bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunocytochemical localization of gamma‐aminobutyric acid (GABA) in the cat superior colliculus
Authors: Ranney Mize R.
Published: January 2005

This paper reports the pattern of labeling in the cat superior colliculus produced by an antiserum raised against BSA‐conjugated gamma aminobutyric acid (GABA) and visualized by light and electron microscope immunocytochemistry. Neuropil labeling was densest within the zonal and superficial gray layers but was also found in the deep layers. Neurons labeled by the GABA antibody were also most dense within the zonal and superficial gray layers, although many labeled neurons were also found in the deeper layers. The ratio of labeled to unlabeled cells varied from an average of 45% in the superficial subdivision and the intermediate gray layer to less than 30% in the deeper laminae. Almost all intensely labeled cells were small (mean area = 127 μm2) and had varied morphologies.

Several types of labeled cell were observed with the electron microscope. One type had a horizontal, fusiform cell body and a deeply invaginated nucleus. Another type had a small round or ovoid cell body with cytoplasm clumped at one end. Labeled cells with other morphologies were also occasionally seen. No labeled glial cells were found. Two types of vesicle‐containing dendrite were stained by the GABA antibody. One type had loose accumulations of small synaptic vesicles and often received input from retinal terminals. Another type had spines also containing small synaptic vesicles. Labeled dendrites without synaptic vesicles were also seen frequently. Putative axon terminals labeled by the GABA antibody had densely packed synaptic vesicles and formed symmetric synaptic contacts. Labeled myelinated axons were also commonly found.

These results confirm those using uptake of tritiated GABA (Mize et al.: J. Comp. Neurol. 202:385‐396, '81, J. Comp. Neurol, 206:180‐192, '82) in that two of the same classes of GABA neuron, horizontal I and granule I cells, were identified in the superficial laminae. However, the GABA antiserum used in this study also revealed a third class of GABA neuron with vesicle‐containing spines. The antiserum also labeled a significant number of putative GABAergic neurons located in the deep subdivision of the cat superior colliculus which were not previously recognized by using transmitter autoradiography.
Putative glutamatergic and/or aspartatergic cells in the main and accessory olfactory bulbs of the rat
Authors: Fuller T. A. , Price J. L.
Published: January 2005

The “transmitter‐specific” retrograde axonal tracer 3H‐D‐asparate has been used to demonstrate neurons in the olfactory bulb which putatively utilize aspartate and/or glutamate as their neurotransmitter and which send an axon either to the piriform cortex or within the bulb itself.

Injections of 3H‐D‐aspartate into layer I of the anterior piriform cortex, in the zone of termination of axons from the olfactory bulb, labeled only a few cells in the main olfactory bulb, located in the mitral and external plexiform layers. Although these cells resembled mitral and external plexiform layers. Although these cells resembled mitral and tufted cells, they tended to have smaller somata than other mitral or tufted cells and apparently form a distinct subpopulation of relay cells. In contrast, many of the mitral cells of the accessory olfactory bulb were labeled by the same injections of 3H‐D‐aspartate, probably as a result of involvement of the accessory olfactory tract or its bed nucleus in the injection site. Similar injections of the “nonspecific” tracer HRP into the anterior piriform cortex labeled most of the cells in the mitral cell layer of both the main and accessory olfactory bulbs, and some tufted cells in the external plexiform layer. It is concluded that only a small, distinct subpopulation of the mitral or tufted cells of the main olfactory bulb are aspartatergic and/or glutamatergic, while many (at least) of the mitral cells of the accessory olfactory bulb use the excitatory amino acids as transmitters.

Injections of 3H‐D‐aspartate directly into the main olfactory bulb also failed to label the mitral and deeply situated tufted cells. However, a few cells were labeled in the periglomerular region, the superficial external plexiform layer, and the granule cell layer near the injection site. These labeled cells were smaller than mitral and tufted cells but generally larger than periglomerular or granule cells. They may represent a population of glutamatergic or aspartatergic short axon cells. In addition, small cells of an unknown type were labeled in the olfactory nerve layer following injections in the deepest part of the bulb. These cells do not correspond to any of the well characterized cell types of the olfactory bulb.
Distribution of corticotropin‐releasing‐factor‐like immunoreactivity in brainstem of two monkey species (Saimiri sciureus and Macaca fascicularis): An immunohistochemical study
Authors: Foote Stephen L. , Cha Choong I.
Published: January 2005

Immunohistochemical methods were utilized to systematically map the distribution of corticotropin‐releasing‐factor‐like immunoreactivity (CRF‐LI) in the diencephalon, mesencephalon, and rhombencephalon of two monkey species (Saimiri sciureus and Macaca fascicularis). A primary antiserum directed against the human form of the peptide was utilized. Immunoreactive neuronal perikarya and processes were evident in numerous areas, and the distributions of these elements were similar for the two species. As previously reported for rats, monkeys, and human, intense immunoreactivity was evident in putative hypophyseal neurons in the parvicellular component of the paraventricular nucleus of the hypothalamus and in fibers extending from this area into the median eminence. The results for other brainstem regions, most of which have been previously examined for CRF‐LI only in rats, indicate that many similarities exist between rats and monkeys in the distribution of this peptide in brainstem extrahypophyseal neuronal circuits, although substantial differences are also evident. For example, immunoreactive perikarya previously observed in other hypothalamic nuclei in rats were not evident in monkeys. Conversely, in monkeys, unlike rats, labeled perikarya were evident in several thalamic nuclei, especially in the intralaminar complex. Also, two large groups of immunoreactive neurons which have generally not been observed in rat studies were present in the mesencephalon and rhombencephalon. In the mesencephalon this consisted of a group of neurons just lateral to the mesencephalic tegmentum, extending throughout the rostral‐caudal extent of the midbrain. In the rhombencephalon, labeled perikarya were observed throughout the inferior olive. Some of the differences between rats and monkeys in the locations of labeled perikarya may be due to differences in antiserum specificity and/or sensitivity, or they may result from the fact that colchicine pretreatment was not utilized in the present study.

