Improved Efficiency and Sensitivity Analysis of 3-D Agent-based Model for Pain-related Neural Activity in the Amygdala.

Neuropathic pain is caused by nerve injury and involves brain areas such as the central nucleus of the amygdala (CeA). We developed the first 3-D agent-based model (ABM) of neuropathic pain-related neurons in the CeA using NetLogo3D. The execution time of a single ABM simulation using realistic parameters (e.g., 13,000 neurons and 22,000+ neural connections) is an important factor in the model's usability. In this paper, we describe our efforts to improve the computational efficiency of our 3-D ABM, which resulted in a 28% reduction in execution time on average for a typical simulation. With this upgraded model, we performed one- and two-parameter sensitivity analyses to study the sensitivity of model output to variability in several key parameters along the anterior to posterior axis of the CeA. These results highlight the importance of computational modeling in exploring spatial and cell-type specific properties of brain regions to inform future wet lab experiments.

The modulatory role of serotonin-1A receptors of the basolateral amygdala and dorsal periaqueductal gray on the impact of hormonal variation on the conditioned fear response.

Despite significant advances in the study of fear and fear memory formation, little is known about fear learning and expression in females. This omission has been proven surprising, as normal and pathological behaviors are highly influenced by ovarian hormones, particularly estradiol and progesterone. In the current study, we investigated the joint influence of serotonin (5-HT) neurotransmission and estrous cycle phases (low or high levels of estradiol and progesterone) on the expression of conditioned fear in a group of female rats that were previously divided according to their response to stressful stimuli into low or high anxiety-like subjects. The baseline amplitude of the unconditioned acoustic startle responses was high in high-anxiety female rats, with no effect on the estrous cycle observed. Data collected during the proestrus-estrus phase revealed that low-anxiety rats had startle amplitudes similar to those of high-anxiety rats. It is supposed that high-anxiety female rats benefit from increased estradiol and progesterone levels to achieve comparable potentiated startle amplitudes. In contrast, female rats experienced a significant decrease in hormone levels during the Diestrus phase. This decrease is believed to play a role in preventing them from displaying a heightened startle response when faced with strongly aversive stimuli. Data collected after 5-HT and 8-OH-DPAT were administered into the basolateral nuclei and dorsal periaqueductal gray suggest that 5-HT neurotransmission works with progesterone and estrogen to reduce startle potentiation, most likely by activating the serotonin-1A receptor subtype.

Scopolamine infusion in the basolateral amygdala after saccharin intake induces conditioned taste avoidance in rats.

RATIONALE: Muscarinic receptor activity in the basolateral amygdala (BLA) is known to be involved in plasticity mechanisms that underlie emotional learning. The BLA is involved in the Attenuation of Neophobia, an incidental taste learning task in which a novel taste becomes familiar and recognized as safe. OBJECTIVE: Here we assessed the role of muscarinic receptor activity in the BLA in incidental taste learning. METHODS: Young adult male Wistar rats were bilaterally implanted with cannulas aimed at BLA. After recovery, rats were randomly assigned to either vehicle or muscarinic antagonist group, for each experiment. We tested the effect of specific and non-specific muscarinic antagonists administered either 1) 20 min before novel taste presentation; 2) immediately after novel taste presentation; 3) immediately after retrieval (the second taste presentation on Day 5 -S2-) or immediately after the fifth taste presentation on Day 8 (S5). RESULTS: Non-specific muscarinic receptor antagonist scopolamine infused prior to novel taste, while not affecting novel taste preference, abolished AN, i.e., the increased preference observed in control animals on the second presentation. When administered after taste consumption, intra-BLA scopolamine not only prevented AN but caused a steep decrease in the taste preference on the second presentation. This scopolamine-induced taste avoidance was not dependent on taste novelty, nor did it generalize to another novel taste. Targeting putative postsynaptic muscarinic receptors with specific M1 or M3 antagonists appeared to produce a partial taste avoidance, while M2 antagonism had no effect. CONCLUSION: These data suggest that if a salient gustatory experience is followed by muscarinic receptors antagonism in the BLA, it will be strongly and persistently avoided in the future. The study also shows that scopolamine is not just an amnesic drug, and its cognitive effects may be highly dependent on the task and the structure involved.

