RESUMEN

The effect of visual deprivation followed by light exposure on the tangential organisation of dendritic bundles passing through layer 4 of the rat visual cortex was studied quantitatively in the light microscope. Four groups of animals were investigated: (I) rats reared in an environment illuminated normally--group 52 dL; (II) rats reared in the dark until 21 days postnatum (DPN) and subsequently light exposed for 31 days-group 21/31; (III) rats dark reared until 52 DPN and then subsequently light exposed for 3 days--group 3 dL; and (IV) rats totally dark reared until 52 DPN--group 52 DPN. Each group contained five animals. Semithin 0.5-1-µm thick resin-embedded sections were collected from tangential sampling levels through the middle of layer 4 in area 17 and stained with Toluidine Blue. These sections were used to quantitatively analyse the composition and distribution of dendritic clusters in the tangential plane. The key result of this study indicates a significant reduction in the mean number of medium- and small-sized dendritic profiles (diameter less than 2 µm) contributing to clusters in layer 4 of groups 3 dL and 52 dD compared with group 21/31. No differences were detected in the mean number of large-sized dendritic profiles composing a bundle in these experimental groups. Moreover, the mean number of clusters and their tangential distribution in layer 4 did not vary significantly between all four groups. Finally, the clustering parameters were not significantly different between groups 21/31 and the normally reared group 52 dL. This study demonstrates, for the first time, that extended periods of dark rearing followed by light exposure can alter the morphological composition of dendritic bundles in thalamorecipient layer 4 of rat visual cortex. Because these changes occur in the primary region of thalamocortical input, they may underlie specific alterations in the processing of visual information both cortically and subcortically during periods of dark rearing and light exposure.

Asunto(s)

Oscuridad/efectos adversos , Dendritas/patología , Privación Sensorial/fisiología , Baja Visión/fisiopatología , Corteza Visual/patología , Animales , Cuerpos Geniculados/crecimiento & desarrollo , Cuerpos Geniculados/patología , Cuerpos Geniculados/fisiopatología , Ratas , Corteza Visual/crecimiento & desarrollo , Corteza Visual/fisiopatología , Vías Visuales/crecimiento & desarrollo , Vías Visuales/patología , Vías Visuales/fisiopatología

RESUMEN

Long-term morphological synaptic changes associated with homosynaptic long-term potentiation (LTP) and heterosynaptic long-term depression (LTD) in vivo, in awake adult rats were analyzed using three-dimensional (3-D) reconstructions of electron microscope images of ultrathin serial sections from the molecular layer of the dentate gyrus. For the first time in morphological studies, the specificity of the effects of LTP and LTD on both spine and synapse ultrastructure was determined using an N-methyl-d-aspartate (NMDA) receptor antagonist CPP (3-[(R)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid). There were no differences in synaptic density 24 h after LTP or LTD induction, and CPP alone had no effect on synaptic density. LTP increased significantly the proportion of mushroom spines, whereas LTD increased the proportion of thin spines, and both LTP and LTD decreased stubby spine number. Both LTP and LTD increased significantly spine head evaginations (spinules) into synaptic boutons and CPP blocked these changes. Synaptic boutons were smaller after LTD, indicating a pre-synaptic effect. Interestingly, CPP alone decreased bouton and mushroom spine volumes, as well as post-synaptic density (PSD) volume of mushroom spines.These data show similarities, but also some clear differences, between the effects of LTP and LTD on spine and synaptic morphology. Although CPP blocks both LTP and LTD, and impairs most morphological changes in spines and synapses, CPP alone was shown to exert effects on aspects of spine and synaptic structure.

Asunto(s)

Espinas Dendríticas/efectos de los fármacos , Giro Dentado/efectos de los fármacos , Antagonistas de Aminoácidos Excitadores/farmacología , Plasticidad Neuronal/efectos de los fármacos , Piperazinas/farmacología , Sinapsis/efectos de los fármacos , Animales , Espinas Dendríticas/fisiología , Espinas Dendríticas/ultraestructura , Giro Dentado/fisiología , Giro Dentado/ultraestructura , Potenciación a Largo Plazo/efectos de los fármacos , Potenciación a Largo Plazo/fisiología , Depresión Sináptica a Largo Plazo/efectos de los fármacos , Depresión Sináptica a Largo Plazo/fisiología , Masculino , Plasticidad Neuronal/fisiología , Neuronas/efectos de los fármacos , Neuronas/fisiología , Neuronas/ultraestructura , Terminales Presinápticos/efectos de los fármacos , Terminales Presinápticos/fisiología , Terminales Presinápticos/ultraestructura , Ratas , Ratas Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapsis/fisiología , Sinapsis/ultraestructura , Vigilia

