Calcium-binding Proteins Calbindin Research Articles

Parvalbumin, calbindin, and calretinin immunostaining of 10 neural structures within the cerebellar cortex of 143 mammal species

In the current study we employed immunohistochemical techniques to investigate the localisation of three calcium-binding proteins (parvalbumin, calbindin, and calretinin) in 10 neuronal structures of the cerebellar cortex (stellate cells, basket cells, parallel fibres, climbing fibres, Purkinje cells, granule cells, Golgi type II cells, Lugaro neurons, unipolar brush neurons, and mossy fibres) in 143 species from across the mammalian radiation. Most often, parvalbumin was localised in the neural structures of the molecular and Purkinje cell layers but was absent in the granule cell layer. Calbindin was most often immunolocalised in the neural structures of the Purkinje cell layer and mossy fibres, whereas calretinin was most often immunolocalised in the climbing fibres of the molecular layer and all neural structures of the granule cell layer. Despite this general consistency, variations in the localisation of these three calcium-binding proteins were found in every lineage, and almost every species, the one exception being the western tree hyrax that showed the full suite of most often observed calcium-binding protein chemoarchitecture for the mammalian cerebellar cortex. These consistencies and variances in the calcium-binding protein chemoarchitecture of the cerebellar cortex of mammals may play significant roles in the species-specific learning and refining of motor, perceptual, and cognitive skills and capacities required to survive in the environments they inhabit.

Deletion of transcription factor Satb1 leads to disturbance in mice behavior through changes in the expression of genes-regulators of the excitive component of neurotransmission

The transcription factor Satb1 exhibits widespread expression in multiple tissues and different regions of the brain. Notable levels of expression are observed in the neocortex, the nucleus of the diagonal band, the amygdala, and the tegmental area. In the ventral midbrain, Satb1-positive neurons are only found in a small portion of the substantia nigra, the ventral tegmental area, and the retrorubral field, and none were detected in the inferior colliculus. The transcription factor Satb1 is highly expressed in interneurons labeled as SST+, CR+, and NPY+, but not VIP+ interneurons. In mice with the Satb1 mutation, incomplete eye opening and a constriction reflex were observed. Behavioral tests revealed that mice lacking Satb1 exhibited deficits in motor coordination, characterized by reduced mobility on flat bars and decreased grip strength on metal wires. In addition, these mice exhibited elevated levels of motor activity in novel environments and heightened anxiety in the light-dark test. Satb1-deficient males demonstrated proficiency in passive avoidance tests, while their female counterparts exhibited no significant difference in entrance time to the dark compartment between the reproduction and learning stages, indicating an impairment in the process of conditioned response formation. To investigate the expression patterns of genes encoding vital protein kinases and proteins associated with neurotransmission, we extracted total RNA from the cerebral cortex of adult males with an incomplete deletion of Satb1. Real-time PCR analysis was conducted, which revealed a higher expression level of the pik3ca, pik3cb, and pic3cg genes responsible for phosphoinositide-3-kinase isoforms in Satb1-deficient mice compared to wild-type mice. The expression levels of genes encoding protein kinase C (Prkce and Prkcg) as well as Ca2+/calmodulin-dependent protein kinase II (Camk2) were lower in comparison to wild-type mice. Satb1-deficient mice displayed notably higher expression levels of genes encoding NMDA receptor subunits (Grin1, Grin2a, and Grin2b), whereas the expression of Gria1 (encoding the Glua2 subunit of AMPA receptors responsible for Ca2+ receptor conductance) decreased. The influence on excitatory glutamate receptor expression can cause hyperexcitability in animals, particularly when inhibitory neurotransmission is suppressed due to decreased Gabra1 and Gad65/67 expression encoding the GABA(A) receptor and glutamate decarboxylase. In addition, the levels of expression for the Calb1, Calb2, and Pvalb genes responsible for encoding the calcium-binding proteins calbindin, calretinin, and parvalbumin decreased in comparison to the wild-type mice. Thus, a correlation was found between behavioral disturbances and expression of genes that encode proteins related to brain development and neurotransmission after deleting the Satb1 transcription factor. Satb1-deleted mice exhibited hyperexcitation and impaired motor activity due to impaired gene expression.