Circadian Synchronization of Feeding Attenuates Rats' Food Restriction-Induced Anxiety and Amygdalar Thyrotropin-Releasing Hormone Downregulation.

Anxiety is a common comorbidity of obesity, resulting from prescribing long-term caloric restriction diets (CRDs); patients with a reduced food intake lose weight but present anxious behaviors, poor treatment adherence, and weight regain in the subsequent 5 years. Intermittent fasting (IF) restricts feeding time to 8 h during the activity phase, reducing patients' weight even with no caloric restriction; it is unknown whether an IF regime with ad libitum feeding avoids stress and anxiety development. We compared the corticosterone blood concentration between male Wistar rats fed ad libitum or calorie-restricted with all-day or IF food access after 4 weeks, along with their anxiety parameters when performing the elevated plus maze (EPM). As the amygdalar thyrotropin-releasing hormone (TRH) is believed to have anxiolytic properties, we evaluated its expression changes in association with anxiety levels. The groups formed were the following: a control which was offered food ad libitum (C-adlib) or 30% of C-adlib's energy requirements (C-CRD) all day, and IF groups provided food ad libitum (IF-adlib) or 30% of C-adlib's requirements (IF-CRD) with access from 9:00 to 17:00 h. On day 28, the rats performed the EPM and, after 30 min, were decapitated to analyze their amygdalar TRH mRNA expression by in situ hybridization and corticosterone serum levels. Interestingly, circadian feeding synchronization reduced the body weight, food intake, and animal anxiety levels in both IF groups, with ad libitum (IF-adlib) or restricted (IF-CRD) food access. The anxiety levels of the experimental groups resulted to be negatively associated with TRH expression, which supported its anxiolytic role. Therefore, the low anxiety levels induced by synchronizing feeding with the activity phase would help patients who are dieting to improve their diet therapy adherence.

Amygdala-specific changes in Cacna1c, Nfat5, and Bdnf expression are associated with stress responsivity in mice: A possible mechanism for psychiatric disorders.

The CACNA1C gene encodes the alpha-1c subunit of the Cav1.2 calcium channel, a regulator of neuronal calcium influx involved in neurotransmitter release and synaptic plasticity. Genetic data show a role for CACNA1C in depressive symptoms underlying different psychiatric diagnoses. However, the mechanisms involved still require further exploration. This study aimed to investigate sex and region-specific changes in the Cacna1c gene and behavioral outcomes in mice exposed to chronic stress. Moreover, we evaluated the Nuclear factor of activated T-cells 5 (Nfat5) and the Brain-derived neurotrophic factor (Bdnf) as potential upstream and downstream Cacna1c targets and their correlation in stressed mice and humans with depression. Male and female Swiss mice were exposed to chronic unpredictable stress (CUS) for 21 days. Animal-integrated emotionality was assessed using the sucrose splash test, the tail suspension, the open-field test, and the elevated-plus-maze. Gene expression analysis was performed in the amygdala, prefrontal cortex, and hippocampus. Human data for in silico analysis was obtained from the Gene Expression Omnibus. CUS-induced impairment in integrated emotional regulation was observed in males. Gene expression analysis showed decreased levels of Cacna1c and Nfat5 and increased levels of Bdnf transcripts in the amygdala of stressed male mice. In contrast, there were no major changes in behavioral responses or gene expression in female mice after stress. The expression of the three genes was significantly correlated in the amygdala of mice and humans. The strong and positive correlation between Canac1c and Nfat5 suggests a potential role for this transcription factor in Canac1c expression. These changes could impact amygdala reactivity and emotional responses, making them a potential target for psychiatric intervention.

Social-Single Prolonged Stress affects contextual fear conditioning in male and female Wistar rats: Molecular insights in the amygdala.

