Aerobic exercise upregulates the BDNF-Serotonin systems and improves the cognitive function in rats.

Aerobic exercise (AE) benefits brain health and behavior. Serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) are known to mediate and shape cognitive processes. Both systems share some actions: BDNF is involved in the maturation and function of 5-HT neurons. In turn, 5-HT is involved in neuroplasticity phenomena mediated by BDNF and stimulated by exercise. The aim of this work was to study the long-term effects of AE on BDNF- 5-HT systems and cognitive function in rats at different ages. A lifelong moderate-intensity aerobic training program was designed, in which aerobically exercised (E) and sedentary control (C) rats were studied at middle (8 months) and old age (18 months) by means of biochemical, immunohistochemical and behavioral assays. The levels and expression of BDNF, 5-HT, serotonin transporter (SERT) and 5-HT1A receptor were determined in selected brain areas involved in memory and learning. Immunopositive cells to neuronal nuclear protein (NeuN) in the hippocampus CA1 area were also quantified. The cognitive function was evaluated by the object recognition test (ORT). Results indicate that AE enhanced spatial and non-spatial memory systems, modulated by age. This outcome temporarily correlated with a significant upregulation of cortical, hippocampal and striatal BDNF levels in parallel with an increase in the number of hippocampal CA1-mature neurons. AE also increased brain and raphe 5-HT levels, as well as the expression of SERT and 5-HT1A receptor in the cortex and hippocampus. Old AE rats showed a highly conserved response, indicating a remarkable protective effect of exercise on both systems. In summary, lifelong AE positively affects BDNF-5-HT systems, improves cognitive function and protects the brain against the deleterious effects of sedentary life and aging.

Dinámica de la córticoangiogénesis en el sistema nervioso central / Dinamics of the cortico-angiogenesis in the central nervous system

This study analyzes the temporal-spatial correlation between angio-and corticogenesis in the developing chick optic tectum (OT) by means of NADPH-diaphorase and immunolabeling methods. Qualitative and quantitative parameters were used to analyze a new vessels formation and growth of preexisting ones as a function of time and space...

The role of nitric oxide on matrix metalloproteinase 2 (MMP2) and MMP9 in placenta and fetus from diabetic rats.

Matrix metalloproteinases (MMPs) play an important role in tissue remodeling that accompanies the rapid growth, differentiation, and structural changes of the placenta and several fetal organs. In the present study, we investigated whether the diabetic maternal environment may alter the regulatory homeostasis exerted by nitric oxide (NO) on MMPs activity in the feto-placental unit from rats at midgestation. We found that NADPH-diaphorase activity, which reflects the distribution and activity of NO synthases (NOS), was increased in both placenta and fetuses from diabetic rats when compared with controls. In addition, while a NO donor enhanced MMP2 and MMP9 activities, a NOS inhibitor reduced these activities in the maternal side of the placenta from control rats. This regulatory effect of NO was only observed on MMP9 in the diabetic group. On the other hand, the NO donor did not modify MMP2 and MMP9 activities, while the NOS inhibitor reduced MMP9 activity in the fetal side of both control and diabetic placentas. In the fetuses, MMP2 was enhanced by the NO donor and reduced by the NO inhibitor in both fetuses from control and diabetic rats. Overall, this study demonstrates that NO is able to modulate the activation of MMPs in the feto-placental unit, and provides supportive evidence that increased NOS activity leads to NO overproduction in the feto-placental unit from diabetic rats, an alteration closely related to the observed MMPs dysregulation that may have profound implications in the formation and function of the placenta and the fetal organs.

Nitric oxide increases in the rat retina after continuous illumination.

Continuous illumination (CI) of the retina induces an oxidative stress followed by the degeneration of photoreceptors. This phenomenon may be partially related to the excessive production of nitric oxide (NO). In order to confirm this hypothesis, the aims of this work are to determine NO levels during the illumination of the retina by electron paramagnetic resonance (EPR), and if an increase of NO is found, to characterize the NOS isoform responsible of the increment by using Western blot. Sprague-Dawley rats were continuously illuminated with white light (12,000 lux) for 2, 24, 48 h, 5 and 7 days while control rats were maintained at light/dark cycles of 12/12 h. Using EPR, an increase of NO signal was observed in the light exposed retinas peaking at 24 h of CI. Western blot analysis showed the expression of iNOS in the illuminated retinas with a peak after 24 h of CI, but did not show significant differences of nNOS among illuminated and control retinas. In summary, there is an increase of NO during CI. Further studies will reveal whether this mechanism is responsible for light induced photoreceptor degeneration.

