Gray Type Research Articles

Catecholaminergic neurons in medullary nuclei are among the post-synaptic targets of descending projections from infralimbic area 25 of the rat medial prefrontal cortex

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.

Oxford Textbook of Psychotherapyedited by Glen O. Gabbard, Judith S. Beck, and Jeremy Holmes; Oxford and New York, Oxford University Press, 2005, 552 pages, $98.50

Back to table of contents Previous article Next article Book ReviewFull AccessOxford Textbook of PsychotherapyNorman A. Clemens M.D.Norman A. Clemens M.D.Search for more papers by this authorPublished Online:1 Sep 2006https://doi.org/10.1176/ps.2006.57.9.1347aAboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail Aiming to be a definitive, comprehensive textbook of psychotherapy, this tome covers the sweep of significant psychotherapies extant today. It contains 43 chapters by authors from both sides of the Atlantic, and many of them are prominent in their particular fields. The editors take on the challenge of doing justice to each modality of psychotherapy while integrating their perspectives in certain ways and making the presentations clinically relevant.The organization of the book is felicitous. It starts with a section on the major modalities of treatment—psychoanalytic and psychodynamic, which are regrettably not distinguished from each other; cognitive and behavioral therapies; and interpersonal individual therapies, followed by group, family, couples, and art interventions. The final chapter in the section makes a strong try at integrating the various psychotherapeutic methods while defining elements that are common to all. Every effort is made to present the evidence base, and frequent citations refer the reader to voluminous bibliographies. There is no overall index of references listed by author, and the general index is inconsistent in tracking major authors named in the text.The second section addresses psychotherapy for numerous axis I psychiatric disorders. From here on, most chapters are coauthored by proponents of multiple therapies, especially psychodynamic and cognitive-behavioral. This usually results in subsections on one school and then the other, which is followed by some effort at an integrated discussion with conclusions at the end of each chapter.Section III describes psychotherapy for personality disorders, which necessitates weaving together the therapeutic management of presenting symptoms and behavior with the long-term effort to modify the underlying personality structure. For example, the chapter on borderline personality disorder does a creditable job of portraying cognitive, behavioral, dialectic-behavioral, and psychoanalytic perspectives and then addresses general management issues that challenge all approaches.Section IV divides the field in yet another direction, psychotherapy across the life cycle. The chapters on children and adolescents fill in more of the developmental perspective. Chapters on psychotherapy during the reproductive years and psychotherapy with older adults complete the spectrum.Section V presents issues in specific populations: medical patients, issues of gender and sexual orientation, and cross-cultural psychotherapy. The final section on special topics addresses a number of important subjects. An especially provocative chapter explores the implications of research in cognitive neuroscience for cognitive behavior therapy and psychodynamic psychotherapy. A more general chapter on research is followed by discourses on psychotherapy and medication, ethics, clinical-legal issues, and supervision of psychotherapy. Brief and time-limited therapies bring this lengthy book to a close.This book is daunting to read. It crams an enormous amount of material into 552 pages of a coffee-table-sized, attractive volume by setting it in tiny type that is conducive to eye strain. Many pages of gray type are intermittently broken up by topic headings, but the occasional chart or table is a welcome break from the onslaught of words. The writing is clear and informative but variable in its liveliness and ease of flow. Fortunately, many authors make their points with brief clinical illustrations. Covering so much territory means that this is not the definitive text from which to learn any one psychotherapy, but it makes an excellent reference and overview.Dr. Clemens is clinical professor of psychiatry at Case Western Reserve University, Cleveland, Ohio. FiguresReferencesCited byDetailsCited ByNone Volume 57Issue 9 September, 2006Pages 1347-1348PSYCHIATRIC SERVICES September 2006 Volume 57 Number 9 Metrics PDF download History Published online 1 September 2006 Published in print 1 September 2006

Patterns of expression of brain-derived neurotrophic factor and tyrosine kinase B mRNAs and distribution and ultrastructural localization of their proteins in the visual pathway of the adult rat