Stress exposure can lead to post-traumatic stress disorder (PTSD) in male and female rats. Social-Single Prolonged Stress (SPS) protocol has been considered a potential PTSD model. This study aimed to pharmacologically validate the Social-SPS as a PTSD model in male and female rats. Male and female Wistar rats (60-day-old) were exposed to Social-SPS protocol and treated with fluoxetine (10 mg/Kg) or saline solution intraperitoneally 24 h before euthanasia. Two cohorts of animals were used; for cohort 1, male and female rats were still undisturbed until day 7 post-Social-SPS exposure, underwent locomotor and conditioned fear behaviors, and were euthanized on day 9. Animals of cohort 2 were subjected to the same protocol but were re-exposed to contextual fear behavior on day 14. Results showed that fluoxetine-treated rats gained less body weight than control and Social-SPS in both sexes. Social-SPS effectively increased the freezing time in male and female rats on day eight but not on day fourteen. Fluoxetine blocked the increase of freezing in male and female rats on day 8. Different mechanisms for fear behavior were observed in males, such as Social-SPS increased levels of glucocorticoid receptors and Beclin-1 in the amygdala. Social-SPS was shown to increase the levels of NMDA2A, GluR-1, PSD-95, and CAMKII in the amygdala of female rats. No alterations were observed in the amygdala of rats on day fourteen. The study revealed that Social-SPS is a potential PTSD protocol applicable to both male and female rats.

Neuroinflammation in the prefrontal-amygdala-hippocampus network is associated with maladaptive avoidance behaviour.

Maladaptive avoidance behaviour is often observed in patients suffering from anxiety and trauma- and stressor-related disorders. The prefrontal-amygdala-hippocampus network is implicated in learning and memory consolidation. Neuroinflammation in this circuitry alters network dynamics, resulting in maladaptive avoidance behaviour. The two-way active avoidance test is a well-established translational model for assessing avoidance responses to stressful situations. While some animals learn the task and show adaptive avoidance (AA), others show strong fear responses to the test environment and maladaptive avoidance (MA). Here, we investigated if a distinct neuroinflammation pattern in the prefrontal-amygdala-hippocampus network underlies the behavioural difference observed in these animals. Wistar rats were tested 8 times and categorized as AA or MA based on behaviour. Brain recovery followed for the analysis of neuroinflammatory markers in this network. AA and MA presented distinct patterns of neuroinflammation, with MA showing increased astrocyte, EAAT-2, IL-1ß, IL-17 and TNF-ɑ in the amygdala. This neuroinflammatory pattern may underlie these animals' fear response and maladaptive avoidance. Further studies are warranted to determine the specific contributions of each inflammatory factor, as well as the possibility of treating maladaptive avoidance behaviour in patients with psychiatric disorders with anti-inflammatory drugs targeting the amygdala.

Multiple metabolic signals in the CeA regulate feeding: The role of AMPK.

BACKGROUND: The central nucleus of the amygdala (CeA) is part of the dopaminergic reward system and controls energy balance. Recently, a cluster of neurons was identified as responsive to the orexigenic effect of ghrelin and fasting. However, the signaling pathway by which ghrelin and fasting induce feeding is unknown. AMP-activated protein kinase (AMPK) is a cellular energy sensor, and its Thr172 phosphorylation (AMPKThr172) in the mediobasal hypothalamus regulates food intake. However, whether the expression and activation of AMPK in CeA could be one of the intracellular signaling activated in response to ghrelin and fasting eliciting food intake is unknown. AIM: To evaluate the activation of AMPK into CeA in response to ghrelin, fasting, and 2-deoxy-D-glucose (2DG) and whether feeding accompanied these changes. In addition, to investigate whether the inhibition of AMPK into CeA could decrease food intake. METHODS: On a chow diet, eight-week-old Wistar male rats were stereotaxically implanted with a cannula in the CeA to inject several modulators of AMPKα1/2Thr172 phosphorylation, and we performed physiological and molecular assays. KEY FINDINGS: Fasting increased, and refeeding reduced AMPKThr172 in the CeA. Intra-CeA glucose injection decreased feeding, whereas injection of 2DG, a glucoprivation inductor, in the CeA, increased food intake and blood glucose, despite faint increases in AMPKThr172. Intra-CeA ghrelin injection increased food intake and AMPKThr172. To further confirm the role of AMPK in the CeA, chronic injection of Melanotan II (MTII) in CeA reduced body mass and food intake over seven days together with a slight decrease in AMPKThr172. SIGNIFICANCE: Our findings identified that AMPK might be part of the signaling machinery in the CeA, which responds to nutrients and hormones contributing to feeding control. The results can contribute to understanding the pathophysiological mechanisms of altered feeding behavior/consumption, such as binge eating of caloric-dense, palatable food.

