Aspiny Cells Research Articles

Quantitative analysis of the Golgi impregnated human (neo)striatal neurons: Observation of the morphological characteristics followed by an emphasis on the functional diversity of cells

BackgroundThe (neo)striatum is the major input structure of the basal nuclei, which is involved in the execution of voluntary movements, but also in controlling the processes that lead to the movement, such as motivation and cognition. The striatum provides its function through an interaction between projection neurons and interneurons. The aim of this study was to quantify the morphological properties of neurons in the precommissural putamen and precommissural caudate nucleus head and to evaluate whether there is a difference in cell morphology between different cell groups within one part and between the same cell groups within different parts of the striatum. MethodsA total of 652 neuronal images of human striatum were observed. The features of the neuronal morphology (soma size, dendritic field size, shape of neuronal image, dendritic curviness, dendritic branching complexity) were observed by determining appropriate parameters of digital images of neurons. ResultsAccording to the presence of spines on the soma and/or dendrites, neurons were qualitatively classified into 446 spiny and 206 aspiny cells. The analysis of the distribution of the dendritic field area shows that spiny and aspiny neurons from both parts of the neostriatum can be decomposed into two distributions, which means that they can be classified into subgroups. A quantitative analysis of the spiny/aspiny neurons in the human putamen or caudate nucleus head has shown that there is a statistically significant difference between them. By comparing the morphology of neurons of the same group between different parts of the human neostriatum (putamen and caudate nucleus), it was also determined that there is a statistically significant difference. ConclusionSince the morphology and function of neurons are in close correlation, it can be assumed that different groups of neurons in the human striatum might support functional diversity of the studied area.

On the existence of mechanoreceptors within the neurovascular unit of the mammalian brain.

We describe a set of perivascular interneurons (PINs) with series of fibro-vesicular complexes (FVCs) throughout the gray matter of the adult rabbit and rat brains. PIN-FVCs are ubiquitous throughout the brain vasculature as detected in Golgi-impregnated specimens. Most PINs are small, aspiny cells with short or long (> 1mm) axons that split and travel along arterial blood vessels. Upon ramification, axons form FVCs around the arising vascular branches; then, paired axons run parallel to the vessel wall until another ramification ensues, and a new FVC is formed. Cytologically, FVCs consist of clusters of perivascular bulbs (PVBs) encircling the precapillary and capillary wall surrounded by end-feet and the extracellular matrix of endothelial cells and pericytes. A PVB contains mitochondria, multivesicular bodies, and granules with a membranous core, similar to Meissner corpuscles and other mechanoreceptors. Some PVBs form asymmetrical, axo-spinous synapses with presumptive adjacent neurons. PINs appear to correspond to the type 1 nNOS-positive neurons whose FVCs co-label with markers of sensory fiber-terminals surrounded by astrocytic end-feet. The PIN is conserved in adult cats and rhesus monkey specimens. The location, ubiquity throughout the vasculature of the mammalian brain, and cytological organization of the PIN-FVCs suggests that it is a sensory receptor intrinsic to the mammalian neurovascular unit that corresponds to an afferent limb of the sensorimotor feed-back mechanism controlling local blood flow.

Two Dimensional Grayscale Images of the Aspiny Neurons from the Human Neostriatum: Monofractal and Gray Level Co-occurrence Matrix Analysis

