was associated with a selective reduction of parvalbumin interneurons in hippocampus and cortex. Clstn2(-/-) mice showed normal behavior in elevated plus maze, forced swim test, and novel object recognition assays. However, Clstn2(-/-) mice were hyperactive in the open field and showed deficits in spatial learning and memory in the Morris water maze and Barnes maze. These results confirm a function for calsyntenin-2 in cognitive performance and indicate an underlying mechanism that involves parvalbumin interneurons and aberrant inhibitory transmission.

Overexpression of Dyrk1A is implicated in several cognitive, electrophysiological and neuromorphological alterations found in a mouse model of Down syndrome

Down syndrome (DS) phenotypes result from the overexpression of several dosage-sensitive genes. The DYRK1A (dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A) gene, which has been implicated in the behavioral and neuronal alterations that are characteristic of DS, plays a role in neuronal progenitor proliferation, neuronal differentiation and long-term potentiation (LTP) mechanisms that contribute to the cognitive deficits found in DS. The purpose of this study was to evaluate the effect of Dyrk1A overexpression on the behavioral and cognitive alterations in the Ts65Dn (TS) mouse model, which is the most commonly utilized mouse model of DS, as well as on several neuromorphological and electrophysiological properties proposed to underlie these deficits. In this study, we analyzed the phenotypic differences in the progeny obtained from crosses of TS females and heterozygous Dyrk1A (+/-) male mice. Our results revealed that normalization of the Dyrk1A copy number in TS mice improved working and reference memory based on the Morris water maze and contextual conditioning based on the fear conditioning test and rescued hippocampal LTP. Concomitant with these functional improvements, normalization of the Dyrk1A expression level in TS mice restored the proliferation and differentiation of hippocampal cells in the adult dentate gyrus (DG) and the density of GABAergic and glutamatergic synapse markers in the molecular layer of the hippocampus. However, normalization of the Dyrk1A gene dosage did not affect other structural (e.g., the density of mature hippocampal granule cells, the DG volume and the subgranular zone area) or behavioral (i.e., hyperactivity/attention) alterations found in the TS mouse. These results suggest that Dyrk1A overexpression is involved in some of the cognitive, electrophysiological and neuromorphological alterations, but not in the structural alterations found in DS, and suggest that pharmacological strategies targeting this gene may improve the treatment of DS-associated learning disabilities.

Erythropoietin protects newborn rat against sevoflurane-induced neurotoxicity

INTRODUCTION

Recent data on newborn animals exposed to anesthetics have raised safety concerns regarding anesthesia practices in young children. Indeed, studies on rodents have demonstrated a widespread increase in brain apoptosis shortly after exposure to sevoflurane, followed by long-term neurologic impairment. In this context, we aimed to evaluate the protective effect of rh-EPO, a potent neuroprotective agent, in rat pups exposed to sevoflurane.

MATERIAL AND METHODS

At postnatal day 7, 75 rat pups were allocated into three groups: SEVO + EPO (n = 27) exposed to sevoflurane 2 vol% (0.5 MAC) for 6 h in an air/O2 mixture (60/40) + 5000 UI.kg(-1) rh-EPO IP; SEVO (n = 27) exposed to sevoflurane + vehicle IP; and CONTROL (n = 21) exposed to the mixture without sevoflurane + vehicle IP. Three days after anesthesia (D10), apoptosis was quantified on brain extract with TUNEL method and caspase 3. NGF and BDNF expression was determined by Western blotting. Rats reaching adulthood were evaluated in terms of exploration capacities (object exploration duration) together with spatial and object learning (water maze and novel object test).