RESUMEN

The infralimbic (IL) 'visceromotor' area of the rat medial prefrontal cortex projects to strategic subcortical nuclei involved in autonomic functions. Central among these targets are the nucleus tractus solitarius (NTS) and the rostral ventrolateral medulla (rVLM). By combining tract-tracing using the anterograde tracer biotinylated dextran amine (BDA) with immunolabeling for tyrosine hydroxylase (TH; an enzyme marker of catecholaminergic neurons), a limited proportion of BDA-labeled IL axonal boutons in the NTS and rVLM was found to be closely associated with TH immunopositive (+) target structures. Such structural appositions were mainly located proximally over the labeled dendritic arbors of identified TH+ neurons. Quantitative ultrastructural examination revealed that in NTS, TH+ dendritic shafts comprised 7.0% of the overall post-synaptic target population innervated by BDA-labeled IL boutons, whereas TH+ dendritic spines represented 1.25% of targets. In rVLM, TH+ shafts represented 9.0% and TH+ spines 2.5% of IL targets. Labeled IL boutons established exclusively asymmetric Gray Type 1 (presumed excitatory) synaptic junctions. The results indicate that subpopulations of catecholaminergic neurons in the NTS and rVLM are among the spectrum of post-synaptic neurons monosynaptically innervated by descending 'excitatory' input from IL cortex. Such connectivity, albeit restricted, identifies the potential direct influence of IL cortex on the processing and distribution of cardiovascular, respiratory and related autonomic information by catecholaminergic neurons in the NTS and VLM of the rat.

Asunto(s)

Vías Aferentes/fisiología , Bulbo Raquídeo/citología , Neuronas/metabolismo , Corteza Prefrontal/fisiología , Sinapsis/metabolismo , Tirosina 3-Monooxigenasa/metabolismo , Animales , Biotina/análogos & derivados , Biotina/metabolismo , Dextranos/metabolismo , Inmunohistoquímica/métodos , Masculino , Microscopía Inmunoelectrónica/métodos , Modelos Biológicos , Neuronas/ultraestructura , Ratas , Ratas Sprague-Dawley , Sinapsis/ultraestructura

RESUMEN

Chronic restraint stress is known to affect the morphology and synaptic organization of the hippocampus, predominantly within CA3 but also in CA1 and dentate gyrus. In this study, we provide the first evidence for specific ultrastructural alterations affecting asymmetric axo-spinous synapses in CA1 stratum lacunosum-moleculare following chronic restraint stress (6 h/day, 21 days) in the rat. The structure of asymmetric axo-spinous post-synaptic densities was investigated using serial section three-dimensional reconstruction procedures in control (n=4) and chronic restraint stress (n=3) animals. Dendritic spine profiles (spine head+neck) associated with the sampled synaptic contacts (30 per animal) were also reconstructed in three-dimensions. Morphometric analyses revealed a significant increase in post-synaptic density surface area (+36%; P=0.03) and a highly significant increase in post-synaptic density volume (+79%; P=0.003) in the chronic restraint stress group. These changes were directly associated with 'non-macular' (perforated, complex and segmented) post-synaptic densities. A highly significant overall increase in the 'post-synaptic density surface area/spine surface area' ratio was also detected in the chronic restraint stress group (+27%; P=0.002). In contrast, no quantitative changes in spine parameters were found between groups. The Cavalieri method was used to assess the effects of chronic restraint stress exposure upon CA1 hippocampal volume. The mean volume of total dorsal anterior CA1 hippocampus was significantly lower in the chronic restraint stress group (-16%; P=0.036). However, when corrected for volume changes, no significant alteration in a relative estimate of the mean number of asymmetric axo-spinous synapses was detected in CA1 stratum lacunosum-moleculare between control and chronic restraint stress groups. The data indicate a structural remodeling of excitatory axo-spinous synaptic connectivity in rat CA1 stratum lacunosum-moleculare as a result of chronic restraint stress.