Increased matrix metalloproteinases 2 and 9 in placenta of diabetic rats at midgestation.

Matrix metalloproteinases (MMPs) are involved in placental remodelling throughout pregnancy. Diabetes mellitus induces alterations in tissue production of NO, a regulator of MMPs activity. The present work evaluates placental and fetal MMPs and NO levels during midpregnancy in neonatal streptozotocin-induced diabetic rats. MMP-2 and MMP-9 immunolabelling was increased both in the labyrinth zone (p<0.001) and in the giant trophoblast cells of the junctional zone (p<0.001) from diabetic placenta, when compared with controls. Also MMP-2 (p<0.01) and MMP-9 (p<0.005) activities were increased in both maternal and fetal sides of diabetic placenta when related to controls. In both sides of the diabetic placenta, nitrate/nitrite concentrations (which indicate NO production) were higher than in controls (p<0.05). An intense immunostaining for nitrotyrosine, indicating peroxynitrite-induced damage, was found in both labyrinth (p<0.001) and junctional zones (p<0.001) of diabetic placenta. Enhanced MMP-2 activity (p<0.05) and NO production were also higher in the fetuses from diabetic rats when compared to controls (p<0.005). These findings demonstrate alterations in MMPs and NO in the feto-placental unit of diabetic rats, anomalies that are likely to be involved in the developmental alterations induced by maternal diabetes.

Expression of GAP-43 in the retina of rats following protracted illumination.

Distribution of GAP-43 was studied in the retinas of rats after continuous illumination followed by different darkness periods. GAP-43 immunoreactivity was maximum in regenerating outer photoreceptor segments of rats kept in total darkness for 10 days, while in the inner plexiform layer, immunoreactivity was maximum immediately after illumination. Changes in GAP-43 expression could participate in retinal repair/regeneration after light-induced damage.

Increased nitric oxide synthase activity in a model of serotonin depletion.

Serotonin (5HT) containing cell bodies are localized in mesencephalic and rhombencephalic raphe nuclei. It has been proposed that 5HT could be involved in neuronal development and plasticity. In the central nervous system, nitric oxide (NO) has been postulated as a neurotransmitter and neuromodulator, and has been implicated in neurotoxicity as well as in neuroprotection. Using the nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) technique, NO synthesizing neurons were described in raphe nuclei. By immunohistochemistry, nitric oxide synthase (NOS) was found colocalized with 5HT in some dorsal raphe nucleus (DRN) neurons. In a model of inhibition of 5HT synthesis produced by daily administration of parachlorophenilalanine during 14 days, we have studied the relationship between 5HT and NO systems after 5HT depletion by histochemical and immunocytochemical methods. After the treatment, we observed an important reduction of 5HT immunostaining in the DRN and enhanced NOS activity demonstrated by NADPH-d technique, especially in the dorsomedial and ventromedial subgroups. In spite of the increased NOS activity, we could not observe significant changes in the NOS-immunoreactivity in the DRN after 5HT depletion. These results could indicate that 5HT depletion is concomitant with changes in NOS activity without affecting NOS expression in the DRN.

Immuno and cytochemical localization of Trypanosoma cruzi nitric oxide synthase

The localization and subcellular distribution of Trypanosoma cruzi nitric oxide synthase was investigated in epimastigote cells by immunocytochemistry at electron and light microscope level, using a polyclonal antibody to neuronal nitric oxide synthase, and also, at light microscope level, by the nicotinamide adenine dinucleotide phosphate-diaphorase histochemical reaction. The immunoreactivity was ultrastructurally localized by electron microscopy in the inner surface of cell membranes and in free cytosolic clusters in the body, flagellum and apical extreme. Light microscopy showed that immunoprecipitates, specific for the Trypanosoma cruzi nitric oxide synthase, co-localized with the formazan precipitates generated by the diaphorase reaction in the same areas identified by electron microscopy. These results, taken together with previous finding from our laboratory could help to explain the involvement of the nitric oxide transduction pathway in T. cruzi epimastigote motility.

