Adrenergic receptor ß3 is involved in the memory consolidation process in mice

Attention and emotion have a positive impact on memory formation, which is related to the activation of the noradrenergic system in the brain. The hippocampus and amygdala are fundamental structures in memory acquisition, which is modulated by noradrenaline through the noradrenergic receptors. Pharmacological studies suggest that memory acquisition depends on the action of both the β3 (β3-AR) and β2 (β2-AR) receptor subtypes. However, the use of animal models with specific knockout for the β3-AR receptor only (β3-ARKO) allows researchers to more accurately assess its role in memory formation processes. In the present study, we evaluated short- and long-term memory acquisition capacity in β3-ARKO mice and wild-type mice at approximately 60 days of age. The animals were submitted to the open field test, the elevated plus maze, object recognition, and social preference. The results showed that the absence of the β3-AR receptor caused no impairment in locomotion and did not cause anxious behavior, but it caused significant impairment of short- and long-term memory compared to wild-type animals. We also evaluated the expression of genes involved in memory consolidation. The mRNA levels for GLUT3, a glucose transporter expressed in the central nervous system, were significantly reduced in the amygdala, but not in the hippocampus of the β3-ARKO animals. Our results showed that β3-AR was involved in the process of acquisition of declarative memory, and its action may be due to the facilitation of glucose absorption in the amygdala.

Impaired executive functions in experimental model of temporal lobe epilepsy / Prejuízo das funções executivas no modelo experimental de epilepsia do lobo temporal

ABSTRACT Objective The present study aimed to investigate cognitive and behavioural changes consistent with attention deficit hyperactivity disorder (ADHD -like behavior in male Wistar rats with temporal lobe epilepsy (TLE). Method Male Wistar rats at 25 day of age were submitted to animal model of TLE by pilocarpine injection (350 mg/kg, ip) and a control group received saline 0.9%. The animals were continuously video monitored up to the end of experiments. The behavioural tests (open field, elevated plus maze and operant conditioning box) started from 60 days postnatal. Results Animals with TLE exhibited elevated locomotor activity, reduced level of anxiety-related behavior, impulsivity and impaired visuospatial working memory. Conclusion Taken as a whole, we concluded that animals with TLE exhibited some cognitive and behavioural changes consistent with ADHD-like behavior.

RESUMO Objetivo O presente estudo teve como objetivo investigar as alterações cognitivas e comportamentais consistentes com o comportament de transtorno de deficit de atenção e hiperatividade (TDAH) -like em ratos Wistar machos com epilepsia do lobo temporal (ELT). Método Ratos Wistar machos com 25 dias de vida foram submetidos a modelo animal de ELT pela injeção de pilocarpina (350 mg / kg, ip) e grupo controle recebeu salina 0,9%. Os animais foram monitorados continuamente por vídeo até ao final dos experimentos. Os testes comportamentais (campo aberto, labirinto em cruz elevado e caixa de condicionamento operante) começaram a partir de 60 dias pós-natal. Resultados Os animais com ELT exibiram aumento da atividade locomotora, redução do comportamento relacionado com a ansiedade, impulsividade e prejuízo da memória de trabalho visuospatial. Conclusão Em conjunto, concluímos que os animais com ELT apresentaram algumas alterações cognitivas e comportamentais consistentes com o comportamento TDAH-like.

The influence of enriched environment on spatial memory in Swiss mice of different ages / A influência do ambiente enriquecido na memória espacial de camundongos Swiss em diferentes faixas etárias

The objective of this study was to evaluate the influence of enriched environment on spatial memory acquisition in mice of three different age groups. Weanling, young, and young adult female Swiss mice were housed in a standard control or enriched environment for 50 days, and their spatial memory was tested with the Morris Water Maze. We did not observe an experimental effect for spatial memory acquisition, and there was neither an effect of time of analysis nor an interaction between experimental group and time of analysis. Regarding effects of experimental group and training day in relation to latency in finding the hidden platform, we did find an effect in the experimental young adult mice group (p = 0.027), but there was no interaction between these factors in all three groups. Based on these findings environmental enrichment did not enhance spatial memory acquisition in female Swiss mice in the tested age groups.

