RESUMEN
OBJECTIVE: T1-weighted MRI images are commonly used for volumetric assessment of brain structures. Magnetization prepared 2 rapid gradient echo (MP2RAGE) sequence offers superior gray (GM) and white matter (WM) contrast. This study aimed to quantitatively assess the agreement of whole brain tissue and deep GM (DGM) volumes obtained from MP2RAGE compared to the widely used MP-RAGE sequence. METHODS: Twenty-nine healthy participants were included in this study. All subjects underwent a 3T MRI scan acquiring high-resolution 3D MP-RAGE and MP2RAGE images. Twelve participants were re-scanned after one year. The whole brain, as well as DGM segmentation, was performed using CAT12, volBrain, and FSL-FAST automatic segmentation tools based on the acquired images. Finally, contrast-to-noise ratio between WM and GM (CNRWG), the agreement between the obtained tissue volumes, as well as scan-rescan variability of both sequences were explored. RESULTS: Significantly higher CNRWG was detected in MP2RAGE vs. MP-RAGE (Mean ± SD = 0.97 ± 0.04 vs. 0.8 ± 0.1 respectively; p<0.0001). Significantly higher total brain GM, and lower cerebrospinal fluid volumes were obtained from MP2RAGE vs. MP-RAGE based on all segmentation methods (p<0.05 in all cases). Whole-brain voxel-wise comparisons revealed higher GM tissue probability in the thalamus, putamen, caudate, lingual gyrus, and precentral gyrus based on MP2RAGE compared with MP-RAGE. Moreover, significantly higher WM probability was observed in the cerebellum, corpus callosum, and frontal-and-temporal regions in MP2RAGE vs. MP-RAGE. Finally, MP2RAGE showed a higher mean percentage of change in total brain GM compared to MP-RAGE. On the other hand, MP-RAGE demonstrated a higher overtime percentage of change in WM and DGM volumes compared to MP2RAGE. CONCLUSIONS: Due to its higher CNR, MP2RAGE resulted in reproducible brain tissue segmentation, and thus is a recommended method for volumetric imaging biomarkers for the monitoring of neurological diseases.
Asunto(s)
Encéfalo/diagnóstico por imagen , Sustancia Gris/diagnóstico por imagen , Imagen por Resonancia Magnética , Sustancia Blanca/diagnóstico por imagen , Amígdala del Cerebelo/diagnóstico por imagen , Amígdala del Cerebelo/ultraestructura , Encéfalo/ultraestructura , Mapeo Encefálico , Sistema Nervioso Central/diagnóstico por imagen , Sistema Nervioso Central/ultraestructura , Líquido Cefalorraquídeo/metabolismo , Femenino , Sustancia Gris/ultraestructura , Voluntarios Sanos , Hipocampo/diagnóstico por imagen , Hipocampo/ultraestructura , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Masculino , Persona de Mediana Edad , Manejo de Especímenes , Tálamo/diagnóstico por imagen , Tálamo/ultraestructura , Sustancia Blanca/ultraestructuraRESUMEN
R. vomitoria (RV), a plant used locally in the management of psychotic disorders, adversely affects the brain functionally and structurally. Such adverse reports, as well as the potential of G. latifolium (GL) to mitigate same warranted this investigation on the combined actions of RV and GL on the amygdala. Twenty-four male CD-1 mice weighing 22-27 g were divided into four groups (n = 6): Control (20 ml/kg body weight, b.w., distilled water); RV (200 mg/kg b.w.), GL (200 mg/kg b.w.), and RV (200 mg/kg b.w.) and GL (200 mg/kg b.w.) combination orally, and for 14 days. On day 15, the elevated-plus maze test was carried out and the animals sacrificed, and processed for histological and immunohistochemical studies. Neurobehavioural results showed significant decrease (p[Formula: see text] 0.001) in stretch-attend posture, time spent in closed arms, grooming frequency, protected head-dip, as well as significantly (p [Formula: see text] 0.01) increased time spent in the open arms and unprotected head-dips of the RV group. The combined RV and GL groups showed no such differences in these parameters. Histologically, the amygdala showed hypertrophied cells, with pyknotic and karyorrhectic nuclei, and reduced expression of Nissl substance in the RV group, while the combined RV and GL group showed less degenerative features. Glial fibrillary acidic protein expression (GFAP) was increased in the RV group, while the combined RV and GL group showed reduced expression. In conclusion, RV root bark extract has adverse effects on the microstructure of murines' amygdala and their behaviour, which may be ameliorated by GL.
Asunto(s)
Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/ultraestructura , Aprendizaje por Laberinto/efectos de los fármacos , Corteza de la Planta/química , Extractos Vegetales/efectos adversos , Hojas de la Planta/química , Rauwolfia/química , Animales , Apocynaceae/química , Masculino , Ratones , Extractos Vegetales/aislamiento & purificación , Extractos Vegetales/farmacologíaRESUMEN
Prediction error signals are fundamental to learning. Here, in mice, we show that aversive prediction signals are found in the hemodynamic responses and theta oscillations recorded from the basolateral amygdala. During fear conditioning, amygdala responses evoked by footshock progressively decreased, whereas responses evoked by the auditory cue that predicted footshock concomitantly increased. Unexpected footshock evoked larger amygdala responses than expected footshock. The magnitude of the amygdala response to the footshock predicted behavioral responses the following day. The omission of expected footshock led to a decrease below baseline in the amygdala response suggesting a negative aversive prediction error signal. Thus, in mice, amygdala activity conforms to temporal difference models of aversive learning.