RESULTS

Sevoflurane exposure impaired normal behavior in adult rats by reducing the exploratory capacities during the novel object test and impaired both spatial and object learning capacities in adult rats (water maze, ratio time to find platform 3rd trial/1st trial: 1.1 ± 0.2 vs 0.4 ± 0.1; n = 9, SEVO vs CONTROL; P = 0.01). Rh-EPO reduced sevoflurane-induced behavior and learning abnormalities in adult rats (water maze, ratio time to find platform 3rd trial/1st trial: 0.3 ± 0.1 vs 1.1 ± 0.2; n = 9, SEVO + EPO vs SEVO; P = 0.01). Three days after anesthesia, rh-EPO prevented sevoflurane-induced brain apoptosis (5 ± 3 vs 35 ± 6 apoptotic cells·mm(-2) ; n = 6, SEVO + EPO vs SEVO; P = 0.01) and elevation of caspase three level and significantly increased the brain expression of BDNF and NGF (n = 6, SEVO + EPO vs SEVO; P = 0.01).

CONCLUSION

Six hours of sevoflurane anesthesia in newborn rats induces significant long-term cognitive impairment. A single administration of rh-EPO immediately after postnatal exposure to sevoflurane reduces both early activation of apoptotic phenomenon and late onset of neurologic disorders.

Tetrahydropalmatine protects against methamphetamine-induced spatial learning and memory impairment in mice

OBJECTIVE

The purpose of this study was to investigate the effect of methamphetamine (MA) on spatial learning and memory and the role of tetrahydropalmatine (THP) in MA-induced changes in these phenomena in mice.

METHODS

Male C57BL/6 mice were randomly divided into eight groups, according to different doses of MA, different doses of THP, treatment with both MA and THP, and saline controls. Spatial learning and memory were assessed using the Morris water maze. Western blot was used to detect the expression of extracellular signal-regulated protein kinase (ERK) in the mouse prefrontal cortex (PFC) and hippocampus.

RESULTS

Repeated MA treatment significantly increased the escape latency in the learning phase and decreased the number of platform site crossings in the memory-test phase. ERK1/2 expression was decreased in the PFC but not in the hippocampus of the MA-treated mice. Repeated THP treatment alone did not affect the escape latency, the number of platform site crossings or the total ERK1/2 expression in the brain. Statistically significantly shorter escape latencies and more platform site crossings occurred in MA+THP-treated mice than in MA-treated mice.

CONCLUSION

Repeated MA administration impairs spatial learning and memory in mice, and its co-administration with THP prevents this impairment, which is probably attributable to changed ERK1/2 expression in the PFC. This study contributes to uncovering the mechanism underlying MA abuse, and to exploring potential therapies.

An examination of early neural and cognitive alterations in hippocampal-spatial function of ghrelin receptor-deficient rats

Ghrelin, a hormone implicated in the regulation of feeding and energy balance, has also been associated with neural function underlying learning and memory. These effects are thought to be mediated by ghrelin targeting receptors at extra hypothalamic sites such as the hippocampus. Exogenous ghrelin administration increases dendritic spine density in the hippocampal CA1 region and neurogenesis in the dentate gyrus (DG), while improving memory in rats. In the present study, we sought to determine whether rats lacking the ghrelin receptor would show early neural or cognitive decline measured via hippocampal integrity (spine density and neurogenesis) and spatial learning and memory. As such, we used young and middle-aged adult rats with mutations to the gene encoding for the ghrelin receptor (GHS-R KO) and wildtype (WT) littermates to determine differences in performance on hippocampal-dependent tasks (the water maze and radial arm maze). In addition, we examined the hippocampal dentate gyrus of these rats for differences in dendritic spine density and cell proliferation (doublecortin). Overall, results demonstrated that spine density and doublecortin staining in the dentate gyrus of the young GHS-R KO group was similar to that seen in middle-aged groups (both KO and WT) and lower than the young WT group. Middle-aged GHS-R KO and WT groups showed deficits on the radial arm maze food-motivated task but not the water maze task. These data suggest that impaired ghrelin signaling leads to an early onset decrement in hippocampal structural integrity that may manifest in non- spatial-related behavioral deficits.