The striatum (neostriatum) is one of the principal constituents of the basal nuclei. It is a complex structure which consists of a dorsal and the ventral components. According to the spine distribution and their density, neurons of the human striatum can be classified into two main types: spiny and aspiny cells. Further classification recognizes two groups of spiny, and three groups of aspiny neurons. The goal of this study was to analyze different morphometric properties of the digital images of the group IV and group V aspiny neurons, from the dorsal striatum of both cerebral hemispheres. In this study, a total of 175 two-dimensional images of aspiny neurons were analyzed. Image reconstruction and measurement was performed with the specialized, public software Image J. Four parameters of standard fractal analysis were quantified from these binary images. In addition, five textural parameters were obtained by analyzing grayscale images of the entire neuron. Results of both analyses show that six of nine parameters differed between the group IV and group V aspiny neurons. Moreover, in both groups of neurons, one parameter of the fractal and three of the texture analyses differed between the putamen and the caudate nucleus neurons. Thus, this study corroborates previous classification of aspiny neurons. Although they belong to the same aspiny group, different type of cells can qualify nerve signals in their own way. Therefore, this study supports the hypothesis that neuronal morphology differences can reflect their functional diversity and their role in communication.

Neuronal images of the putamen in the adult human neostriatum: a revised classification supported by a qualitative and quantitative analysis

A qualitative analysis of the morphology of human putamen nerve cells involves a detailed description of the structure and features of neurons and, accordingly, their classification into already defined classes and types. In our sample of 301 neurons, 64.78 % (195) were spiny and 35.22 % (106) aspiny cells. By analyzing cell bodies and dendritic trees, we subdivided spiny cells into two types (I and II) and aspiny cells into three types (III, IV and V). Our sample of neurons, classified according to the previously described scheme, consisted of 80 type I, 115 type II, 16 type III, 42 type IV and 48 type V nerve cells. In the present study, after qualitative analysis of microscopic images of the Golgi impregnated neurons of the putamen, we measured/quantified five morphological properties, i.e., the sizes of the soma and dendritic field, shape of the neuron, straightness of individual dendrites and the branching complexity of the dendritic tree, using eight morphometric parameters. Hence, we identify five types of nerve cells in the human putamen: type I-small spiny neurons; type II-large spiny neurons; type III-large aspiny neurons; type IV-neurons with a large soma and a medium dendritic field; and type V-small aspiny neurons. By performing an adequate statistical analysis on these parameters, we point out that the proposed types differ enough in their morphology to warrant our qualitative classification.

Cellular factors controlling neuronal vulnerability in the brain: a lesson from the striatum.

In many acute and chronic neurologic disorders, both deficits in energy metabolism and defects in glutamate-mediated excitatory synaptic transmission have been proposed as important pathogenic factors. Brain cells, however, express variable vulnerability to these insults, as indicated by the fact that certain brain areas and even different cell types in the same area are preferentially spared until the very late stages of various diseases. This can be clearly seen in the striatum, where GABAergic projection cells but not cholinergic interneurons are precociously damaged in the course of both acute metabolic insults (such as hypoxia, hypoglycemia, and ischemia) and chronic neurodegenerative disorders (such as Huntington's disease). A well-mapped pattern of cell loss, in fact, is a common finding in the striatum of patients suffering from these pathologic conditions. Physiologic and molecular studies have been directed in recent years to the identification of the cellular mechanisms underlying the cell-type specific vulnerability of striatal cells. These studied recognized that, in striatal spiny and aspiny cells, specific membrane ion channels, glutamate receptor subtypes and subunits, and intracellular enzymatic activities are involved in the cascade of events responsible for opposite responses and vulnerabilities to oxygen or glucose deprivation and to glutamate receptor-mediated toxicity. Specific molecules able to target these cellular factors might be employed as therapeutic agents during acute and chronic neurologic disorders affecting this brain area.

Cellular distribution of the NMDA receptor subunit NMDAR1 in fetal ventral mesencephalon transplants in the dopamine-depleted striatum of a rat.