Immuno and cytochemical localization of Trypanosoma cruzi nitric oxide synthase

The localization and subcellular distribution of Trypanosoma cruzi nitric oxide synthase was investigated in epimastigote cells by immunocytochemistry at electron and light microscope level, using a polyclonal antibody to neuronal nitric oxide synthase, and also, at light microscope level, by the nicotinamide adenine dinucleotide phosphate-diaphorase histochemical reaction. The immunoreactivity was ultrastructurally localized by electron microscopy in the inner surface of cell membranes and in free cytosolic clusters in the body, flagellum and apical extreme. Light microscopy showed that immunoprecipitates, specific for the Trypanosoma cruzi nitric oxide synthase, co-localized with the formazan precipitates generated by the diaphorase reaction in the same areas identified by electron microscopy. These results, taken together with previous finding from our laboratory could help to explain the involvement of the nitric oxide transduction pathway in T. cruzi epimastigote motility.(AU)

Development of nitric oxide neurons in the chick embryo retina.

Nitric oxide (NO) is a gas involved in neurotransmission in the central nervous system (CNS) and in vertebrate retinas. This paper describes five types of nitrergic neurons in developing and adult chick retina using the nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) reaction. Three of them, nitrergic types 1, 2 and 3, were observed in the inner nuclear layer, while nitrergic type 4 was observed in the ganglion cell layer; nitrergic type 5 were the retinal photoreceptors. Cell processes formed four nitrergic networks, which could be observed in the inner plexiform layer (IPL), at sublayers 1, 3a, 3b and 4. Another nitrergic network was observed in the outer plexiform layer (OPL). From hatching, the dendritic branches were completely developed in the IPL and in the OPL, forming the mentioned networks. Current evidence suggests that NO is coexpressed with other neurotransmitters in neurons of the CNS. Double-staining procedures, using NADPHd and 5HT immunohistochemistry in chicken retina, in a sequential or in an alternative manner, did not reveal the coexistence of these two neurotransmitters in the same neurons, but their networks matched in sublayers 1 and 4 of the IPL.

Immuno and cytochemical localization of Trypanosoma cruzi nitric oxide synthase.

The localization and subcellular distribution of Trypanosoma cruzi nitric oxide synthase was investigated in epimastigote cells by immunocytochemistry at electron and light microscope level, using a polyclonal antibody to neuronal nitric oxide synthase, and also, at light microscope level, by the nicotinamide adenine dinucleotide phosphate-diaphorase histochemical reaction. The immunoreactivity was ultrastructurally localized by electron microscopy in the inner surface of cell membranes and in free cytosolic clusters in the body, flagellum and apical extreme. Light microscopy showed that immunoprecipitates, specific for the Trypanosoma cruzi nitric oxide synthase, co-localized with the formazan precipitates generated by the diaphorase reaction in the same areas identified by electron microscopy. These results, taken together with previous finding from our laboratory could help to explain the involvement of the nitric oxide transduction pathway in T. cruzi epimastigote motility.

Immuno and cytochemical localization of Trypanosoma cruzi nitric oxide synthase.

The localization and subcellular distribution of Trypanosoma cruzi nitric oxide synthase was investigated in epimastigote cells by immunocytochemistry at electron and light microscope level, using a polyclonal antibody to neuronal nitric oxide synthase, and also, at light microscope level, by the nicotinamide adenine dinucleotide phosphate-diaphorase histochemical reaction. The immunoreactivity was ultrastructurally localized by electron microscopy in the inner surface of cell membranes and in free cytosolic clusters in the body, flagellum and apical extreme. Light microscopy showed that immunoprecipitates, specific for the Trypanosoma cruzi nitric oxide synthase, co-localized with the formazan precipitates generated by the diaphorase reaction in the same areas identified by electron microscopy. These results, taken together with previous finding from our laboratory could help to explain the involvement of the nitric oxide transduction pathway in T. cruzi epimastigote motility.

Atrial natriuretic peptide effect on NADPH-diaphorase in rat intestinal tract.

Histochemical reaction of NADPH-diaphorase (NOS-NADPH-d) was used to identify NO synthesis. A 30-min 0.1 microg microg/kg/min ANP infusion led to about a 10% and 35% increase in small and large intestine enterocytes stain respectively. This increase was abolished by a bolus of 1 mg/kg L-NAME before ANP infusion in small intestine, and partially abolished it in colon. Incubation of small and large intestine with 0.5 microM ANP increased stain at about 20%. In both tissues the preincubation with 0.1 mM L-NAME abolished the ANP effect. Incubation with 0.1 mM 8-Br-cGMP enhanced staining about 70% and 30% in small and large intestine respectively. Our results show that ANP enhances NOS-NADPH-d activity, suggesting that ANP stimulates NO synthase in enterocytes by L-arginine-NO pathway. 8-Br-cGMP mimicked the effect of ANP described above. Therefore, the guanylate cyclase-coupled natriuretic receptors, NPR-A and NPR-B, probably mediate this ANP effect.

