bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunohistochemical analysis of the visual wulst of the pigeon (Columba livia)
Authors: Shimizu Toru , Karten Harvey J.
Published: January 2005

The avian wulst, a laminated “bulge” in the dorsal telencephalon, contains several distinct regions. The posterolateral portion (visual wulst) has been proposed to be an avian equivalent of the mammalian striate cortex. The present study examines specific neurotransmitters and neuropeptides within the visual wulst by immunohistochemical techniques. Antisera and monoclonal antibodies against choline acetyltransferase (ChAT), nicotinic acetylcholine receptor (nAChR), tyrosine hydroxylase (TH), serotonin (5‐HT), glutamic acid decarboxylase (GAD), gammaaminobutyric acid A receptor (GABAAR), cholecystokinin (CCK), substance P (SP), leucine‐enkephalin (L‐ENK), neurotensin (NT), neuropeptide Y (NPY), somatostatin (SRIF), corticotropin‐releasing factor (CRF), and vasoactive intestinal polypeptide (VIP) were used. Somata and neuropil displaying specific immunoreactivity were generally distributed in accordance with the laminar cytoarchitectonic organization of the wulst. The superficial layer of the wulst, the hyperstriatum accessorium, contained the highest densities of TH‐, 5‐HT‐, SP‐, NPY‐, SRIF‐, CRF‐, and VIP‐positive neuropil in the wulst, whereas the highest density of CCK‐ and NT‐staining was found in the deepest layer of the wulst, the hyperstriatum dorsale, In addition to the traditionally defined four laminae of the wulst, the immunoreactive staining revealed several subregions within each lamina. The most dorsolateral portion of the wulst contained the highest densities of ChAT‐ and L‐ENK‐stained fibers in the wulst, as well as moderately dense staining of neuropil for 5‐HT‐, TH‐, SP‐, and CCK‐like immunoreactivity. The nACh‐Rimmunoreactivity was faint and distributed rather uniformly throughout the wulst. The results suggest that the wulst consists of multiple regional variations within layers comparable to laminar variations found within different cytoarchitectonic areas of the mammalian neocortex.
Proportion of parvalbumin‐positive basket cells in the GABAergic innervation of pyramidal and granule cells of the rat hippocampal formation
Authors: Ribak Charles E. , Nitsch Robert , Seress László
Published: January 2005

Recent studies have indicated that hippocampal GABAergic neurons in both the dentate gyrus and Ammon's horn contain immunoreactivity for the calcium‐binding protein parvalbumin (PARV). Although the distribution of PARV‐positive neurons has been previously described, detailed quantitative electron microscopic studies of the PARV‐positive axon terminals in the hippocampal formation are lacking. In the present study, immunocytochemical methods were used to localize PARV‐positive neurons and axon terminals to determine their similarity to GABAergic neurons. The PARV‐positive cells and axon terminals are associated closely with the pyramidal and granule cell layers. In agreement with previous studies, the morphology of PARV‐positive neurons is similar to that of GABAergic cells, including the basket cells of both the dentate gyrus and Ammon's horn. The PARV‐positive axon terminals form exclusively symmetric synapses with somata, dendrites, dendritic spines, and axon initial segments. However, these terminals represent only a portion of the total number of terminals that form symmetric synapses. Quantitative results indicate that only 32–38% of the total number of terminals forming symmetric axosomatic synapses with principal cells of the dentate gyrus and Ammon's horn are PARV positive. Together with previous findings from light microscopic double‐labeling studies, these data indicate that the PARV‐positive terminals arise from a subpopulation of GABAergic hippocampal neurons. Finally, it is important to note that the terminal plexus of PARV‐positive hippocampal axons overlaps at all postsynaptic sites with a plexus of PARV‐negative axons.
Evaluation of the activity of chemically identified enteric neurons through the histochemical demonstration of cytochrome oxidase
Authors: Kirchgessner A. L. , Gershon M. D. , Mawe G. M.
Published: January 2005