Asunto(s)

Daño Encefálico Crónico/patología , Hipocampo/patología , Trastornos de la Memoria/patología , Estrés Psicológico/complicaciones , Sinapsis/patología , Animales , Atrofia/etiología , Atrofia/patología , Atrofia/fisiopatología , Daño Encefálico Crónico/etiología , Daño Encefálico Crónico/fisiopatología , Enfermedad Crónica , Espinas Dendríticas/patología , Modelos Animales de Enfermedad , Hipocampo/fisiopatología , Citometría de Imagen , Masculino , Trastornos de la Memoria/etiología , Trastornos de la Memoria/fisiopatología , Microscopía Electrónica de Transmisión , Plasticidad Neuronal/fisiología , Terminales Presinápticos/patología , Células Piramidales/patología , Ratas , Ratas Wistar , Receptores AMPA/fisiología , Restricción Física/efectos adversos , Membranas Sinápticas/patología , Transmisión Sináptica/fisiología

RESUMEN

The projection from the basolateral nucleus of the amygdala (BLA) conveys information about the affective significance of sensory stimuli to the medial prefrontal cortex (mPFC). By using an anterograde tract-tracing procedure combined with immunocytochemistry and correlated light/electron microscopical examination, labeled BLA afferents to layers 2-6 of the rat mPFC are shown to establish asymmetrical synaptic contacts, not only with dendritic spines (approximately 95.7% of targets innervated), but also with the aspiny dendritic shafts and somata of multipolar parvalbumin immunopositive (PV+) neurons. A population of PV- dendritic shafts was also innervated. Labeled BLA synaptic input to identified PV+ structures occurred in layers 2-6 of mPFC. The results indicate that labeled BLA afferents predominantly contact the spiny processes of presumed pyramidal cells and also provide a direct and specific innervation to a sub-population of local circuit neurons in mPFC containing PV. Since PV+ cells include two significant classes of fast-spiking GABAergic inhibitory interneuron (basket and axo-axonic cells), these novel observations indicate that the amygdalocortical pathway in the rat has the ability to directly influence functionally strategic 'feed-forward' inhibitory mechanisms at the first stage of processing amygdalocortical information.

Asunto(s)

Vías Aferentes/citología , Amígdala del Cerebelo/citología , Neuronas/citología , Parvalbúminas/metabolismo , Corteza Prefrontal/citología , Vías Aferentes/metabolismo , Amígdala del Cerebelo/metabolismo , Animales , Inmunohistoquímica , Masculino , Microscopía Electrónica de Transmisión , Neuronas/metabolismo , Corteza Prefrontal/metabolismo , Ratas , Ratas Sprague-Dawley

RESUMEN

Chronic stress and spatial training have been proposed to affect hippocampal structure and function in opposite ways. Previous morphological studies that addressed structural changes after chronic restraint stress and spatial training were based on two-dimensional morphometry which does not allow a complete morphometric characterisation of synaptic features. Here, for the first time in such studies, we examined these issues by using three-dimensional (3-D) reconstructions of electron microscope images taken from thorny excrescences of hippocampal CA3 pyramidal cells. Ultrastructural alterations in postsynaptic densities (PSDs) of thorny excrescences receiving input from mossy fibre boutons were also determined, as were changes in numbers of multivesicular bodies (endosome-like structures) within thorny excrescences and dendrites. Quantitative 3-D data demonstrated retraction of thorny excrescences after chronic restraint stress which was reversed after water maze training, whilst water maze training alone increased thorny excrescence volume and number of thorns per thorny excrescence. PSD surface area was unaffected by restraint stress but water maze training increased both number and area of PSDs per thorny excrescence. In restrained rats that were water maze trained PSD volume and surface area increased significantly. The proportion of perforated PSDs almost doubled after water maze training and restraint stress. Numbers of endosome-like structures in thorny excrescences decreased after restraint stress and increased after water maze training. These findings demonstrate that circuits involving contacts between mossy fibre terminals and CA3 pyramidal cells at stratum lucidum level are affected conversely by water maze training and chronic stress, confirming the remarkable plasticity of CA3 dendrites. They provide a clear illustration of the structural modifications that occur after life experiences noted for their different impact on hippocampal function.

Asunto(s)

Hipocampo/anatomía & histología , Hipocampo/fisiopatología , Aprendizaje por Laberinto/fisiología , Células Piramidales/fisiología , Estrés Psicológico , Sinapsis/fisiología , Sinapsis/ultraestructura , Animales , Dendritas/ultraestructura , Modelos Animales de Enfermedad , Células Piramidales/ultraestructura , Ratas , Valores de Referencia , Restricción Física

RESUMEN

In anaesthetised rats, long-term potentiation (LTP) was induced unilaterally in the dentate gyrus by tetanic stimulation of the perforant path. Animals were killed 6 h after LTP induction and dendritic spines and synapses in tetanised and untetanised (contralateral) hippocampal tissue from the middle molecular layer (MML) were examined in the electron microscope using stereological analysis. Three-dimensional reconstructions were also used for the first time in LTP studies in vivo, with up to 130 ultrathin serial sections analysed per MML dendritic segment. A volume sampling procedure revealed no significant changes in hippocampal volume after LTP and an unbiased counting method demonstrated no significant changes in synapse density in potentiated compared with control tissue. In the potentiated hemisphere, there were changes in the proportion of different spine types and their synaptic contacts. We found an increase in the percentage of synapses on thin dendritic spines, a decrease in synapses on both stubby spines and dendritic shafts, but no change in the proportion of synapses on mushroom spines. Analysis of three-dimensional reconstructions of thin and mushroom spines following LTP induction revealed a significant increase in their volume and area. We also found an increase in volume and area of unperforated (macular) and perforated (segmented) postsynaptic densities. Our data demonstrate that whilst there is no change in synapse density 6 h after the induction of LTP in vivo, there is a considerable restructuring of pre-existing synapses, with shaft and stubby spines transforming to thin dendritic spines, and mushroom spines changing only in shape and volume.