Asunto(s)
Amígdala del Cerebelo/fisiología , Reacción de Prevención/fisiología , Condicionamiento Clásico/fisiología , Miedo/fisiología , Estimulación Acústica , Amígdala del Cerebelo/irrigación sanguínea , Amígdala del Cerebelo/ultraestructura , Animales , Anticipación Psicológica/fisiología , Aprendizaje Discriminativo/fisiología , Electrochoque , Reacción Cataléptica de Congelación , Hemodinámica , Locomoción , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos CBA , Ritmo Teta/fisiologíaRESUMEN
There is growing evidence that astrocytes, long held to merely provide metabolic support in the adult brain, participate in both synaptic plasticity and learning and memory. Astrocytic processes are sometimes present at the synaptic cleft, suggesting that they might act directly at individual synapses. Associative learning induces synaptic plasticity and morphological changes at synapses in the lateral amygdala (LA). To determine whether astrocytic contacts are involved in these changes, we examined LA synapses after either threat conditioning (also called fear conditioning) or conditioned inhibition in adult rats by using serial section transmission electron microscopy (ssTEM) reconstructions. There was a transient increase in the density of synapses with no astrocytic contact after threat conditioning, especially on enlarged spines containing both polyribosomes and a spine apparatus. In contrast, synapses with astrocytic contacts were smaller after conditioned inhibition. This suggests that during memory consolidation astrocytic processes are absent if synapses are enlarging but present if they are shrinking. We measured the perimeter of each synapse and its degree of astrocyte coverage, and found that only about 20-30% of each synapse was ensheathed. The amount of synapse perimeter surrounded by astrocyte did not scale with synapse size, giving large synapses a disproportionately long astrocyte-free perimeter and resulting in a net increase in astrocyte-free perimeter after threat conditioning. Thus astrocytic processes do not mechanically isolate LA synapses, but may instead interact through local signaling, possibly via cell-surface receptors. Our results suggest that contact with astrocytic processes opposes synapse growth during memory consolidation.
Asunto(s)
Amígdala del Cerebelo/fisiología , Astrocitos/fisiología , Condicionamiento Clásico/fisiología , Miedo/fisiología , Sinapsis/fisiología , Estimulación Acústica , Amígdala del Cerebelo/ultraestructura , Animales , Astrocitos/ultraestructura , Percepción Auditiva/fisiología , Axones/fisiología , Axones/ultraestructura , Espinas Dendríticas/fisiología , Espinas Dendríticas/ultraestructura , Electrochoque , Procesamiento de Imagen Asistido por Computador , Masculino , Microscopía Electrónica de Transmisión , Ratas , Sinapsis/ultraestructuraRESUMEN
Social isolation during the vulnerable period of adolescence produces emotional dysregulation manifested by abnormalities in adult behaviors that require emotional processing. The affected brain regions may include the basolateral amygdala (BLA), where plasticity of glutamatergic synapses in principal neurons plays a role in conditioned emotional responses. This plasticity is dependent on NMDA receptor trafficking denoted by intracellular mobilization of the obligatory NR1 NMDA subunit. We tested the hypothesis that the psychosocial stress of adolescent social isolation (ASI) produces a lasting change in NMDA receptor distribution in principal neurons in the BLA of adults that express maladaptive emotional responses to sensory cues. For this, we used behavioral testing and dual electron microscopic immunolabeling of NR1 and calcium calmodulin-dependent protein kinase II (CaMKII), a protein predominantly expressed in principal neurons of the BLA in adult C57Bl/6 mice housed in isolation or in social groups from post-weaning day 22 until adulthood (â¼3 months of age). The isolates showed persistent deficits in sensorimotor gating evidenced by altered prepulse inhibition (PPI) of acoustic startle and hyperlocomotor activity in a novel environment. Immunogold-silver labeling for NR1 alone or together with CaMKII was seen in many somatodendritic profiles in the BLA of all mice irrespective of rearing conditions. However, isolates compared with group-reared mice had a significantly lower cytoplasmic (4.72 ± 0.517 vs 6.31 ± 0.517) and higher plasmalemmal (0.397 ± 0.0779 vs 0.216 ± 0.026) density of NR1 immunogold particles in CaMKII-containing dendritic spines. There was no rearing-dependent difference in the size or number of these spines or those of other dendritic profiles within the neuropil, which also failed to show an impact of ASI on NR1 immunogold labeling. These results provide the first evidence that ASI enhances the surface trafficking of NMDA receptors in dendritic spines of principal neurons in the BLA of adult mice showing maladaptive behaviors that are consistent with emotional dysregulation.