Immunohistochemistry was performed to demonstrate the cellular distribution of N-methyl-D-aspartate (NMDA) receptor subunit NMDAR1 in the intrastriatal grafts of a rat model of Parkinson's disease. Unilateral 6-hydroxydopamine (6-OHDA) lesions of the mesostriatal pathway were produced in young adult female rats. Neural transplantation was performed with fetal ventral mesencephalon (VM) tissue (at embryonic day 15) 3 weeks after the 6-OHDA lesions. In the fetal VM in which the tyrosine hydroxylase (TH) immunoreactivity was intensely observed, no NMDAR1 subunit immunoreactivity was detected. Immunopositive cells of NMDAR1 were densely distributed in the intact SNc contralateral to the lesions, in which intense immunoreactivity for TH was observed. In contrast, the cells positive for NMDAR1 in the SNr were scattered. The immunoreactivity for NMDAR1 was markedly decreased in the SNc, but not in the SNr on the lesioned side. Double immunostaining revealed that most TH-positive cells in the SNc showed moderate NMDAR1 immunoreactivity. Within the intrastriatal fetal VM grafts containing TH-positive cells, NMDAR1-positive cells tended to locate homogeneously within the grafts. These were composed of various cell sizes and shapes, but they were mainly medium-sized and aspiny cells. Double immunostaining revealed that a part of the TH-positive cells in the grafts was also immunopositive for NMDAR1. Taken together with our previous studies, it is suggested that both dopaminergic neurons and nondopaminergic neurons in the VM transplants appear to be modified functionally by glutamatergic afferents via various glutamate receptors, including NMDAR1.

Cellular distributions of AMPA glutamate receptor subunits in fetal ventral mesencephalon transplants in the dopamine-depleted striatum of a rat

To demonstrate the cellular distributions of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor subunits (GluR1, GluR2/3, and GluR4) in the intrastriatal grafts of a rat model of Parkinson’s disease, immunocytochemistry was performed in 6-hydroxydopamine rats with intrastriatal transplants of fetal ventral mesencephalon (VM). In the fetal VM (at embryonic day 15) in which the tyrosine hydroxylase (TH) immunoreactivity was intensely observed, no GluR subunit immunoreactivity was detected. Within the intrastriatal fetal VM grafts containing TH-positive cells, a large number of cells immunoreactive for GluR1 and GluR2/3 were observed. However, the GluR1- and GluR2/3-positive cells tended to locate homogeneously within the grafts and were composed of various cell sizes and shapes, mainly medium-sized and aspiny cells. Weak GluR4-positive cells were seen in the grafts, although in some cases the staining was too faint to see any immunoreactive cells at all. Double immunostaining revealed that a part of TH-positive cells in the grafts was also immunopositive for GluR1 or GluR2/3. Both dopaminergic neurons and nondopaminergic neurons in the VM transplants appear to be modified functionally by glutamatergic afferents via various glutamate receptors, including GluR1 and GluR2/3 and, to a lesser extent, GluR4.

Dopaminergic Neurons Intrinsic to the Primate Striatum

Intrinsic, striatal tyrosine hydroxylase-immunoreactive (TH-i) cells have received little consideration. In this study we have characterized these neurons and their regulatory response to nigrostriatal dopaminergic deafferentation. TH-i cells were observed in the striatum of both control and 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP)-treated monkeys; TH-i cell counts, however, were 3.5-fold higher in the striatum of MPTP-lesioned monkeys. To establish the dopaminergic nature of the TH-i cells, sections were double-labeled with antibodies to dopamine transporter (DAT). Immunofluorescence studies demonstrated that nearly all TH-i cells were double-labeled with DAT, suggesting that they contain the machinery to be functional dopaminergic neurons. Two types of TH-i cells were identified in the striatum: small, aspiny, bipolar cells with varicose dendrites and larger spiny, multipolar cells. The aspiny cells, which were more prevalent, corresponded morphologically to the GABAergic interneurons of the striatum. Double-label immunofluorescence studies using antibodies to TH and glutamate decarboxylase (GAD67), the synthetic enzyme for GABA, showed that 99% of the TH-i cells were GAD67-positive. Very few (<1%) of the TH-i cells, however, were immunoreactive for the calcium-binding proteins calbindin and parvalbumin. In summary, these results demonstrate that the dopaminergic cell population of the striatum responds to dopamine denervation by increasing in number, apparently to compensate for loss of extrinsic dopaminergic innervation. Moreover, this population of cells corresponds largely with the intrinsic GABAergic cells of the striatum. This study also suggests that the adult primate striatum does retain some intrinsic capacity to compensate for dopaminergic cell loss.