Characterization of the superior olivary complex of chimpanzees (Pan troglodytes) in comparison to humans

The superior olivary complex (SOC) is a collection of nuclei in the hindbrain of mammals with numerous roles in hearing, including localization of sound sources in the environment, encoding temporal and spectral elements of sound, and descending modulation of the cochlea. While there have been several investigations of the SOC in primates, there are discrepancies in the descriptions of nuclear borders and even the presence of certain cell groups among studies and species. Herein, we aimed to clarify some of these issues by characterizing the SOC from chimpanzees using Nissl staining, quantitative morphometry and immunohistochemistry. We found the medial superior olive (MSO) to be the largest of the SOC nuclei and the arrangement of its neurons and peri-MSO to be very similar to humans. Additionally, we found neurons in the medial nucleus of the trapezoid body (MNTB) to be immunopositive for the calcium binding protein calbindin. Further, most neurons in the MNTB, and some neurons in the lateral nucleus of the trapezoid body were associated with large, calretinin-immunoreactive calyx terminals. Together, these findings indicate the organization of the SOC of chimpanzees is organized very similar to the SOC in humans and suggests modifications to this region among species consistent with differences in head/body size, restricted hearing range and sensitivity to low frequency sounds.

Neuronal Calcium Sensor-1 Protects Cortical Neurons from Hyperexcitation and Ca2+ Overload during Ischemia by Protecting the Population of GABAergic Neurons.

A defection of blood circulation in the brain leads to ischemia, damage, and the death of nerve cells. It is known that individual populations of GABAergic neurons are the least resistant to the damaging factors of ischemia and therefore they die first of all, which leads to impaired inhibition in neuronal networks. To date, the neuroprotective properties of a number of calcium-binding proteins (calbindin, calretinin, and parvalbumin), which are markers of GABAergic neurons, are known. Neuronal calcium sensor-1 (NCS-1) is a signaling protein that is expressed in all types of neurons and is involved in the regulation of neurotransmission. The role of NCS-1 in the protection of neurons and especially their individual populations from ischemia and hyperexcitation has not been practically studied. In this work, using the methods of fluorescence microscopy, vitality tests, immunocytochemistry, and PCR analysis, the molecular mechanisms of the protective action of NCS-1 in ischemia/reoxygenation and hyperammonemia were established. Since NCS-1 is most expressed in GABAergic neurons, the knockdown of this protein with siRNA led to the most pronounced consequences in GABAergic neurons. The knockdown of NCS-1 (NCS-1-KD) suppressed the basic expression of protective proteins without significantly reducing cell viability. However, ischemia-like conditions (oxygen-glucose deprivation, OGD) and subsequent 24-h reoxygenation led to a more massive activation of apoptosis and necrosis in neurons with NCS-1-KD, compared to control cells. The mass death of NCS-1-KD cells during OGD and hyperammonemia has been associated with the induction of a more pronounced network hyperexcitation symptom, especially in the population of GABAergic neurons, leading to a global increase in cytosolic calcium ([Ca2+]i). The symptom of hyperexcitation of neurons with NCS-1-KD correlated with a decrease in the level of expression of the calcium-binding protein-parvalbumin. This was accompanied by an increase in the expression of excitatory ionotropic glutamate receptors, N-methyl-D-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (NMDAR and AMPAR) against the background of suppression of the expression of glutamate decarboxylase (synthesis of γ-aminobutyric acid).

The retrosplenial cortex of Carollia perspicillata, Seba's short‐tailed fruit bat

Retrosplenial cortex (RSC) is a brain region involved in critical cognitive functions including memory, planning, and spatial navigation and is commonly affected in neurodegenerative diseases. Subregions of RSC are typically described as Brodmann areas 29 and 30, which are defined by cytoarchitectural features. Using immunofluorescence, we studied the distributions of neurons immunoreactive for NeuN, latexin, and calcium binding proteins (calbindin, calretinin, and parvalbumin) in RSC of Carollia perspicillata, Seba's short-tailed fruit bat. We observed that latexin was specifically present in areas 29a and 29b but not 29c and 30. We further identified distribution patterns of calcium binding proteins that group areas 29a and 29b separately from areas 29c and 30. We conclude first that latexin is a useful marker to classify subregions of RSC and second that these subregions contain distinct patterns of neuronal immunoreactivity for calcium binding proteins. Given the long lifespan of Carollia, bat RSC may be a useful model in studying age-related neurodegeneration.