The measurement of the density of the reaction product produced by the histochemical demonstration of cytochrome oxidase activity provides a method for the visual identification of physiologically active enteric neurons. The current study utilized the cytochrome oxidase technique in order to evaluate the metabolic history of neurons in different regions of the bowel and in chemically identified types of neuron. In addition, the effect of drugs or neurotoxins commonly used in the immunocytochemical identification of enteric neuronal phenotypes was also analyzed. Cytochrome oxidase activity was visualized with a blue‐black reaction product resulting from the cobalt‐intensified oxidation of 3,3′‐diaminobenzidine. Peptides or 5—hydroxytryptamine (5‐HT) were localized with biotinylated secondary antibodies and alkaline phosphatase‐labeled avidin. Bound avidin or endogenous alkaline phosphatase was visualized with a red reaction product in the presence or absence, respectively, of levamisole. Use of monochromatic red light permitted the cytochrome oxidase reaction product density to be measured without interference from a simultaneously demonstrated histo‐or immunochemical marker. A multi‐peptidergic class of cholinergic submucosal secretomotor neuron containing neuropeptide Y (NPY) and calcitonin gene related peptide (CGRP)immunoreactivities was found to be less metabolically active than the average of all submucosal neurons. In contrast, a non‐cholinergic submucosal secretomotor neuron containing dynorphin (which is also known to contain vasoactive intestinal peptide) immunoreactivity was more metabolically active than submucosal neurons that do not contain this peptide. On average, submucosal neurons were more metabolically active than those of the myenteric plexus, and levels of metabolic activity in the myenteric plexus were found to be higher in the duodenum and the cecum than in the jejunum‐ileum or colon. Myenteric neurons characterized by CGRP or NPY immunoreactivities or by endogenous alkaline phosphatase activity, were all less metabolically active than the average of all neurons in myenteric ganglia. Colchicine, which stimulates intestinal motility, was observed to increase cytochrome oxidase activity in enteric neurons, suggesting that an effect on the enteric nervous system contributes to its action on the bowel. The neurotoxins, 6‐hydroxydopamine and 5,7‐dihydroxytryptamine (5,7‐DHT) were each found to stimulate neuronal metabolic activity. 5,7‐DHT appeared to activate excitatory subtypes of 5‐HT receptor since its effects were blocked or mimicked by compounds that act as antagonists or agonists, respectively, at these receptors. The cytochrome oxidase technique is thus useful for studying the metabolic activity of chemically identified types of enteric neuron as well as for evaluating the action of experimental procedures on these cells.
Somatodendritic morphology of on‐ and off‐cells in the rostral ventromedial medulla
Authors: Mason P. , Floeter M. K. , Fields H. L.
Published: January 2005

The rostral ventromedial medulla (RVM) contains two classes of physiologically defined neurons, on‐cells and off‐cells, that are implicated in nociceptive modulation. In a continuing effort to detail the neural circuitry that underlies the activity of these two distinct neuronal types, the somatodendritic morphology of on‐ and off‐cells was studied in the cat, rat, and ferret.

In lightly anesthetized animals, on‐cells increased and off‐cells decreased their discharge rate during a withdrawal reflex evoked by noxious stimuli. Following their physiological characterization by using intracellular recording, on‐ and off‐cells were injected with either horseradish peroxidase or biocytin and their somatodendritic arborizations were examined.

Labeled on‐ and off‐cells included fusiform and stellate cells of all sizes as well as large multipolar neurons. Although the somatic shape of both on‐ and off‐cells in RVM was heterogeneous, off‐cells tended to be fusiform neurons whose long axis was oriented mediolaterally.

The dendritic domains of both on‐ and off‐cells extended bilaterally past the lateral edge of the trapezoid body or pyramid and ventrally to, and sometimes including, the trapezoid body or pyramid. In contrast to their extensive mediolateral spread, the dendritic domains of both cell types were limited to the ventral half of the reticular formation and were compressed along the rostrocaudal axis. The dendritic arbor of individual on‐ and off‐cells extended well beyond the cytoarchitechtonic boundaries of any single nuclear region, within the domain delineated as the RVM. The spatial domains of the dendritic arbors of on‐ and off‐cells are further evidence that the on‐ and off‐cells throughout the RVM constitute an integrated unit in the modulation of nociceptive transmission.
Quantitative analysis of a vulnerable subset of pyramidal neurons in Alzheimer's disease: I. Superior frontal and inferior temporal cortex
Authors: Hof Patrick R. , Morrison John H. , Cox Kevin
Published: January 2005

Various cytoskeletal proteins have been implicated in the cellular pathology of Alzheimer's disease. A monoclonal antibody (SMI32) that recognizes nonphosphorylated epitopes on the medium (168 kDa) and heavy (200 kDa) subunits of neurofilament proteins has been used to label and analyze a specific subpopulation of pyramidal neurons in the prefrontal and inferior temporal cortices of normal and Alzheimer's disease brains. In Alzheimer's disease, the distribution of neuropathological markers predominates in layers III and V in these association areas. In these neocortical regions, SMI32 primarily labels the perikarya and dendrites of large pyramidal neurons, predominantly located within layers III and V. In Alzheimer's disease, a dramatic loss of SMI32‐immunoreactive (ir) cells was observed, affecting particularly the largest cells (i.e., cells with a cross‐sectional perikaryal area larger than 350 m̈m2). The staining intensity of the largest SMI32‐ir neurons was significantly reduced in Alzheimer's disease cases, suggesting that an inappropriate phosphorylation of these cytoskeletal proteins may take place in the course of the pathological process. In addition, the SMI32‐ir neuron loss and total neuron loss were highly correlated with neurofibrillary tangle counts, whereas such a correlation was not observed with neuritic plaque counts.