μ-Opioid Receptors Are Localized to Extrasynaptic Plasma Membranes of GABAergic Neurons and Their Targets in the Rat Nucleus Accumbens

The activation of mu-opioid receptors in the nucleus accumbens (Acb) produces changes in locomotor and rewarding responses that are believed to involve neurons, including local gamma-aminobutyric acid (GABA)ergic neurons. We combined immunogold-silver detection of an antipeptide antiserum against the cloned mu-opioid receptor (MOR) and immunoperoxidase labeling of an antibody against GABA to determine the cellular basis for the proposed opioid modulation of GABAergic neurons in the rat Acb. MOR-like immunoreactivity (MOR-LI) was localized prominently to plasma membranes of neurons having morphological features of both spiny and aspiny cells, many of which contained GABA. Of 351 examples of profiles that contained MOR-LI and GABA labeling, 65% were dendrites. In these dendrites, MOR-LI was seen mainly along extrasynaptic portions of the plasma membrane apposed to unlabeled terminals and/or glial processes. Dually labeled dendrites often received convergent input from GABAergic terminals and/or from unlabeled terminals forming asymmetric excitatory-type synapses. Of all profiles that contained both MOR and GABA immunoreactivity, 28% were axon terminals. MOR-containing GABAergic terminals and terminals separately labeled for MOR or GABA formed synapses with unlabeled dendrites and also with dendrites containing MOR or GABA. Our results indicate that MOR agonists could modulate the activity of GABA neurons in the Acb via receptors located mainly at extrasynaptic sites on dendritic plasma membranes. MOR ligands also could alter the release of GABA onto target dendrites that contain GABA and/or respond to opiate stimulation.

S-8-5 - Cholinergic and GABAergic interneurons in the striatum

In the striatum, interneurons have not been as well characterized physiologically as the spiny projection cells. We found that the neostriatal interneurons can be divided at least into three classes by physiological, chemical and morphological criteria. The first was FS cells (fast-spiking cells) which fired very short-duration action potentials at constant spike frequency during depolarizing pulses, were immunoreactive for parvalbumin (calcium-binding protein), and had axons with very dense collateralization within or near their dendritic fields. Another class was identified as those which fired low-threshold spikes (LTS cells) from hyperpolarized potentials, were positive for somatostatin and nitric oxide synthase (NOS), and had the largest axonal fields. The other class of interneurons had longer-lasting afterhyperpolarizations (LA cells), were positive for choline acetyltransferase, and were mostly large aspiny cells. Glutamic acid decarboxylase (GAD67) or GABA immunoreactivity was detected at the somata or terminals of parvalbumin FS cells and somatostatin/NOS LTS cells, but not of cholinergic LA cells. Substance P, probably released from the collaterals of cells projecting to the substantia nigra, excited LA cells and LTS cells, but not FS cells. These results suggest that the striatum has at least one type of cholinergic and two types of GABAergic interneurons which are different in physiological, chemical and pharmacological characteristics.

The distribution of GABAergic cells, fibers, and terminals in the monkey amygdaloid complex: an immunohistochemical and in situ hybridization study