Role of amygdala astrocytes in different phases of contextual fear memory.

Growing evidence indicates a critical role of astrocytes in learning and memory. However, little is known about the role of basolateral amygdala complex (BLA-C) astrocytes in contextual fear conditioning (CFC), a paradigm relevant to understand and generate treatments for fear- and anxiety-related disorders. To get insights on the involvement of BLA-C astrocytes in fear memory, fluorocitrate (FLC), a reversible astroglial metabolic inhibitor, was applied at critical moments of the memory processing in order to target the acquisition, consolidation, retrieval and reconsolidation process of the fear memory. Adult Wistar male rats were bilaterally cannulated in BLA-C. Ten days later they were infused with different doses of FLC (0.5 or 1 nmol/0.5 µl) or saline before or after CFC and before or after retrieval. FLC impaired fear memory expression when administered before and shortly after CFC, but not one hour later. Infusion of FLC prior and after retrieval did not affect the memory. Our findings suggest that BLA-C astrocytes are critically involved in the acquisition/early consolidation of fear memory but not in the retrieval and reconsolidation. Furthermore, the extinction process was presumably not affected (considering that peri-retrieval administration could also affect this process).

Morphological heterogeneity of neurons in the human central amygdaloid nucleus.

The central amygdaloid nucleus (CeA) has an ancient phylogenetic development and functions relevant for animal survival. Local cells receive intrinsic amygdaloidal information that codes emotional stimuli of fear, integrate them, and send cortical and subcortical output projections that prompt rapid visceral and social behavior responses. We aimed to describe the morphology of the neurons that compose the human CeA (N = 8 adult men). Cells within CeA coronal borders were identified using the thionine staining and were further analyzed using the "single-section" Golgi method followed by open-source software procedures for two-dimensional and three-dimensional image reconstructions. Our results evidenced varied neuronal cell body features, number and thickness of primary shafts, dendritic branching patterns, and density and shape of dendritic spines. Based on these criteria, we propose the existence of 12 morphologically different spiny neurons in the human CeA and discuss the variability in the dendritic architecture within cellular types, including likely interneurons. Some dendritic shafts were long and straight, displayed few collaterals, and had planar radiation within the coronal neuropil volume. Most of the sampled neurons showed a few to moderate density of small stubby/wide spines. Long spines (thin and mushroom) were observed occasionally. These novel data address the synaptic processing and plasticity in the human CeA. Our morphological description can be combined with further transcriptomic, immunohistochemical, and electrophysiological/connectional approaches. It serves also to investigate how neurons are altered in neurological and psychiatric disorders with hindered emotional perception, in anxiety, following atrophy in schizophrenia, and along different stages of Alzheimer's disease.

