Embryonic macrophages and microglia ablation alter the development of dorsal root ganglion sensory neurons in mouse embryos.

Microglia are known to regulate several aspects of the development of the central nervous system. When microglia colonize the spinal cord, from E11.5 in the mouse embryo, they interact with growing central axons of dorsal root ganglion sensory neurons (SNs), which suggests that they may have some functions in SN development. To address this issue, we analyzed the effects of embryonic macrophage ablation on the early development of SNs using mouse embryo lacking embryonic macrophages (PU.1 knock-out mice) and immune cell ablation. We discovered that, in addition to microglia, embryonic macrophages contact tropomyosin receptor kinase (Trk) C+ SN, TrkB+ SN, and TrkA+ SN peripheral neurites from E11.5. Deprivation of immune cells resulted in an initial reduction of TrkC+ SN and TrkB+ SN populations at E11.5 that was unlikely to be related to an alteration in their developmental cell death (DCD), followed by a transitory increase in their number at E12.5. It also resulted in a reduction of TrkA+ SN number during the developmental period analyzed (E11.5-E15.5), although we did not observe any change in their DCD. Proliferation of cells negative for brain fatty acid-binding protein (BFABP- ), which likely correspond to neuronal progenitors, was increased at E11.5, while their proliferation was decreased at E12.5, which could partly explain the alterations of SN subtype production observed from E11.5. In addition, we observed alterations in the proliferation of glial cell progenitors (BFABP+ cells) in the absence of embryonic macrophages. Our data indicate that embryonic macrophages and microglia ablation alter the development of SNs.

Can coconut oil and treadmill exercise during the critical period of brain development ameliorate stress-related effects on anxiety-like behavior and episodic-like memory in young rats?

OBJECTIVE: Virgin coconut oil (CO) and treadmill exercise have been reported to improve memory performance in young rats. CO has also been associated with antistress properties in young, stressed mice. Therefore, in this study we aimed to investigate whether CO and treadmill exercise could synergistically ameliorate the effects of chronic stress on anxiety-like behavior and episodic-like memory in young rats. METHODS: The rats received CO and were exercised (Ex) from the 15th to the 45th day of life. The animals were supplemented with CO (10 mL kg-1 day-1) or a vehicle (V, distilled water and 0.009% Cremophor) via oral gavage. The Ex animals were placed for 30 min day-1 on a treadmill, with the speed gradually increasing from the first week to the last. From the 46th to the 54th postnatal day, with the exception of the 51st and the 52nd day, all rats were subjected to restraint stress. Afterwards, all rats underwent the open-field test to evaluate locomotor activity and anxiety-like behavior. To evaluate episodic-like memory, all animals underwent tests to recognize object identity and special location. Lastly, lipid profile and murinometric parameters were evaluated. RESULTS: A two-way ANOVA test followed by a Tukey test demonstrated that the CO&Ex group explored more of the unprotected central area of the OFT (27.04 ± 4.03 s, p < 0.01), when compared to the control group (15.36 ± 2.54 s). CO&Ex spent more time exploring the novel location of the object (71.62 ± 3.04%, p < 0.01), when compared to the control group (58.62 ± 2.48%). DISCUSSION: CO and exercise during lactation can ameliorate the effects of stress on anxiety-like behavior and episodic-like memory in young rats.

Do the accelerating actions of tianeptine and l-arginine on cortical spreading depression interact? An electrophysiological analysis in young and adult rats.

In the rat, we previously demonstrated that serotonin-enhancing drugs impair cortical spreading depression (CSD) and that l-arginine (arginine) treatment enhances CSD. Here, we investigated the interaction between topical application of the serotonin uptake enhancer tianeptine and systemic arginine administration on CSD. From postnatal day 7-28, female Wistar rats (n=40) received by gavage 300mg/Kg/day arginine (n=20) or water (n=20). Half of the arginine- or water-treated rats underwent CSD recording at 30-40days of age (young), while the other half was recorded at 90-120days (adult). Following baseline recording (four episodes of CSD), we applied tianeptine solution (10mg/ml) to a rectangular portion of the intact dura mater for 10-min and then elicited CSD. This procedure was repeated three times. Compared to baseline values, CSD velocities and amplitudes following tianeptine application increased, and CSD duration decreased significantly (p<0.05) in both young and adult rats, regardless of treatment group. CSD acceleration caused by systemic treatment with arginine is in agreement with previous findings. Topical cortical application of tianeptine replicated the effect of systemic application, suggesting a cortically based mechanism for tianeptine's action. However, the absence of interaction between arginine and tianeptine treatments suggests that they probably act through separate mechanisms.