Asunto(s)
Amígdala del Cerebelo/crecimiento & desarrollo , Amígdala del Cerebelo/fisiología , Espinas Dendríticas/metabolismo , Neuronas/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Aislamiento Social , Estimulación Acústica , Amígdala del Cerebelo/ultraestructura , Animales , Ansiedad , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/metabolismo , Citoplasma/metabolismo , Citoplasma/ultraestructura , Dendritas/metabolismo , Dendritas/ultraestructura , Espinas Dendríticas/ultraestructura , Vivienda para Animales , Técnicas para Inmunoenzimas , Inmunohistoquímica , Ratones , Ratones Endogámicos C57BL , Microscopía Electrónica , Actividad Motora , Neuronas/ultraestructura , Filtrado SensorialRESUMEN
Projections from the central amygdala (CeA) and lateral hypothalamus (LH) modulate the activity of gustatory brainstem neurons, however, the role of these projections in gustatory behaviors is unclear. The goal of the current study was to determine the effects of electrical stimulation of the CeA or LH on unconditioned taste reactivity (TR) behaviors in response to intra-oral infusion of tastants. In conscious rats, electrical stimulation of the CeA or LH was delivered with and without simultaneous intra-oral infusion of taste solutions via an intra-oral cannula. Immunohistochemistry for the Fos protein was used to identify neurons in the gustatory brainstem activated by the electrical and/or intra-oral stimulation. In the absence of intra-oral infusion of a tastant, electrical stimulation of either the CeA or the LH increased the number of ingestive, but not aversive, TR behaviors performed. During intra-oral infusions of taste solutions, CeA stimulation tended to increase aversive behaviors whereas LH stimulation dramatically reduced the number of aversive responses to quinine hydrochloride (QHCl). These data indicate that projections from the CeA and LH alter TR behaviors. A few of the behavioral effects were accompanied by changes in the number of Fos-immunoreactive neurons in the gustatory brainstem, suggesting a possible anatomical substrate for these effects.
Asunto(s)
Amígdala del Cerebelo/fisiología , Estimulación Eléctrica , Hipotálamo/fisiología , Neuronas/citología , Proteínas Proto-Oncogénicas c-fos/análisis , Percepción del Gusto , Amígdala del Cerebelo/ultraestructura , Animales , Conducta Animal , Estado de Conciencia , Hipotálamo/ultraestructura , Masculino , Ratas , Ratas WistarRESUMEN
The group III metabotropic glutamate (mGlu) receptors mGlu7 and mGlu8 are receiving increased attention as potential novel therapeutic targets for anxiety disorders. The effects mediated by these receptors appear to result from a complex interplay of facilitatory and inhibitory actions at different brain sites in the anxiety/fear circuits. To better understand the effect of mGlu7 and mGlu8 receptors on extinction of contextual fear and their critical sites of action in the fear networks, we focused on the amygdala. Direct injection into the basolateral complex of the amygdala of the mGlu7 receptor agonist AMN082 facilitated extinction, whereas the mGlu8 receptor agonist (S)-3,4-DCPG sustained freezing during the extinction acquisition trial. We also determined at the ultrastructural level the synaptic distribution of these receptors in the basal nucleus (BA) and intercalated cell clusters (ITCs) of the amygdala. Both areas are thought to exert key roles in fear extinction. We demonstrate that mGlu7 and mGlu8 receptors are located in different presynaptic terminals forming both asymmetric and symmetric synapses, and that they preferentially target neurons expressing mGlu1α receptors mostly located around ITCs. In addition we show that mGlu7 and mGlu8 receptors were segregated to different inputs to a significant extent. In particular, mGlu7a receptors were primarily onto glutamatergic afferents arising from the BA or midline thalamic nuclei, but not the medial prefrontal cortex (mPFC), as revealed by combined anterograde tracing and pre-embedding electron microscopy. On the other hand, mGlu8a showed a more restricted distribution in the BA and appeared absent from thalamic, mPFC and intrinsic inputs. This segregation of mGlu7 and mGlu8 receptors in different neuronal pathways of the fear circuit might explain the distinct effects on fear extinction training observed with mGlu7 and mGlu8 receptor agonists. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.