Dopamine Dynamics in the Amygdala Influence Emotional Changes in the Early Stage of Systemic Inflammatory Response Syndrome in Rats / La Dinámica de la Dopamina en la Amígdala Influye en los Cambios Emocionales en la Etapa Temprana del Síndrome de Respuesta Inflamatoria Sistémica en Ratas

SUMMARY: Systemic inflammatory response syndrome (SIRS) is a potentially fatal reaction to various forms of tissue damage and infections that cause damage to various organs. Furthermore, the brain is damaged earlier than other organs, resulting in diffuse brain dysfunction. The central clinical symptom of SIRS is delirium and emotional changes are involved in disease development. Although the amygdala is known to play a major role, the mechanisms underlying emotional changes in the early stages of SIRS have not been elucidated. Therefore, changes to dopamine levels in the amygdala were observed using an in vivo model of lipopolysaccharide (LPS)- induced SIRS to clarify the biochemical mechanisms activated in the early stages of SIRS. Extracellular dopamine was collected from the amygdala of free moving rats via microdialysis and then analyzed by high-performance liquid chromatography. In addition, emotional changes were assessed with the open field and sucrose preference tests. In the LPS group, dopamine release in the amygdala increased remarkably immediately after LPS administration, peaking at 120 min. Thereafter, dopamine release temporarily decreased, but then significantly increased again after 180 min. The present results suggest that diffuse brain dysfunction in the early stages of SIRS may involve altered dopamine levels in the amygdala.

El síndrome de respuesta inflamatoria sistémica (SRIS) es una reacción potencialmente fatal a diversas formas de daño tisular e infecciones que causan injuria a varios órganos. Además, el cerebro se daña antes que otros órganos, lo que provoca una disfunción cerebral difusa. El síntoma clínico central del SIRS es el delirio y los cambios emocionales están involucrados en el desarrollo de la enfermedad. Aunque se sabe que la amígdala desempeña un papel importante, no se han dilucidado los mecanismos que subyacen a los cambios emocionales en las primeras etapas del SRIS. Por lo tanto, en el estudio se provocaron cambios en los niveles de dopamina en la amígdala utilizando un modelo in vivo de SRIS inducido por lipopolisacáridos (LPS) para dilucidar los mecanismos bioquímicos activados en las primeras etapas del SRIS. La dopamina extracelular se recogió de la amígdala de ratas en movimiento libre mediante microdiálisis y luego se analizó mediante cromatografía líquida de alta resolución. Además, se evaluaron los cambios emocionales con las pruebas de campo abierto y de preferencia de sacarosa. En el grupo de LPS, la liberación de dopamina en la amígdala aumentó de manera notable inmediatamente después de la administración de LPS, alcanzando un máximo a los 120 minutos. A partir de entonces, la liberación de dopamina disminuyó temporalmente, pero luego volvió a aumentar significativamente después de 180 min. Los resultadosactuales sugieren que la disfunción cerebral difusa en las primeras etapas del SIRS puede implicar niveles alterados de dopamina en la amígdala.

Distinct engrams control fear and extinction memory.

Memories are stored in engram cells, which are necessary and sufficient for memory recall. Recalling a memory might undergo reconsolidation or extinction. It has been suggested that the original memory engram is reactivated during reconsolidation so that memory can be updated. Conversely, during extinction training, a new memory is formed that suppresses the original engram. Nonetheless, it is unknown whether extinction creates a new engram or modifies the original fear engram. In this study, we utilized the Daun02 procedure, which uses c-Fos-lacZ rats to induce apoptosis of strongly activated neurons and examine whether a new memory trace emerges as a result of a short or long reactivation, or if these processes rely on modifications within the original engram located in the basolateral amygdala (BLA) and infralimbic (IL) cortex. By eliminating neurons activated during consolidation and reactivation, we observed significant impacts on fear memory, highlighting the importance of the BLA engram in these processes. Although we were unable to show any impact when removing the neurons activated after the test of a previously extinguished memory in the BLA, disrupting the IL extinction engram reactivated the aversive memory that was suppressed by the extinction memory. Thus, we demonstrated that the IL cortex plays a crucial role in the network involved in extinction, and disrupting this specific node alone is sufficient to impair extinction behavior. Additionally, our findings indicate that extinction memories rely on the formation of a new memory, supporting the theory that extinction memories rely on the formation of a new memory, whereas the reconsolidation process reactivates the same original memory trace.

Partial Klüver-Bucy syndrome in a Paediatric patient: A post-neurosurgical and neuropsychological cases.