These quantitative data suggest that SMI32‐ir neurons represent a small subset of pyramidal cells that share certain anatomical and molecular characteristics and are highly vulnerable in Alzheimer's disease. Other studies have suggested that SMI32‐ir neurons are likely to furnish long corticocortical projections. Thus, their loss would substantially diminish the effectiveness of the distributed processing capacity of the neocortex, resulting in a neocortical isolation syndrome as reflected by the clinical symptomatology observed in these patients. Such correlations between the expression of a selective cellular pathology and specific elements of cortical circuitry will increase our understanding of the molecular and cellular characteristics underlying a given neuronal subclass vulnerability in Alzheimer's disease or other neurodegenerative disorders.
Quantitative analysis of a vulnerable subset of pyramidal neurons in Alzheimer's disease: II. Primary and secondary visual cortex
Authors: Hof Patrick R. , Morrison John H.
Published: January 2005

In this study we investigated the primary and secondary visual areas of normal and Alzheimer's disease brains by using the SMI32 antibody. It is known that in Alzheimer's disease primary sensory areas are usually less devastated than association cortices, although visual symptomatology has been documented early in the course of the disease. In area 17, the SMI32 antibody primarily labeled the perikarya and dentritic tree of the large Meynert cells and cells in layer IVB. Smaller neurons in layers III, V, and VI were also immunoreactive (ir). In area 18, very large SMI32‐ir pyramidal neurons in layers III and V were observed. In both areas, staining intensity was correlated with cell size, the largest neurons being the most intensely stained. Only a few changes were observed in the Alzheimer's disease cases. The only statistically significant differences in SMI32‐ir neuron counts between control and Alzheimer's disease brains occurred in layer IVB cells and Meynert cells in area 17, and in layer III cells in area 18. In contrast with association cortices, there were no changes in staining intensity in the visual areas. There were fewer neurofibrillary tangles and neuritic plaques in these areas than in prefrontal and inferior temporal cortex, and a correlation between neurofibrillary tangle counts and SMI32‐ir neuron loss was only observed in layer III of area 18.

These observations show that in the primary and secondary visual cortex, SMI32 also labeled a distinct subset of pyramidal cells that are known from data obtained in the monkey brain to furnish long corticocortical as well as subcortical projections. Interestingly, although there is much less cell and/or neurofibrillary tangle formation in these occipital regions than in prefrontal and temporal association areas, there is significant loss within key subsets of pyramidal cells. The selective loss of this particular subpopulation of pyramidal neurons will disrupt association pathways linking primary visual cortex with areas involved in higher level visual processing. The partial disconnection of such pathways may be relevant to the visual symptomatology frequently observed in Alzheimer's disease patients. These data further support the hypothesis that subtypes of pyramidal neurons with specific anatomical and molecular profiles may display a differential vulnerability in Alzheimer's disease.
Simultaneous labeling of vagal innervation of the gut and afferent projections from the visceral forebrain with Dil injected into the dorsal vagal complex in the rat
Authors: Berthoud Hans‐Rudolf , Jedrzejewska Agnes , Powley Terry L.
Published: January 2005

The vagal innervation of the different layers of the rat gastrointestinal wall was identified with the fluorescent carbocyanine dye Dil, injected into the dorsal motor nucleus of the vagus (dmnX). Multiple, bilateral injections were used to label all dmnX preganglionic motoneurons, and as a consequence, most of the vagal primary afferents that terminate in the adjacent nucleus of the solitary tract (nts) were also retrogradely and transganglionically labeled. With Fluorogold used to label the enteric nervous system completely and specifically, the Dil‐labeled vagal profiles could be visualized and quantified in their anatomical relation to the neurons of the myenteric and submucous ganglia. In the myenteric plexus, vagal fibers and terminals were found throughout the gastrointestinal tract as far caudal as the descending colon, but there was a general decreasing proximodistal gradient in the density of vagal innervation. All parts of the gastric myenteric plexus (fundus, corpus, antrum), as well as the proximal duodenum, were extremely densely innervated, with vagal fibers and terminals in virtually every ganglion and connective. Further caudally, both the percentage of innervated myenteric ganglia and the average density of label within the ganglia rapidly decreased, with the exception of the cecum and proximal colon, where up to 65% of the ganglia were innervated. In the gastric and duodenal submucosa very few and in the mucosa no vagal fibers and terminals were found. With both normal epifluorescence and laser scanning confocal microscopy, highly varicose or beaded terminal structures of various size and geometry could be identified. The Dil injections, which impregnated the dmnX as well as the adjacent nts, resulted in retrograde and anterograde labeling of all the previously reported forebrain connections with the dorsal vagal complex. We conclude that the myenteric plexus is the primary target of vagal innervation throughout the gastrointestinal tract, and that its innervation is more complete than previously assumed. In contrast, vagal afferent (and efferent) innervation of mucosa and submucosa seems conspicuously sparse or absent. Furthermore, the use of more focal injections of Dil offers the prospect to simultaneously identify specific subsets of vagal preganglionics and their central nervous inputs.
Topography and synaptology of mamillary body projections to the mesencephalon and pons in the rat
Authors: Allen Gary V. , Hopkins David A.
Published: January 2005

The anterograde and retrograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (WGA‐HRP) was used to study the anatomical organization of descending projections from the mamillary body (MB) to the mesencephalon and pons at light and electron microscopic levels. Injections of WGA‐HRP into the medial mamillary nucleus resulted in dense anterograde and retrograde labeling in the ventral tegmental nucleus, while injections in the lateral mamillary nucleus resulted in dense anterograde labeling in the dorsal tegmental nucleus pars dorsalis and dense anterograde and retrograde labeling in the pars ventralis of the dorsal tegmental nucleus. Anterogradely labeled fibers in the mamillotegmental tract diverged from the principal mamillary tract in an extensive dorsocaudally oriented swath of axons which extended to the dorsal and ventral tegmental nuclei, and numerous axons turned sharply ventrally and rostrally to terminate topographically in the dorsomedial nucleus reticularis tegmenti pontis and rostromedial pontine nuclei. The anterograde labeling in these two precerebellar relay nuclei was distributed near the midline such that projections from the lateral mamillary nucleus terminated mainly dorsomedial to the terminal fields of projections from the medial mamillary nucleus.