We have examined the cellular and subcellular distribution and the patterns of expression of brain-derived neurotrophic factor (BDNF), and of its high affinity receptor, tyrosine kinase B (TrkB), in retinorecipient regions of the brain, including the superior colliculus, the lateral geniculate nucleus and the olivary pretectal nucleus. In the retinorecipient layers of the superior colliculus, BDNF protein and mRNA were present in the cell bodies of a subpopulation of neurons, and BDNF protein was present in the neuropil as punctate or fiber-like structures. In the lateral geniculate nucleus, however, BDNF mRNA was not detected, and BDNF protein was restricted to punctate and fiber-like structures in the neuropil, especially in the most superficial part of the dorsal lateral geniculate nucleus, just below the optic tract. At the ultrastructural level, BDNF protein was localized predominantly to axon terminals containing round synaptic vesicles and pale mitochondria with irregular cristae, which made asymmetric (Gray type I) synaptic specializations (R-boutons). Enucleation of one eye was followed by loss of BDNF immunoreactivity and disappearance of BDNF-positive R-boutons in the contralateral visual centers, confirming the retinal origin of at least most of these terminals. TrkB was present in postsynaptic densities apposed to immunoreactive R-boutons in the superior colliculus and lateral geniculate nucleus, and was also associated with axonal and dendritic microtubules. These findings suggest that BDNF is synthesized by a subpopulation of retinal ganglion cells and axonally transported to visual centers where this neurotrophin is assumed to play important roles in visual system maintenance and/or in modulating the excitatory retinal input to neurons in these centers.

Clonal diversity and rare phenes in Taraxacum officinale s.l. coenopopulations from the East-Ural radioactive trace zone

The East-Ural radioactive trace (EURT) resulting from an accident at the Mayak Production Association in 1957 is a unique region for estimating the genetic consequences of long-term exposure of natural populations to ionizing radiation. We previously used the example of Taraxacum officinale to demonstrate an increased variation in the viability and radiosensitivity of seed progeny, as well as higher frequencies of abnormal morphogenesis, chromosomal aberrations, and allozyme diversity of plant samples [10, 12]. In this study, we estimated the clonal diversity and qualitative composition of rare morphs in dandelion populations from the EURT zone. The dandelion Taraxacum officinale s.l. is a perennial herbaceous polycarpic plant from the Asteraceae Dumort family. This is an apomictic, triploid ( n = 8), polymorphic species [9]. Within the EURT, two experimental plots located on the central axis of the trail were studied. The impact plot was located in the EURT head (13 km away from the accident center); the buffer plot was located in the middle of the trail (86 km from the center). The background plot was outside the region of radionuclide pollution. Etiolated plant leaves (from at least 70 plants) were used for allozyme analysis in 6.4% polyacrylamide gel in a Tris‐EDTA‐borate system [14]. The gel was stained using the standard technique [13]. The clones, i.e., plant groups with identical multilocal allozyme phenotypes, were distinguished from the allozyme spectra of PGI (two zones of activity), 6-PGDH, FDH, EST, GDH, and GOT. Rare morphs were those represented by one to three plants per sample [3]. Detailed radioecological characteristic of the EURT zone were reported earlier [8, 10]. Note that, taking into account the natural radiation background, additional exposure of meristematic plant tissues on the buffer and impact plots exceeded the background level by factors of 4 and 240, respectively. The community was of the secondary dry herb‐grass meadow type in all plots; the soil of the gray forest type in all plots. In total, 21 clones were identified in all populations studied, most of these clones being unique (figure). In the background and buffer samples, ten and seven allozyme phenotypes were determined, which were represented by 32 (78%) and 82 (87%) plants, respectively. In the impact coenopopulation containing 18 plants (42%), six clones were identified. The only common clone (no. 2) was found in chronically irradiated conopopulations. Although this clone dominated in both plots (53.7 and 27.8% in the middle and head EURT regions, respectively), the proportions of this plant phenotype differed almost twofold in the samples. Coenopopulations of the buffer and background regions also contained a common clone (no. 1), and the corresponding proportions of plants were similar. No common allozyme phenotypes were found in the background and impact coenopopulations. Each population from the EURT zone contained five unique clones,