Asunto(s)
Condicionamiento Psicológico/fisiología , Extinción Psicológica/fisiología , Miedo/psicología , Terminales Presinápticos/metabolismo , Receptores de Glutamato Metabotrópico/fisiología , Amígdala del Cerebelo/anatomía & histología , Amígdala del Cerebelo/metabolismo , Amígdala del Cerebelo/fisiología , Amígdala del Cerebelo/ultraestructura , Animales , Compuestos de Bencidrilo/administración & dosificación , Compuestos de Bencidrilo/farmacología , Benzoatos/administración & dosificación , Benzoatos/farmacología , Agonistas de Aminoácidos Excitadores/administración & dosificación , Agonistas de Aminoácidos Excitadores/farmacología , Miedo/fisiología , Glicina/administración & dosificación , Glicina/análogos & derivados , Glicina/farmacología , Masculino , Ratones , Ratones Endogámicos C57BL , Microinyecciones , Actividad Motora/efectos de los fármacos , Actividad Motora/fisiología , Vías Nerviosas/metabolismo , Técnicas de Trazados de Vías Neuroanatómicas/métodos , Corteza Prefrontal/metabolismo , Terminales Presinápticos/efectos de los fármacos , Receptores de Glutamato Metabotrópico/agonistas , Receptores de Glutamato Metabotrópico/biosíntesis , Receptores de Glutamato Metabotrópico/metabolismo , Tálamo/metabolismoRESUMEN
Changes in glutamatergic transmission in the nucleus accumbens play a key role in mediating reward-related behaviors and addiction to psychostimulants. Glutamatergic inputs to the accumbens originate from multiple sources, including the prefrontal cortex, basolateral amygdala, and midline thalamus. The group I metabotropic glutamate receptors (mGluRs) are found throughout the core and shell of the nucleus accumbens, but their localization and function at specific glutamatergic synapses remain unknown. To further characterize the substrate that underlies group I mGluR functions in the accumbens, we combined anterograde tract tracing method with electron microscopy immunocytochemistry to study the ultrastructural relationships between specific glutamatergic afferents and mGluR1a- or mGluR5-containing neurons in the rat nucleus accumbens. Although cortical, thalamic, and amygdala glutamatergic terminals contact both mGluR1a- and mGluR5-immunoreactive dendrites and spines in the shell and core of the accumbens, they do so to varying degrees. Overall, glutamatergic terminals contact mGluR1a-positive spines about 30% of the time, whereas they form synapses twice as frequently with mGluR5-labeled spines. At the subsynaptic level, mGluR5 is more frequently expressed perisynaptically and closer to the edges of glutamatergic axospinous synapses than mGluR1a, suggesting a differential degree of activation of the two group I mGluRs by transmitter spillover from glutamatergic synapses in the rat accumbens. These results lay the foundation for a deeper understanding of group I mGluR-mediated effects in the ventral striatum, and their potential therapeutic benefits in drug addiction and other neuropsychiatric changes in reward-related behaviors.
Asunto(s)
Encéfalo/ultraestructura , Ácido Glutámico/metabolismo , Neuronas/ultraestructura , Núcleo Accumbens/ultraestructura , Receptores de Glutamato Metabotrópico/metabolismo , Amígdala del Cerebelo/metabolismo , Amígdala del Cerebelo/ultraestructura , Animales , Encéfalo/metabolismo , Corteza Cerebral/metabolismo , Corteza Cerebral/ultraestructura , Dendritas/metabolismo , Dendritas/ultraestructura , Espinas Dendríticas/metabolismo , Espinas Dendríticas/ultraestructura , Inmunohistoquímica , Masculino , Microscopía Electrónica , Vías Nerviosas/metabolismo , Vías Nerviosas/ultraestructura , Trazadores del Tracto Neuronal , Neuronas/metabolismo , Núcleo Accumbens/metabolismo , Ratas , Ratas Sprague-Dawley , Receptor del Glutamato Metabotropico 5 , Sinapsis/metabolismo , Sinapsis/ultraestructura , Tálamo/metabolismo , Tálamo/ultraestructuraRESUMEN
Several evidences suggest that the posterodorsal medial amygdala (MePD) can be a relevant part of the rat neural circuitry for the regulation of hypothalamic neuroendocrine secretion and for ontogenetically different behavioral displays. The dendritic spine density of Golgi-impregnated neurons from the MePD was evaluated in young rats following acute or chronic restraint stress and in aged animals (24 months old). Compared to the control group, a single 1 h restraint stress session promoted a decreased spine density (p<0.01) whereas a single 6 h restraint stress session or daily 6-h restraint sessions for 28 consecutive days did not lead to the same effect (p>0.05). Aged rats showed no difference in this dendritic spine parameter when compared to young adults (p>0.05). These results indicate that short-term stress (1 h) can affect MePD dendritic spines and that neural plasticity is involved with adaptive responses onwards in restrained rats. On the other hand, brain structural modifications related with ageing appear not to influence the number of certain postsynaptic sites in the MePD of rats.
Asunto(s)
Envejecimiento/patología , Amígdala del Cerebelo/patología , Espinas Dendríticas/patología , Estrés Psicológico/patología , Adaptación Fisiológica/fisiología , Amígdala del Cerebelo/fisiopatología , Amígdala del Cerebelo/ultraestructura , Animales , Espinas Dendríticas/ultraestructura , Hipotálamo/metabolismo , Hipotálamo/fisiopatología , Masculino , Vías Nerviosas/fisiopatología , Plasticidad Neuronal/fisiología , Sistemas Neurosecretores/patología , Sistemas Neurosecretores/fisiopatología , Sistemas Neurosecretores/ultraestructura , Ratas , Ratas Wistar , Restricción Física , Estrés Psicológico/fisiopatologíaRESUMEN
The amygdala complex participates in multiple systems having to do with affective processes. It has been implicated in human disorders of social and emotional behavior, such as autism. Of the interconnected functional networks, considerable research in rodents and primates has focused on connections between the amygdala and orbitofrontal cortex (OFC). The amygdala projects to OFC by both a direct amygdalocortical (AC) pathway and an indirect pathway through mediodorsal thalamus. In the rat, retrograde tracer experiments indicate that the AC and amygdalothalamic (AT) pathways originate from separate populations, and may therefore convey distinctive information, although the characteristics of these pathways remain unclear. To investigate this issue in monkeys we made anterograde tracer injections in the basolateral amygdala complex (BLC; n = 3). Three distinctive features were found preferentially associated with the AT or AC pathways. First, AT terminations are large (average diameter = 3.5 microm; range = 1.2-7.0 microm) and cluster around proximal dendrites, in contrast with small-bouton AC terminations. Second, AT terminations form small arbors (diameter approximately 0.1 mm), while AC are widely divergent (often >1.0 mm long). The AT terminations features are reminiscent of large bouton, "driver" corticothalamic terminations. Finally, AC but not AT terminations are positive for zinc (Zn), a neuromodulator associated with synaptic plasticity. From these results we suggest that AC and AT terminations originate from distinct populations in monkey as well as in rodent. Further work is necessary to determine the degree and manner of their segregation and how these subsystems interact within a broader connectivity network.