Asunto(s)

Giro Dentado/fisiología , Giro Dentado/ultraestructura , Potenciación a Largo Plazo/fisiología , Plasticidad Neuronal , Sinapsis/fisiología , Sinapsis/ultraestructura , Animales , Espinas Dendríticas/ultraestructura , Procesamiento de Imagen Asistido por Computador , Imagenología Tridimensional , Masculino , Microscopía Electrónica , Ratas , Ratas Sprague-Dawley

Asunto(s)

Enfermedades del Sistema Nervioso Autónomo/complicaciones , Enfermedades de la Laringe/etiología , Pliegues Vocales/inervación , Humanos , Enfermedades de la Laringe/fisiopatología , Trastornos Respiratorios/etiología , Enfermedades del Nervio Vago/complicaciones , Pliegues Vocales/fisiopatología

RESUMEN

The medial prefrontal cortex (mPFC) projects to the nucleus accumbens shell, core and rostral pole. In this retrograde tract-tracing study of rat mPFC to nucleus accumbens projection neurons, the advantages of Neurobiotin are utilised in order to reveal the detailed morphology of labelled projection cells, and to permit an examination of the laminar projections to shell and core compartments The retrogradely transported Neurobiotin was found in somata, proximal and distal dendrites of neurons that project from the mPFC to the nucleus accumbens. The morphology of these projection neurons was revealed in great detail and confirmed that the projection arises wholly from pyramidal cells. Interestingly, it was also found that retrogradely labelled neurons were exclusively located in prelimbic and infralimbic regions in layers V and VI, after shell injections, but also in layer II following core sites. This observation may reflect possibly different roles for cortical laminae on the nucleus accumbens.

Asunto(s)

Biotina/análogos & derivados , Núcleo Accumbens/fisiología , Corteza Prefrontal/fisiología , Transmisión Sináptica/fisiología , Animales , Masculino , Neuronas/citología , Neuronas/fisiología , Núcleo Accumbens/citología , Ratas , Ratas Wistar

RESUMEN

The calcium-binding protein calretinin (CR) is present in a subpopulation of local-circuit neurons in the mammalian cerebral cortex containing gamma-aminobutyric acid. This light microscopic investigation provides a detailed qualitative and quantitative morphological analysis of CR-immunoreactive (CR+) neurons in the medial prefrontal cortex (mPFC; areas 24a,b,c, 32', and 25) of the normal adult human. The morphology of CR+ neurons and their areal and laminar distributions were consistent across human mPFC. The principal organisational features of CR+ labelling were the marked laminar distribution of immunoreactive somata and the predominantly vertical orientation of labelled axon-like and dendritic processes. Several types of CR- neurons were present in layer 1, including horizontally aligned Cajal-Retzius cells. In layers 2-6, CR+ neurons displayed a variety of morphologies: bipolar cells (49% of CR+ population), vertically bitufted cells (35%), and horizontally bitufted cells (3.5%). These neuron types were mainly located in layer 2/upper layer 3, and their dendritic processes were commonly aspiny and sometimes highly beaded. Aspiny (8%) and sparsely spiny multipolar (5%) CR+ neurons were also found. The mean somatic profile diameter of CR+ cells was 11.6 +/- 0.3 microm (mean +/- S.D). CA+ puncta formed pericellular baskets around unlabelled circular somatic profiles in layers 2/3 and around unlabelled pyramidal-shaped somata in layers 5/6. The somatic sizes of these unlabelled cell populations were significantly different. Immunolabelled puncta were also found in close contact with CR+ somata. Cortical depth distribution histograms and laminar thickness measurements defined the proportions of the overall CR- cell population in each layer: 7% in layer 1, 78% in layers 2/3, 14% in layers 5/6, and 1% in the white matter. In the tangential plane, CR+ neurons were distributed uniformly at all levels of the cortex. By using stereological counting procedures on immunoreacted Nissl-stained sections, CR+ neurons were estimated to constitute a mean 8.0% (7.2-8.7%) of the total neuron population in each cortical area. These data are compared with similar information obtained for the mPFC in monkey and rat (Gabbott and Bacon [1996b] J. Comp. Neurol. 364:657-608; Gabbott et al., [1997] J. Comp. Neurol. 377:465-499). This study provides important morphological insights into a neurochemically distinct subclass of local-circuit inhibitory neurons in the human mPFC.

