RESUMEN
Many cortical brain regions are spatially organized to optimize sensory representation. Such topographic maps have so far been elusive in the olfactory cortex. A high-throughput tracing study reveals that the neural circuits connecting olfactory regions are indeed topographically organized.
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Mapeo Encefálico , Corteza Olfatoria , Animales , Ratones , Corteza Olfatoria/citología , Corteza Olfatoria/fisiología , Neurociencias/métodos , Neuronas/citologíaRESUMEN
BACKGROUND: The ability to correctly associate cues and contexts with threat is critical for survival, and the inability to do so can result in threat-related disorders such as posttraumatic stress disorder. The prefrontal cortex (PFC) and hippocampus are well known to play critical roles in cued and contextual threat memory processing. However, the circuits that mediate prefrontal-hippocampal modulation of context discrimination during cued threat processing are less understood. Here, we demonstrate the role of a previously unexplored projection from the ventromedial region of PFC (vmPFC) to the lateral entorhinal cortex (LEC) in modulating the gain of behavior in response to contextual information during threat retrieval and encoding. METHODS: We used optogenetics followed by in vivo calcium imaging in male C57/B6J mice to manipulate and monitor vmPFC-LEC activity in response to threat-associated cues in different contexts. We then investigated the inputs to, and outputs from, vmPFC-LEC cells using Rabies tracing and channelrhodopsin-assisted electrophysiology. RESULTS: vmPFC-LEC cells flexibly and bidirectionally shaped behavior during threat expression, shaping sensitivity to contextual information to increase or decrease the gain of behavioral output in response to a threatening or neutral context, respectively. CONCLUSIONS: Glutamatergic vmPFC-LEC cells are key players in behavioral gain control in response to contextual information during threat processing and may provide a future target for intervention in threat-based disorders.
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Conducta , Miedo , Vías Nerviosas , Corteza Olfatoria , Corteza Prefrontal , Animales , Masculino , Ratones , Conducta/fisiología , Señalización del Calcio , Channelrhodopsins/metabolismo , Señales (Psicología) , Ácido Glutámico/metabolismo , Ratones Endogámicos C57BL , Corteza Olfatoria/citología , Corteza Olfatoria/fisiología , Optogenética , Corteza Prefrontal/citología , Corteza Prefrontal/fisiología , Trastornos por Estrés Postraumático/fisiopatología , Técnicas de Placa-ClampRESUMEN
During adult rodent life, newborn neurons are added to the olfactory bulb (OB) in a tightly controlled manner. Upon arrival in the OB, input synapses from the local bulbar network and the higher olfactory cortex precede the formation of functional output synapses, indicating a possible role for these regions in newborn neuron survival. An interplay between the environment and the piriform cortex in the regulation of newborn neuron survival has been suggested. However, the specific network and the neuronal cell types responsible for this effect have not been elucidated. Furthermore, the role of the other olfactory cortical areas in this process is not known. Here we demonstrate that pyramidal neurons in the mouse anterior olfactory nucleus, the first cortical area for odor processing, have a key role in the survival of newborn neurons. Using DREADD (Designer Receptors Exclusively Activated by Designer Drugs) technology, we applied chronic stimulation to the anterior olfactory nucleus and observed a decrease in newborn neurons in the OB through induction of apoptosis. These findings provide further insight into the network regulating neuronal survival in adult neurogenesis and strengthen the importance of the surrounding network for sustained integration of new neurons.
Asunto(s)
Neurogénesis/fisiología , Neuronas/fisiología , Bulbo Olfatorio/citología , Bulbo Olfatorio/fisiología , Corteza Olfatoria/citología , Corteza Olfatoria/fisiología , Factores de Edad , Animales , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Femenino , Ratones , Ratones Endogámicos C57BL , Neurogénesis/efectos de los fármacos , Neuronas/efectos de los fármacos , Odorantes , Bulbo Olfatorio/efectos de los fármacos , Corteza Olfatoria/efectos de los fármacos , Vías Olfatorias/citología , Vías Olfatorias/efectos de los fármacos , Vías Olfatorias/fisiología , Olfato/fisiologíaRESUMEN
The neocortex and olfactory cortices share many features including their laminar organization, developmental sequences, and cell types. Previous work indicates that neocortical pyramidal cells exhibit a gradient of dendritic size: cells involved in the initial processing of information are less complex than those in subsequent, higher processing areas. Results presented here confirm that the same is true for the olfactory cortex: pyramidal cells in the region closest to the olfactory bulb, the anterior olfactory nucleus, have smaller total dendritic length and occupy less neural space than those in the posterior piriform cortex. These findings add to the evidence for general rules of development, organization, and function across forebrain cortices.