A variety of cognitive, behavioural, and emotional impairments have been reported in the literature that are associated with the resection of the temporal cortex. Klüver-Bucy syndrome is one infrequently reported disorder in the paediatric population. This paper describes the neuropsychological findings of a female paediatric patient at 7 and 10 years of age with a diagnosis of partial Klüver-Bucy syndrome (pKBS) following total resection of the amygdala and right hippocampus to resect a glioma. The patient presented emotional problems, aggressiveness, hypermetamorphosis, social indifference, and behavioural dysexecutive syndrome, which was found at both 7 and 10 years, but with a decrease in the severity of alterations in attention, impulsivity, hyperactivity, and aggressive behaviour in a second evaluation after she had a neuropsychological intervention. These findings describe the neuropsychological profile of paediatric case with resection of the amygdala and right temporal lobe.

The anterior insula and its projection to amygdala nuclei modulate the abstinence-exacerbated expression of conditioned place preference.

RATIONALE: Relapse into substance use is often triggered by exposure to drug-related environmental cues. The magnitude of drug seeking depends on the duration of abstinence, a phenomenon known as the incubation of drug craving. Clinical and preclinical research shows that the insular cortex is involved in substance use disorders and cue-induced drug seeking. However, the role of the insula on memory retrieval and motivational integration for cue-elicited drug seeking remains to be determined. OBJECTIVES: We investigated the role of the anterior insular cortex (aIC) and its glutamatergic projection to amygdala nuclei (aIC-AMY) on the expression of conditioned place preference (CPP) during early and late abstinence. METHODS: Male adult C57BL/6J mice underwent amphetamine-induced CPP, and their preference was tested following 1 or 14 days of abstinence. aIC and aIC-AMY functional role in CPP expression was assessed at both abstinence periods by employing optogenetic silencing and behavioral pharmacology. RESULTS: Compared to a single day, an exacerbated preference for the amphetamine-paired context was observed after 14 days of abstinence. Photoinhibition of either aIC or aIC-AMY projection reduced CPP expression following late but not early abstinence. Similarly, the antagonism of aIC NMDA receptors reduced CPP expression after 14 days of abstinence but not 1 day. CONCLUSIONS: These results suggest that aIC and its glutamatergic output to amygdala nuclei constitute critical neurobiological substrates mediating enhanced motivational cue reactivity during the incubation of amphetamine craving rather than contextual memory recall. Moreover, cortical NMDA receptor signaling may become sensitized during abstinence, ultimately modulating disproportioned drug seeking.

Differential Effects of Neonatal Ventral Hippocampus Lesion on Behavior and Corticolimbic Plasticity in Wistar-Kyoto and Spontaneously Hypertensive Rats.

Dysfunction of the corticolimbic system, particularly at the dendritic spine level, is a recognized core mechanism in neurodevelopmental disorders such as schizophrenia. Neonatal ventral hippocampus lesion (NVHL) in Sprague-Dawley rats induces both a schizophrenia-related behavioral phenotype and dendritic spine pathology (reduced total number and mature spines) in corticolimbic areas, which is mitigated by antipsychotics. However, there is limited information on the impact of rat strain on NVHL outcomes and antipsychotic effects. We compared the behavioral performance in the open field, novel object recognition (NORT), and social interaction tests, as well as structural neuroplasticity with the Golgi-Cox stain in Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) male rats with and without NVHL. Additionally, we explored the effect of the atypical antipsychotic risperidone (RISP). WKY rats with NVHL displayed motor hyperactivity without impairments in memory and social behavior, accompanied by dendritic spine pathology in the neurons of the prefrontal cortex (PFC) layer 3 and basolateral amygdala. RISP treatment reduced motor activity and had subtle and selective effects on the neuroplasticity alterations. In SH rats, NVHL increased the time spent in the border area during the open field test, impaired the short-term performance in NORT, and reduced social interaction time, deficits that were corrected after RISP administration. The NVHL caused dendritic spine pathology in the PFC layers 3 and 5 of SH rats, which RISP treatment ameliorated. Our results support the utility of the NVHL model for exploring neuroplasticity mechanisms in schizophrenia and understanding pharmacotherapy.