Asunto(s)

Neuronas/citología , Corteza Prefrontal/citología , Proteína G de Unión al Calcio S100/análisis , Adulto , Anciano , Animales , Axones/ultraestructura , Calbindina 2 , Dendritas/ultraestructura , Haplorrinos , Humanos , Inmunohistoquímica , Mamíferos , Proteínas del Tejido Nervioso , Corteza Prefrontal/anatomía & histología , Ratas , Especificidad de la Especie , Ácido gamma-Aminobutírico/análisis

RESUMEN

Calcineurin (CN) is a Ca2+/calmodulin-dependent phosphatase present in brain tissue. In this immunocytochemical study of rat prelimbic cortex (area 32), a gradient of CN immunolabelling was found in the somata and processes of pyramidal cells and in interneurones. Some apical dendritic spines were weakly immunoreactive. The results suggest that CN is differentially present in prelimbic cortical neurones--this may reflect possible differences in intracellular Ca2+ signalling mechanisms.

Asunto(s)

Proteínas de Unión a Calmodulina/análisis , Interneuronas/enzimología , Sistema Límbico/enzimología , Fosfoproteínas Fosfatasas/análisis , Corteza Prefrontal/enzimología , Células Piramidales/enzimología , Animales , Calcineurina , Femenino , Inmunohistoquímica , Sistema Límbico/citología , Masculino , Corteza Prefrontal/citología , Ratas , Ratas Sprague-Dawley

RESUMEN

Neurones immunoreactive for vasoactive intestinal polypeptide (VIP) were studied in monkey medial prefrontal cortex. The majority (78.0%) of VIP+ neurones were bipolar cells located mainly in layers 2/3. Calretinin (CR) immunoreactivity was colocalised in 80.5% of VIP+ neurones. Furthermore, VIP+ puncta formed pericellular baskets around GABA immunonegative somata in layers 2/3. These results indicate that VIP/CR are colocalised in some bipolar cells and superficial pyramidal somata are likely targets of VIP+ neurones.

Asunto(s)

Interneuronas/química , Corteza Prefrontal/citología , Proteína G de Unión al Calcio S100/análisis , Péptido Intestinal Vasoactivo/análisis , Animales , Calbindina 2 , Tamaño de la Célula , Femenino , Técnica del Anticuerpo Fluorescente , Interneuronas/citología , Sistema Límbico/química , Sistema Límbico/fisiología , Macaca fascicularis , Proteínas del Tejido Nervioso/análisis , Inhibición Neural/fisiología , Corteza Prefrontal/química

RESUMEN

This paper is a light microscopical study describing the detailed morphology and quantitative distribution of local circuit neurones in areas 25, 32, and 24b of the medial prefrontal cortex (mPFC) in the rat. Cortical interneurones were identified immunocytochemically by their expression of calretinin (CR), parvalbumin (PV), and calbindin D-28k (CB) immunoreactivity. Neurones immunoreactive for gamma-aminobutyric acid (GABA) were also investigated, as were interneurones containing reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity. Several distinct classes of CR+, PV+, and CB+ neurones were identified; the most frequent were: bipolar/bitufted CR+ cells in upper layer 3; multipolar PV+ neurones in layers 3 and 5; and bitufted/multipolar CB+ neurones in lower layer 3. CB+ neurones resembling Martinotti and neurogliaform cells were also present in layers 5/6. The morphologies and depth distributions of each cell type were consistent across the three areas of mPFC studied. Seven classes of diaphorase-reactive mPFC neurone are described; these cells were composed about 0.8% of the total neurone population and had a peak distribution located in mid- to lower layer 5 in each area. In areas 32 and 25, three defined bands of diffuse NADPH diaphorase staining were located in layer 2 and in upper and deep layer 5. Diaphorase reactivity was very infrequently colocalised with either CR, PV, or CB immunoreactivities. The numerical densities of neurones (N(V), number of cells per mm3) in each layer were calculated stereologically. The mean total neuronal N(V) estimate for areas 25, 32, and 24b was 51,603 +/- 3,324 (mean +/- S.D.; n = 8). Significant interareal differences were detected. From cortical thickness data and neuronal N(V) estimates, the absolute number of neurones under 1 mm2 of cortical surface (N(C)) have been derived. The mean N(C) value for areas 25, 32, and 24b was 57,328 +/- 7,505 neurones. In immunolabelled Nissl-stained sections, CR+ neurones constituted an overall 4.0%, PV+ cells 5.6%, and CB+ 3.4% of the total neurone populations in mPFC. GABA+ cells represented a mean of 16.2% (14.8-17.2%) of neurones in areas 25, 32 and 24b. The absolute numbers of CR+, PV+, CB+, and GABA+ neurones within individual layers in a column of cortex under 1 mm2 of cortical surface (N(L)) have also been derived, with significant interareal differences in N(L) values being detected. The data provide the structural basis for a qualitative and quantitative definition of local cortical circuits in the rat mPFC.