Asunto(s)
Amígdala del Cerebelo/anatomía & histología , Corteza Cerebral/anatomía & histología , Macaca/anatomía & histología , Tálamo/anatomía & histología , Amígdala del Cerebelo/metabolismo , Amígdala del Cerebelo/ultraestructura , Animales , Biotina/análogos & derivados , Biotina/farmacocinética , Corteza Cerebral/metabolismo , Corteza Cerebral/ultraestructura , Dextranos/farmacocinética , Inmunohistoquímica , Microscopía Electrónica de Transmisión/métodos , Vías Nerviosas/anatomía & histología , Vías Nerviosas/metabolismo , Vías Nerviosas/ultraestructura , Parvalbúminas/metabolismo , Terminales Presinápticos/ultraestructura , Tálamo/metabolismo , Tálamo/ultraestructuraRESUMEN
Changes in dendritic spine number and shape are believed to reflect structural plasticity consequent to learning. Previous studies have strongly suggested that the dorsal subnucleus of the lateral amygdala is an important site of physiological plasticity in Pavlovian fear conditioning. In the present study, we examined the effect of auditory fear conditioning on dendritic spine numbers in the dorsal subnucleus of the lateral amygdala using an immunolabelling procedure to visualize the spine-associated protein spinophilin. Associatively conditioned rats that received paired tone and shock presentations had 35% more total spinophilin-immunoreactive spines than animals that had unpaired stimulation, consistent with the idea that changes in the number of dendritic spines occur during learning and account in part for memory.
Asunto(s)
Amígdala del Cerebelo/metabolismo , Condicionamiento Psicológico/fisiología , Espinas Dendríticas/metabolismo , Proteínas de Microfilamentos/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Plasticidad Neuronal/fisiología , Sinapsis/metabolismo , Estimulación Acústica , Amígdala del Cerebelo/ultraestructura , Animales , Reacción de Prevención/fisiología , Espinas Dendríticas/ultraestructura , Estimulación Eléctrica/efectos adversos , Miedo/fisiología , Inmunohistoquímica , Masculino , Memoria/fisiología , Microscopía Electrónica de Transmisión , Ratas , Ratas Sprague-Dawley , Sinapsis/ultraestructuraRESUMEN
Nitric oxide (NO) has been widely implicated in synaptic plasticity and memory formation. In studies of long-term potentiation (LTP), NO is thought to serve as a 'retrograde messenger' that contributes to presynaptic aspects of LTP expression. In this study, we examined the role of NO signaling in Pavlovian fear conditioning. We first show that neuronal nitric oxide synthase is localized in the lateral nucleus of the amygdala (LA), a critical site of plasticity in fear conditioning. We next show that NO signaling is required for LTP at thalamic inputs to the LA and for the long-term consolidation of auditory fear conditioning. Collectively, the findings suggest that NO signaling is an important component of memory formation of auditory fear conditioning, possibly as a retrograde signal that participates in presynaptic aspects of plasticity in the LA.
Asunto(s)
Amígdala del Cerebelo/metabolismo , Condicionamiento Clásico/fisiología , Miedo/fisiología , Aprendizaje/fisiología , Memoria/fisiología , Óxido Nítrico/metabolismo , Estimulación Acústica , Amígdala del Cerebelo/ultraestructura , Animales , Inmunohistoquímica , Masculino , Microscopía Electrónica de Transmisión , Vías Nerviosas/metabolismo , Vías Nerviosas/ultraestructura , Plasticidad Neuronal/fisiología , Neuronas Nitrérgicas/metabolismo , Óxido Nítrico Sintasa/metabolismo , Técnicas de Cultivo de Órganos , Terminales Presinápticos/metabolismo , Terminales Presinápticos/ultraestructura , Ratas , Ratas Sprague-Dawley , Transducción de Señal/fisiología , Tálamo/metabolismo , Tálamo/ultraestructuraRESUMEN
We have mapped the macaque amygdala for the distribution of synaptic zinc (Zn), a co-factor of glutamate implicated in plasticity, as well as in several excitotoxic and other pathophysiological conditions. In brief, we found that the amygdala is Zn enriched in all nuclear groups (i.e., basolateral and cortical groups, as well as central and medial nuclei) but with marked differences in density. By comparing parallel tissue series histologically reacted for Zn and parvalbumin (PV), we further found that regions high in Zn are typically low in PV neuropil. In the basolateral group, there is a particularly distinct dorsoventral gradation such that Zn levels are most dense ventrally, i.e., in the paralaminar nucleus, the ventral division of the lateral nucleus, and the parvicellular divisions of both the basal nucleus and the accessory basal nucleus. PV levels are least dense in these same regions. For the central and medial nuclei, there is a slight mediolateral gradient, with Zn levels being higher medially. PV is low overall in these nuclei. Electron microscopic results confirmed that Zn is contained in synaptic boutons. These form asymmetrical, presumably excitatory, synapses, and the postsynaptic targets are mainly spines of projection neurons. The inhomogeneous distribution of Zn in the monkey amygdala may be related to different types or degrees of plasticity among the amygdaloid subnuclei. The complementary distribution with PV parallels that of several other substances and is interesting in the context of subnuclear vulnerability for human neuronal disease, such as seizure and Alzheimer's disease.