The primate amygdaloid complex is a prominent structure in the medial temporal lobe that comprises a variety of cytoarchitectonically distinct nuclei and cortical regions. The present study employed immunohistochemical and in situ hybridization techniques to determine the distribution of GABAergic cells, fibers, and terminals in the macaque monkey amygdala. Using a monoclonal antibody to GABA, immunoreactive neurons were observed throughout the amygdaloid complex (constituting approximately 20% of the neurons in the lateral nucleus), with higher densities located in the intercalated nuclei, amygdalohippocampal area, and posterior cortical nucleus. The lowest densities of labeled cells were observed in the central and medial nuclei. Interestingly, despite the low number of GABA-immunoreactive neurons, the terminal density in the central nucleus was among the highest in the amygdala. The GABAergic neurons in the amygdala were heterogeneous in morphology, and three general classes of immunopositive aspiny cells were observed. Using mRNA probes for glutamic acid decarboxylase (GAD: GAD65 and GAD67), in situ hybridization demonstrated distributions of labeled cells that generally replicated the immunohistochemical findings. One exception was in the central nucleus where, in contrast to the low number of immunohistochemically labeled cells, both GAD probes labeled large numbers of neurons. These studies on the organization of GABAergic circuits in the primate amygdala are significant because alterations of function in the human amygdala have been implicated in the pathogenesis of temporal lobe epilepsy and in the etiology of affective and other behavioral disorders. The present study provides baseline information with which to evaluate the role of GABAergic systems in amygdala-mediated behaviors and the potential contribution of GABAergic dysfunction in amygdala-associated disorders.

Physiological, morphological, and histochemical characterization of three classes of interneurons in rat neostriatum

Interneurons in lateral part of neostriatum were studied in isolated slices from juvenile rats (16-20 d postnatal) by whole-cell, current-clamp recording at 33-34 degrees C, followed by intracellular staining with biocytin and double immunocytochemical or histochemical staining for parvalbumin, ChAT, and NADPH diaphorase. Medium-sized spiny neurons (MS cells) had distal dendrites with many spines and were likely projection cells, while interneurons had dendrites with fewer spines. The neostriatal interneurons could be further divided into three classes by physiological, chemical, and morphological criteria. The first class of interneurons (fast-spiking cells, FS cells) fired very short-duration action potentials with short-duration afterhyperpolarizations at constant spike frequency during depolarizing current pulses. FS cells had more negative resting potentials and lower input resistances than the other two classes. At depolarized potentials, FS cells fired repetitive spikes in response to synaptic excitation. FS cells were immunoreactive for parvalbumin. As all parvalbumin-immunoreactive cells in the neostriatum were also immunoreactive for GABA, FS cells were considered to be GABAergic. FS cells were further divided into two morphological types: FS cells with local dendritic fields and FS cells with extended dendritic fields. The axons of both types of FS cells had their densest collateralization within or near their dendritic fields. The other two classes of interneuron, PLTS cells (persistent and low-threshold spike cells) and LA cells (long-lasting afterhyperpolarization cells), were distinguished from FS cells by longer-duration action potentials and larger input resistances, had less negative resting potentials, and had longer-lasting afterhyperpolarizations. Afterhyperpolarizations of PLTS cells had a shorter time to peak than those of LA cells. PLTS cells fired both Na(+)-dependent, persistent depolarization spikes and Ca(2+)-dependent, low-threshold spikes in addition to fast spikes. Low-threshold spikes in PLTS cells were induced only from hyperpolarized potentials. Both persistent depolarizations and low-threshold spikes could also be evoked by synaptic activation. PLTS cells were histochemically identified as NADPH diaphorase-positive cells. As all NADPH diaphorase-positive cells in the same tissue were immunoreactive for nitric oxide (NO) synthase, PLTS cells were considered to release NO. PLTS cells had the largest axonal fields. Some PLTS cells appeared to have two axonal origins from the somata and dendrites. LA cells were mostly large aspiny cells with Ca(2+)-dependent long-lasting afterhyperpolarizations and strong time-dependent hyperpolarizing rectification. As this slowly occurring anomalous rectification was blocked by 2 mM cesium, this potential was considered to be due to activation of Ih.(ABSTRACT TRUNCATED AT 400 WORDS)

Spatial distributions of chemically identified intrinsic neurons in relation to patch and matrix compartments of rat neostriatum