Asunto(s)

Proteínas de Unión al Calcio/análisis , Proteínas del Tejido Nervioso/análisis , Neuronas/ultraestructura , Corteza Prefrontal/citología , Animales , Calbindina 2 , Calbindinas , Recuento de Células , Tamaño de la Célula , Dendritas/ultraestructura , Femenino , Técnicas para Inmunoenzimas , Masculino , NADPH Deshidrogenasa/análisis , Parvalbúminas/análisis , Ratas , Ratas Sprague-Dawley , Proteína G de Unión al Calcio S100/análisis , Ácido gamma-Aminobutírico/análisis

RESUMEN

Using an antibody against microtubule associated protein 2 (MAP-2; a specific marker for neuronal dendrites), this paper reports the structural organisation of pyramidal cell apical dendrites in the rat prelimbic (PL) cortex. In the coronal plane, MAP-2-immunoreactive apical dendrites of pyramidal neurons in layers 5, 3 and 2 were found bundled together as they ascended radially through the cortex. These bundles of dendrites dispersed in upper layer 2 to form apical dendritic tufts in layer 1. In tangential cross-section, the immunolabelled bundles were organised into a latticework of discrete clusters of differentially sized profiles. At the boundary between layers 3 and 5, clusters were composed of 26 +/- 8 dendritic profiles (group mean value +/- S.D., five animals), whereas clusters in layer 2 contained 55 +/- 15 profiles. The number of clusters per unit surface area was not significantly different throughout layers 5, 3 and 2 (760 +/- 75 per mm2) with the average centre-to-centre intercluster distance in these layers being 44.2 +/- 4.9 microns. The data indicate that apical dendritic bundles are a feature of the radial organisation of PL cortex. These structural subunits may subserve specific integrative functions in the PL area of the rat medial prefrontal cortex.

Asunto(s)

Dendritas/ultraestructura , Sistema Límbico/ultraestructura , Animales , Dendritas/metabolismo , Femenino , Inmunohistoquímica , Sistema Límbico/citología , Sistema Límbico/metabolismo , Masculino , Proteínas Asociadas a Microtúbulos/metabolismo , Células Piramidales/metabolismo , Ratas , Ratas Sprague-Dawley , Distribución Tisular

RESUMEN

This paper describes the termination pattern and synaptic connectivity of the pathway from the basolateral nucleus of the amygdala (BLA) to the medial prefrontal cortex (mPFC; areas 25, 32, and 24b) of the rat. Discrete injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) were made in the BLA and detailed light microscopical observations made of the distribution of PHA-L labelled fibres and boutons in the mPFC. Labelled fibres were distributed in two tiers: predominantly within deep layer 1/layer 2 and also in layers 5/6. Fibre plexi in layers 2 and 5 were highly varicose. Electron microscopical examination of 120 labelled boutons in area 32 (60 in layer 2 and 60 in layer 5) indicated that 116 (97%) established asymmetrical synaptic contacts with dendritic spines and 4 (3%) were in synaptic contact with small dendritic shafts. No significant differences in target structures were found between layers 2 and 5. The results indicate that BLA input to mPFC in the rat predominantly innervates spine bearing dendrites in layers 2 and 5. This suggests that the neuronal operations of these processes are influenced by direct feedforward excitation from the BLA.

Asunto(s)

Amígdala del Cerebelo/fisiología , Corteza Prefrontal/fisiología , Vías Aferentes/fisiología , Vías Aferentes/ultraestructura , Amígdala del Cerebelo/ultraestructura , Animales , Axones/fisiología , Axones/ultraestructura , Dendritas/fisiología , Dendritas/ultraestructura , Masculino , Microscopía Electrónica , Fitohemaglutininas , Corteza Prefrontal/ultraestructura , Ratas , Ratas Sprague-Dawley , Sinapsis/fisiología , Sinapsis/ultraestructura

RESUMEN

This study demonstrates the co-localisation of NADPH diaphorase activity and GFAP immunoreactivity in non-neuronal cells in weakly fixed brain sections from normal adult rats. The presence of GFAP immunoreactivity in these cells indicates that they are astroglia. In addition, cells possessing the morphological characteristics of astroglia were weakly immunoreactive for the endothelial isoform of nitric oxide synthase (eNOS)--these cells also co-localised NADPH diaphorase activity. Furthermore, cells immunoreactive for eNOS displayed GFAP immunoreactive processes. This cytochemical evidence strongly suggests that resting astroglia are potential sources of nitric oxide--a powerful modulator of cell activity.