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Corteza Olfatoria/metabolismo , Células Piramidales/metabolismo , Animales , Ratones , Corteza Olfatoria/citología , Células Piramidales/citologíaRESUMEN
Sjögren's syndrome (SS) is a systemic autoimmune disease characterized by progressive inflammation and tissue damage in salivary glands and lacrimal glands. Our previous studies showed that myeloid-derived suppressor cells (MDSCs) exhibited impaired immunosuppressive function during disease progression in patients with SS and mice with experimental Sjögren's syndrome (ESS), but it remains unclear whether restoring the function of MDSCs can effectively ameliorate the development of ESS. In this study, we found that murine olfactory ecto-mesenchymal stem cell-derived exosomes (OE-MSC-Exos) significantly enhanced the suppressive function of MDSCs by upregulating arginase expression and increasing ROS and NO levels. Moreover, treatment with OE-MSC-Exos via intravenous injection markedly attenuated disease progression and restored MDSC function in ESS mice. Mechanistically, OE-MSC-Exo-secreted IL-6 activated the Jak2/Stat3 pathway in MDSCs. In addition, the abundant S100A4 in OE-MSC-Exos acted as a key factor in mediating the endogenous production of IL-6 by MDSCs via TLR4 signaling, indicating an autocrine pathway of MDSC functional modulation by IL-6. Taken together, our results demonstrated that OE-MSC-Exos possess therapeutic potential to attenuate ESS progression by enhancing the immunosuppressive function of MDSCs, possibly constituting a new strategy for the treatment of Sjögren's syndrome and other autoimmune diseases.
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Exosomas/metabolismo , Trasplante de Células Madre Mesenquimatosas/métodos , Células Madre Mesenquimatosas/citología , Células Supresoras de Origen Mieloide/inmunología , Corteza Olfatoria/citología , Síndrome de Sjögren/terapia , Linfocitos T Reguladores/inmunología , Animales , Femenino , Ratones , Ratones Endogámicos C57BL , Transducción de Señal , Síndrome de Sjögren/inmunología , Síndrome de Sjögren/patologíaRESUMEN
The volume of the olfactory bulbs (OBs) relative to the brain has been used previously as a proxy for olfactory capabilities in many vertebrate taxa, including fishes. Although this gross approach has predictive power, a more accurate assessment of the number of afferent olfactory inputs and the convergence of this information at the level of the telencephalon is critical to our understanding of the role of olfaction in the behaviour of fishes. In this study, we used transmission electron microscopy to assess the number of first-order axons within the olfactory nerve (ON) and the number of second-order axons in the olfactory peduncle (OP) in established model species within cartilaginous (brownbanded bamboo shark, Chiloscyllium punctatum [CP]) and bony (common goldfish, Carassius auratus [CA]) fishes. The total number of axons varied from a mean of 18.12 ± 7.50 million in the ON to a mean of 0.38 ± 0.21 million in the OP of CP, versus 0.48 ± 0.16 million in the ON and 0.09 ± 0.02 million in the OP of CA. This resulted in a convergence ratio of approximately 50:1 and 5:1, respectively, for these two species. Based on astroglial ensheathing, axon type (unmyelinated [UM] and myelinated [M]) and axon size, we found no differentiated tracts in the OP of CP, whereas a lateral and a medial tract (both of which could be subdivided into two bundles or areas) were identified for CA, as previously described. Linear regression analyses revealed significant differences not only in axon density between species and locations (nerves and peduncles), but also in axon type and axon diameter (p < 0.05). However, UM axon diameter was larger in the OPs than in the nerve in both species (p = 0.005), with no significant differences in UM axon diameter in the ON (p = 0.06) between species. This study provides an in-depth analysis of the neuroanatomical organisation of the ascending olfactory pathway in two fish taxa and a quantitative anatomical comparison of the summation of olfactory information. Our results support the assertion that relative OB volume is a good indicator of the level of olfactory input and thereby a proxy for olfactory capabilities.