Abnormal vestibular brainstem structure and function in an animal model of autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that includes several key neuropathological changes and behavioral impairments. In utero exposure to the anti-epileptic valproic acid (VPA) increases risk of an ASD diagnosis in human subjects and timed in utero exposure to VPA is a clinically relevant animal model of ASD. Many human subjects with ASD have cerebellar hypoplasia, fewer Purkinje cells, difficulties with balance, ophthalmic dysfunction and abnormal responses to vestibular stimulation and such vestibular difficulties are likely under reported in ASD. We have recently shown that animals exposed to VPA in utero have fewer neurons in their auditory brainstem, reduced axonal projections to the auditory midbrain and thalamus, reduced expression of the calcium binding protein calbindin (CB) in the brainstem and cerebellum, smaller and occasionally ectopic cerebellar Purkinje cells and ataxia on several motor tasks. Based on these findings, we hypothesized that in utero VPA exposure similarly impacts structure and function of the vestibular brainstem. We investigated this hypothesis using quantitative morphometric analyses, immunohistochemistry for CB, a battery of vestibular challenges, recording of vestibular-evoked myogenic potentials and spontaneous eye movements. Our results indicate that VPA exposure results in fewer neurons in the vestibular nuclei, fewer CB-positive puncta, difficulty on certain motor tasks, longer latency VEMPs and significantly more horizontal eye movements. These findings indicate that the vestibular nuclei are impacted by in utero VPA exposure and provide a basis for further study of vestibular circuits in human cases of ASD.

Molecular and functional characterization of the mouse intrinsic cardiac nervous system.

The intrinsic cardiac nervous system (ICNS) refers to clusters of neurons, located within the heart, that participate in the neuronal regulation of cardiac functions and that are involved in the initiation of cardiac arrhythmias. Therefore, deciphering its role in cardiac physiology and physiopathology is mandatory. The aim of this study was to provide a phenotypic, electrophysiological, and pharmacological characterization of the mouse ICNS, which is still poorly characterized. Global cardiac innervation and phenotypic diversity were investigated using immunohistochemistry on cleared murine hearts and on tissue sections. The patch clamp technique was used for the electrophysiological and pharmacological characterization of isolated mouse intracardiac neurons. We have identified the expression of 7 distinct neuronal markers within the mouse ICNS, thus proving the neurochemical diversity of this network. Of note, it was the first time that the existenceof neurons expressing the calcium-binding protein calbindin, neuropeptide Y, and cocaine and amphetamine regulated transcript peptide was described in the mouse. Electrophysiology studies also revealed the existence of 4 different neuronal populations on the basis of their electrical behavior. Finally, we showed that these neurons can be modulated by several neuromodulators. This study showed that the mouse ICNS presents a molecular and functional complexity similar to other species and is therefore a suitable model to decipher the role of individual neuronal subtypes regarding the modulation of cardiac function and the initiation of cardiac arrhythmias.

Time course of dorsolateral geniculate nucleus plasticity in adult monkeys with laser-induced retinal lesions.

We studied changes in the expression of growth-associated protein 43 (GAP43), glial fibrillary acidic protein (GFAP), and calcium-binding proteins (calbindin [Cb] and parvalbumin [Pv]) in the dorsal lateral geniculate nucleus (dLGN) of four capuchin monkeys with laser-induced retinal lesions. The lesions were generated with the aid of a neodymium-YAG dual-frequency laser with shots of different intensity and at different survival time in each animal. The expression of these proteins in the layers of the dLGN was evaluated by performing histodensitometry of coronal sections throughout the nucleus. High-power laser shots administered at the border of the optic disc (OD)-injured fibers resulted in large scotomas. These lesions produced a devastating effect on fibers in this passage, resulting in large deafferentation of the dLGN. The time course of plasticity expressed in this nucleus varied with the degree of the retinal lesion. Topographically, corresponding portions of the dLGN were inferred by the extent of the ocular dominance column revealed by cytochrome oxidase histochemistry in flattened preparations of V1. In the region representing the retinal lesion, the expression of GFAP, GAP43, Pv, and Cb increased and decreased in the corresponding dLGN layers shortly after lesion induction and returned to their original values with different time courses. Synaptogenesis (indicated by GAP43 expression) appeared to be increased in all layers, while "cleansing" of the glial-damaged region (indicated by GFAP expression) was markedly greater in the parvocellular layers, followed by the magnocellular layers. Schematic drawings of optic discs laser lesions and of series of coronal sections of the dLGN, in three monkeys, depicting the areas of the nucleus deafferented by the lesions.