O objetivo deste estudo foi avaliar a influência do ambiente enriquecido na aquisição da memória espacial de camundongos em três diferentes faixas etárias. Camundongos fêmeas Swiss recém-desmamados, jovens e adultos jovens foram alojados em ambiente controle ou em ambiente enriquecido durante 50 dias, e sua memória espacial foi testada por meio do Labirinto Aquático de Morris. Não houve efeito do grupo experimental na aquisição de memória espacial, do momento de análise, tampouco da interação entre o grupo experimental e o momento de análise. Quanto aos efeitos do grupo experimental e do dia de treino em relação à latência para encontrar a plataforma escondida, houve efeito do grupo experimental apenas para o grupo experimental adulto jovem (p = 0,027), com menor latência do grupo controle, porém sem interação entre esses fatores para todos os grupos. O enriquecimento ambiental não interferiu na aquisição de memória espacial de camundongos fêmeas Swiss nas faixas etárias analisadas.

Relative luminosity in the plus maze upon the exploratory behaviour of female Wistar rats / Efeito da luminosidade relativa em labirinto em cruz sobre o comportamento exploratório de fêmeas Wistar

Objective This study evaluated the provision of two configuration of the Elevated Pluz-Maze (EPM) by analizing the exploratory behaviour of female Wistar rats in different phases of the estrous cycle in EPMs with different gradients of luminosity between the open and enclosed arms (O/E∆Lux).Methods Female Wistar rats were treated with Midazolam (MDZ, 1.0 mg.kg-1) and were tested for their exploratory behaviour in either the EPM 10 O/E∆Lux or EPM 96 O/E∆Lux.Results A multiple regression analysis indicated that the O/E∆Lux is negatively associated with the %Open arm entries and %Open arm time, suggesting that as O/E∆Lux increases, the open arm exploration decreases. The estrous cycle phase did not influence the open-arm exploration in either EPM. MDZ- induced anxiolysis was detected in 96 O/E∆Lux EPM in all phases of the EC.Discussion Results of this study suggest the importance of the O/E∆Lux to establish the arm preference in the EPM, and to preserve the predictive validity of the EPM.

Objetivo Avaliar a provisão de duas configuracōes do Labirinto Elevado em Cruz (LEC) através do comportamento exploratório de ratas Wistar em diferentes fases do ciclo estral (CE) em LEC com diferentes gradientes de luminosidade entre os braços aberto e fechado (A/F∆Lux).Método Ratas Wistar foram tratadas com Midazolam (MDZ, 1.0 mg.kg-1) e foram testadas no LEC 10 A/F∆Lux ou LEC 96 A/F∆Lux.Resultados A análise de regressão múltipla indicou que o A/F∆Lux está negativamente associado com a % de entrada no braço aberto e % de tempo no braço aberto, sugerindo que no aumento do A/F∆Lux, a exploração do braço aberto diminui. A fase do CE não influenciou a exploração do braço aberto no LEC. A ansiólise induzida pelo MDZ foi demonstrada no 96 LEC A/F∆Lux em todas as fases do CE.Discussão Estes resultados sugerem a importância do A/F∆Lux para estabelecer a preferência da exploração do LEC e preservar a validade do LEC.

Sensory evaluation of dairy supplements enriched with reduced iron, ferrous sulfate or ferrous fumarate / Evaluación sensorial de suplementos lácteos enriquecidos con hierro reducido, sulfato ferroso o fumarato ferroso

Objective. To determine the degree of liking of the Oportunidades programme dietary supplements (DS) -purees and beverages- added with different iron salts (IS): reduced iron (RI), ferrous sulphate (FS) or ferrous fumarate (FF) during 24 weeks of storage. Materials and methods. The DS were evaluated through a hedonic scale for aroma, flavour and colour attributes; at time zero and every eight weeks, each panel member evaluated three DS with same flavour and presentation but different IS. Seventy women participated as panel members. Results. The chocolate and banana DS exhibited a change in preference by colour and flavour due to storage. DS with FS or RI showed the least preference by flavour and colour in the context of the three IS considered. The chocolate and neutral DS enriched with FS changed their colour and flavour. Conclusion. DS were, in general, well-liked; nonetheless, for purees enriched with FS and for beverages enriched with RI, the less-liked attributes were colour and flavour.