The spatial distributions and dendritic branching patterns of chemically identified subpopulations of striatal intrinsic neurons, defined by immunoreactivity for choline acetyltransferase (ChAT), neuropeptide Y or parvalbumin, were studied in relation to patch and matrix compartments of rat neostriatum. ChAT-immunoreactive cells and fibers showed an uneven pattern of distribution in the striatum. ChAT immunoreactivity was higher in the dorsolateral part and lower in the ventromedial part of the striatum. This regional gradient pattern is the inverse of the overall pattern of calbindin D28k immunoreactivity. However, in small regions close to the lateral ventricle and globus pallidus, areas containing fewer ChAT-immunoreactive cells and fibers coincided with those containing low calbindin D28k immunoreactivity. Neuropeptide Y immunoreactivity was uniform in the neostriatum. Certain neuropeptide Y cells (about 20%) were also immunoreactive for calbindin D28k, indicating that at least a small population of calbindin D28k-immunoreactive cells are medium aspiny cells. Parvalbumin immunoreactivity was not uniform in the striatum. A higher density of parvalbumin immunoreactivity was found in the neuropil in lateral and caudal parts than in the medial part. Small regions with weaker parvalbumin-immunoreactive neuropil partially corresponded to calbindin D28k poor patches. Larger cells immunoreactive for parvalbumin were preferentially located in lateral and caudal parts of the striatum. Cells immunoreactive for ChAT, neuropeptide Y or parvalbumin showed basically similar distribution patterns in relation to the patch and matrix compartments. Most stained cells were located in the matrix, but some were located at the borders of patches and a few were inside patches. Most primary dendrites of stained cells in the matrix or patches remained confined to these compartments, but cells on the borders invariably extended dendrites into both compartments. The striatal intrinsic neurons form chemically differentiated neuronal circuits within the matrix, and the patches and those whose dendrites cross the borders may contribute to associational interconnections between the two compartments, unlike the spiny projection neurons whose dendrites are confined to one or the other compartment.

Temporal filtering properties of midbrain neurons in an electric fish: implications for the function of dendritic spines

Electrosensory neurons in the torus semicircularis (midbrain) of the weakly electric fish Eigenmannia vary considerably in their dendritic structure and responses to modulations of the amplitude of electric organ discharges. We investigated possible relations between these properties by recording intracellularly and labeling individual neurons while modulating stimulus amplitude over rates of approximately 2-20 Hz. Morphologically distinct cell types generally differed in their responses to these stimuli. The amplitude envelope of the stimulus was nicely reflected in fluctuations of the membrane potential of heavily spined neurons. The amplitude of these stimulus-related depolarizations decreased markedly as the stimulus modulation rate was increased. For aspiny or sparsely spined neurons, however, the amplitude of stimulus-related depolarizations either increased or remained constant over this range of modulation rates. In these cells, the amplitude envelope of the stimulus was not well represented in the membrane potential. Instead, fast EPSPs were observed that varied in number over time in accordance with the amplitude envelope of the stimulus. Aspiny neurons in the tectum also coded the amplitude envelope of stimuli with poor fidelity. The amplitude of stimulus-related depolarizations, however, decreased as the rate of modulation of stimulus amplitude was increased, consistent with the notion that tectal neurons receive afferent input from the spiny toral neurons. Spiny neurons appear, therefore, to act as low-pass filters of temporal information in sensory signals. Aspiny cells, however, code high temporal frequencies. These data support the hypothesis that dendritic spines contribute to the low-pass filtering of inputs to neurons.

Spiny neurons of area CA3c in rat hippocampal slices have similar electrophysiological characteristics and synaptic responses despite morphological variation.