Dual medial prefrontal cortex and hippocampus projecting neurons in the paraventricular nucleus of the thalamus.

The paraventricular nucleus (PVT) of the midline thalamus is a critical higher-order cortico-thalamo-cortical integration site that plays a critical role in various behaviors including reward seeking, cue saliency, and emotional memory. Anatomical studies have shown that PVT projects to both medial prefrontal cortex (mPFC) and hippocampus (HC). However, dual mPFC-HC projecting neurons which could serve a role in synchronizing mPFC and HC activity during PVT-dependent behaviors, have not been explored. Here we used a dual retrograde adenoassociated virus (AAV) tracing approach to characterize the location and proportion of different projection populations that send collaterals to mPFC and/or ventral hippocampus (vHC) in rats. Additionally, we examined the distribution of calcium binding proteins calretinin (CR) and calbindin (CB) with respect to these projection populations in PVT. We found that PVT contains separate populations of cells that project to mPFC, vHC, and those that innervate both regions. Interestingly, dual mPFC-HC projecting cells expressed neither CR nor CB. Topographically, CB+ and CR+ containingcells clustered around dual projecting neurons in PVT. These results are consistent with the features of dual mPFC-vHC projecting cells in the nucleus reuniens (RE) and suggestive of a functional mPFC-PVT-vHC system that may support mPFC-vHC interactions in PVT-dependent behaviors.

Identifying Types of Neurons in the Human Colonic Enteric Nervous System.

Distinguishing and characterising the different classes of neurons that make up a neural circuit has been a long-term goal for many neuroscientists. The enteric nervous system is a large but moderately simple part of the nervous system. Enteric neurons in laboratory animals have been extensively characterised morphologically, electrophysiologically, by projections and immunohistochemically. However, studies of human enteric nervous system are less advanced despite the potential availability of tissue from elective surgery (with appropriate ethics permits). Recent studies using single cell sequencing have confirmed and extended the classification of enteric neurons in mice and human, but it is not clear whether an encompassing classification has been achieved. We present preliminary data on a means to distinguish classes of myenteric neurons in specimens of human colon combining immunohistochemical, morphological, projection and size data on single cells. A method to apply multiple layers of antisera to specimens was developed, allowing up to 12 markers to be characterised in individual neurons. Applied to multi-axonal Dogiel type II neurons, this approach demonstrated that they constitute fewer than 5% of myenteric neurons, are nearly all immunoreactive for choline acetyltransferase and tachykinins. Many express the calcium-binding proteins calbindin and calretinin and they are larger than average myenteric cells. This methodology provides a complementary approach to single-cell mRNA profiling to provide a comprehensive account of the types of myenteric neurons in the human colon.

Pathways for Memory, Cognition and Emotional Context: Hippocampal, Subgenual Area 25, and Amygdalar Axons Show Unique Interactions in the Primate Thalamic Reuniens Nucleus.