The role of N-methyl-D-aspartate receptor in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive disorder and memory dysfunction. This kind of cognitive impairment is closely related to synaptic plasticity, in which N-methyl-D-aspartate receptor (NMDAR), which is one of the glutamate receptors, plays a critical role. Therefore the present study was designed to investigate whether the cognitive impairment of AD rat model has relation to the change of NMDAR. The adult male rats were randomly divided into three groups: control, AD and AD+APV (the competitive but not selective blocker of NMDAR) groups. The synaptic plasticity was measured by recording long-term potentiation (LTP) and depression (LTD) in the perforant path (PP) to dentate gyrus (DG) of hippocampus. The spatial memory and reversal learning were examined by Morris water maze (MWM) test. Results showed that the spatial learning performance of MWM was significantly impaired in AD group compared to that of control group. Rats of APV group showed a higher LTP and better performance in spatial memory, but worse performance in reversal learning test and lower LTD than those of AD group. In conclusion, the high concentration of APV influenced LTD and enhanced LTP in AD rats through changing the proportion of NMDAR, which suggested that the change of NMDAR may participate in the pathogenesis of AD at the synaptic level.

Changes in the brain and plasma Aβ peptide levels with age and its relationship with cognitive impairment in the APPswe/PS1dE9 mouse model of Alzheimer's disease

Double transgenic mice expressing mutant amyloid precursor protein (APPswe) and mutant presenilin 1 (PS1dE9) are a model of Alzheimer-type amyloidosis and are widely used in experimental studies. In the present work, the relationships between brain and plasma amyloid-β peptide (Aβ) levels and cognitive impairments were examined in male APPswe/PS1dE9 double transgenic mice at different ages. When compared with non-transgenic littermates, APPswe/PS1dE9 mice exhibited significant learning deficits from the age of 6months (M6), which were aggravated at later stages of life (M8 and M12). Sporadic brain amyloid plaques were observed in mice as early as M3 and progressively increased in number and size up to M12. A similar increase was observed in brain insoluble Aβ levels as assessed by enzyme-linked immunosorbent assay (ELISA). In particular, the levels of brain insoluble Aβ peptides rose steeply from M4 to M6. Interestingly, this pronounced amyloid deposition was accompanied by a temporary fall in the concentration of brain soluble and membrane-bound Aβ peptides at M6 that rose again at M8 and M12. The plasma levels of Aβ40 and Aβ42 decreased with advancing age up to M8, when they stabilized at M12. This decrease in plasma Aβ levels coincided with the observed increase in insoluble brain Aβ levels. These results could be useful for developing plasma Aβ levels as possible biomarkers of the cerebral amyloidosis and provide advances in the knowledge of the Aβ peptide biochemical changes that occur in the brain of Alzheimer's disease patients.

Neuron-specific expression of tomosyn1 in the mouse hippocampal dentate gyrus impairs spatial learning and memory

Tomosyn, a syntaxin-binding protein, is known to inhibit vesicle priming and synaptic transmission via interference with the formation of SNARE complexes. Using a lentiviral vector, we specifically overexpressed tomosyn1 in hippocampal dentate gyrus neurons in adult mice. Mice were then subjected to spatial learning and memory tasks and electrophysiological measurements from hippocampal slices. Tomosyn1-overexpression significantly impaired hippocampus-dependent spatial memory while tested in the Morris water maze. Further, tomosyn1-overexpressing mice utilize swimming strategies of lesser cognitive ability in the Morris water maze compared with control mice. Electrophysiological measurements at mossy fiber-CA3 synapses revealed impaired paired-pulse facilitation in the mossy fiber of tomosyn1-overexpressing mice. This study provides evidence for novel roles for tomosyn1 in hippocampus-dependent spatial learning and memory, potentially via decreased synaptic transmission in mossy fiber-CA3 synapses. Moreover, it provides new insight regarding the role of the hippocampal dentate gyrus and mossy fiber-CA3 synapses in swimming strategy preference, and in learning and memory.