Area CA3c is an area of morphologically diverse neurons. In addition to the presence of interneurons and pyramidal cells that are similar to those found in other subfields of area CA3, many neurons of area CA3c are different. They do not resemble interneurons, since they bear numerous spines, yet they also differ substantially from pyramidal cells in their morphology. To determine if the variants of area CA3c spiny cells are distinct physiologically as well as morphologically, intracellular recordings were made to record the electrophysiological properties of area CA3c cells in rat hippocampal slices, and each cell was identified morphologically following intracellular dye injection. The results show that the spiny cells, regardless of their often extensive morphological variation, have relatively uniform, pyramidal-like electrophysiological properties. The aspiny cells are quite different from the spiny cells morphologically (i.e., in their paucity or complete lack of spines), and are also extremely different electrophysiologically, exhibiting features of "fast-spiking" cells. Thus, spiny cells in area CA3c correspond to cells with pyramidal-like electrophysiology, and the aspiny cells in area CA3c correspond to cells with interneuronal physiological properties. This correlation between structure and function appears to be a rule that pertains to each of the subfields of the hippocampus.

Chapter 10 Chemical signalling and striatal interneurones

Publisher Summary The majority of neostriatal neurones are mediumsized spiny neurones, which have diameters between 10 and 20 pm. These cells were originally believed to be interneurones; however, retrograde transport studies established them as projection neurones. Parallel studies showed that GABA inhibition (or more strictly disinhibition) controls the majority of the functional activity in the basal ganglia. In addition to the medium-sized spiny cells, the larger aspiny cells, 20–60 pm diameters, constitute some 4%– 5 % of all striatal neurones, and these are now known to be short axoned interneurones, although there are occasional reports of aspiny projection neurones. These interneurones integrate activity between output pathways through the striatum providing feed forward and feedback loops. In addition, interneurones may represent relatively specific targets for cortical or thalamic inputs. This chapter discusses some of the recent work exploring the phenotypes of striatal interneurones and present evidence indicating that nitric oxide may be a novel intercellular messenger in the striatum modulating the effects of glutamate on N-methyl-D-aspartate (NMDA) receptors expressed by striatal neurones. Stimulation of NMDA receptors in vivo activates local acetylcholine (ACh) release as does local application of substance P and substance P agonists. The exquisite sensitivity of cholinergic neurones to substance P and NMDA suggests that these neurones represent an important target both for local striatal axon collaterals containing substance P, and thalamic excitatory inputs releasing glutamate.

Localization of the protein kinase C phosphorylation/calmodulin-binding substrate RC3 in dendritic spines of neostriatal neurons.

The rodent protein RC3 is expressed mainly by forebrain neurons during postnatal development and maturity. RC3 and its bovine homolog neurogranin/B-50 immunoreactive C-kinase substrate (BICKS) contain overlapping sites for protein kinase C phosphorylation and calmodulin binding that resemble those of the presynaptic 43-kDa growth-associated protein (GAP-43). However, morphological evidence suggests that RC3 has a postsynaptic localization. To test this hypothesis, we used two polyclonal antisera against synthetic peptides corresponding to nonoverlapping sequences within RC3 and compared cellular distributions of their binding in neostriatum of adult rats by immunohistochemistry, Golgi impregnation/gold toning, and correlative light/electron microscopy. Somatic and punctate patterns of RC3 immunoreactivity were observed. Somatic RC3 was found in cyto- and nucleoplasmic compartments of all neuronal phenotypes (medium spiny, medium aspiny, and large aspiny cells). Punctate RC3 was found mostly in dendritic spines. In contrast to the 43-kDa growth-associated protein, RC3 was seen infrequently in axons. We conclude that RC3 accumulates postsynaptically in dendritic spines of neostriatal neurons. We propose that RC3 acts as a "third messenger" substrate of protein kinase C-mediated molecular cascades during synaptic development and remodeling.

Large aspiny cells in the matrix of the rat neostriatum in vitro: physiological identification, relation to the compartments and excitatory postsynaptic currents.