Genomic glucocorticoid receptor effects guide acute stress-induced delayed anxiety and basolateral amygdala spine plasticity in rats.

Anxiety, a state related to anticipatory fear, can be adaptive in the face of environmental threats or stressors. However, anxiety can also become persistent and manifest as anxiety- and stress-related disorders, such as generalized anxiety or post-traumatic stress disorder (PTSD). In rodents, systemic administration of glucocorticoids (GCs) or short-term restraint stress induces anxiety-like behaviors and dendritic branching within the basolateral complex of the amygdala (BLA) ten days later. Additionally, increased arousal-related memory retention mediated by elevated GCs requires concomitant noradrenaline (NE) signaling, both acting in the BLA. It is unknown whether GCs and NE play a role in the delayed acute stress-induced effects on behavior and BLA dendritic plasticity. Here, inhibiting corticosterone (CORT) elevation during 2 h of restraint stress prevents stress-induced increases in delayed anxiety-like behavior and BLA dendritic spine density in rats. Also, we show that the delayed acute stress-induced effects on behavior and morphological alterations are critically dependent on genomic glucocorticoid receptor (GR) actions in the BLA. Unlike CORT, the pharmacological enhancement of NE signaling in the BLA was insufficient to drive delayed anxiety-related behavior. Nonetheless, the delayed anxiety-like behavior ten days after acute stress requires NE signaling in the BLA during stress exposure. Therefore, we define the essential roles of two stress-related hormones for the late stress consequences, acting at two separate times: CORT, via GR, immediately during stress, and NE, via beta-adrenoceptors, during the expression of delayed anxiety.

Morphological Features of Human Dendritic Spines.

Dendritic spine features in human neurons follow the up-to-date knowledge presented in the previous chapters of this book. Human dendrites are notable for their heterogeneity in branching patterns and spatial distribution. These data relate to circuits and specialized functions. Spines enhance neuronal connectivity, modulate and integrate synaptic inputs, and provide additional plastic functions to microcircuits and large-scale networks. Spines present a continuum of shapes and sizes, whose number and distribution along the dendritic length are diverse in neurons and different areas. Indeed, human neurons vary from aspiny or "relatively aspiny" cells to neurons covered with a high density of intermingled pleomorphic spines on very long dendrites. In this chapter, we discuss the phylogenetic and ontogenetic development of human spines and describe the heterogeneous features of human spiny neurons along the spinal cord, brainstem, cerebellum, thalamus, basal ganglia, amygdala, hippocampal regions, and neocortical areas. Three-dimensional reconstructions of Golgi-impregnated dendritic spines and data from fluorescence microscopy are reviewed with ultrastructural findings to address the complex possibilities for synaptic processing and integration in humans. Pathological changes are also presented, for example, in Alzheimer's disease and schizophrenia. Basic morphological data can be linked to current techniques, and perspectives in this research field include the characterization of spines in human neurons with specific transcriptome features, molecular classification of cellular diversity, and electrophysiological identification of coexisting subpopulations of cells. These data would enlighten how cellular attributes determine neuron type-specific connectivity and brain wiring for our diverse aptitudes and behavior.

Evidence for the existence of facilitatory interactions between the dopamine D2 receptor and the oxytocin receptor in the amygdala of the rat. Relevance for anxiolytic actions.