In the dorsal and ventral tegmental nuclei, labeled axon terminals contained round synaptic vesicles and formed asymmetric synaptic junctions primarily with small diameter dendrites and to a lesser extent with neuronal somata. A few labeled terminals contained pleomorphic vesicles and formed symmetric synaptic junctions with dendrites and neuronal somata. Labeled axon terminals were also frequently found in synaptic contact with retrogradely labeled dendrites and neuronal somata in the dorsal and ventral tegmental nuclei. These findings indicate that neurons in the dorsal and ventral tegmental nuclei are reciprocally connected with MB projection neurons. In the nucleus reticularis tegmenti pontis and medial pontine nuclei, labeled axon terminals contained round synaptic vesicles and formed asymmetric synaptic junctions primarily with small diameter dendrites. The present study demonstrates that projections from the medial and lateral nuclei of the MB are topographically organized in the mesencephalon and pons. The synaptic morphology of mamillotegmental projections suggests that they may have excitatory influences primarily on the distal dendrites of neurons in these brain regions.
Structure of the olfactory bulb of the hedgehog (Erinaceus europaeus): A Golgi study of the intrinsic organization of the superficial layers
Authors: López‐Mascaraque Laura , de Carlos Juan A. , Valverde Facundo
Published: January 2005

The intrinsic organization of the mitral cell, external plexiform, and glomerular layers of the main olfactory bulb of the insectivore hedgehog were studied with the Golgi method. This study completes our previous description of the cell types in the granule cell layer in the same subject (López‐Mascaraque et al., J. Comp. Neurol. 253:135–152, '86). In the present contribution the morphology of mitral, internal, and middle tufted cells is described with particular interest in the formation and arrangement of glomerular tufts by the primary dendrites, and the disposition of the secondary dendrites. Three types of intrinsic cells were found in the external plexiform layer: Van Gehuchten cells, satellite cells, and horizontal cells. All these cells display unusual patterns of branching processes that were difficult to classify as dendritic or axonal. The close relationship between some processes of the satellite cells with the mitral or tufted cell dendrites is noted, suggesting that these cells may be inhibitory in nature. The external tufted cells are described, and several aspects pertaining to their morphology were considered in order to distinguish them from periglomerular cells and from the remaining tufted cells. External tufted and periglomerular cells appear to be intrinsic neurons, having axons distributed in the periglomerular region, most probably devoted to relating different olfactory glomeruli. The arrangement of glomeruli in the glomerular layer and distinctive characteristics with respect to other mammals were considered from a comparative point of view.
Prolonged sojourn of developing pyramidal cells in the intermediate zone of the hippocampus and their settling in the stratum pyramidale
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

In radiograms of rat embryos that received a single dose of [3H] thymidine between days E16 and E20 and were killed 24 hours after the injection, the heavily labeled cells (those that ceased to multiply soon after the injection) form a horizontal layer in the intermediate zone of the hippocampus, called the inferior band. The fate of these heavily labeled cells was traced in radiograms of the dorsal hippocampus in embryos that received [3H] thymidine on day E18 and were killed at different intervals thereafter. Two hours after injection the labeled proliferative cells are located in the Ammonic neuroepithelium. The heavily labeled cells that leave the neuroepithelium and aggregate in the inferior band 1 day after the injection become progressively displaced toward the stratum pyramidale 2–3 days later, and penetrate the stratum pyramidale of the CA1 region on the 4th day. In the stratum pyramidale of the CA3 region, farther removed from the Ammonic neuroepithelium, the heavily labeled cells are still sojourning in the intermediate zone 4 days after labeling.

Observations in methacrylate sections suggest that two morphogenetic features of the developing hippocampus may contribute to the long sojourn of young pyramidal cells in the intermediate zone: the way in which the stratum pyramidale forms and the way in which the alveolar channels develop. The stratum pyramidale of the CA1 region forms before that of the CA3 region, which is the reverse of the neurogenetic gradient in the production of pyramidal cells. We hypothesize that this is so because the pyramidal cells destined to settle in the CA3 region, which will be contacted by granule cells axons (the mossy fibers), have to await the formation of the granular layer on days E21–E22. Concordant with this is the observation that the hippocampal intermediate zone, which contains the sojourning young pyramidal cells, greatly enlarges between days E16 and E20, then suddenly diminishes and disappears by day E22. The other factor that may contribute to the prolonged sojourn of pyramidal cells, specifically those destined to settle in the CA1 region, is the pattern of alveolar channel development. This transient extracellular matrix begins to form several days after the onset of pyramidal cell neurogenesis, grows in a direction opposite to the settling of pyramidal cells in the stratum pyramidale, and does not reach the subicular end of Ammon's horn until day E21. We postulate that the CA1 pyramidal cells may have to wait in the intermediate zone for the formation of the alveolar channels, which are gradually filled with axons (as yet of unknown origin), before they can settle in the stratum pyramidale.
Afferent and efferent innervation of the cat cochlea: Quantitative analysis with light and electron microscopy
Authors: Liberman M. Charles , Dodds Leslie W. , Pierce Sarah
Published: January 2005