Effects of Water Stress and Mulch on Grean Bean Yield and Yield Components in Greenhouse Condition

In this research effects of water stress levels (I,,,, I,,, I,, and I,) and mulch types (gray-Mg; black- Mb- and mulchless-Mo) on green bean yield and yield components in greenhouse condition were studed. The inigation levels applied in thls study significantly affected the yield and almost all yield parameters. The irrigation at I,,, level gave the highest green bean yield. Un-inigated treatment (IJ gave the lowest values for yield and yeld parameters. The inigation level x mulch treatment interactions were significant on pod width, length of pod and branch number per plant. The yield and almost all of yield components were not affected by mulch types. However, the yields for the mulch treatments of Mg and Mb were hgher than the mulchless treatment (Mo) under the water stress condition. The yield was not significantly affected by the mulch types, but gray mulch type (Mg) has the hghest yield. The highest WUE was obtained in I,.Mg conditions.

Fine structural survey of the intermediate subnucleus of the nucleus tractus solitarii and its glossopharyngeal afferent terminals

The intermediate subnucleus of the nucleus tractus solitarii (imNTS) receives somatosensory inputs from the soft palate and pharynx, and projects onto the nucleus ambiguus, thus serving as a relay nucleus for swallowing. The ultrastructure and synaptology of the rat imNTS, and its glossopharyngeal afferent terminals, have been examined with cholera toxin-conjugated horseradish peroxidase (CT-HRP) as an anterograde tracer. The imNTS contained oval or ellipsoid-shaped, small to medium-sized neurons (18.2 x 11.4 microm) with little cytoplasm, few cell organelles and an irregularly shaped nucleus. The cytoplasm often contained one or two nucleolus-like stigmoid bodies. The average number of axosomatic terminals was 1.8 per profile. About 83% of them contained round vesicles and formed asymmetric synaptic contacts (Gray's type I), while about 17% contained pleomorphic vesicles and formed symmetric synaptic contacts (Gray's type II). The neuropil contained small or large axodendritic terminals, and about 92% of them were Gray's type I. When CT-HRP was injected into the nodose ganglion, many labeled terminals were found in the imNTS. All anterogradely labeled terminals contacted dendrites but not somata. The labeled terminals were usually large (2.69+/-0.09 mum) and exclusively of Gray's type I. They often contacted more than two dendrites, were covered with glial processes, and formed synaptic glomeruli. A small unlabeled terminal occasionally made an asymmetric synaptic contact with a large labeled terminal. The large glossopharyngeal afferent terminals and the neurons containing stigmoid bodies characterized the imNTS neurons that received pharyngeal afferents.

Cyto‐ and chemoarchitecture of the cerebral cortex of an echidna (Tachyglossus aculeatus). II. Laminar organization and synaptic density

We have examined the distribution and morphology of neurons immunoreactive for nonphosphorylated neurofilament protein (SMI-32 antibody), calcium-binding proteins (parvalbumin, calbindin, calretinin), and neuropeptide Y as well as neurons reactive for NADPH diaphorase in the cerebral cortex of the Australian short-beaked echidna (Tachyglossus aculeatus). We have also studied synaptic morphology and density in S1 somatosensory cortex and assessed parameters associated with metabolic activity of the cerebral cortex (vessel volume density, mitochondrial volume density, and mitochondrial numerical density) in semi- and ultrathin sections. SMI-32 immunoreactivity was found mostly in layer V pyramidal neurons in selected cortical regions (S1, PV, V1, A). These neurons often showed atypical morphology compared with therian cortex. Neurons immunoreactive for calcium-binding proteins were broadly similar in both morphology and distribution to those seen in therian cortex, although calretinin-immunoreactive neurons were rare. Both Gray type I and Gray type II synapses could be identified in echidna S1 cortex and were similar to those seen in therian cortex. Peak synaptic density was in upper layer IV, followed by layer I, lower layer II, and upper layer III. Most synapses were of type I (72%), although types I and II were encountered with similar frequency in lower layer II and upper layer III. The capillary volume fraction values obtained for the echidna (from 1.18% in V1 to 1.34% in S1 cortex) fall within the values for rodent cortex. Similarly, values for mitochondrial volume fraction in echidna somatosensory cortex (4.68% +/- 1.76%) were comparable to those in eutherian cortex.