Objetivo. Determinar el nivel de agrado de los suplementos alimenticios (SA) (papillas y bebidas) del Programa Oportunidades, adicionados con diferentes sales de hierro (SH): hierro reducido (HR), sulfato ferroso (SF) o fumarato ferroso (FF), durante 24 semanas de almacenamiento. Material y métodos. Se evaluaron mediante una escala hedónica los atributos olor, sabor y color; a tiempo cero y cada ocho semanas, cada juez evaluó tres suplementos, mismo sabor, presentación y diferente SH. Participaron 70 mujeres. Resultados. Los SA sabor chocolate y plátano presentaron modificación del agrado por color y sabor durante el almacenamiento. Los SA con SF o HR presentaron el menor agrado para sabor y olor por efecto de las SH. En los SA sabor chocolate y natural adicionados con SF se afectó el color y el sabor. Conclusión. Los SA en general presentaron agrado; sin embargo, en las papillas adicionadas con SF y las bebidas con HR los atributos limitantes fueron color y sabor.

Neurobiological effect of 7-nitroindazole, a neuronal nitric oxide synthase inhibitor, in experimental paradigm of Alzheimer’s disease.

Nitric oxide plays a role in a series of neurobiological functions, underlying behaviour and memory. The functional role of nNOS derived nitric oxide in cognitive functions is elusive. The present study was designed to investigate the effect of specific neuronal nitric oxide synthase inhibitor, 7-nitroindazole, against intracerebroventricular streptozotocin-induced cognitive impairment in rats. Learning and memory behaviour was assessed using Morris water maze and elevated plus maze. 7-nitroindazole (25 mg/kg, ip) was administered as prophylactically (30 min before intracerebroventricular streptozotocin injection on day 1) and therapeutically (30 min before the assessment of memory by Morris water maze on day 15). Intracerebroventricular streptozotocin produced significant cognitive deficits coupled with alterations in biochemical indices.These behavioural and biochemical changes were significantly prevented by prophylactic treatment of 7-nitroindazole. However, therapeutic intervention of 7-nitroindazole did not show any significant reversal. The results suggests that 7-nitroindazole can be effective in the protection of dementiainduced by intracerebroventricular streptozotocin only when given prophylactically but not therapeutically.

Sleep pattern and learning in knockdown mice with reduced cholinergic neurotransmission

Impaired cholinergic neurotransmission can affect memory formation and influence sleep-wake cycles (SWC). In the present study, we describe the SWC in mice with a deficient vesicular acetylcholine transporter (VAChT) system, previously characterized as presenting reduced acetylcholine release and cognitive and behavioral dysfunctions. Continuous, chronic ECoG and EMG recordings were used to evaluate the SWC pattern during light and dark phases in VAChT knockdown heterozygous (VAChT-KDHET, n=7) and wild-type (WT, n=7) mice. SWC were evaluated for sleep efficiency, total amount and mean duration of slow-wave, intermediate and paradoxical sleep, as well as the number of awakenings from sleep. After recording SWC, contextual fear-conditioning tests were used as an acetylcholine-dependent learning paradigm. The results showed that sleep efficiency in VAChT-KDHET animals was similar to that of WT mice, but that the SWC was more fragmented. Fragmentation was characterized by an increase in the number of awakenings, mainly during intermediate sleep. VAChT-KDHET animals performed poorly in the contextual fear-conditioning paradigm (mean freezing time: 34.4±3.1 and 44.5±3.3 s for WT and VAChT-KDHET animals, respectively), which was followed by a 45% reduction in the number of paradoxical sleep episodes after the training session. Taken together, the results show that reduced cholinergic transmission led to sleep fragmentation and learning impairment. We discuss the results on the basis of cholinergic plasticity and its relevance to sleep homeostasis. We suggest that VAChT-KDHET mice could be a useful model to test cholinergic drugs used to treat sleep dysfunction in neurodegenerative disorders.