The reuniens nucleus (RE) is situated at the most ventral position of the midline thalamus. In rats and mice RE is distinguished by bidirectional connections with the hippocampus and medial prefrontal cortex (mPFC) and a role in memory and cognition. In primates, many foundational questions pertaining to RE remain unresolved. We addressed these issues by investigating the composition of the rhesus monkey RE in both sexes by labeling for GABA, a marker of inhibitory neurons, and for the calcium-binding proteins parvalbumin (PV), calbindin (CB), and calretinin (CR), which label thalamic excitatory neurons that project to cortex. As in rats and mice, the macaque RE was mostly populated by CB and CR neurons, characteristic of matrix-dominant nuclei, and had bidirectional connections with hippocampus and mPFC area 25 (A25). Unlike rodents, we found GABAergic neurons in the monkey RE and a sparser but consistent population of core-associated thalamocortical PV neurons. RE had stronger connections with the basal amygdalar complex than in rats or mice. Amygdalar terminations were enriched with mitochondria and frequently formed successive synapses with the same postsynaptic structures, suggesting an active and robust pathway to RE. Significantly, hippocampal pathways formed multisynaptic complexes that uniquely involved excitatory projection neurons and dendrites of local inhibitory neurons in RE, extending this synaptic principle beyond sensory to high-order thalamic nuclei. Convergent pathways from hippocampus, A25, and amygdala in RE position it to flexibly coordinate activity for memory, cognition, and emotional context, which are disrupted in several psychiatric and neurologic diseases in humans.SIGNIFICANCE STATEMENT The primate RE is a central node for memory and cognition through connections with the hippocampus and mPFC. As in rats or mice, the primate RE is a matrix-dominant thalamic nucleus, suggesting signal traffic to the upper cortical layers. Unlike rats or mice, the primate RE contains inhibitory neurons, synaptic specializations with the hippocampal pathway, and robust connections with the amygdala, suggesting unique adaptations. Convergence of hippocampal, mPFC, and amygdalar pathways in RE may help unravel a circuit basis for binding diverse signals for conscious flexible behaviors and the synthesis of memory with affective significance in primates, whereas disruption of distinct circuit nodes may occur in psychiatric disorders in humans.

Immuno-histological detection of resistant columnar units and vulnerable networks in the rat retina after asphyxia-induced transient cardiac arrest.

Stroke-related loss of vision is one of the residual impairments, restricting the quality of life. However, studies of the ocular manifestations of asphyxia cardiac arrest/resuscitation (ACA/R) have reported very heterogeneous results. We aimed to evaluate the ACA/R-induced degeneration pattern of the different retinal cell populations in rats using different immuno-histological stainings. The staining pattern of toluidine blue and the ganglion cell markers β-III-tubulin and NeuN; the calcium-binding protein parvalbumin, indicating ganglion, amacrine, and horizontal cells; calretinin D28k, indicating ganglion and amacrine cells; calbindin, indicating horizontal cells; Chx 10, indicating cone bipolar cells; PKCα, indicating ON-type rod bipolar cells; arrestin, indicating cones; and rhodopsin, a marker of rods, as well as the glial cell markers GFAP (indicating astroglia and Müller cells) and IBA1 (indicating microglia), were evaluated after survival times of 7 and 21 days in an ACA/R rat model. Moreover, quantitative morphological analysis of the optic nerve was performed. The ACA/R specimens were compared with those from sham-operated and completely naïve rats. ACA/R-induced effects were: (i) a significant reduction of retinal thickness after long-term survival; (ii) ganglion cell degeneration, including their fiber network in the inner plexiform layer; (iii) degeneration of amacrine and cone bipolar cells; (iv) degeneration of cone photoreceptors; (v) enhanced resistance to ACA/R by rod photoreceptors, ON-type rod bipolar and horizontal cells, possibly caused by the strong upregulation of the calcium-binding proteins calretinin, parvalbumin, and calbindin, counteracting the detrimental calcium overload; (vi) significant activation of Müller cells as further element of retinal anti-stress self-defense mechanisms; and (vii) morphological alterations of the optic nerve in form of deformed fibers. Regardless of the many defects, the surviving neuronal structures seemed to be able to maintain retinal functionality, which can be additionally improved by regenerative processes true to the "use it or lose it" dogma.

Molecular predictors of response to selinexor in advanced unresectable de-differentiated liposarcoma (DDLS).