Age-related ultrastructural changes in hypocretinergic terminals in the brainstem and spinal cord of cats

In a previous study, we noted the presence of enlarged “spot-like” structures that are immunoreactive to hypocretin in specific regions of brainstem of aged cats; similar structures were not seen in the same regions of adult cats. In the present study, electron microscopy was combined with hypocretin immunohistochemistry to examine the ultrastructure of these enlarged “spot-like” structures, which were found to consist of enlarged axonal terminals. The terminals were comprised of a large pale core with a dark peripheral rim. Many granules were present within the core; most of these granular structures were not immunostained. On the other hand, the rim contained a high density of hypocretin immunoreactivity; in this peripheral region, large dense-core vesicles and small synaptic vesicles without dense cores were observed. In addition, mitochondria in the peripheral rim region exhibited high electron density, which is indicative of the presence of age-related degenerative changes. Synaptic contacts were observed between the enlarged terminals and adjacent dendrites. Most of these synapses were asymmetric (Gray type I), although a few of them were symmetric (Gray type II). These data suggest that hypocretin transmission is altered during aging, which would be expected to result in age-related changes in the functioning of the hypocretinergic system.

Edward George Gray. 11 January 1924 – 14 August 1999

George Gray was an early contributor to our knowledge of the electron microscopic appearance of the central nervous system. He was skillful with the difficult techniques for preparing the tissues, worked rapidly, and was an astute observer. Sitting with him in the dark, staring at a dim image that George was moving rapidly as he searched for significant detail, could be an exciting experience. He had clear ideas about features that mattered and could quickly relate the two-dimensional electron microscopic images to the three-dimensional neural structures under investigation. He is best known for his detailed and perspective description of synaptic junctions in the mammalian neocortex, and his name is still linked to two distinct junctional types (Gray's type 1 and Gray's type 2), now recognized as generally distinguishing excitatory from inhibitory junctions. He studied a wide range of neural tissues, played a significant role in the early isolation of 'synaptosomes', contributed greatly to the rapid advance of knowledge that accompanied the early application of the electron microscope to neural tissues, and influenced a great many later fine-structural studies of the nervous system.

Professor Edward George Gray, FRS (1924-1999).

Professor George Gray, who died in August 1999, had a notable career as a pioneer electron microscopist of neural tissues. His name is still attached to synapses, which can be classified as Gray type 1 (symmetric) or type 2 (asymmetric), and in addition he made a number of other profound contributions to our knowledge of synaptic structures.He started his academic career late, having worked before the second World War as a bank clerk, and then serving in the Navy, patrolling for U-boats in the North Sea and Atlantic for 4 years during the latter part of the war. He had an early interest in zoology, particularly in marine biology and microscopy and when he left the Navy he took the opportunity to work for a degree in Zoology at the University of Wales in Aberystwyth. A first class honours degree was followed by a PhD on melanophores in teleosts. It was fortunate that the external examiner for the thesis was J. Z. Young, who was impressed by the work and by George, and who invited George to work as his assistant in the preparation of The Life of the Mammals in the Anatomy Department at University College London.