Learning and survival memory undergoing a permanent bilateral carotid ligation in rats

PURPOSE: To evaluate the effect of cerebral hypoxia-ischemia on memory and learning survival of rats submitted to permanent bilateral carotid ligation (PBCL). METHODS: Twenty-four survivors of PBCL were evaluated after 30 days with regard to memory and learning using a water survival maze. Twenty-three healthy rats were used as control group. The results were expressed by their means and standard error of the mean (SEM). p<0.05 was used for rejecting the null hypothesis. The study was approved by the Ethics Committee for animal investigation. RESULTS: The mortality rate for the surgery was 44.4%. The latency time to find the survival platform was higher in rats that underwent PBCL (Normal: 10.24 ± 1.85s - Study: 25.30 ± 4.69s - Mann - Whitney p=0.0388). Additionally, the type of swimming and the spatial stability of the studied rats on the survival platform were compromised in these animals. CONCLUSION: The permanent bilateral carotid ligation induces change in the learning and survival memory.

effect of synchronized forced running with chronic stress on short, mid and long- term memory in rats

Impairment of learning and memory processes has been demonstrated by many studies using different stressors. Other reports suggested that exercise has a powerful behavioral intervention to improve cognitive function and brain health. In this research, we investigated protective effects of treadmill running on chronic stress-induced memory deficit in rats. Fifty male Wistar rats were randomly divided into five groups [n=10] as follows: Control [Co], Sham [Sh], Stress [St], Exercise [Ex] and Stress and Exercise [St and Ex] groups. Chronic restraint stress was applied by 6h/day/21days and also treadmill running at a speed 20-21m/min for 1h/day/21days. Memory function was evaluated by the passive avoidance test in different intervals [1, 7 and 21 days] after foot shock. Our results showed that: 1] Although exercise alone showed beneficial effects especially on short and mid-term memory [P<0.05] in comparison with control group, but synchronized exercise with stress had not significantly improved short, mid and long-term memory deficit in stressed rats. 2] Short and mid-term memory deficit was significantly [P<0.05] observed in synchronized exercise with stress and stress groups with respect to normal rats. 3] Memory deficit in synchronized exercise with stress group was nearly similar to stressed rats. 4] Helpful effects of exercise were less than harmful effects of stress when they were associated together. The data correspond to the possibility that although treadmill running alone has helpful effects on learning and memory consolidation, but when it is synchronized with stress there is no significant benefit and protective effects in improvement of memory deficit induced by chronic stress. However, it is has a better effect than no training on memory deficit in stressed rats

Dorsal periaqueductal gray stimulation facilitates anxiety-, but not panic-related, defensive responses in rats tested in the elevated T-maze

The escape response to electrical or chemical stimulation of the dorsal periaqueductal gray matter (DPAG) has been associated with panic attacks. In order to explore the validity of the DPAG stimulation model for the study of panic disorder, we determined if the aversive consequences of the electrical or chemical stimulation of this midbrain area can be detected subsequently in the elevated T-maze. This animal model, derived from the elevated plus-maze, permits the measurement in the same rat of a generalized anxiety- and a panic-related defensive response, i.e., inhibitory avoidance and escape, respectively. Facilitation of inhibitory avoidance, suggesting an anxiogenic effect, was detected in male Wistar rats (200-220 g) tested in the elevated T-maze 30 min after DPAG electrical stimulation (current generated by a sine-wave stimulator, frequency at 60 Hz) or after local microinjection of the GABA A receptor antagonist bicuculline (5 pmol). Previous electrical (5, 15, 30 min, or 24 h before testing) or chemical stimulation of this midbrain area did not affect escape performance in the elevated T-maze or locomotion in an open-field. No change in the two behavioral tasks measured by the elevated T-maze was observed after repetitive (3 trials) electrical stimulation of the DPAG. The results indicate that activation of the DPAG caused a short-lived, but selective, increase in defensive behaviors associated with generalized anxiety.

Effects of bilateral electrolytic lesions of the dorsomedial striatum on motor behavior and spatial learning in rats

The dorsal striatum plays an important role in the control of motor activity and learning processes within the basal ganglia circuitry. Furthermore, recent works have suggested functional differentiation between subregions of the dorsal striatum. The present study examined the effects of bilateral electrolytic lesions of the dorsomedial striatum on motor behavior and learning ability in rats using a series of behavioral tests. 20 male wistar rats were used in the experiment and behavioral assessment were conducted using open field test, rotarod test and 8-arm radial maze. In the open field test, rats with bilateral electrolytic lesions of the dorsomedial striatum showed a normal motor function in the horizontal locomotor activity, while in rearing activity they displayed a statistically significant motor impairment when compared to sham operated group. In the rotarod test, a deficit in motor coordination and acquisition of skilled behavior was observed in rats with bilateral electrolytic lesions of the dorsomedial striatum compared to sham. However, radial maze performance revealed similar capacity in the acquisition of learning task between experimental groups. Our results support the premise of the existence of functional dissociation between the dorsomedial and the dorsolateral regions of the dorsal striatum. In addition, our data suggest that the associative dorsomedial striatum may be as critical in striatum-based motor control