The purpose of the present study was to describe the longitudinal and radial gradients of cochlear innervation in the cat. To this end, afferent and efferent terminals of both the inner (IHC) and outer hair cell (OHC) regions were reconstructed from serial ultrathin sections at six and eight cochlear locations, respectively, corresponding to roughly octave intervals of characteristic frequency (CF). Analysis of the afferent innervation of the IHCs showed (1) the number of radial fibers per IHC rises from 10 per IHC at the 0.25 kHz region to a maximum of 30 per IHC at the 10 kHz locus; (2) branching of radial fibers is essentially restricted to regions apical to the 1.0 kHz point; and (3) there are significant differences in synaptic‐body morphology for synapses on different sides of the IHC, corresponding to known differences in afferent threshold and rate of spontaneous activity. With respect to efferent innervation in the IHC area, we found (1) that there were numerous vesicle‐filled terminals contacting every IHC examined; however, those with obvious synaptic specialization were confined to the most apical regions; and (2) there were roughly the same numbers of efferent synapses per radial fiber at all cochlear locations; however, at each location, radial fibers contacting the modiolar side of the hair cell (corresponding to high‐threshold afferents) showed significantly more efferent synapses than radial fibers contacting the pillar side. Analysis of the OHC afferent innervation showed (1) a clear rise in numbers of terminals per OHC from roughly 3 per cell in the base to 15 per cell in the apex, (2) no systematic differences in the numbers of terminals as a function of OHC row, and (3) that synaptic bodies at the OHC afferent synapse are common only apical to the 1.0 kHz locus. Counts of efferent terminals on OHCs revealed (1) maximal numbers (9 per OHC) between the 6 and 24 kHz regions and (2) striking decrease in terminal counts from first‐ to third‐row OHCs. Ultrastructural data on efferent innervation were compared quantitatively with light‐microscopic analysis of cochleas immunostained (with antibody to synaptophysin) to reveal all vesiculated terminals.
Glial process elongation and branching in the developing murine neocortex: A qualitative and quantitative immunohistochemical analysis
Authors: Takahashi Takao , Misson Jean‐Paul , Caviness Verne S.
Published: January 2005

Cells of astroglial lineage in the murine cerebrum undergo a succession of transformations during prenatal and early postnatal development. The bipolar radial cell, the earliest astroglial form to appear, provides a radially aligned, parallel array of fibers that serves as a guide to neuronal migration. The multipolar astrocyte is the representative of this lineage that persists in the adult cerebrum. The processes of the multipolar astrocytes form a complex reticulum, which is considered critical to the development, function, and maintenance of neural circuits. A monopolar radial cell appears to be transitional between the two. The shift from the radial glial fiber system to a diffuse glial network is achieved largely in the E17‐P2 interval in the mouse. This phenomenon has been studied qualitatively and quantitatively by staining cerebral tissue with monoclonal antibody RC2, a specific and sensitive ligand for cells of astroglial lineage in the mouse.

Elongation and branching of glial processes contribute to the glial transformation. Elongation of radial fibers occurs under the guidance of other radial glial fibers (fasciculated elongation) or independently of other fibers (nonfasciculated elongation). Fasciculated elongation results in an increase in the density of radial glial fibers that span the cortical layers. Nonfasciculated elongation appears to be associated with process branching. This is the initial event in transformation of the bipolar radial cells to monopolar radial or multipolar cells. Only nonfasciculated elongation is characteristic of processes of the monopolar radial cells and multipolar astrocytes. Branching of the processes of all three cell forms appears to occur both by bifurcation at the elongating tip and by sprouting from the fiber shaft.

Elongating fibers are tipped by growth cones that are relatively simple in shape as compared to those observed at the tips of elongating axons. Growth cones at the tips of nonfasciculated fibers are more complex in form than those at the tips of radial fibers elongating in contact with other radial fibers.
Light and electron microscopic evidence for a GABAergic projection from the caudal basal forebrain to the thalamic reticular nucleus in rats
Authors: Asanuma C. , Porter L. L.
Published: January 2005

Neurons in the magnocellular nucleus of the caudal basal forebrain extend an axonal projection which arborizes within the reticular nucleus of the thalamus. The present study addresses the ultrastructure and neurochemistry of this projection in rats. Many labeled terminals are apparent within the thalamic reticular nucleus following Phaseolus vulgaris leucoagglutinin injections into the caudal basal nucleus; anterogradely labeled axon terminals most commonly contact both somata and dendrites of reticular nucleus neurons with symmetric membrane specializations. Thus, the majority of the labeled terminals examined contrast with choline acetyltransferase positive terminals which have been previously identified as contacting dendrites and forming asymmetric synapses within this nucleus.