1. Large aspiny neurons (20-60 microns diam) in the neostriatum were studied in an in vitro rat slice preparation by whole-cell recording to reveal physiological identification from medium-sized spiny projection cells (10-20 microns diam), relation to the patch and matrix compartments, and excitatory synaptic inputs. Recorded cells were identified by intracellular biocytin staining. Compartmental identification was made by calbindinD28K immunohistochemistry in fixed slices. 2. Large stained neurons were morphologically heterogeneous and had aspiny or sparsely spiny dendrites and dense local axonal branches. They were located in the matrix or on the patch-matrix border. Axonal branches of the large aspiny cells were preferentially distributed in the matrix and gave off terminal boutons there. Some of the secondary dendrites arising from stem dendrites running along the border, however, crossed compartment boundaries and made fine branches in a patch. 3. Large aspiny cells had less negative resting membrane potentials and lower thresholds for spike generation than medium spiny cells. They showed longer-duration and larger-amplitude afterhyperpolarizations (AHPs) than medium spiny cells. During hyperpolarizing current pulses, apparent resistance slowly reduced, and a prominent sag was observed in the voltage record, which was absent in medium spiny cells. The large aspiny cells showed no spontaneous firing but had a tendency to fire repetitive spikes in response to depolarizing current pulses, although spike interval tended to increase in later spikes. Spike frequency of large aspiny cells increased less with current intensity than that of medium spiny cells. 4. Most large aspiny cells were considered to belong to a single physiological class, although one large aspiny cells showed shorter-duration AHPs than both most other large aspiny cells and medium spiny cells, and little spike-frequency adaptation. 5. Excitatory postsynaptic currents (EPSCs) of large aspiny cells induced by intrastriatal stimulation had two components. An early, linear component was blocked by 10 microM 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), a selective antagonist of non-N-methyl-D-aspartate (NMDA) receptors. A later component with a nonlinear current-voltage (I-V) relationship was blocked by 50 microM DL-2-amino-5-phosphonovaleric acid (DL-APV), a selective antagonist of NMDA receptors. 6. From these results, four conclusions can be drawn. 1) Most large aspiny neostriatal cells in the matrix, although they take heterogeneous shapes, belong to one physiological class with long-duration AHPs and a strong time-dependent component of anomalous rectification.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrophysiological and morphological properties of rat motor cortex neurons in vivo

This paper describes results obtained from intracellular recordings and stainings of motor cortex neurons in the rat in vivo. Rats were anesthetized with phenobarbital. Neurons were intracellularly recorded with micropipettes filled with K +-methylsulphate + 4% HRP in phosphate buffer (pH 7.4). Successful recordings and stainings were obtained from 31 neurons. Intracellular recordings were distinguished as either intrasomatic or intradendritic. Action potentials (APs) recorded from somata were distinguished by their fast hyperpolarizing afterpotential from those recorded within dendrites. Dendritic APs were broader and often followed by an afterdepolarization. The firing patterns elicited by depolarizing current pulses allowed to distinguish 3 groups of neurons. (a) Group A neurons with a moderate firing-rate of up to 17 APs during a 100 ms depolarizing current pulse of 3.5 nA comprised small and large pyramidal cells and one aspiny multipolar neuron, probably a large basket neuron. (b) Group B neurons generated bursts, which either occurred spontaneously or during low intensity current injection. These neurons were classified as small pyramidal neurons and spiny star cells. (c) Group C neurons had a firing rate 3 times as high as group A neurons. These neurons were small aspiny cells with radial dendritic fields, which were classified as local interneurons. Intradendritic recordings were characterized by the occurrence of broad APs, most likely generated within the dendritic tree. Intracellular current injections produced burst-like potentials consisting of several APs with different amplitude and duration. In 3 penetrations of one apical dendrite up to 4 neurons were stained. In these recordings APs activated by intracellular current injection were particularly broad (up to 40 ms). The results suggest that neuronal firing patterns observed in in-vitro neocortical slices are also observed in in-vivo conditions.

Physiological identification and excitatory synaptic currents of large aspiny cells in the matrix of the neostriatum in vitro

Physiological identification and excitatory synaptic currents of large aspiny cells in the matrix of the neostriatum in vitro