Asunto(s)
Amígdala del Cerebelo/metabolismo , Macaca mulatta/fisiología , Plasticidad Neuronal/fisiología , Sinapsis/metabolismo , Zinc/metabolismo , Amígdala del Cerebelo/ultraestructura , Animales , Inmunohistoquímica , Microscopía Electrónica , Parvalbúminas/metabolismo , Sinapsis/ultraestructuraRESUMEN
Much evidence indicates that fear conditioning involves potentiation of some thalamic inputs to the lateral amygdala (LA). In turn, the LA would excite more neurons in the central nucleus (CE), leading to the generation of fear responses via their brainstem and hypothalamic projections. However, the posterior thalamus not only projects to LA but also to the medial sector of CE (CEm), suggesting that CEm might also be a site of plasticity. To test whether CEm also exhibits activity-dependent synaptic plasticity, we performed whole-cell recordings of CEm neurons in amygdala slices and stimulated thalamic axons coursing through the internal capsule and, as a control, the basolateral (BL) nucleus. High-frequency stimulation of thalamic inputs led to a long-lasting potentiation of thalamic responses, whereas BL-evoked responses remained unchanged. This thalamic long-term potentiation (LTP) developed even when slices were prepared with a cut severing the connections between the LA and CEm but was greatly reduced when an NMDA receptor antagonist was added to the perfusate shortly before and during LTP induction. Yet, intracellular dialysis with the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate did not prevent induction of the thalamic LTP, suggesting that presynaptic NMDA receptors are required for its induction. Consistent with this, the thalamic LTP also developed when the cells were dialyzed with a calcium chelator or kept hyperpolarized during induction. Finally, this thalamic LTP was associated with reduced amounts of paired-pulse facilitation, suggesting that it is expressed presynaptically. These results are consistent with the idea that the CEm plays an active role in fear conditioning.
Asunto(s)
Amígdala del Cerebelo/fisiología , Miedo/fisiología , Plasticidad Neuronal/fisiología , 2-Amino-5-fosfonovalerato/farmacología , 6-Ciano 7-nitroquinoxalina 2,3-diona/farmacología , Vías Aferentes/fisiología , Amígdala del Cerebelo/ultraestructura , Animales , Quelantes/farmacología , Condicionamiento Clásico/fisiología , Maleato de Dizocilpina/farmacología , Estimulación Eléctrica , Antagonistas de Aminoácidos Excitadores/farmacología , Potenciales Postsinápticos Excitadores , Cobayas , Técnicas In Vitro , Técnicas de Placa-Clamp , Picrotoxina/farmacología , Tiempo de Reacción , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Receptores Presinapticos/fisiología , Tálamo/fisiologíaRESUMEN
The amygdalohypothalamic projection, a major component of the stria terminalis, is involved in the conduction of emotional and olfactory information integrated in the amygdala to the hypothalamus to elicit emotional reactions. Despite the extensive studies on functional aspects of the amygdaloid complex, developmental mechanisms of the amygdala and related structures are still poorly understood. To investigate the development of the amygdalohypothalamic projection in the mouse embryonic brain, carbocyanine dye was applied to the amygdala to label the growing axons anterogradely and to the hypothalamus to label the amygdaloid neurons retrogradely. The initial outgrowth of the stria terminalis was found to be as early as E11.5. The pathway crossed in a saddle over the internal capsule, another prominent connection in the developing forebrain of the mammalian embryo. Bipolar immature neurons were distributed along the stria terminalis at the telencephalo-diencephalic boundary, and the internal capsule was also surrounded by these cells. These cells expressed immunoreactivities to calretinin and the lot-1 antigen which has been shown to be involved in guidance of the developing lateral olfactory tract. Ultrastructural analysis revealed an adherens-like junction between the stria terminalis and the apposed cells, implying contact-mediated guidance. These results suggest that, in the development of the stria terminalis, the axonal outgrowth is guided by a mechanism similar to that of the developing lateral olfactory tract, a major amygdalopetal connection.