Asunto(s)

Astrocitos/enzimología , Encéfalo/enzimología , NADPH Deshidrogenasa/metabolismo , Óxido Nítrico Sintasa/metabolismo , Animales , Femenino , Inmunohistoquímica , Masculino , Ratas , Ratas Sprague-Dawley

RESUMEN

The companion paper (Gabbott and Bacon [1996] J. Comp. Neurol.) describes the morphology of calretinin (CR)-, parvalbumin (PV)-, calbindin (CB)-, and GABA-immunoreactive neurons, and NADPH diaphorase-reactive cells, in the medial prefrontal cortex (mPFC; areas 24a, 24b, 24c, 25 and 32) of the adult monkey. Since these local circuit neurons play crucial functional roles, the aim of this study was to provide supportive quantitative data defining their areal and laminar distribution in mPFC. The numerical densities of neurons (Nv, number of cells per mm3) in each area and layer were calculated stereologically. The mean total neuronal NV estimates across mPFC was 55,727 +/- 3,319 per mm3 (mean +/- S.D.; n = 3); values ranged from 50,489 +/- 8,374 per mm3 (area 24a) to 59,938 +/- 7,214 per mm3 (area 24c). Interareal differences were not significant. Cortical depth measurements and neuronal NV estimates for each area allowed the absolute number of neurons in a column of cortex under 1 mm2 of surface to be calculated; values varied between 86,457 +/- 15,063 (area 24a) and 128,464 +/- 24,050 (area 24c). Using immunolabelled Nissl-stained sections of mPFC, CR+ neurons constituted 11.2%, PV+ neurons 5.9%, and CB+ neurons 5.0% of the total neuron population. GABA+ neurons represented an overall 24.9% (23.5-27.3%) of neurons in the mPFC. Differences between areas were not significant. The cortical depth distribution histograms of CR+, PV+, CB+, and GABA+ cell populations in each area were derived and the percentage of a given cell population in each layer subsequently calculated. Peaks in the cortical depth distributions of CR+ and CB+ neurons occurred in layer 2 and upper layer 3, respectively; the peak distribution of PV+ neurons occurred between lower layer 3 and upper layer 5. The depth distribution of GABA+ cells reflected the combined distributions of CR+, PV+ and CR+ neurons. In all areas, the majority (74.4-84.0%) of the GABA cell population was located in layers 2/3. The depth distributions for each cell type were similar between areas. Diaphorase-reactive neurons accounted for 0.25% (0.2-0.32%) of all cortical neurons in mPFC and were distributed in two horizontal strata, in midlayer 3 and in mid/upper layer 6. A large population of diaphorase-reactive cells was present in the white matter. The absolute numbers of CR+, PV+, CB+ and GABA+ neurons within individual layers in a column of cortex under 1 mm2 and 50 x 50 microns of cortical surface have been derived. The data presented provide the basis for a quantitative definition of cortical circuits in monkey mPFC.

Asunto(s)

Neuronas/fisiología , Corteza Prefrontal/citología , Vías Aferentes/anatomía & histología , Vías Aferentes/citología , Animales , Calbindina 2 , Calbindinas , Recuento de Células , Dendritas/ultraestructura , Vías Eferentes/anatomía & histología , Vías Eferentes/citología , Femenino , Inmunohistoquímica , Macaca fascicularis , NADPH Deshidrogenasa/metabolismo , Neuronas/ultraestructura , Parvalbúminas/metabolismo , Corteza Prefrontal/anatomía & histología , Proteína G de Unión al Calcio S100/metabolismo , Sinapsis/fisiología , Adhesión del Tejido , Ácido gamma-Aminobutírico/metabolismo