Behavioral investigation of mice with experimental autoimmune encephalomyelitis / Investigação comportamental de camundongos com encefalomielite autoimune experimental

Multiple sclerosis is a neuroinflammatory disease that results in serious neurological disability. Besides physical impairment, behavioral symptoms are also common in patients with multiple sclerosis. Experimental autoimmune encephalomyelitis (EAE) is considered to be a model of multiple sclerosis and mimics the main features of the disease, such as demyelination and motor impairment. In this work, we aimed to study behavioral parameters in animals with EAE using the MOG35-55 model in C57BL/6 mice. We analyzed memory and anxiety in animals using the elevated plus maze, the step down inhibitory avoidance task and the memory recognition test. No differences in any tests were found when comparing controls and animals induced with EAE. Therefore, we conclude that behavioral changes in animals with EAE induced with MOG35-55 are probably subtle or absent.

Esclerose múltipla é uma doença neuroinflamatória que resulta em séria incapacidade neurológica. Além do comprometimento físico, sintomas comportamentais também são comuns em pacientes com esclerose múltipla. A encefalomielite autoimune experimental (EAE) é considerada um modelo de esclerose múltipla e mimetiza as principais caracte-rísticas da doença, como a desmielinização e a fraqueza motora. Neste trabalho, objetivamos estudar parâmetros comportamentais em animais com EAE usando o modelo de MOG35-55 em camundongos C57BL/6. Analisamos memória e ansiedade em animais utilizando o labirinto em cruz elevado, o teste da esquiva inibitória e o teste de memória de reconhecimento. Nenhuma diferença em quaisquer dos testes foi encontrada comparando animais controles e animais induzidos com EAE. Assim, concluímos que alterações comportamentais em animais com EAE induzidos com MOG35-55 são provavelmente sutis ou ausentes.

L-histidine provokes a state-dependent memory retrieval deficit in mice re-exposed to the elevated plus-maze

The effects of L-histidine (LH) on anxiety and memory retrieval were investigated in adult male Swiss Albino mice (weight 30-35 g) using the elevated plus-maze. The test was performed on two consecutive days: trial 1 (T1) and trial 2 (T2). In T1, mice received an intraperitoneal injection of saline (SAL) or LH before the test and were then injected again and retested 24 h later. LH had no effect on anxiety at the dose of 200 mg/kg since there was no difference between the SAL-SAL and LH-LH groups at T1 regarding open-arm entries (OAE) and open-arm time (OAT) (mean ± SEM; OAE: 4.0 ± 0.71, 4.80 ± 1.05; OAT: 40.55 ± 9.90, 51.55 ± 12.10, respectively; P > 0.05, Kruskal-Wallis test), or at the dose of 500 mg/kg (OAE: 5.27 ± 0.73, 4.87 ± 0.66; OAT: 63.93 ± 11.72, 63.58 ± 10.22; P > 0.05, Fisher LSD test). At T2, LH-LH animals did not reduce open-arm activity (OAE and OAT) at the dose of 200 mg/kg (T1: 4.87 ± 0.66, T2: 5.47 ± 1.05; T1: 63.58 ± 10.22; T2: 49.01 ± 8.43 for OAE and OAT, respectively; P > 0.05, Wilcoxon test) or at the dose of 500 mg/kg (T1: 4.80 ± 1.60, T2: 4.70 ± 1.04; T1: 51.55 ± 12.10, T2: 43.88 ± 10.64 for OAE and OAT, respectively; P > 0.05, Fisher LSD test), showing an inability to evoke memory 24 h later. These data suggest that LH does not act on anxiety but does induce a state-dependent memory retrieval deficit in mice.