Asunto(s)
Amígdala del Cerebelo/embriología , Hipotálamo/embriología , Vías Nerviosas/embriología , Prosencéfalo/embriología , Uniones Adherentes/metabolismo , Uniones Adherentes/ultraestructura , Amígdala del Cerebelo/metabolismo , Amígdala del Cerebelo/ultraestructura , Animales , Calbindina 2 , Carbocianinas , Femenino , Colorantes Fluorescentes , Proteína GAP-43/metabolismo , Conos de Crecimiento/metabolismo , Conos de Crecimiento/ultraestructura , Hipotálamo/metabolismo , Hipotálamo/ultraestructura , Inmunohistoquímica , Cápsula Interna/embriología , Ratones , Ratones Endogámicos ICR , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Vías Nerviosas/metabolismo , Vías Nerviosas/ultraestructura , Vías Olfatorias/embriología , Prosencéfalo/metabolismo , Prosencéfalo/ultraestructura , Proteína G de Unión al Calcio S100/metabolismoRESUMEN
Fatty acid amide hydrolase (FAAH) and monoglyceride lipase (MGL) catalyse the hydrolysis of the endocannabinoids anandamide and 2-arachidonoyl glycerol. We investigated their ultrastructural distribution in brain areas where the localization and effects of cannabinoid receptor activation are known. In the hippocampus, FAAH was present in somata and dendrites of principal cells, but not in interneurons. It was located mostly on the membrane surface of intracellular organelles known to store Ca(2+) (e.g. mitochondria, smooth endoplasmic reticulum), less frequently on the somatic or dendritic plasma membrane. MGL immunoreactivity was found in axon terminals of granule cells, CA3 pyramidal cells and some interneurons. In the cerebellum, Purkinje cells and their dendrites are intensively immunoreactive for FAAH, together with a sparse axon plexus at the border of the Purkinje cell/granule cell layers. Immunostaining for MGL was complementary, the axons in the molecular layer were intensively labelled leaving the Purkinje cell dendrites blank. FAAH distribution in the amygdala was similar to that of the CB(1) cannabinoid receptor: evident signal in neuronal somata and proximal dendrites in the basolateral nucleus, and hardly any labelling in the central nucleus. MGL staining was restricted to axons in the neuropil, with similar relative signal intensities seen for FAAH in different nuclei. Thus, FAAH is primarily a postsynaptic enzyme, whereas MGL is presynaptic. FAAH is associated with membranes of cytoplasmic organelles. The differential compartmentalization of the two enzymes suggests that anandamide and 2-AG signalling may subserve functional roles that are spatially segregated at least at the stage of metabolism.
Asunto(s)
Amidohidrolasas/metabolismo , Amígdala del Cerebelo/enzimología , Cerebelo/enzimología , Hipocampo/enzimología , Monoacilglicerol Lipasas/metabolismo , Terminales Presinápticos/enzimología , Sinapsis/enzimología , Amidohidrolasas/genética , Amígdala del Cerebelo/ultraestructura , Animales , Calbindina 2 , Calbindinas , Cerebelo/ultraestructura , Colecistoquinina/metabolismo , Técnica del Anticuerpo Fluorescente/métodos , Glutamato Descarboxilasa/metabolismo , Hipocampo/ultraestructura , Isoenzimas/metabolismo , Masculino , Ratones , Ratones Noqueados , Microscopía Inmunoelectrónica/métodos , Parvalbúminas/metabolismo , Ratas , Ratas Wistar , Proteína G de Unión al Calcio S100/metabolismo , Sinapsis/ultraestructuraRESUMEN
As members of the steroid receptor superfamily, androgen receptors (ARs) have been traditionally identified as transcription factors. In the presence of ligand, ARs reside in the nucleus, where, upon ligand binding, the receptors dimerize and bind to specific response elements in the promoter region of hormone-responsive genes. However, in this report, we describe the discovery that ARs are also present in axons and dendrites within the mammalian central nervous system. AR expression in axons was identified in the rat brain at the light microscopic level using two different antibodies directed against the N terminus of the AR protein and nickel intensified 3'-3'-diaminobenzidine, and also using fluorescence methods and confocal microscopy. This distribution was confirmed at the ultrastructural level. In addition, AR immunoreactivity was identified in small dendrites at the ultrastructural level. AR-immunoreactive axons were observed primarily in the cerebral cortex and were rare in regions where nuclear AR expression is abundant. The observation that ARs are present in axons and dendrites highlights the possibility that androgens play an important and novel extra-nuclear role in neuronal function.
Asunto(s)
Axones/química , Dendritas/química , Prosencéfalo/ultraestructura , Receptores Androgénicos/análisis , Amígdala del Cerebelo/ultraestructura , Animales , Núcleo Celular/química , Corteza Cerebral/ultraestructura , Técnica del Anticuerpo Fluorescente , Hipotálamo/ultraestructura , Inmunohistoquímica , Masculino , Microscopía Confocal , Área Preóptica/ultraestructura , Prosencéfalo/química , Ratas , Ratas Wistar , Núcleos Septales/ultraestructura , Distribución TisularRESUMEN
To elucidate the organization and evolution of the tectorotundotelencephalic pathways in birds and reptiles, we reinvestigated at both light and electron microscopic levels the efferent projections of nucleus rotundus in a lizard, using the sensitive tracer biotinylated dextran amine. Our results indicate that nucleus rotundus projects to targets in the basal ganglia (lateral parts of striatum and olfactory tubercle and possibly the globus pallidus), the anterior dorsal ventricular ridge (ADVR), and the amygdaloid complex (the central and possibly lateral amygdaloid nuclei). In these targets, the rotundal axon terminals establish asymmetric, presumably excitatory synaptic contacts, usually with dendrites of local cells. In the ADVR, the rotundal projection terminates in two separate radial regions showing distinct cytoarchitecture: 1) a dorsolateral region that extends radially from the dorsolateral ADVR ventricular surface to the ventral part of the lateral cortex and 2) the lateral part of a ventromedial region that extends radially from the dorsomedial and medial ADVR ventricle to a superficial area interposed between the dorsolateral ADVR and the striatum. These two ADVR regions have different connections with the thalamus and telencephalon, which suggests that they may be involved in different degrees of integration. Our study also suggests that the rotundal projection to the ventromedial ADVR field of lizards may be comparable to the rotundoectostriatal/periectostriatal projection of birds. The connections and pathways involving nucleus rotundus suggest that this nucleus conveys visual information which may play a role in visuomotor, emotional, and visceral functions.