EFFICACY OF GRANULAR AND LIQUID INSECTICIDES AGAINST CORN ROOTWORM LARVAE, 2000

An experiment was conducted at the Virginia Tech Kentland Research Farm in Montgomery County, VA, to determine the effectiveness of several granular and liquid insecticides, applied in-furrow or T-band at planting, against western corn rootworm larvae on Pioneer variety ‘3394’ corn. The experiment was conducted in a 5-acre, continuous cornfield with a McGary and Purdy dark gray silt loam soil type. Plots of 30 x 10 ft (four rows wide) were arranged in an RCBD, with all insecticide treatments and an untreated check replicated four times. An Almaco, 2-row Max-Emerge planter was used to plant the plots on 12 May at the rate of 28,000 seeds/acre on 30-inch rows. Insecticide granules were applied in front of the presswheels either directly in the seed furrow or in a 5-inch wide T-band over the furrow, depending on the treatment. The standard granular insecticide applicator was removed from each row unit and replaced with a wooden holder that held an inverted pint canning jar (Mason) used to dispense the insecticide granules. Attached to the underside of the wooden holder was a plastic funnel and tube through which the insecticide granules flowed. A single opening, drilled into the lid of each jar, was calibrated in the laboratory to deliver insecticide granules accurately at a speed of 3 mph. The possibility of mixing one or more insecticides was avoided by using a separate jar and lid for each treatment. At the start of application, a jar containing the appropriate insecticide was inverted and placed in each of the wooden holders. This method helped minimize soil compaction because the tractor made only one up and back pass per plot. The liquid insecticide Regent 4SC was applied in-furrow at a rate of 0.13 lb (AI)/acre using a backpack sprayer calibrated to deliver 20 gpa at 40 psi. The sprayer setup involved a two-nozzle spray boom with each nozzle inserted into its own clear plastic delivery tube. Immediately before application of the liquid insecticide, the regular in-furrow tubes for the granular insecticides were replaced with the liquid delivery tubes. The roots of ten consecutive corn plants, five from each of the center two rows, were dug from each plot on 11 Jul and washed of excess soil before damage ratings were made. Corn rootworm damage ratings were based on the Iowa 1–6 scale (1 = no feeding damage, 6 = three or more root nodes completely destroyed). Stand counts were determined in each plot on 17 Jul by counting the number of stalks per 20 row-ft. A two-way ANOVA and Fisher’s protected LSD were used to analyze differences among treatments in root damage ratings and stand counts.

4-5 フレームベース・ユニットセルを用いた連続体の位相最適化

Since structural topology optimization using the homogenization method was introduced by Bendsoe and Kikuchi in 1988, this method has been applied to the various kind of problem and also become one of the CAE tool at the begining of conceptual design in many industries. However, the result of optimal topology calculated has unclear part such as gray zone or checker-board type density distribution. Many researchers studied various kinds of methodology to obtain the clear configuration from the result of topology optimization. In this paper, we introduce the new type of unit-cell so called 'Frame based unit-cell' to improve the result of optimized topology. Some examples resulting from the proposed method are presented and compared with the density approach and the homogenization method which are widely used in the structural topology optimization.

Immunoelectron microscopic study of glutamate inputs from the retrosplenial granular cortex to identified thalamocortical projection neurons in the anterior thalamus of the rat