Many of the neurons within the caudal basal nucleus which are retrogradely labeled following tracer injections into the thalamic reticular nucleus are γ‐aminobutyric acid (GABA) immunoreactive. In addition, following injections of Phaseolus vulgaris leucoagglutinin or fluoro‐ruby into the caudal basal forebrain, some of the labeled axonal swellings and boutons within the thalamic reticular nucleus also contain glutamic acid decarboxylase. These results indicate that a significant component of the projection is GABAergic.

These anatomical observations suggest that the projection from the caudal basal nucleus onto the thalamic reticular nucleus could facilitate the relay of information through the dorsal thalamus by inhibiting reticular nucleus neurons, and thus, in turn, disinhibiting thalamic relay neurons.
Two transpallidal pathways originating in the rat nucleus accumbens
Authors: Zahm D. S. , Heimer Lennart
Published: January 2005

The striatopallidal projection originating in the nucleus accumbens was investigated by using anterograde transport of PHA‐L in combination with peptide immunohistochemistry in order to localize the injection sites and transported lectin with respect to neurochemically defined subterritories in the nucleus accumbens and subcommissural ventral pallidum. The results reported here supplement our previous observations, which indicated that the subcommissural ventral pallidum of the rat comprises two immunohistochemically defined subterritories (Zahm and Heimer, '88: J. Comp. Neurol., 272:516–535) which give rise to dichotomous downstream projection systems (Zahm, '89: Neuroscience, 30:33–50). The present data indicate that the neurotensin immunoreactivity‐rich ventromedial district of ventral pallidum receives its accumbal input almost exclusively from the shell district of the nucleus accumbens. The accumbal core, alternatively, projects to the dorsolateral ventral pallidal subterritory that lacks appreciable neurotensin immunoreactivity and in many other respects more resembles the adjoining striatopallidal components of the caudate‐putamen. In addition to direct topographic relationships in the frontal plane among the accumbal injection sites and ventral pallidal terminations, it was observed that more caudally placed core injections resulted in patches of striatopallidal terminations that were more caudally located in ventral pallidum. Shell injections, in contrast, produced columns of terminations that extended continuously from the rostralmost level that they appeared to the caudal end of ventromedial ventral pallidum. The accumbal shell, its exclusive projection to the ventromedial subterritory in the subcommissural ventral pallidum, and the previously reported, almost exclusive projection of that pallidal subdistrict to the mesencephalic ventral tegmental area are discussed in terms of a number of other neurochemical and hodological features that serve to distinguish them sufficiently to suggest that they represent a uniquely specialized part of the basal ganglia.
Bilaterally projecting neurones in pregenital abdominal ganglia of the locust: Anatomy and peripheral targets
Authors: Ferber M. , Pflüger H. J.
Published: January 2005

The anatomy and physiology of neurones with axons in left and right homologous nerves was studied in abdominal ganglia of the migratory locust, Locusta migratoria, by using a differential cobalt/nickel staining method. These neurones reside within two clusters at the anterior and posterior ends of all unfused abdominal ganglia. Each cluster contains at least seven neurones with bilaterally projecting axons.

All neurones of the anterior cluster possess bilaterally projecting axons which leave the ganglion through nerve 2 (=sternal nerve) or nerve 1 (=tergal nerve). Additional axon collaterals, which are present in some of these neurones leave through either nerve 1 or nerve 2 of the right or left side of the ganglion. With few exceptions, the neurones show further asymmetries in their dendritic arborizations.

Neurones of the posterior group also have bilaterally projecting axons that leave the ganglion through nerve 1 or nerve 2. Among these neurones are the two large posterior dorsal unpaired median (DUM) neurones with bilaterally symmetrical axons that were described earlier as DUM1 and DUM2. They innervate the skeletal muscles of an abdominal segment. Two other cells of this cluster have anatomical properties similar to the DUM1 neurone and were termed DUMheart1A and DUMheart1B. The rest resemble the bilaterally projecting neurones of the anterior group.

With the exception of the two classic DUM neurones (DUM1 and DUM2), all neurones of the anterior and posterior cluster innervate the heart or a neurohaemal area.
Development of spinal neurons and tracts in the zebrafish embryo
Authors: Kuwada John Y. , Bernhardt Robert R. , Nguyen Nguyen
Published: January 2005

We have analyzed pathfinding by growth cones in the spinal cord of the early zebrafish embryo, because it is an extremely simple system. At 18–20 hours of development the spinal cord contains approximately 18 lateral and presumably post‐mitotic cell bodies per hemisegment. Of these 8–11 have projected growth cones by 18 hr of development and fall into five classes of neurons (Bernhardt et al., J. Comp. Neurol, preceding paper), including a set of mechanosensory (RB) neurons, three classes of interneurons (DoLA, ascending commissural, and VeLD), and previously characterized primary motor neurons (Eisen et al., '86: Nature 320:269–271). Of these five classes we analyzed pathfinding by the RB, DoLA, early ascending commissural, and VeLD neurons. These neurons are distinguishable at the earliest stages of axonogenesis based on the location of their somata and the number and initial directionality of their growth cones. In each case they follow stereotyped, cell‐specific pathways to reach their termination sites. Up through larval stages exuberant axons have not been observed.