Acute pharmacokinetics of memantine in the mouse

The pharmacokinetics of memantine, a widely prescribed medication in the United States and the European Union for the treatment of moderate-to-severe Alzheimer's disease (AD), have not been well explored in the mouse. Memantine is a highly unspecific blocker of many channels and how memantine may be of benefit in AD remains a mystery. Therefore, the investigation of memantine in the mouse, the most commonly chosen subject for modeling AD, has strong potential to lead to better therapies. Here, we present an acute pharmacokinetic analysis of memantine in mouse brain tissue and blood serum for a variety of experimentally relevant doses. The data help shed light on the mechanism of memantine action in vivo, and demonstrate that subcutaneous doses above 10 mg/kg in the mouse are most likely not therapeutically relevant to the human.

Chronic impairments in spatial learning and memory in rats previously exposed to chlorpyrfos or diisopropylfluorophosphate

The acute toxicity of organophosphates (OPs) has been studied extensively; however, much less attention has been given to the subject of repeated exposures that are not associated with overt signs of toxicity (i.e., subthreshold exposures). The objective of this study was to determine if the protracted spatial learning impairments we have observed previously after repeated subthreshold exposures to the insecticide chlorpyrifos (CPF) or the alkylphosphate OP, diisopropylfluorophosphate (DFP) persisted for longer periods after exposure. Male Wistar rats (beginning at two months of age) were initially injected subcutaneously with CPF (10.0 or 18.0mg/kg) or DFP (0.25 or 0.75 mg/kg) every other day for 30 days. After an extended OP-free washout period (behavioral testing begun 50 days after the last OP exposure), rats previously exposed to CPF, but not DFP, were impaired in a radial arm maze (RAM) win-shift task as well as a delayed non-match to position procedure. Later experiments (i.e., beginning 140 days after the last OP exposure) revealed impairments in the acquisition of a water maze hidden platform task associated with both OPs. However, only rats previously exposed to DFP were impaired in a second phase of testing when the platform location was changed (indicative of deficits of cognitive flexibility). These results indicate, therefore, that repeated, subthreshold exposures to CPF and DFP may lead to chronic deficits in spatial learning and memory (i.e., long after cholinesterase inhibition has abated) and that insecticide and alkylphosphate-based OPs may have differential effects depending on the cognitive domain evaluated.

IGF-I ameliorates hippocampal neurodegeneration and protects against cognitive deficits in an animal model of temporal lobe epilepsy

Epilepsy is a major neurological disease, and patients often show spatial memory deficits. Thus, there is a need of effective new therapeutic approaches. IGF-I has been shown to be neuroprotective following a number of experimental insults to the nervous system, and in a variety of animal models of neurodegenerative diseases. In the present work, we investigated the possible neuroprotective effects of IGF-I following unilateral intrahippocampal administration of kainic acid (KA), an animal model of temporal lobe epilepsy (TLE). KA induced cell death, as shown by FluoroJade B, and extensive cell loss in both the ipsilateral and contralateral CA3 and CA4 areas, as well as granule cell dispersal in the DG, as revealed by Cresyl violet staining. KA also resulted in intense astrogliosis and microgliosis, as assessed by the number of GFAP and CD11b immunopositive cells, respectively, and increased hippocampal neurogenesis. Exposure to the Morris Water Maze task revealed that mice injected with KA were deficient in spatial learning and both short- and long-term memories, when tested in a larger diameter pool, which requires the use of allocentric strategies. When tested in a smaller pool, only long-term memory was impaired. Administration of IGF-I decreased seizure severity, hippocampal neurogenesis, and protected against neurodegeneration at the cellular level as assessed by FluoroJade B and Cresyl violet staining, as well as the number of GFAP and CD11b immunopositive cells. Furthermore, IGF-I abolished the cognitive deficits. Our results support that IGF-I could have a possible therapeutic potential in TLE.