We have carried out an ultrastructural study to determine the characteristics and distribution of glutamate-containing constituents of the anterodorsal (AD) and anteroventral (AV) thalamic nuclei in adult rats. We used a polyclonal antibody to glutamate and a postembedding immunogold detection method in animals in which the neurons of AD/AV projecting to the cortex had been retrogradely labelled and the terminals of corticothalamic afferents anterogradely labelled by injection of cholera toxin-horseradish peroxidase (HRP) into the retrosplenial granular cortex. The heaviest immunogold labelling was over axon terminals 0.42 to 2.2 μm in diameter containing round synaptic vesicles and establishing Gray type 1 (asymmetric) synaptic contact (type 1 terminals) on HRP-labelled or non-labelled dendrites. Mean gold particle densities over such terminals were 3–4 times higher than the densities over the dendrites to which they were presynaptic and 5–6 times higher than over terminals establishing Gray type 2 (symmetric) synaptic contacts (type 2 terminals). Gold particle densities over neuronal cell bodies and dendrites and over a subpopulation of myelinated axons were intermediate between the densities over type 1 and type 2 terminals. In adjacent serial sections immunoreacted for gamma aminobutyric acid, type 2 terminals were heavily immunolabelled whereas type 1 terminals and other profiles with moderate gold particle densities after glutamate immunoreaction displayed very low labelling. A subpopulation of small type 1 axon terminals (up to 1 μm diameter) contained HRP reaction product identifying them as cortical in origin; they contacted small dendritic profiles (most <1 μm diameter) many of which also contained HRP reaction product. We conclude that terminals of the corticothalamic projection from retrosplenial granular cortex to AD/AV are glutamatergic and innervate predominantly distal dendrites of thalamocortical projection neurons. All rights reserved

Involvement of tryptophan metabolism in the body color of crustacea.

The terrestrial isopod, Armadillidium vulgare is usually grey or black in color, however, red ones are occasionally found in the field. This is caused by the mutation of the ommochrome genesis in the integument. We focused our experiments on the mechanism of pigment genesis in which tryptophan metabolism had been expected to be different from the grey or black wild types. We obtained the result that 3-hydroxyanthranilic acid content was significantly higher in the red phenotype than in the wild type, and kynureninase activity was also higher in the red phenotype.

Structure and Function of Gustatory Neurons in the Nucleus of the Solitary Tract. III. Classification of Terminals Using Cluster Analysis

In sensory systems, insight into synaptic arrangements on cells of known physiological response properties has helped our understanding of the structural basis for these properties. To carry out these types of studies, however, synaptic types in the region of interest must be defined. Unfortunately, defining synaptic types in the brainstem has proved to be a challenging enterprise. Our study was done to classify synapses in the gustatory part of the nucleus solitarius using objective quantitative criteria and a cluster analysis procedure. Cluster analysis allows classification of a population of objects, such as synaptic terminals, into groups that exhibit similar characteristics. Six terminal types were identified using cluster analysis and subsequent analyses of variance and post hoc tests. Unlike classification schemes used for the cerebral cortex, where synaptic apposition density thickness and shape of vesicles is useful (Gray's Type I and II synapses), the concentration of vesicles in a terminal was a more useful measurement with which to classify terminals in the nucleus solitarius. To validate that vesicle density (vesicles/μm2) is a useful defining characteristic to classify terminals in the nucleus solitarius, terminals of a known type were used. GABAergic terminals were identified using postembedding immunohistochemical techniques, and their vesicle density was determined. GABAergic terminals fall into the range of two of the terminal types defined by the cluster analysis and, based on vesicle density, two types of GABAergic terminals were identified. We conclude that vesicle density is a helpful means to identify synapses in this brainstem nucleus.

The ultrastructure of the olivary pretectal nucleus in rats. A tracing and GABA immunohistochemical study.