11509 Background: Patients (pts) with recurrent inoperative DDLS have a poor prognosis and limited treatment options. Selinexor is an oral, selective inhibitor of nuclear export (SINE) compound approved for previously treated pts with myeloma and diffuse large B-cell lymphoma. SEAL was a Phase 2-3 randomized, double-blind, study of selinexor versus placebo in pts with progressive DDLS and 2-5 prior systemic therapies. SEAL showed significantly prolonged progression-free survival (PFS, HR = 0.70, p = 0.0228) with well managed toxicity. A biomarker predictive of clinical activity could be used to optimize selection of pts with DDLS for selinexor. Methods: Pts were randomized 2:1 for Phase 3: 188 received twice weekly selinexor (60mg) and 97 received placebo. Three exploratory biomarker analyses (RNA sequencing of biopsies) from selinexor-treated pts were performed: discovery set of sensitive (n = 8) or resistant (n = 9) tumors; a validation set of pts with favorable (n = 19) or poor (n = 14) tumor control based on PFS, and paired lesions from a pt who harbored both a responsive and resistant lesion. Tumor biopsies from 24 pts on placebo with short ( < 5 months, n = 18) and long ( > 6 months, n = 6) PFS were RNA sequenced. Gene expressions were compared using a negative binomial distribution with DeSeq2. Pathway analyses were performed using Gene Set Enrichment Analysis (GSEA) with MSigDB Cancer Gene Neighborhoods. Results: RNA sequencing analysis comparing 17 sensitive and resistant tumors identified 114 differentially expressed genes (adjusted p-values < 0.05). Expression of CALB1, which encodes the calcium-binding protein calbindin, was significantly lower in sensitive tumors (adjusted P [Padj] = 7.5x10-20), and expression of GRM1, which encodes a metabotropic glutamate receptor that activates phospholipase C, was higher in selinexor sensitive tumors (Padj= 0.003). These findings were confirmed in an independent validation set (Padj = 0.01 – 0.02). In the pt with paired sensitive and resistant lesions, CALB1 expression was 52-fold lower in the sensitive tumor. In a comparison of placebo-treated pts, neither CALB1 or GRM1 was differentially expressed between pts with short or long PFS, indicating they are markers of response to selinexor treatment, rather than general markers of disease aggressiveness. Gene set enrichment analyses revealed that selinexor sensitive tumors in the discovery and validation sets showed upregulation of cancer genes related to SNRK and the netrin 1 receptor tumor suppressor DCC. The resistant tumors showed upregulated EIF3S2 translation initiator-related genes. Conclusions: Selinexor sensitive DDLS tumors showed low expression of CALB1 and high GRM1. If validated, pts with DDLS whose tumors match this expression profile are especially likely to benefit from selinexor. Clinical trial information: NCT02606461.

Characterization of basal forebrain glutamate neurons suggests a role in control of arousal and avoidance behavior.

The basal forebrain (BF) is involved in arousal, attention, and reward processing but the role of individual BF neuronal subtypes is still being uncovered. Glutamatergic neurons are the least well-understood of the three main BF neurotransmitter phenotypes. Here we analyzed the distribution, size, calcium-binding protein content and projections of the major group of BF glutamatergic neurons expressing the vesicular glutamate transporter subtype 2 (vGluT2) and tested the functional effect of activating them. Mice expressing Cre recombinase under the control of the vGluT2 promoter were crossed with a reporter strain expressing the red fluorescent protein, tdTomato, to generate vGluT2-cre-tdTomato mice. Immunohistochemical staining for choline acetyltransferase and a cross with mice expressing green fluorescent protein selectively in GABAergic neurons confirmed that cholinergic, GABAergic and vGluT2+ neurons represent distinct BF subpopulations. Subsets of BF vGluT2+ neurons expressed the calcium-binding proteins calbindin or calretinin, suggesting that multiple subtypes of BF vGluT2+ neurons exist. Anterograde tracing using adeno-associated viral vectors expressing channelrhodopsin2-enhanced yellow fluorescent fusion proteins revealed major projections of BF vGluT2+ neurons to neighboring BF cholinergic and parvalbumin neurons, as well as to extra-BF areas involved in the control of arousal or aversive/rewarding behavior such as the lateral habenula and ventral tegmental area. Optogenetic activation of BF vGluT2+ neurons elicited a striking avoidance of the area where stimulation was given, whereas stimulation of BF parvalbumin or cholinergic neurons did not. Together with previous optogenetic findings suggesting an arousal-promoting role, our findings suggest that BF vGluT2 neurons play a dual role in promoting wakefulness and avoidance behavior.