The anteromedial extrastriate complex is critical for the use of allocentric visual cues and in the retention of the Lashley III maze task in rats

The anteromedial extrastriate complex has been proposed to play an essential role in a spatial orientation system in rats. To gain more information about that possible role, in the present work, two questions were addressed: 1. Are allocentric visual cues relevant for acquisition of the orientation task in the Lashley III maze? 2. Is this integration of allocentric inputs in the anteromedial visual complex relevant in the retention of this test? While a control group of rats was trained keeping the maze in the same position, the experimental group was trained with the maze rotated counterclockwise by 144 degrees from session to session. Control rats reached learning criterion significantly earlier and with less errors than the experimental ones (p<.05). After 11 sessions, rats of both groups received stereotaxic injections of ibotenic acid in the anteromedial complex. In the retention test one week after surgery, the control group, which had been able to learn using egocentric and allocentric visual cues, showed a greater deficit than the experimental animals (p<.05). These results confirm the role of the anteromedial complex in the processing of visuospatial orientation tasks and demonstrate the integration of allocentric visual cues in the solution of those tasks.

Effects of acute and chronic physical exercise and stress on different types of memory in rats

Here we study the effect of acute and chronic physical exercise in a treadmill and of daily stress (because forced exercise involves a degree of stress) during 2 or 8 weeks on different types of memory in male Wistar rats. The memory tests employed were: habituation in an open field, object recognition and spatial learning in the Morris water maze. Daily foot-shock stress enhanced habituation learning after 2 but not after 8 weeks; it hindered both short- (STM) and long-term memory (LTM) of the recognition task at 2 weeks but only STM after 8 weeks and had no effect on spatial learning after either 2 or 8 weeks. Acute but not chronic exercise also enhanced habituation in the open field and hindered STM and LTM in the recognition task. Chronic exercise enhanced one important measure of spatial learning (latency to escape) but not others. Our findings indicate that some care must be taken when interpreting effects of forced exercise on brain parameters since at least part of them may be due to the stress inherent to the training procedure.

Neste trabalho estudamos os efeitos do exercício forçado diário em esteira rolante e da exposição diária ao estresse (porque o exercício forçado envolve um certo grau de estresse) durante 2 ou 8 semanas em diferentes tipos de memória em ratos Wistar machos. Os testes de memória utilizados foram: habituação da exploração em um campo aberto, reconhecimento de objetos, e memória espacial no labirinto aquático de Morris. O estresse diário facilitou a memória de habituação, os animais aprenderam após 2 mas não após 8 semanas; houve prejuízo na memória curta (STM) e de longa duração (LTM) no teste de reconhecimento em 2 semanas, mas somente de STM após 8 semanas; não houve nenhum efeito na memória espacial após 2 ou 8 semanas. O protocolo do exercício facilitou também a memória de habituação no campo aberto após 2 mas não após 8 semanas; prejudicou STM e LTM na tarefa do reconhecimento após 2 mas não após 8 semanas; e facilitou uma medida importante da aprendizagem espacial após 8 semanas (latência de escape), mas não outras medidas. Nossos resultados indicam que algum cuidado deve ser tomado ao se interpretar efeitos de exercício forçado sobre as funções cognitivas, já que uma parte deles, embora não todos, podem ser atribuídos ao estresse inerente ao exercício.

Chlorpheniramine impairs spatial choice learning in telencephalon-ablated fish

This work investigated the effect of the Hj receptor blockade in the forebrain of ablated Carassius auratus in a simple stimulus-response learning task using a T-maze test with positive reinforcement. The goldfish were submitted to surgery for removal of both telencephalic lobes five days before beginning the experiment. A T-shaped glass aquarium was employed, with two feeders located at the extremities of the long arm. One of the two feeders was blocked. The experimental triáis were performed in nine consecutive days. Each fish was individually placed in the short arm and confined there for thirty seconds, then it was allowed to swim through the aquarium to search for food for ten minutes (máximum period). Time to find food was analysed in seconds. Animáis were injected intraperitoneally with chlorpheniramine (CPA) at 16 mg/kg of body weight or saline after every trial, ten minutes after being placed back in the home aquarium. The results show that all the training latencies of the A-SAL group were higher than the latencies of the S-SAL group. The S-SAL group had decreased latencies from the second trial on, while the S-CPA group showed decreased latencies after the fourth trial. The A-SAL group showed reduced latencies after the fifth trial, but the A-CPA group mainteined the latencies throughout the experiment. This suggests that CPA impairs the consolidation of learning both on telencephalon ablated animáis and in sham-operated ones through its action on mesencephalic structures of the brain and/or on the cerebellum in teleost fish.