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Axones/ultraestructura , Carpa Dorada/anatomía & histología , Bulbo Olfatorio/citología , Nervio Olfatorio/citología , Vías Olfatorias/citología , Tiburones/anatomía & histología , Animales , Microscopía Electrónica de Transmisión , Bulbo Olfatorio/ultraestructura , Corteza Olfatoria/citología , Nervio Olfatorio/ultraestructura , Vías Olfatorias/ultraestructuraRESUMEN
Sensory systems detect environmental stimuli and transform them into electrical activity patterns interpretable by the central nervous system. En route to higher brain centers, the initial sensory input is successively transformed by interposed secondary processing centers. Mapping the neuronal activity patterns at all of those stages is essential to understand sensory information processing. Larval Xenopus laevis is very well-suited for whole-brain imaging of neuronal activity. This is mainly due to its small size, transparency, and the accessibility of both peripheral and central parts of sensory systems. Here we describe a protocol for calcium imaging at several levels of the olfactory system using focal injection of chemical calcium indicator dyes or a Xenopus transgenic line with neuronal GCaMP6s expression. In combination with fast volumetric multiphoton microscopy, the calcium imaging methods described can provide detailed insight into spatiotemporal activity of entire brain regions at different stages of sensory information processing. Although the methods are broadly applicable to the central nervous system, in this work we focus on protocols for calcium imaging of glomeruli in the olfactory bulb and odor-responsive neurons in the olfactory amygdala.
Asunto(s)
Encéfalo/metabolismo , Calcio/metabolismo , Microscopía de Fluorescencia por Excitación Multifotónica/métodos , Xenopus laevis/metabolismo , Animales , Animales Modificados Genéticamente , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Larva/genética , Larva/metabolismo , Odorantes , Bulbo Olfatorio/citología , Bulbo Olfatorio/metabolismo , Corteza Olfatoria/citología , Corteza Olfatoria/metabolismo , Neuronas Receptoras Olfatorias/metabolismo , Neuronas Receptoras Olfatorias/fisiología , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Olfato/fisiología , Xenopus laevis/genética , Xenopus laevis/fisiologíaRESUMEN
Among the numerous candidates for cell therapy of the central nervous system (CNS), olfactory progenitors (OPs) represent an interesting alternative because they are free of ethical concerns, are easy to collect, and allow autologous transplantation. In the present study, we focused on the optimization of neuron production and maturation. It is known that plated OPs respond to various trophic factors, and we also showed that the use of Nerve Growth Factor (NGF) allowed switching from a 60/40 neuron/glia ratio to an 80/20 one. Nevertheless, in order to focus on the integration of OPs in mature neural circuits, we cocultured OPs in primary cultures obtained from the cortex and hippocampus of newborn mice. When dissociated OPs were plated, they differentiated into both glial and neuronal phenotypes, but we obtained a 1.5-fold higher viability in cortex/OP cocultures than in hippocampus/OP ones. The fate of OPs in cocultures was characterized with different markers such as BrdU, Map-2, and Synapsin, indicating a healthy integration. These results suggest that the integration of transplanted OPs might by affected by trophic factors and the environmental conditions/cell phenotypes of the host tissue. Thus, a model of coculture could provide useful information on key cell events for the use of progenitors in cell therapy.