The longitudinal axons of each neuronal class form bundles in the early cord. This apparently occurs because growth cones extend in close association with the longitudinal axons of the same neuronal class. At later stages spatially discrete commissural tracts are found in the cord suggesting that commissural growth cones may follow earlier commissural axons as well.
Sex difference in the bed nucleus of the stria terminalis of the human brain
Authors: Allen Laura S. , Gorski Roger A.
Published: January 2005

A quantitative analysis of the volume of the darkly staining region of the posteromedial bed nucleus of the stria terminalis was performed on the brains of 26 age‐matched male and female human subjects. We suggest the term “darkly staining posteromedial” component of the bed nucleus of the stria terminalis (BNST‐dspm) to describe this sexually dimorphic region of the human brain. The volume of the BNST‐dspm was 2.47 times greater in males than in females. This region in humans appears to correspond to an area of the bed nucleus of the stria terminalis in laboratory animals that exhibits volumetric and neurochemical sexual dimorphisms, concentrates gonadal steroids, and is anatomically connected to several other sexually dimorphic nuclei. Furthermore, the bed nucleus of the stria terminalis is involved in sexually dimorphic functions, including aggressive behavior, sexual behavior, and gonadotropin secretion, which are also influenced by gonadal steroids. Therefore, it is possible that in human beings as well, gonadal hormones influence the sexual dimorphism in the BNST‐dspm and that this morphological difference, in part, underlies sexually dimorphic function.
Ventral respiratory group projections to phrenic motoneurons: Electron microscopic evidence for monosynaptic connections
Authors: Ellenberger Howard H. , Feldman Jack L. , Goshgarian Harry G.
Published: January 2005

The hypothesis that excitatory drive is transmitted monosynaptically from bulbospinal medullary respiratory neurons to spinal respiratory motoneurons was tested by an ultrastructural analysis of the phrenic motoneuronal pool in the rat. Combined anterograde labeling of the principal inspiratory bulbospinal neuron population (ventral respiratory group) and retrograde labeling of the phrenic motoneuron pool demonstrated the presence of labeled synaptic profiles, indicating that at least some bulbospinal inspiratory neurons make monosynaptic contacts with phrenic motoneurons. The synaptic boutons of ventral respiratory group neurons that were labeled in the phrenic nucleus had asymmetrical membrane densities at sites of synaptic contact with labeled phrenic somal or dendritic profiles, supporting the notion that this bulbospinal pathway has excitatory contacts with phrenic motoneurons. The morphological types of labeled boutons included three of the eight previously identified bouton types in the phrenic nucleus (Goshgarian and Rafols: Journal of Neurocytology 13:85–109, 1984), including the “S”‐terminal, the “NFs”‐terminal, and the “F”‐terminal. There was no conclusive evidence of labeled double synapses, indicating that this type of synaptic contact is not common in the intact bulbospinal pathway.
Two classes of Limulus ventral photoreceptors
Authors: Herman Karen G.
Published: January 2005

Ventral photoreceptors of the horseshoe crab, Limulus polyphemus, have been important in the study of visual transduction, due to their large size and hardiness in vitro. This study shows that there are two classes of ventral photoreceptors that can be distinguished on the basis of differences in cellular and nuclear dimensions, soma and rhabdom morphology, and axon size. Large photoreceptors, which have been the subject of many physiological studies, have an extensive superficial rhabdom, a nuclear diameter of 20–24 μm, and measure 100–150 μm in length. In contrast, small photoreceptors measure 45–65 μm in length and have a nucleus 13–16 μm across. Small photoreceptors are found singly or in association with large photoreceptors. The rhabdom of isolated small photoreceptors is surrounded by a calyx originating from the soma, so that it appears to be located internally. The rhabdomeral lobe of small photoreceptors associated with large photoreceptors characteristically is divided into several segments, each of which invaginates the rhabdomeral lobe of the adjacent large photoreceptor. The entire external rhabdom of the associated small photoreceptor abuts the rhabdom of the large photoreceptor. Morphometric analysis of the ventral nerves shows that there are two size classes of photoreceptor axons, corresponding to the two classes of photoreceptors. The numbers of axons in each size class are nearly equal. Unlike the ventral eye, none of the other eyes of Limulus have been reported to have more than one morphological class of photoreceptor. Functional differences between the two classes of ventral photoreceptors are suggested by experiments, reported in the accompanying paper (Herman (1991), J. Comp. Neurol. 303:11–21), showing that the large photoreceptors exhibit light‐stimulated rhabdom turnover while the small ones do not.
The cells of origin of the spinohypothalamic tract in cats
Authors: Katter James T. , Burstein Rami , Giesler Glenn J.
Published: January 2005