Neuroprotective effect of ketamine/xylazine on two rat models of Parkinson's disease

There is a great concern in the literature for the development of neuroprotectant drugs to treat Parkinson's disease. Since anesthetic drugs have hyperpolarizing properties, they can possibly act as neuroprotectants. In the present study, we have investigated the neuroprotective effect of a mixture of ketamine (85 mg/kg) and xylazine (3 mg/kg) (K/X) on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 6-hydroxydopamine (6-OHDA) rat models of Parkinson's disease. The bilateral infusion of MPTP (100 æg/side) or 6-OHDA (10 æg/side) into the substantia nigra pars compacta of adult male Wistar rats under thiopental anesthesia caused a modest (~67 percent) or severe (~91 percent) loss of tyrosine hydroxylase-immunostained cells, respectively. On the other hand, an apparent neuroprotective effect was observed when the rats were anesthetized with K/X, infused 5 min before surgery. This treatment caused loss of only 33 percent of the nigral tyrosine hydroxylase-immunostained cells due to the MPTP infusion and 51 percent due to the 6-OHDA infusion. This neuroprotective effect of K/X was also suggested by a less severe reduction of striatal dopamine levels in animals treated with these neurotoxins. In the working memory version of the Morris water maze task, both MPTP- and 6-OHDA-lesioned animals spent nearly 10 s longer to find the hidden platform in the groups where the neurotoxins were infused under thiopental anesthesia, compared to control animals. This amnestic effect was not observed in rats infused with the neurotoxins under K/X anesthesia. These results suggest that drugs with a pharmacological profile similar to that of K/X may be useful to delay the progression of Parkinson's disease.

A link between the hippocampal and the striatal memory systems of the brain

Ao longo dos anos, têm-se identificado dois sistemasprincipais de memória (Squire 1992): o sistema das memórias declarativas, que está sob o controle do hipocampo e estruturas relacionadas do lobo temporal e o sistema das memórias procedimentais ou memórias para hábitos, que está sob controle do corpo estriado e suas conexões. Porém, quase todas as tarefas de aprendizado utilizadas para estudar a formação de memórias em animais envolvem a realização ou a supressão de movimentos e, se bem aprendidas poderia interpretar-se que essas memórias se converteram em um hábito. Sabe-se que os processos envolvidos na formação de memórias mudam na medida em que a associação original torna-se fortalecida através do treinamento. Será que esta mudança também envolve a passagem de um sistema de memória para outro? Aqui nós iremos comentar a respeito 1) do aprendizado reverso na tarefa do labirinto aquático de Morris (LAM), na qual o componente declarativo da tarefa muda, mas o componente procedimental (nadar para um lugar seguro) persiste e precisa ser re-associado a um grupo distinto de dicas espaciais e 2) a respeito de uma série de observações relacionadas com a tarefa de esquiva inibitória que indicam que os sistemas neurais envolvidos no processamento mnemônico mudam na medida em que o aprendizado original é reforçado.

Effect of yoga training on maze learning.

The performance in a maze learning task was assessed in adults of either sex (n = 31) before and after 30 days of yoga training and in an age and gender matched control group of subjects who did not receive training in yoga. Subjects were blind folded and used the dominant hand to trace the path in a wooden pencil maze. At each assessment, subjects were given 5 trials, without a gap between them. Performance was based on the time taken to complete the maze and the number of blind alleys taken. The time and error scores of Trial 1 were significantly less after yoga (two-factor ANOVA, Tukey test). Repeating trials significantly decreased time scores at Trial 5 versus Trial 1, for both groups on Day 1 and for the control group on Day 30. Hence the yoga group showed improved performance in maze tracing at retest 30 days later, which may be related to this group being faster learners and also the effect of yoga itself. Yoga training did not influence maze learning, based on the performance in 5 repeat trials.

Effects of emotional reactivity on inhibitory avoidance in the elevated T-maze

The possibility of the presence of inter-individual emotional differences and the memory performance of rats was examined in the elevated T-maze. Two kinds of aversively motivated behaviors, inhibitory avoidance and escape learning, were measured. Based on the number of trials to achieve a learning criterion, rats were divided into two subgroups with either low or high avoidance reactivity (LAR or HAR, respectively). Retention test avoidance latencies showed that HAR animals had better avoidance memory (Mann-Whitney rank sum test, P = 0.0035). No such differences were found for the escape component of this test. These data suggest that individual emotional differences affect inhibitory avoidance performance, which may help to explain the dispersion of the data observed in other studies using this paradigm