Asunto(s)
Encéfalo/metabolismo , Neuronas/metabolismo , Corteza Olfatoria/metabolismo , Trasplante de Células Madre , Células Madre/citología , Animales , Encéfalo/citología , Encéfalo/crecimiento & desarrollo , Diferenciación Celular/genética , Linaje de la Célula/genética , Sistema Nervioso Central/metabolismo , Técnicas de Cocultivo , Humanos , Ratones , Factor de Crecimiento Nervioso/genética , Neuroglía/citología , Neuroglía/metabolismo , Neuroglía/trasplante , Neuronas/trasplante , Corteza Olfatoria/citología , Corteza Olfatoria/trasplante , Oligodendroglía/citología , Oligodendroglía/metabolismo , Oligodendroglía/trasplante , Células Madre/metabolismoRESUMEN
Olfaction in most animals is mediated by neurons bearing cilia that are accessible to the environment. Olfactory sensory neurons (OSNs) in chordates usually have multiple cilia, each with a centriole at its base. OSNs differentiate from stem cells in the olfactory epithelium, and how the epithelium generates cells with many centrioles is not yet understood. We show that centrioles are amplified via centriole rosette formation in both embryonic development and turnover of the olfactory epithelium in adult mice, and rosette-bearing cells often have free centrioles in addition. Cells with amplified centrioles can go on to divide, with centrioles clustered at each pole. Additionally, we found that centrioles are amplified in immediate neuronal precursors (INPs) concomitant with elevation of mRNA for polo-like kinase 4 (Plk4) and SCL/Tal1-interrupting locus gene (Stil), key regulators of centriole duplication. These results support a model in which centriole amplification occurs during a transient state characterized by elevated Plk4 and Stil in early INP cells. These cells then go on to divide at least once to become OSNs, demonstrating that cell division with amplified centrioles, known to be tolerated in disease states, can occur as part of a normal developmental program.
Asunto(s)
División Celular/fisiología , Centriolos/fisiología , Células-Madre Neurales/citología , Células-Madre Neurales/fisiología , Neuronas Receptoras Olfatorias/fisiología , Envejecimiento/fisiología , Animales , Ciclo Celular/fisiología , Células Cultivadas , Embrión de Mamíferos , Desarrollo Embrionario/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Corteza Olfatoria/citología , Corteza Olfatoria/embriología , Mucosa Olfatoria/citología , Mucosa Olfatoria/embriología , Mucosa Olfatoria/ultraestructura , Neuronas Receptoras Olfatorias/citología , Neuronas Receptoras Olfatorias/ultraestructuraRESUMEN
The cortex organizes sensory information to enable discrimination and generalization1-4. As systematic representations of chemical odour space have not yet been described in the olfactory cortex, it remains unclear how odour relationships are encoded to place chemically distinct but similar odours, such as lemon and orange, into perceptual categories, such as citrus5-7. Here, by combining chemoinformatics and multiphoton imaging in the mouse, we show that both the piriform cortex and its sensory inputs from the olfactory bulb represent chemical odour relationships through correlated patterns of activity. However, cortical odour codes differ from those in the bulb: cortex more strongly clusters together representations for related odours, selectively rewrites pairwise odour relationships, and better matches odour perception. The bulb-to-cortex transformation depends on the associative network originating within the piriform cortex, and can be reshaped by passive odour experience. Thus, cortex actively builds a structured representation of chemical odour space that highlights odour relationships; this representation is similar across individuals but remains plastic, suggesting a means through which the olfactory system can assign related odour cues to common and yet personalized percepts.
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Odorantes/análisis , Corteza Olfatoria/anatomía & histología , Corteza Olfatoria/fisiología , Vías Olfatorias , Compuestos Orgánicos/análisis , Compuestos Orgánicos/química , Animales , Masculino , Ratones , Bulbo Olfatorio/citología , Bulbo Olfatorio/fisiología , Corteza Olfatoria/citología , Percepción Olfatoria/fisiología , OlfatoAsunto(s)
Conocimientos, Actitudes y Práctica en Salud , Bulbo Olfatorio/fisiología , Corteza Olfatoria/fisiología , Vías Olfatorias/fisiología , Olfato/fisiología , Animales , Humanos , Bulbo Olfatorio/citología , Bulbo Olfatorio/diagnóstico por imagen , Corteza Olfatoria/citología , Corteza Olfatoria/diagnóstico por imagen , Vías Olfatorias/citología , Vías Olfatorias/diagnóstico por imagenRESUMEN
Imagine smelling a novel perfume with only one nostril and then smelling it again with the other nostril. Clearly, you can tell that it is the same perfume both times. This simple experiment demonstrates that odor information is shared across both hemispheres to enable perceptual unity. In many sensory systems, perceptual unity is believed to be mediated by inter-hemispheric connections between iso-functional cortical regions. However, in the olfactory system, the underlying neural mechanisms that enable this coordination are unclear because the two olfactory cortices are not topographically organized and do not seem to have homotypic inter-hemispheric mapping. This review presents recent advances in determining which aspects of odor information are processed unilaterally or bilaterally, and how odor information is shared across the two hemispheres. We argue that understanding the mechanisms of inter-hemispheric coordination can provide valuable insights that are hard to achieve when focusing on one hemisphere alone.