The olivary pretectal nucleus is a primary visual centre, involved in the pupillary light reflex. In the present study an ultrastructural analysis was made of the olivary pretectal nucleus by means of separate, anterograde and retrograde tracing techniques and immunohistochemistry of gamma-aminobutyric acid. Large-projection neurons and two types of gamma-aminobutyric acid-immunoreactive (GABA-ir) neurons are observed in the olivary pretectal nucleus. The primary dendrites of the projection neurons have a dichotomous appearance, the secondary dendrites a multipolar appearance. At the ultrastructural level the projection neurons have well-developed Golgi fields, abundant rough endoplasmic reticulum and the nucleus is always heavily indented. Numerous small GABA-ir neurons and a few medium-sized GABA-ir neurons are found. The small GABA-ir neurons contain a few stacks of rough endoplasmic reticulum and the nucleus is oval-shaped. The medium-sized GABA-ir neurons have well-developed Golgi fields, a moderate number of rough endoplasmic reticulum stacks and an indented nucleus. GABA-positive dendritic profiles containing vesicles also are observed. In the neuropil of the olivary pretectal nucleus, retinal terminals are found that contain round clear vesicles and electron-lucent mitochondria. They make asymmetric synaptic contacts (Gray type I) with dendritic profiles and with profiles containing vesicles. Terminals originating from the contralateral olivary pretectal nucleus exhibit small, round clear vesicles, electron-dense mitochondria and make asymmetric synaptic contacts (Gray type I) mainly with dendritic profiles. Two types of GABA-ir terminals were found. One type is incorporated in glomerulus-like arrangements, whereas the other type is not. GABA-ir terminals contain pleomorphic vesicles, electron-dense mitochondria and make symmetric synaptic contacts (Gray type II). Retinal terminals, terminals originating from the contralateral olivary pretectal nucleus and GABA-ir terminals are organized in glomerulus-like structures, in which dendrites of the large projection neurons form the central elements. Triadic arrangements are observed in these structures; a retinal terminal contacts a dendrite and a GABA-ir terminal and the GABA-ir terminal also contacts the dendrite. The complexity of the synaptic organization and the abundancy of inhibitory elements in the olivary pretectal nucleus suggest that the olivary pretectal nucleus is strongly involved in processing visual information in the pupillary light reflex arc.

An electron microscopic tracer study of the projections from entopeduncular nucleus to the ventrolateral nucleus of the rat

The entopeduncular (EP) nucleus is considered to be the major outflow nucleus of the basal ganglia (BG). The anterograde tracer dextran biotin was injected into EP to investigate its connections with the thalamus. Terminals from EP were found in the ipsilateral ventroanterior-ventrolateral (VAL) and ventromedial thalamic nuclei (VM), lateral habenular and centromedian-parafascicular complex. Electron microscopy of the terminals in VAL/VM revealed densely labelled small synapses that had prominent post-synaptic densities and round vesicles. Synapses were observed onto dendrites and dendritic spines but not onto other synapses or somas. No symmetrical synapses with pleomorphic vesicles were labelled. It is concluded that the synaptic contacts between EP and thalamus are Gray type 1. These findings have implications regarding current theories of BG pathophysiology.

Synaptic organization of afferent projections to the supramammillary nucleus of the rat.

We studied the fine structure of afferent terminals from the preoptic area, the nucleus of the diagonal band of Broca, the infralimbic cortex and the laterodorsal tegmental nucleus within the supramammillary nucleus (SUM) using the anterograde tracing method of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP). Injection of WGA-HRP into the preoptic area permitted ultrastructural recognition of many anterogradely labeled terminals in the SUM. Almost all labeled terminals (99%) contained clear round synaptic vesicles and formed asymmetric synaptic contacts (Gray's type I). About 86% of labeled terminals from the nucleus of the diagonal band were asymmetric (Gray's type I), whereas 14% contained pleomorphic synaptic vesicles and formed symmetric synaptic contacts (Gray's type II). Almost all labeled terminals from the infralimbic cortex were located in the ventral part of the SUM, and 95% of labeled terminals were Gray's type I. The majority of labeled terminals (90%) from the laterodorsal tegmental nucleus were Gray's type I, and the remaining (10%) were Gray's type II. The percentage of labeled terminals with dense-cored vesicles was very high in terminals from the preoptic area (70%), and low in terminals from the infralimbic cortex (19%). Labeled terminals in all cases contacted mainly intermediate-sized dendrites (0.5-1.0 micron diameter). All cases had only a few labeled axosomatic terminals. The cases of injections into the preoptic area and the diagonal band nucleus had some reciprocal connections at the ultrastructural level.

Presynaptic metabotropic glutamate receptors in adult and developing neurons: autoexcitation in the olfactory bulb.