Asunto(s)
Amígdala del Cerebelo/ultraestructura , Ganglios Basales/ultraestructura , Lagartos/anatomía & histología , Vías Nerviosas/ultraestructura , Tálamo/citología , Amígdala del Cerebelo/fisiología , Animales , Axones/fisiología , Axones/ultraestructura , Ganglios Basales/fisiología , Emociones/fisiología , Lagartos/fisiología , Microscopía Electrónica , Vías Nerviosas/fisiología , Desempeño Psicomotor/fisiología , Sinapsis/fisiología , Sinapsis/ultraestructura , Tálamo/fisiologíaRESUMEN
The amplitude of the acoustic startle response is reliably enhanced when elicited in the presence of bright light (light-enhanced startle) or in the presence of cues previously paired with shock (fear-potentiated startle). Light-enhanced startle appears to reflect an unconditioned response to an anxiogenic stimulus, whereas fear-potentiated startle reflects a conditioned response to a fear-eliciting stimulus. We examine the involvement of the basolateral nucleus of the amygdala, the central nucleus of the amygdala, and the bed nucleus of the stria terminalis in both phenomena. Immediately before light-enhanced or fear-potentiated startle testing, rats received intracranial infusions of the AMPA receptor antagonist 2, 3-dihydroxy-6-nitro-7-sulphamoylbenzo(F)-quinoxaline (3 microg) or PBS. Infusions into the central nucleus of the amygdala blocked fear-potentiated but not light-enhanced startle, and infusions into the bed nucleus of the stria terminalis blocked light-enhanced but not fear-potentiated startle. Infusions into the basolateral amygdala disrupted both phenomena. These findings indicate that the neuroanatomical substrates of fear-potentiated and light-enhanced startle, and perhaps more generally of conditioned and unconditioned fear, may be anatomically dissociated.
Asunto(s)
Amígdala del Cerebelo/fisiología , Reacción de Prevención/fisiología , Condicionamiento Clásico/fisiología , Miedo/fisiología , Hipotálamo/fisiología , Receptores AMPA/fisiología , Reflejo de Sobresalto/fisiología , 6-Ciano 7-nitroquinoxalina 2,3-diona/farmacología , Estimulación Acústica , Vías Aferentes/efectos de los fármacos , Vías Aferentes/fisiología , Vías Aferentes/ultraestructura , Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/ultraestructura , Animales , Ansiedad/fisiopatología , Reacción de Prevención/efectos de los fármacos , Oscuridad , Antagonistas de Aminoácidos Excitadores/farmacología , Hipotálamo/efectos de los fármacos , Hipotálamo/ultraestructura , Masculino , Estimulación Luminosa , Quinoxalinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptores AMPA/antagonistas & inhibidores , Reflejo de Sobresalto/efectos de los fármacos , Reflejo de Sobresalto/efectos de la radiaciónRESUMEN
Projections from the medial geniculate body (MGB) to the lateral nucleus of the amygdala (LA) have been implicated in the conditioning of emotional reactions to acoustic stimuli. Anatomical and physiological studies indicate that this pathway uses the excitatory amino acid L-glutamate as a transmitter. Recent physiological studies have demonstrated that synaptic transmission in the thalamo-amygdala pathway requires the activation of both N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors, two of the major classes of ionotrophic glutamate receptors. In order to characterize the nature of thalamoamygdala interactions, we examined the synaptic associations between thalamic afferents and amygdala neurons that contain at least one glutamate receptor subtype. Thalamic afferents to the amygdala were identified by lesion-induced anterograde degeneration and anterograde transport of biotinylated dextran-amine, while postsynaptic glutamate receptors were labeled immunocytochemically using antisera directed the R1 subunit of the NMDA receptor and the GluR1 and GluR2/3 subunits of the AMPA receptors. Both methods demonstrated that the majority (77%) of thalamic afferents contact dendritic spines, and most (60%) of these spines express at least one glutamate receptor subtype. To a lesser extent, identified afferents also contacted small and large dendritic shafts, and many of these were immunoreactive. Thalamic afferents terminated on approximately the same proportion (60%) of immunoreactive targets for each glutamate receptor studied. These data provide morphological evidence that thalamic afferents directly synapse onto amygdala neurons that express glutamate receptors and suggest ways in which thalamic afferents activate and influence amygdala circuitry.