Neonatal exposure to monosodium glutamate results in impaired auditory brainstem structure and function

Excitotoxic injury during the neonatal period has been shown to result in neurodegenerative changes in several different brain regions. Exposure to monosodium glutamate (MSG) during the first two postnatal weeks results in glutamate neurotoxicity in the cochlea and has been shown to result in damage to cochlear hair cells and fewer neurons in the spiral ganglion. Further, we have shown that such exposure results in fewer neurons in the cochlear nucleus and superior olivary complex and abnormal expression of the calcium binding proteins calbindin and calretinin. Based on these findings, we hypothesized that neonatal MSG exposure would result in loss of neurons at more rostral levels in the auditory brainstem, and this exposure would result in abnormal brainstem auditory evoked potentials. We identified a significantly lower density of neurons in the spiral ganglion, heterogenous loss of neurons in the globular bushy cell-trapezoid body circuit, and fewer neurons in the nuclei of the lateral lemniscus and central nucleus of the inferior colliculus. The most severe loss of neurons was found in the inferior colliculus. Click-evoked auditory brainstem responses revealed significantly higher thresholds and longer latency responses, but these did not deteriorate with age. These results, together with our previous findings, indicate that neonatal exposure to MSG results in fewer neurons throughout the entire auditory brainstem and results in abnormal auditory brainstem responses.

Neonatal proinflammatory challenge evokes a microglial response and affects the ratio between subtypes of GABAergic interneurons in the hippocampus of juvenile rats: sex-dependent and sex-independent effects.

Neonatal proinflammatory challenge (NPC) may contribute to the development of psychiatric disorders in adults. A double exposure of neonatal rats to lipopolysaccharide, a component of cellular wall of gram-negative bacteria, on postnatal days 3 and 5 provokes the development of depressive- and anxiety-like behaviors. NPC impairs neuroplasticity and cognition in adult animals, significant modifications of neuroplasticity being evident even in adolescence. We studied effects of NPC on microglia and GABAergic neuronal population of the dorsal hippocampus in juvenile male and female rats using immunofluorescent histochemistry. The expression of glutamic acid decarboxylase-67 (GAD67) and calcium-binding proteins calretinin, calbindin, and parvalbumin were used as quantitative markers of GABAergic interneurons and their specific subpopulations, respectively. NPC induced changes of microglial morphology indicating inflammatory activation mostly expressed in CA3 field; the effect was similar in males and females. The number of GAD67 expressing neurons was similar in the dorsal hippocampus of females and males independently on the NPC. The portion of calbindin-immunoreactive GAD67-positive neurons significantly increased while the portion of calretinin-immunoreactive GAD67-positive neurons significantly decreased in the CA1 field of rats exposed to NPC independently on their sex. NPC did not affect the parvalbumin-positive subpopulation of GABAergic neurons in the hippocampus of rats of either sex. These data suggest that NPC-induced modification of GABAergic neuronal population composition under the proinflammatory conditions is involved in the maintenance of excitation/inhibition homeostatic balance in the hippocampus.

Нейрохимические особенности нейропептид-Y-ергических энтеральных нейронов подслизистого сплетения тонкой кишки в постнатальном онтогенезе

Neuropeptide Y (NPY) plays an important role in the nervous system, including the regulation of vascular tone and gastrointestinal secretion, has a direct inhibitory effect on intestinal motility and secretion. Colocalization of NPY with the enzyme for the synthesis of acetylcholine - choline acetyltransferase (ChAT), neuronal NO synthase (nNOS), vasoactive intestinal peptide (VIP) and calcium-binding protein calbindin (CB) was detected in the neurons of the submucous plexus of the small intestine of rats from the moment of birth until old age using immunohistochemical method of double labeling with antibodies and fluorescence microscopy. From the moment of birth, all NPY-immunoreactive neurons colocalize ChAT. Most of NPY-containing neurons also contain VIP and CB. In aged rats, the percentage of NPY-immunoreactive neurons containing CB, VIP, and ChAT decreases. In young rats from newborns to 20-day-old as well as in aged rats, nNOS is detected in NPY-positive neurons. Thus, at the early stages of ontogenesis and in the senescence, the enteric metasympathetic NPY-immunoreactive submucous neurons contain a wider range of neurotransmitters when compared to adult animals.

Densities and numbers of calbindin and parvalbumin positive neurons across the rat and mouse brain.