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Lateralidad Funcional , Odorantes , Corteza Olfatoria/fisiología , Mucosa Olfatoria/inervación , Vías Olfatorias/fisiología , Percepción Olfatoria , Olfato , Animales , Discriminación en Psicología , Humanos , Memoria , Bulbo Olfatorio/fisiología , Corteza Olfatoria/citología , Vías Olfatorias/citología , Neuronas Receptoras Olfatorias/fisiología , Receptores Odorantes/fisiologíaRESUMEN
Accumulating evidence confirms that the exposure of neonatal rats to maternal separation can significantly alter individual processes of postnatal neurogenesis in the olfactory neurogenic region - the subventricular zone (SVZ) and the rostral migratory stream (RMS). To establish the stressful influence of MS on postnatal neurogenesis we have investigated whether altered olfactory environment caused by short-term MS induces expression of Fos protein in the SVZ/RMS and in the olfactory cortical area - anterior olfactory nucleus (AON) of neonatal rats. Pups were separated from mothers for 2 hours at the postnatal days 7, 14 and 21. Immunohistochemically labeled Fos protein was assessed. Our results revealed that single exposure to MS is a stressful event that selectively and in age-dependent manner stimulates cellular activity in the SVZ and AON. A few Fos+ cells were found in the SVZ of P21 control animals and MS significantly increased their number. This suggests that some SVZ cells are included in the circuitry, which is activated by MS and that these cells have complete equipment for the Fos signal transduction. MS significantly increased the number of Fos+ cells in the AON in all age stages examined suggesting that its effect is mediated by olfaction.
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Regulación de la Expresión Génica , Ventrículos Laterales/metabolismo , Privación Materna , Neurogénesis , Corteza Olfatoria/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Animales , Animales Recién Nacidos , Femenino , Ventrículos Laterales/citología , Corteza Olfatoria/citología , Ratas , Ratas WistarRESUMEN
BACKGROUND: Cellular imagery using histology sections is one of the most common techniques used in Neuroscience. However, this inescapable technique has severe limitations due to the need to delineate regions of interest on each brain, which is time consuming and variable across experimenters. NEW METHOD: We developed algorithms based on a vectors field elastic registration allowing fast, automatic realignment of experimental brain sections and associated labeling in a brain atlas with high accuracy and in a streamlined way. Thereby, brain areas of interest can be finely identified without outlining them and different experimental groups can be easily analyzed using conventional tools. This method directly readjusts labeling in the brain atlas without any intermediate manipulation of images. RESULTS: We mapped the expression of cFos, in the mouse brain (C57Bl/6J) after olfactory stimulation or a non-stimulated control condition and found an increased density of cFos-positive cells in the primary olfactory cortex but not in non-olfactory areas of the odor-stimulated animals compared to the controls. COMPARISON WITH EXISTING METHOD(S): Existing methods of matching are based on image registration which often requires expensive material (two-photon tomography mapping or imaging with iDISCO) or are less accurate since they are based on mutual information contained in the images. Our new method is non-imaged based and relies only on the positions of detected labeling and the external contours of sections. CONCLUSIONS: We thus provide a new method that permits automated matching of histology sections of experimental brains with a brain reference atlas.