GABA release mechanism in the golden hamster retina.

High K+ medium and glutamate elicited a significant [3H]-GABA release in the golden hamster retina. High K+ -induced GABA release was largely calcium-dependent, while the effect of glutamate was Ca2+ -independent. After replacing Na+ by Li+, glutamate-evoked [3H]-GABA release was abolished, while high K+ -evoked release remained unchanged. The effect of glutamate was completely blocked by DNQX but not by APV. Furthermore, kainate induced [3H]-GABA release, whereas NMDA was ineffective. Assessment of endogenous GABA efflux further confirmed results obtained for [3H]-GABA. GABA-like immunoreactivity was observed in amacrine cells, in neurons localized in ganglion cell layer, as well as in fibers and terminals at the inner plexiform layer. In addition a few horizontal cells showed GABA-like immunolabeling. The present results suggest the existence of at least two pools of GABA in the hamster retina, compatible with both vesicular and carrier-mediated mechanisms of transmitter release, being the amacrine cells the main gabaergic source in this tissue.

Serotonergic ependymal fibres in rat and monkey: light and electron microscopic immunocytochemical study

The distribution of serotonin (5HT) immunoreactive fibres in the ependymal epithelium of aqueductus cerebri in adult rat and monkey was studied by means of immunocytochemical methods using specific antibodies against 5HT. Light microscopic examination of immunostained coronal sections of mesencephalon showed, in tryptophan and pargylin pretreated animals, abundant serotonergic fibres distributed along the ependymal cells of the aqueduct, forming supraependymal and subependymal plexi. Serotonin fibres lying either supraependymally or ending freely in the aqueduct lumen contributed to the formation of a rich 5HT containing network on the ependymal surface. Electron microscope images showed dense 5HT-immunoreactive (5HT-IR) profiles with ultrastructural characteristics of axon terminals ending on the ependymal cells. Dense diaminobenzidine (DAB) deposits were found in the axoplasm, on outer mitochondrial surface and in vesicles. No synaptic contacts were observed between 5HT-IR terminals and ependymal cells. Unstained microvilli and cilia were also observed in the aqueduct lumen. Serotonin immunoreactivity disappeared from ependymal fibres in animals treated with parachlorophenylalanine, an inhibitor of 5HT synthesis. 5HT containing fibres described in this paper may be the source of 5HT and its metabolite 5-hydroxyindoleacetic acid (5HIAA) found in cerebrospinal fluid (CSF) and of clinical relevance in some psychiatric conditions such as depression, suicidal attempts, etc

Distribution of GABA in the golden hamster retina: An immunocytochemical study

Distribution of the inhibitory neurotransmitter GABA was studied in the golden hamster retina using immunocytochemistry at cellular and subcellular levels. GABA-immunoreactivity was observed in somata of amacrine, displaced amacrine and horizontal cells. GABA immunoreactive fibers were abundant in the inner plexiform layer. Ultrastructural analysis exhibited dense GABA-immunoreactive deposits in amacrine cell somata, processes and terminals. Immunolabelling was also observed in the cytoplasm of horizontal or interplexiform cells and displaced amacrine cells. In every case DAB deposits were observed in the cytosolic compartment, attached to the inner surface of cell membranes and to outer mitochondrial membranes. Immunolabeled terminals predominated in the inner plexiform layer and immunoprecipitates were also observed attached to the outer face of vesicle membranes as well as completely filling synaptic vesicles. Both clear and dense core vesicles were observed. The present results are similar to those obtained in other mammalian species showing GABA immunoreactivity in amacrine, displaced amacrine and horizontal cells

Serotonergic ependymal fibres in rat and monkey: light and electron microscopic immunocytochemical study