The mitral cell of the olfactory bulb is the primary relay neuron that transmits information from the olfactory receptors to the rest of the brain. This excitatory neuron releases glutamate from presynaptic dendrites and axon terminals. All rat mitral cells studied showed strong, selective, and widespread metabotropic glutamate receptor mGluR1 alpha immunoreactivity on the presynaptic membrane of dendrites, often at the synaptic vesicle release site, when examined with light and electron microscopy. The finding of glutamate receptors on mitral cell secondary dendrites supports the conclusion that not all dendritic membrane with glutamate receptors necessarily have gray type I asymmetrical synaptic specializations. In contrast, the metabotropic glutamate receptor mGluR5 was not found in mitral cells but was expressed by granule cells and astrocytes around mitral dendrites. Both mGluR1 alpha and mGluR5 were expressed early in development, with strong immunostaining present by postnatal day 1. MGluR1 alpha staining at birth mirrored the adult staining pattern. MGluR5 staining at birth showed different patterns of immunostaining than that found in the adult, particularly in the external plexiform layer. In vitro olfactory bulb neurons and their dendrites from embryonic day (E) 18 olfactory bulbs responded to t-ACPD and quisqualate, selective and nonselective metabotropic glutamate receptor agonists, and to several ionotropic glutamate agonists with increases in intracellular Ca2+ as studied with fura-2 digital imaging. These data indicate that the receptors were functionally active at an early stage of development. Application of the glutamate receptor blockers d-2-amino-5-phosphonovalerate (AP5) and 6-cyano-7-nitroquinoxaline (CNQX) to E17 olfactory bulb neurons after only 4 days in vitro resulted in a dramatic decrease in Ca2+ levels in 70% of 128 cells tested, suggesting that embryonic neurons after a short time in vitro can actively secrete glutamate. The presence of glutamate receptors on the long mitral cell dendrite suggests that it would be able to respond to release of its own excitatory transmitter, probably at an early stage of development. In the probable absence of other excitatory input to the secondary mitral dendrites, it would be the only excitatory "input." This autoexcitatory response would be modulated by release of GABA from olfactory interneurons occurring milliseconds after glutamate release induced by olfactory nerve activation. This novel type of neuronal microcircuitry would potentially amplify signal transmission and current spread along the long mitral dendrites and could play an important role in lateral inhibition of olfactory neurons.

Efferent synaptic organization of the olivary pretectal nucleus in the albino rat. An ultrastructural tracing study.

In this study an ultrastructural analysis was made of the efferent projections of the olivary pretectal nucleus in the rat. The anterograde tracer Phaseolus vulgaris leucoagglutinin was injected iontophoretically into the olivary pretectal nucleus. Ascending and descending pathways were studied. In the descending pathway special attention was paid to the fine structural features of the olivary pretectal nucleus efferents projecting to the Edinger-Westphal nucleus, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch and the periaqueductal gray. The projection to the superior colliculus and the pontine nucleus was also studied at the ultrastructural level. All the labeled terminals in the descending pathway showed ultrastructurally similar features: clear, round vesicles and electron dense mitochondria. The terminals made asymmetric synaptic membrane specializations (Gray type I), the postsynaptic profiles were dendritic. In the interstitial nucleus of Cajal and the superior colliculus the terminals are organized in glomerulus-like structures. The terminals in the descending pathway were enwrapped by astrocytic processes, also in the glomerulus-like structures. In the ascending pathway the projection to the ventral part of the lateral geniculate nucleus was studied. Almost all terminals in the ascending pathway showed similar ultrastructural features as in the descending pathway: electron dense mitochondria, clear, round vesicles and asymmetric synaptic membrane specializations (Gray type I). The terminals are organized in glomerulus-like structures. To identify the projecting neurons in the interstitial nucleus of Cajal and the Edinger-Westphal nucleus, retrograde tracing experiments were performed. Therefore the beta subunit of cholera toxin conjugated with horseradish peroxidase was injected into the facial nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)