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Algoritmos , Mapeo Encefálico , Procesamiento de Imagen Asistido por Computador , Neuronas/metabolismo , Corteza Olfatoria/citología , Tomografía Computarizada por Rayos X , Animales , Recuento de Células , Ratones , Ratones Endogámicos C57BL , Odorantes , Corteza Olfatoria/diagnóstico por imagen , Proteínas Proto-Oncogénicas c-fos/metabolismo , Estadísticas no ParamétricasRESUMEN
Since a significant proportion of diabetic patients have clinical or subclinical neuropathy, there may be concerns about the use of local anaesthetics. The present study was designed to determine and compare the effects of articaine, a widely used anaesthetic in dental practice, and lidocaine on the resting and axonal stimulation-evoked release of [3H]noradrenaline ([3H]NA) in prefrontal cortex slices and the release of [3H]NA in spinal cord slices prepared from non-diabetic and streptozocin (STZ)-induced diabetic (glucose level=22.03±2.31mmol/l) rats. The peak of allodynia was achieved 9 weeks after STZ-treatment. Articaine and lidocaine inhibited the stimulation-evoked release in a concentration-dependent manner and increased the resting release by two to six times. These effects indicate an inhibitory action of these anaesthetics on Na+- and K+-channels. There was no difference in clinically important nerve conduction between non-diabetic and diabetic rats, as measured by the release of transmitter in response to axonal stimulation. The uptake and resting release of NA was significantly higher in the brain slices prepared from diabetic rats, but there were no differences in the spinal cord. For the adverse effects, the effects of articaine on K+ channels (resting release) are more pronounced compared to lidocaine. In this respect, articaine has a thiophene ring with high lipid solubility, which may present potential risks for some patients.
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Neuronas Adrenérgicas/efectos de los fármacos , Carticaína/farmacología , Norepinefrina/fisiología , Anestesia Local , Animales , Axones/efectos de los fármacos , Encéfalo/efectos de los fármacos , Carticaína/metabolismo , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/metabolismo , Lidocaína/metabolismo , Lidocaína/farmacología , Masculino , Conducción Nerviosa/efectos de los fármacos , Norepinefrina/metabolismo , Corteza Olfatoria/citología , Ratas , Ratas Wistar , Médula Espinal/citología , Estreptozocina/farmacologíaRESUMEN
The broadly-distributed, non-topographic projections to and from the olfactory cortex may suggest a flat, non-hierarchical organization in odor information processing. Layer 2 principal neurons in the anterior piriform cortex (APC) can be divided into 2 subtypes: semilunar (SL) and superficial pyramidal (SP) cells. Although it is known that SL and SP cells receive differential inputs from the olfactory bulb (OB), little is known about their projections to other olfactory regions. Here, we examined axonal projections of SL and SP cells using a combination of mouse genetics and retrograde labeling. Retrograde tracing from the OB or posterior piriform cortex (PPC) showed that the APC projects to these brain regions mainly through layer 2b cells, and dual-labeling revealed many cells extending collaterals to both target regions. Furthermore, a transgenic mouse line specifically labeling SL cells showed that they send profuse axonal projections to olfactory cortical areas, but not to the OB. These findings support a model in which information flow from SL to SP cells and back to the OB is mediated by a hierarchical feedback circuit, whereas both SL and SP cells broadcast information to higher olfactory areas in a parallel manner.
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Neuronas/citología , Corteza Olfatoria/citología , Animales , Axones/metabolismo , Biomarcadores , Técnica del Anticuerpo Fluorescente , Expresión Génica , Genes Reporteros , Ratones , Neuronas/clasificación , Neuronas/metabolismo , Bulbo Olfatorio/citología , Bulbo Olfatorio/metabolismo , Corteza Olfatoria/metabolismo , Corteza Piriforme/citología , Corteza Piriforme/metabolismoRESUMEN
In decapod crustaceans, molting is controlled by the pulsatile release of molt-inhibiting hormone (MIH) from neurosecretory cells in the X-organ/sinus gland (XO/SG) complex in the eyestalk ganglia (ESG). A drop in MIH release triggers molting by activating the molting gland or Y-organ (YO). Post-transcriptional mechanisms ultimately control MIH levels in the hemolymph. Neurotransmitter-mediated electrical activity controls Ca2+-dependent vesicular release of MIH from the SG axon terminals, which may be modulated by nitric oxide (NO). In green shore crab, Carcinus maenas, nitric oxide synthase (NOS) protein and NO are present in the SG. Moreover, C. maenas are refractory to eyestalk ablation (ESA), suggesting other regions of the nervous system secrete sufficient amounts of MIH to prevent molting. By contrast, ESA induces molting in the blackback land crab, Gecarcinus lateralis. Double-label immunofluorescence microscopy and quantitative polymerase chain reaction were used to localize and quantify MIH and NOS proteins and transcripts, respectively, in the ESG, brain, and thoracic ganglion (TG) of C. maenas and G. lateralis. In ESG, MIH- and NOS-immunopositive cells were closely associated in the SG of both species; confocal microscopy showed that NOS was localized in cells adjacent to MIH-positive axon terminals. In brain, MIH-positive cells were located in a small number of cells in the olfactory lobe; no NOS immunofluorescence was detected. In TG, MIH and NOS were localized in cell clusters between the segmental nerves. In G. lateralis, Gl-MIH and Gl-crustacean hyperglycemic hormone (CHH) mRNA levels were ~105-fold higher in ESG than in brain or TG of intermolt animals, indicating that the ESG is the primary source of these neuropeptides. Gl-NOS and Gl-elongation factor (EF2) mRNA levels were also higher in the ESG. Molt stage had little or no effect on CHH, NOS, NOS-interacting protein (NOS-IP), membrane Guanylyl Cyclase-II (GC-II), and NO-independent GC-III expression in the ESG of both species. By contrast, MIH and NO receptor GC-I beta subunit (GC-Iß) transcripts were increased during premolt and postmolt stages in G. lateralis, but not in C. maenas. MIH immunopositive cells in the brain and TG may be a secondary source of MIH; the release of MIH from these sources may contribute to the difference between the two species in response to ESA. The MIH-immunopositive cells in the TG may be the source of an MIH-like factor that mediates molt inhibition by limb bud autotomy. The association of MIH- and NOS-labeled cells in the ESG and TG suggests that NO may modulate MIH release. A model is proposed in which NO-dependent activation of GC-I inhibits Ca2+-dependent fusion of MIH vesicles with the nerve terminal membrane; the resulting decrease in MIH activates the YO and the animal enters premolt.
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Proteínas de Artrópodos/metabolismo , Braquiuros/fisiología , Sistema Nervioso Central/metabolismo , Regulación del Desarrollo de la Expresión Génica , Hormonas de Invertebrados/metabolismo , Neuronas/metabolismo , Óxido Nítrico Sintasa/metabolismo , Animales , Acuicultura , Proteínas de Artrópodos/genética , Océano Atlántico , Braquiuros/crecimiento & desarrollo , California , Sistema Nervioso Central/citología , Sistema Nervioso Central/enzimología , República Dominicana , Ojo , Ganglios de Invertebrados/citología , Ganglios de Invertebrados/enzimología , Ganglios de Invertebrados/metabolismo , Hormonas de Invertebrados/genética , Masculino , Muda , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Neuronas/citología , Neuronas/enzimología , Óxido Nítrico Sintasa/genética , Corteza Olfatoria/citología , Corteza Olfatoria/enzimología , Corteza Olfatoria/metabolismo , Especificidad de Órganos , Océano Pacífico , Especificidad de la Especie , TóraxRESUMEN
UNLABELLED: Sensory perception emerges from the confluence of sensory inputs that encode the composition of external environment and top-down feedback that conveys information from higher brain centers. In olfaction, sensory input activity is initially processed in the olfactory bulb (OB), serving as the first central relay before being transferred to the olfactory cortex. In addition, the OB receives dense connectivity from feedback projections, so the OB has the capacity to implement a wide array of sensory neuronal computation. However, little is known about the impact and the regulation of this cortical feedback. Here, we describe a novel mechanism to gate glutamatergic feedback selectively from the anterior olfactory cortex (AOC) to the OB. Combining in vitro and in vivo electrophysiological recordings, optogenetics, and fiber-photometry-based calcium imaging applied to wild-type and conditional transgenic mice, we explore the functional consequences of circuit-specific GABA type-B receptor (GABABR) manipulation. We found that activation of presynaptic GABABRs specifically depresses synaptic transmission from the AOC to OB inhibitory interneurons, but spares direct excitation to principal neurons. As a consequence, feedforward inhibition of spontaneous and odor-evoked activity of principal neurons is diminished. We also show that tunable cortico-bulbar feedback is critical for generating beta, but not gamma, OB oscillations. Together, these results show that GABABRs on cortico-bulbar afferents gate excitatory transmission in a target-specific manner and thus shape how the OB integrates sensory inputs and top-down information. SIGNIFICANCE STATEMENT: The olfactory bulb (OB) receives top-down inputs from the olfactory cortex that produce direct excitation and feedforward inhibition onto mitral and tufted cells, the principal neurons. The functional role of this feedback and the mechanisms regulating the balance of feedback excitation and inhibition remain unknown. We found that GABAB receptors are expressed in cortico-bulbar axons that synapse on granule cells and receptor activation reduces the feedforward inhibition of spontaneous and odor-driven mitral and tufted cells' firing activity. In contrast, direct excitatory inputs to these principal neurons remain unchanged. This study demonstrates that activation of GABAB receptors biases the excitation/inhibition balance provided by cortical inputs to the OB, leading to profound effects on early stages of sensory information processing.