The distribution of serotonin (5HT) immunoreactive fibres in the ependymal epithelium of aqueductus cerebri in adult rat and monkey was studied by means of immunocytochemical methods using specific antibodies against 5HT. Light microscopic examination of immunostained coronal sections of mesencephalon showed, in tryptophan and pargylin pretreated animals, abundant serotonergic fibres distributed along the ependymal cells of the aqueduct, forming supraependymal and subependymal plexi. Serotonin fibres lying either supraependymally or ending freely in the aqueduct lumen contributed to the formation of a rich 5HT containing network on the ependymal surface. Electron microscope images showed dense 5HT-immunoreactive (5HT-IR) profiles with ultrastructural characteristics of axon terminals ending on the ependymal cells. Dense diaminobenzidine (DAB) deposits were found in the axoplasm, on outer mitochondrial surface and in vesicles. No synaptic contacts were observed between 5HT-IR terminals and ependymal cells. Unstained microvilli and cilia were also observed in the aqueduct lumen. Serotonin immunoreactivity disappeared from ependymal fibres in animals treated with parachlorophenylalanine, an inhibitor of 5HT synthesis. 5HT containing fibres described in this paper may be the source of 5HT and its metabolite 5-hydroxyindoleacetic acid (5HIAA) found in cerebrospinal fluid (CSF) and of clinical relevance in some psychiatric conditions such as depression, suicidal attempts, etc

Distribution of GABA in the golden hamster retina: An immunocytochemical study

Distribution of the inhibitory neurotransmitter GABA was studied in the golden hamster retina using immunocytochemistry at cellular and subcellular levels. GABA-immunoreactivity was observed in somata of amacrine, displaced amacrine and horizontal cells. GABA immunoreactive fibers were abundant in the inner plexiform layer. Ultrastructural analysis exhibited dense GABA-immunoreactive deposits in amacrine cell somata, processes and terminals. Immunolabelling was also observed in the cytoplasm of horizontal or interplexiform cells and displaced amacrine cells. In every case DAB deposits were observed in the cytosolic compartment, attached to the inner surface of cell membranes and to outer mitochondrial membranes. Immunolabeled terminals predominated in the inner plexiform layer and immunoprecipitates were also observed attached to the outer face of vesicle membranes as well as completely filling synaptic vesicles. Both clear and dense core vesicles were observed. The present results are similar to those obtained in other mammalian species showing GABA immunoreactivity in amacrine, displaced amacrine and horizontal cells

Distribution of GABA in the golden hamster retina. An immunocytochemical study.

Distribution of the inhibitory neurotransmitter GABA was studied in the golden hamster retina using immunocytochemistry at cellular and subcellular levels. GABA-immunoreactivity was observed in somata of amacrine, displaced amacrine and horizontal cells. GABA immunoreactive fibers were abundant in the inner plexiform layer. Ultrastructural analysis exhibited dense GABA-immunoreactive deposits in amacrine cell somata, processes and terminals. Immunolabelling was also observed in the cytoplasm of horizontal or interplexiform cells and displaced amacrine cells. In every case DAB deposits were observed in the cytosolic compartment, attached to the inner surface of cell membranes and to outer mitochondrial membranes. Immunolabeled terminals predominated in the inner plexiform layer and immunoprecipitates were also observed attached to the outer face of vesicle membranes as well as completely filling synaptic vesicles. Both clear and dense core vesicles were observed. The present results are similar to those obtained in other mammalian species showing GABA immunoreactivity in amacrine, displaced amacrine and horizontal cells.

Serotonergic ependymal fibres in rat and monkey: light and electron microscopic immunocytochemical study.

The distribution of serotonin (5HT) immunoreactive fibres in the ependymal epithelium of aqueductus cerebri in adult rat and monkey was studied by means of immunocytochemical methods using specific antibodies against 5HT. Light microscopic examination of immunostained coronal sections of mesencephalon showed, in tryptophan and pargylin pretreated animals, abundant serotonergic fibres distributed along the ependymal cells of the aqueduct, forming supraependymal and subependymal plexi. Serotonin fibres lying either supraependymally or ending freely in the aqueduct lumen contributed to the formation of a rich 5HT containing network on the ependymal surface. Electron microscope images showed dense 5HT-immunoreactive (5HT-IR) profiles with ultrastructural characteristics of axon terminals ending on the ependymal cells. Dense diaminobenzidine (DAB) deposits were found in the axoplasm, on outer mitochondrial surface and in vesicles. No synaptic contacts were observed between 5HT-IR terminals and ependymal cells. Unstained microvilli and cilia were also observed in the aqueduct lumen. Serotonin immunoreactivity disappeared from ependymal fibres in animals treated with parachlorophenylalanine, an inhibitor of 5HT synthesis. 5HT containing fibres described in this paper may be the source of 5HT and its metabolite 5-hydroxyindoleacetic acid (5HIAA) found in cerebrospinal fluid (CSF) and of clinical relevance in some psychiatric conditions such as depression, suicidal attempts, etc.