Interferência da L-arginina e do exercício físico sobre a morfologia do músculo estriado esquelético em ratos jovens / L-arginine and physical exercise interference on the morphology of the skeletal muscle in young rats

INTRODUÇÃO: O exercício físico pode promover alterações anatomofisiológicas no músculo estriado esquelético e a ingestão do aminoácido L-arginina pode influenciar na morfometria da fibra muscular esquelética. OBJETIVO: Analisar a influência da L-arginina associada ao exercício físico sobre a fibra muscular esquelética. MÉTODOS: Foram utilizados 24 ratos da linhagem Wistar. Aos sete dias de vida, esses animais foram divididos em dois grupos: tratados com L-arginina (grupo-Ar; 300 mg/kg/dia) e tratados com volume equivalente do veículo - água destilada (grupo-Ag; controle). A L-arginina ou a água foi administrada diariamente por gavagem. Aos 15 dias de idade, os animais dos grupos Ar e Ag foram subdivididos de acordo com a condição de exercício físico a que foram submetidos: exercitados em esteira (grupo E) e não exercitado (grupo N). O exercício foi realizado em esteira (ET 2000 Insight) cinco dias por semana com duração diária de 30 minutos. Os grupos foram assim distribuídos (n = 6): AgN, AgE, ArN e ArE. Ao atingirem a idade de 35-45 dias de vida, os animais foram pesados, sacrificados e retidado o músculo gastrocnêmio. Este foi medido, pesado e processado para análise histológica. As imagens do músculo foram capturadas na objetiva de 100x para cálculo do diâmetro médio da fibra muscular. Os dados foram expressos na forma de média ± desvio padrão, analisados através do programa SPSS. Foram utilizados os testes de Shapiro-Wilk, ANOVA one way e teste de Tukey (p < 0,05). RESULTADOS: Não houve diferença entre os grupos, quanto ao peso corporal do animal e ao peso do músculo gastrocnêmio. No entanto, o grupo ArN apresentou diâmetro médio maior significativamente quando comparado aos dos demais grupos. CONCLUSÃO: Isto sugere que a L-arginina, em animais que não realizaram o exercício físico, promove hipertrofia muscular, enquanto que o exercício realizado não foi capaz de promover aumento do diâmetro da fibra muscular.

INTRODUCTION: Exercise and amino acid L-Arginine can promote anatomical and physiological changes in skeletal muscle. OBJECTIVE: The objective of this work was to analise the influence of L-arginine associated with the exercise in skeletal muscle fibers. METHODS: To carry out our research, 24 male Wistar rats divided into 4 groups according to the administration of Arginine and physical exercise wer used. The experimental groups were distributed as follows: Arginine-Exercise (AE, n = 6), Arginine-Not Exercised (AN, n = 6), Water-Exercise (WE, n = 6) and Water-Not Exercised (WN, n = 6). The amino acid L-Arginine was administered via orogastric intubation, at dose of 300mg/kg, daily from the 7th to 35th days of life of the animal. The exercise was performed on motorized treadmill for 30 minutes/day, 5 times a week, from 15th to 35th days of life of the animal. At the age of 35-45 days, the animals were weighed and sacrificed in order to collect the gastrocnemius muscle. The gastrocnemius muscle was measured, weighed and processed for histological analysis. The muscle's images were taken in order to calculate the mean diameter of the muscle fiber. Data were expressed as mean ± standard deviation and analyzed using SPSS. The Shapiro-Wilk, one-way ANOVA and Tukey's tests (p <0.05) were applied. RESULTS: Concerning body weight and gastrocnemius weight, there was no significant difference when all the experimental groups were compared. However, the AN group presented the highest mean diameter when compared to the other groups. CONCLUSION: This fact suggests that orogastric administration of Arginine offered to the animals that were not exercised, promotes muscle hypertrophy. On the other hand, exercise by itself did not lead to increase in mean diameter of skeletal muscle.

Tianeptine facilitates spreading depression in well-nourished and early-malnourished adult rats.