RESUMEN

This paper provides a comprehensive morphological description of local circuit neurons in the medial prefrontal cortex (mPFC: areas 24a, 24b, 24c, 25 and 32) of the monkey. Cortical interneurons were identified immunocytochemically by the expression of the calcium binding proteins calretinin (CR), parvalbumin (PV) and calbindin D-28k (CB). Interneurons were also identified using GABA immunocytochemistry. The areal and laminar distributions of CR, PV, and CB cells were consistent across mPFC; their morphological characteristics identified them as local circuit neurons. Throughout layers 2-6: CR immunoreactivity labelled double bouquet and bipolar neurons, PV was localised in large and small basket neurons and in chandelier (axoaxonic) cells, while CB immunoreactivity was present in double bouquet, Martinotti, and neurogliaform neurons. In addition, some cells in layer 1 (including Cajal-Retzius neurons) were CR immunoreactive. Calbindin immunoreactivity also labelled a population of large nonpyramidal neurons deep in the cortex. Other types of CR, PV and CB cells were also immunolabelled. A small population of layer 3 pyramidal cells was weakly CB immunoreactive. Peak cell densities occurred in layer 2/upper layer 3 for CR+ neurons and in upper to midlayer 3 for CB+ cells. PV+ neuron density peaked in midcortex. These observations support and extend a similar study of monkey prefrontal cortex (Condé et al. [1994] J. Comp. Neurol. 341:95-116). The morphologies and combined cortical depth distributions of CR+, PV+, and CB+ neurons were similar to GABA-immunolabelled cells. Local circuit neurons in mPFC displaying NADPH diaphorase activity composed less than 0.25% of the total neuron population, and were distributed in two horizontal strata, in mid- to lower layer 3 and in lower layer 5/upper layer 6. CR, PV and CB immunoreactivity was colocalised in NADPH diaphorase-reactive neurons. The interrelationships between CR+, PV+ and CB+ neurons were investigated using dual immunocytochemistry. CR+ puncta were found to be closely associated with the cell bodies and proximal processes of PV+ neurons, whereas CR+ puncta were located more distally over processes from CB+ cells. Additionally, PV+ puncta were found closely apposed to PV+ somata and processes and CR+ puncta abutted against CR+ cell bodies. The companion paper (Gabbott and Bacon [1996] J. Comp. Neurol.) presents quantitative data regarding the areal and laminar distributions of the identified cell classes in mPFC. Such data provide a realistic structural framework with which to investigate neuronal operations in monkey mPFC.

Asunto(s)

Neuronas/fisiología , Corteza Prefrontal/citología , Animales , Calbindina 2 , Calbindinas , Dendritas/ultraestructura , Femenino , Inmunohistoquímica , Interneuronas/fisiología , Interneuronas/ultraestructura , Macaca fascicularis , NADPH Deshidrogenasa/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuronas/ultraestructura , Parvalbúminas/metabolismo , Corteza Prefrontal/enzimología , Corteza Prefrontal/fisiología , Proteína G de Unión al Calcio S100/metabolismo , Adhesión del Tejido , Ácido gamma-Aminobutírico/metabolismo

RESUMEN

The density of spines has been calculated over the processes of NADPH diaphorase reactive neurons in the medial prefrontal cortex (mPFC) of the rat. Quantitative data indicate that diaphorase reactive dendrites ranged from being virtually aspiny to possessing moderate numbers of spines (0.66 +/- 0.23 spines/microns; mean +/- S.D.). The size and shape of dendritic spines varied from long thin 'drum sticks' (the most frequent type) to short stubby protrusions.

Asunto(s)

Dendritas/enzimología , NADPH Deshidrogenasa/análisis , Neuronas/enzimología , Corteza Prefrontal/enzimología , Animales , Femenino , Masculino , Neuronas/ultraestructura , Corteza Prefrontal/ultraestructura , Células Piramidales/enzimología , Células Piramidales/ultraestructura , Ratas , Ratas Sprague-Dawley

RESUMEN

This study provides evidence that neurones in the medial prefrontal cortex of the rat (mPFC areas 24b, 25, and 32) containing strong NADPH diaphorase reactivity also contain GABA immunoreactivity. Also demonstrated is the co-localisation of NADPH diaphorase activity with immunoreactivity for the neuronal isoform of nitric oxide synthase (nNOS) in mPFC neurones. Qualitative and quantitative analyses in the light and electron microscopes indicate that strongly NADPH diaphorase reactive cells are a subpopulation of GABAergic local circuit neurones and constitute a very small proportion (0.6-1.1%) of neurones in rat mPFC. These results suggest that NADPH diaphorase reactive cells in rat mPFC can influence neural activity via GABA-mediated and NO-mediated mechanisms.

Asunto(s)

NADPH Deshidrogenasa/inmunología , Corteza Prefrontal/metabolismo , Ácido gamma-Aminobutírico/inmunología , Animales , Femenino , Inmunohistoquímica , Masculino , Microscopía Electrónica , Neuronas/ultraestructura , Corteza Prefrontal/inmunología , Ratas , Ratas Sprague-Dawley