Introduction: The amygdala is a limbic region of high value for understanding anxiety and its treatment. Dopamine D2 receptors (D2Rs) and oxytocin receptors (OXTRs) have both been shown to participate in modulating anxiety involving effects in the amygdala. The goal is to understand if D2R-OXTR heterocomplexes exist in the central amygdala and if, through enhancing allosteric receptor-receptor interactions, may enhance anxiolytic actions. Methods: The methods used involve the shock-probe burying test, the in situ proximity ligation assay (PLA), image acquisition and analysis, and the BRET2 assay. Bilateral cannulas were introduced into the amygdala, and the effects of the coadministration of oxytocin and the D2R-like agonist quinpirole into the amygdala were studied. Results: The combination treatment enhanced the anxiolytic effects compared to the single treatment. The D2R/D3R antagonist raclopride blocked the effects of the combination treatment of oxytocin and the D2R agonist, although oxytocin is regarded as a distinct modulator of fear-mediating anxiolytic effects. In situ PLA results indicate the existence of D2R-OXTR heteroreceptor complexes and/or the co-location of OXTR and D2R within the same cell membrane nanodomains in the central amygdala. With BRET2, evidence is given for the existence of D2R-OXTR heteromers in HEK293 cells upon co-transfection. Discussion: The enhanced behavioral effects observed upon co-treatment with OXTR and D2R agonists may reflect the existence of improved positive receptor-receptor interactions in the putative D2R-OXTR heterocomplexes in certain neuronal populations of the basolateral and central amygdala. The D2R-OXTR heterocomplex, especially upon agonist co-activation in the central amygdala, may open a new pharmacological venue for the treatment of anxiety.

Brain structural correlates of psychopathic traits in elite female combat-sports athletes.

Psychopathy is characterized by glibness and superficial charm, as well as a lack of empathy, guilt and remorse, and is often accompanied by antisocial behaviour. The cerebral bases of this syndrome have been mostly studied in violent subjects or those with a criminal history. However, the antisocial component of psychopathy is not central to its conceptualization, and in fact, psychopathic traits are present in well-adjusted, non-criminal individuals within the general population. Interestingly, certain psychopathy characteristics appear to be particularly pronounced in some groups or professions. Importantly, as these so-called adaptive or successful psychopaths do not show antisocial tendencies or have significant psychiatric comorbidities, they may represent an ideal population to study this trait. Here, we investigated such a group, specifically elite female judo athletes, and compared them with matched non-athletes. Participants completed psychopathy, anger, perspective-taking and empathic concern questionnaires and underwent structural magnetic resonance imaging (MRI). Grey matter volume (GMV) was computed using voxel-based morphometry from the T1-weighted images. Athletes scored significantly higher in primary psychopathy and anger and lower in empathy and perspective taking. They also exhibited smaller GMV in the right temporal pole, left occipital cortex and left amygdala/hippocampus. GMV values for the latter cluster significantly correlated with primary psychopathy scores across both groups. These results confirm and extend previous findings to a little-studied population and provide support for the conceptualization of psychopathy as a dimensional personality trait which not only is not necessarily associated with antisocial behaviour but may potentially have adaptive value.

K252a Prevents Microglial Activation Induced by Anoxic Stimulation of Carotid Bodies in Rats.

Inducing carotid body anoxia through the administration of cyanide can result in oxygen deprivation. The lack of oxygen activates cellular responses in specific regions of the central nervous system, including the Nucleus Tractus Solitarius, hypothalamus, hippocampus, and amygdala, which are regulated by afferent pathways from chemosensitive receptors. These receptors are modulated by the brain-derived neurotrophic factor receptor TrkB. Oxygen deprivation can cause neuroinflammation in the brain regions that are activated by the afferent pathways from the chemosensitive carotid body. To investigate how microglia, a type of immune cell in the brain, respond to an anoxic environment resulting from the administration of NaCN, we studied the effects of blocking the TrkB receptor on this cell-type response. Male Wistar rats were anesthetized, and a dose of NaCN was injected into their carotid sinus to induce anoxia. Prior to the anoxic stimulus, the rats were given an intracerebroventricular (icv) infusion of either K252a, a TrkB receptor inhibitor, BDNF, or an artificial cerebrospinal fluid (aCSF). After the anoxic stimulus, the rats were perfused with paraformaldehyde, and their brains were processed for microglia immunohistochemistry. The results indicated that the anoxic stimulation caused an increase in the number of reactive microglial cells in the hypothalamic arcuate, basolateral amygdala, and dentate gyrus of the hippocampus. However, the infusion of the K252a TrkB receptor inhibitor prevented microglial activation in these regions.