SummaryThe calcium-binding proteins parvalbumin and calbindin are expressed in neuronal populations regulating brain networks involved in spatial navigation, memory processes, and social interactions. Information about the numbers of these neurons across brain regions is required to understand their functional roles but is scarcely available. Employing semi-automated image analysis, we performed brain-wide analysis of immunohistochemically stained parvalbumin and calbindin sections and show that these neurons distribute in complementary patterns across the mouse brain. Parvalbumin neurons dominate in areas related to sensorimotor processing and navigation, whereas calbindin neurons prevail in regions reflecting behavioral states. We also find that parvalbumin neurons distribute according to similar principles in the hippocampal region of the rat and mouse brain. We validated our results against manual counts and evaluated variability of results among researchers. Comparison of our results to previous reports showed that neuron numbers vary, whereas patterns of relative densities and numbers are consistent.

Selective Knockout of the Vesicular Monoamine Transporter 2 (Vmat2) Gene in Calbindin2/Calretinin-Positive Neurons Results in Profound Changes in Behavior and Response to Drugs of Abuse.

The vesicular monoamine transporter 2 (VMAT2) has a range of functions in the central nervous system, from sequestering toxins to providing conditions for the quantal release of monoaminergic neurotransmitters. Monoamine signaling regulates diverse functions from arousal to mood, movement, and motivation, and dysregulation of VMAT2 function is implicated in various neuropsychiatric diseases. While all monoamine-releasing neurons express the Vmat2 gene, only a subset is positive for the calcium-binding protein Calbindin 2 (Calb2; aka Calretinin, 29 kDa Calbindin). We recently showed that about half of the dopamine neurons in the mouse midbrain are positive for Calb2 and that Calb2 is an early developmental marker of midbrain dopamine cells. Calb2-positive neurons have also been identified in other monoaminergic areas, yet the role of Calb2-positive monoaminergic neurons is poorly understood. To selectively address the impact of Calb2-positive monoaminergic neurons in behavioral regulation, we took advantage of the Cre-LoxP system to create a new conditional knockout (cKO) mouse line in which Vmat2 expression is deleted selectively in Calb2-Cre-positive neurons. In this Vmat2lox/lox;Calb2−Cre cKO mouse line, gene targeting of Vmat2 was observed in several distinct monoaminergic areas. By comparing control and cKO mice in a series of behavioral tests, specific dissimilarities were identified. In particular, cKO mice were smaller than control mice and showed heightened sensitivity to the stereotypy-inducing effects of amphetamine and slight reductions in preference toward sucrose and ethanol, as well as a blunted response in the elevated plus maze test. These data uncover new knowledge about the role of genetically defined subtypes of neurons in the brain’s monoaminergic systems.

Functional expression of TrkB receptors on interneurones and pyramidal cells of area CA3 of the rat hippocampus

The dentate gyrus and hippocampal area CA3 region of the mammalian brain contains the highest levels of brain-derived neurotrophic factor (BDNF) and its canonical membrane receptor, tropomyosin-related kinase B (TrkB). Therefore, the present study examines the expression and physiological responses triggered by activation of TrkB on hippocampal area CA3 interneurones and pyramidal cells of the rat hippocampus. Triple immunolabelling for TrkB, glutamate decarboxylase 67, and the calcium-binding proteins parvalbumin, calbindin or calretinin confirms the somatic expression of TrkB in all CA3 sublayers. TrkB-positive interneurones with fast-spiking discharge are restricted to strata oriens and lucidum, whereas regular-spiking interneurones are found in the strata lucidum, radiatum and lacunosum-moleculare. Activation of TrkB receptors with 7,8-dihydroxyflavone (DHF) modulates amplitude and frequency of spontaneous synaptic currents recorded from CA3 interneurones. Furthermore, the isolated excitatory postsynaptic currents (EPSC) of CA3 interneurones evoked by the mossy fibres (MF) or commissural/associational (C/A) axons, show input-specific synaptic potentiation in response to TrkB stimulation. On CA3 pyramidal cells, stimulation with DHF potentiates the MF synaptic transmission and increases the MF-EPSP – spike coupling. The latter exhibits a dramatic increase when picrotoxin is bath perfused after DHF, indicating that local interneurones restrain the excitability mediated by activation of TrkB. Therefore, we propose that release of BDNF on area CA3 reshapes the output of this hippocampal region by simultaneous activation of TrkB on GABAergic interneurones and pyramidal cells.