Various cutaneous and visceral stimuli alter the discharge rates of neurons in the hypothalamus. Changes in the activity of hypothalamic neurons are thought to play important roles in eliciting neuroendocrine, autonomic, and affective responses to somatosensory and visceral stimuli. Information from peripheral structures has been considered generally to reach the hypothalamus via multisynaptic ascending pathways. Recently, a direct projection from the spinal cord to the hypothalamus was demonstrated in rats. The goal of this study was to determine whether a similar projection exists in cats. Either wheat germ agglutinin conjugated to horseradish peroxidase, a mixture of this tracer and the B subunit of cholera toxin conjugated to horseradish peroxidase, or fast blue was injected into the hypothalamus of cats. Injections were centered in the hypothalamus in seven cats and did not spread to the thalamus, zona incerta or midbrain. After these injections, retrogradely labeled neurons were observed bilaterally in each of the 17 spinal segments that were examined. A total of approximately 400–500 labeled neurons was observed in alternate sections through these segments in the most effective cases. Roughly 70% of the labeled neurons were located contralaterally. Labeled neurons were found predominantly in the deep dorsal horn, the intermediate zone/ventral horn and in the area surrounding the central canal. A few were also noted in the superficial dorsal horn. The first and second sacral segments contained the largest numbers of retrogradely labeled neurons in the spinal cord.

The number of spinohypothalamic tract neurons observed in this study in cats was roughly an order of magnitude smaller than that previously reported for rats. This finding suggested either that the spinohypothalamic tract is relatively small in cats or that our tracing techniques did not label many spinohypothalamic tract neurons in cats. To test the sensitivity of one of our tracing techniques, control injections of wheat germ agglutinin conjugated to horseradish peroxidase that filled the ventrobasal thalamus were made in two cats. In both cases, thousands of spinal cord neurons were labeled.

In summary, our results indicate that a spinohypothalamic tract exists in cats. However, our findings also suggest that the total number of spinohypothalamic tract neurons in cats may be an order of magnitude smaller than it is in rats.
Galanin mRNA in the nucleus basalis of Meynert complex of baboons and humans
Authors: Walker Lary C. , Rance Naomi E. , Price Donald L. , Young W. Scott
Published: January 2005

Galanin, a 29‐amino acid peptide, has been shown by immunocytochemistry to occur in most large acetylcholinergic neurons of the complex that includes the nucleus basalis of Meynert and the nucleus of the diagonal band of Broca in nonhuman primates. In contrast, several studies have reported that most large neurons of the human nucleus basalis of Meynert complex appear to lack galanin immunoreactivity. We investigated this apparent species‐difference by hybridization histochemistry for galanin messenger ribonucleic acid (mRNA) in humans and baboons. The results confirm previous immunocytochemical data; very few large neurons of the nucleus basalis of Meynert complex in humans contained detectable galanin messenger RNA, whereas most such cells in baboons were labeled by the oligodeoxynucleotide probe. The few labeled neurons in humans were primarily medial or ventral to the main body of the nucleus basalis of Meynert and corresponded in location to a minor population of relatively intensely labeled cells in baboons. These findings indicate that the indetectability of immunoreactive galanin in most cells of the nucleus basalis of Meynert complex in humans is due to a paucity or an absence of galanin messenger RNA and not to differences in posttranslational processing or transport of the peptide. Inasmuch as the probe labeled neurons in several other nuclei of both species, it is unlikely that differences in galanin messenger RNA sequences underlie the species‐related disparity in hybridization in the nucleus basalis of Meynert complex. The indetectability of galanin messenger RNA in most cells of the human nucleus basalis of Meynert complex indicates that the expression of the galanin gene is regulated by as yet unidentified influences that differ in human and nonhuman primates. The varying phenotypes of galanin in primates suggest potentially important species‐differences in the function of galanin in neurons of the nucleus basalis of Meynert complex.
Distribution and morphology of area 17 neurons that project to the cat's extrastriate cortex
Authors: Einstein Gillian , Fitzpatrick David
Published: January 2005

We used intracellular dye injections in lightly fixed cortical slices to examine the distribution and morphology of area 17 neurons that project to extrastriate cortex. Both the projection to the medial bank of the posterior lateral suprasylvian sulcus (PMLS) and the projection to area 18 arise from a number of different morphological types distributed throughout layers 2–6. The majority are found in the superficial layers and include large, medium, and small pyramidal neurons. Some are also found in the deep layers and they include very large, pyramidal neurons as well as some heretofore undescribed, fusiform neurons. The projection to area 18 contains two types not found in the projection to PMLS: Spinous stellate neurons in layer 4 and inverted pyramidal neurons in layer 3. Finding that a variety of morphological types contribute projections to a single cortical area raises the possibility that corticocortical projections, like retinogeniculate and geniculocortical projections, comprise multiple parallel pathways with different physiological properties and patterns of termination. Finding that the projection to area 18 contains morphological types that do not project to PMLS indicates that the projections from area 17 are likely to contribute to the functional specialization of extrastriate visual areas.