Asunto(s)
Potenciales Postsinápticos Excitadores/fisiología , Retroalimentación , Bulbo Olfatorio/citología , Corteza Olfatoria/citología , Receptores de GABA-B/metabolismo , Olfato/fisiología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Anestésicos Locales/farmacología , Animales , Quinasa de la Proteína Quinasa Dependiente de Calcio-Calmodulina/genética , Quinasa de la Proteína Quinasa Dependiente de Calcio-Calmodulina/metabolismo , Channelrhodopsins , Agonistas de Aminoácidos Excitadores/farmacología , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Técnicas In Vitro , Lidocaína/farmacología , Luz , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Odorantes , Vías Olfatorias/fisiología , Quinoxalinas/farmacología , Receptores de GABA-B/genéticaRESUMEN
Instinctive reactions to danger are critical to the perpetuation of species and are observed throughout the animal kingdom. The scent of predators induces an instinctive fear response in mice that includes behavioural changes, as well as a surge in blood stress hormones that mobilizes multiple body systems to escape impending danger. How the olfactory system routes predator signals detected in the nose to achieve these effects is unknown. Here we identify a specific area of the olfactory cortex in mice that induces stress hormone responses to volatile predator odours. Using monosynaptic and polysynaptic viral tracers, we found that multiple olfactory cortical areas transmit signals to hypothalamic corticotropin-releasing hormone (CRH) neurons, which control stress hormone levels. However, only one minor cortical area, the amygdalo-piriform transition area (AmPir), contained neurons upstream of CRH neurons that were activated by volatile predator odours. Chemogenetic stimulation of AmPir activated CRH neurons and induced an increase in blood stress hormones, mimicking an instinctive fear response. Moreover, chemogenetic silencing of AmPir markedly reduced the stress hormone response to predator odours without affecting a fear behaviour. These findings suggest that AmPir, a small area comprising <5% of the olfactory cortex, plays a key part in the hormonal component of the instinctive fear response to volatile predator scents.
Asunto(s)
Hormonas/metabolismo , Odorantes/análisis , Corteza Olfatoria/anatomía & histología , Corteza Olfatoria/fisiología , Vías Olfatorias , Conducta Predatoria , Olfato/fisiología , Estrés Psicológico , Hormona Adrenocorticotrópica/sangre , Animales , Corticosterona/sangre , Hormona Liberadora de Corticotropina/sangre , Hormona Liberadora de Corticotropina/metabolismo , Reacción de Fuga , Miedo , Femenino , Hipocampo/citología , Hipocampo/fisiología , Hormonas/sangre , Instinto , Masculino , Ratones , Neuronas/metabolismo , Corteza Olfatoria/citología , Percepción Olfatoria/fisiología , Telencéfalo/anatomía & histología , Telencéfalo/citología , Telencéfalo/fisiologíaRESUMEN
The components of the nervous system are assembled in development by the process of cell migration. Although the principles of cell migration are conserved throughout the brain, different subsystems may predominantly utilize specific migratory mechanisms, or may display unusual features during migration. Examining these subsystems offers not only the potential for insights into the development of the system, but may also help in understanding disorders arising from aberrant cell migration. The olfactory system is an ancient sensory circuit that is essential for the survival and reproduction of a species. The organization of this circuit displays many evolutionarily conserved features in vertebrates, including molecular mechanisms and complex migratory pathways. In this review, we describe the elaborate migrations that populate each component of the olfactory system in rodents and compare them with those described in the well-studied neocortex. Understanding how the components of the olfactory system are assembled will not only shed light on the etiology of olfactory and sexual disorders, but will also offer insights into how conserved migratory mechanisms may have shaped the evolution of the brain.