Nutritional status during development can modify the brain's electrophysiological properties and its response to drugs that reduce the serotonin availability in the synaptic cleft. Here we used cortical spreading depression (CSD) in the rat as a neurophysiological parameter to investigate the interaction between nutritional status and treatment with tianeptine, a serotonin uptake enhancer. From postnatal day 2 to 24, well-nourished and early-malnourished rat pups were s.c. injected with tianeptine (5 or 10mg/kg; 10 ml/kg) or equivalent volume of saline solution (control group). When the animals were 25-30 days old, CSD was recorded on the brain cortical surface. In the well-nourished rats, but not in the malnourished group, systemic tianeptine dose-dependently increased the CSD propagation velocity, with 10mg/kg producing a significant (P<0.05) effect. An experiment in adult rats showed that cortical topical application of tianeptine solutions (5mg/ml, 10mg/ml, and 20mg/ml) increased the CSD propagation in both the well-nourished and early-malnourished conditions. In well-nourished animals, 0.5mg/ml topical tianeptine did not affect CSD propagation, and 2mg/ml produced a small, but significant CSD acceleration. Our results indicate a facilitating action of tianeptine on CSD propagation, probably via tianeptine's pharmacological action on the serotonin system. These findings support previous data suggesting an antagonistic role of the serotoninergic system on CSD.

Differential effects of physical exercise and L-arginine on cortical spreading depression in developing rats.

OBJECTIVE: We investigated the effect of early-in-life administration of L-arginine, combined with physical exercise, on cortical spreading depression (CSD) in young and adult rats. METHODS: L-arginine (300 mg/kg/day, n = 40) or distilled water (vehicle, n = 40) was given to the rats during postnatal days 7-35 by gavage. Physical exercise (treadmill) was carried out during postnatal days 15-35 in half of the animals in each gavage condition described above. The other half (non-exercised) was used for comparison. When the animals reached 35-45 days (young groups) or 90-120 days of age (adult) CSD was recorded on two cortical points during 4 hours and CSD propagation velocity was calculated. RESULTS: L-arginine-treated + exercised rats had increased body weight, but not brain weight, in adult age compared to L-arginine + non-exercised ones (P < 0.05). In both young and adult animals, L-arginine increased, whereas exercise decreased the CSD propagation velocity. Analysis of variance revealed a significant interaction between gavage treatment and age (P < 0.001), and also between gavage treatment and exercise (P = 0.004), but not between age and exercise. An additional control group of young rats, treated with 300 mg/kg of L-histidine, presented CSD velocities comparable to the corresponding water-treated controls, suggesting that the CSD acceleration seen in the L-arginine group was an L-arginine-specific effect, rather than an effect due to a non-specific amino acid imbalance. DISCUSSION: L-arginine and exercise affect CSD differentially (L-arginine accelerated, while exercise decelerated CSD), and both effects did interact. Probably, they depend on developmental plasticity changes associated with the treatments.

L-glutamine supplementation during the lactation period facilitates cortical spreading depression in well-nourished and early-malnourished rats.

AIMS: Glutamine (Gln) participates in the so-called "brain glutamine-glutamate cycle" and therefore it is likely to influence brain excitability. Here we investigated, in weaned well-nourished and early-malnourished rats, the effects of previous Gln oral supplementation, during the brain development period, on cortical spreading depression (CSD), an excitability-related brain phenomenon. MAIN METHODS: Male Wistar (W) suckling rat pups, well-nourished (litters with 6 pups) and malnourished (M) during lactation (by increasing the litters to 12 pups), received Gln (500 mg/kg/day) by gavage during postnatal days 7 to 27. At 30-40 days of life, they were submitted to a cortical spreading depression (CSD) recording session during 4 h, on 2 cortical parietal points of the right hemisphere. CSD velocity propagation was calculated from the time required for a CSD wave to cross the inter-electrode distance. KEY FINDINGS: In both nutritional condition, Gln rats presented higher (p<0.05) CSD propagation velocities (W-Gln, 4.22+/-0.23; M-Gln, 4.51+/-0.27 mm/min), as compared to water-treated controls (W-Wa, 3.77+/-0.21; M-Wa, 4.15+/-0.18 mm/min). This water control group did not differ from a naive control group that was not submitted to the gavage procedure. A fourth group, treated with a "placebo amino acid" (glycine), also displayed CSD velocities in the control range. SIGNIFICANCE: The results indicate that Gln supplementation during brain development facilitates cortical spreading depression propagation, as judged by the higher CSD velocities, and this effect is not abolished by malnutrition. Data support the idea of Gln-related changes in brain excitability, during neural development.