The distributions of immunoreactive fibers also exhibited similarities and differences between monkeys and rats. The most striking terminal fields observed in the present study which have not been previously described are a moderate‐to‐dense field within and adjacent to presumed dopamine‐containing neurons in the substantia nigra pars compacta, a dense innervation of certain subdivisions of the interpeduncular nucleus, and a regionally and parasagittally organized distribution of fibers in the Purkinje cell and molecular layers of the cerebellar cortex.

Thus, the present results suggest that there are substantial differences between rodents and primates in the cellular distribution of CRF‐LI in the brain and spinal cord. However, technical differences between the rat and monkey experiments may account for some of these contrasting distributions.
Development of histamine‐immunoreactive neurons in the rat brain
Authors: Auvinen Satu , Panula Pertti
Published: January 2005

This study was undertaken to reveal the cellular stores of histamine in developing rat brain and to determine the stage of development during which the histamine‐immunoreactive neurons can first be detected. Rats from embryonal day 12 to postnatal day 14 were studied. The brains were fixed in 4% 1‐ethyl‐3(3‐dimethylaminopropyl)carbodiimide and standard immunofluorescence technique was used.

The first histamine‐immunoreactive neurons were seen on embryonic day 13 in the border of mesencephalon and metencephalon. On embryonic day 15 immunoreactive neurons were detected in ventral mesencephalon and rhombencephalon. In caudal, tuberal, and postmammillary caudal magnocellular nuclei histamine‐immunoreactive neurons were first detected on embryonic day 20 while those in the hindbrain had disappeared. Histamine‐immunoreactive nerve fibers were first detected on embryonic day 15 in rhombencephalon and mesencephalon and in some areas of diencephalon including the mammillary bodies and frontal cortex. On embryonic day 18 the number of immunoreactive nerve fibers in the hindbrain had decreased considerably, but the olfactory bulb, septal and hypothalamic area, and the cerebral cortex showed immunoreaction in fibers. The density of histamine‐immunoreactive fiber networks increased until postnatal day 14 when an adultlike pattern of neurons and fibers had developed.

Histamine‐immunoreactive neurons are present in embryonal CNS and they develop extensive projections to various brain areas.
Ontogeny of histidine‐decarboxylase‐immunoreactive neurons in the tuberomammillary nucleus of the rat hypothalamus: Time of origin and development of transmitter phenotype
Authors: Reiner P. B. , Semba K. , Fibiger H. C. , McGeer E. G.
Published: January 2005

The ontogeny of the histidine decarboxylase (HDC)‐immunoreactive neurons of the tuberomammillary (TM) nucleus was studied in the rat brain. The time of origin of TM neurons was studied by counting the percentage of HDC‐immunopositive neurons double labelled by autoradiography in adult progeny of dams injected with [3H]‐thymidine at various times during gestation. Neurogenesis began on embryonic day (E) 13, peaked on E16, and was complete by E18. HDC immunoreactivity was first detected in the fetal rat brain on E16. Experiments utilizing short‐survival [3H]‐thymidine autoradiography combined with HDC immunohistochemistry demonstrated that TM neurons undergo their final mitotic division prior to expression of their transmitter phenotype.
Catecholaminergic and cholinergic neurons in the developing retina of the rat
Authors: Mitrofanis John , Maslim Juliani , Stone Jonathan
Published: January 2005

We have examined the development of catecholaminergic and cholinergic neurons in the retina of the rat by using antibodies against the enzymes tyrosine hydroxylase (TH) and choline acetyl transferase (ChAT), respectively. TH‐immunoreactivity was first detected at P (postnatal day) 3 in somata located in the inner part of the cytoblast layer (CBL) and in fine dendrites extending toward the middle of the inner plexiform layer (IPL). These cells were similar in shape and soma size to the class 2 TH‐immunoreactive (TH‐IR) cells of the adult rat. At P6, TH‐immunoreactivity was expressed by a second population of cells. Their somata were in the inner part of the inner nuclear layer (INL), but were distinctly larger, with short thick dendrites extending into the outer and/or middle parts of the IPL. Over subsequent days, the dendrites of these larger cells spread profusely in the outer part of the IPL, making it likely that they are the class 1 TH‐IR cells of the adult. ChAT‐immunoreactive (ChAT‐IR) cells were not detected until P15, when ChAT‐IR somata were observed in the ganglion cell layer (GCL) and INL, and their dendrites were observed already segregated into the distinct strata of the IPL in which they are found in the adult.

The subsequent growth of TH‐IR somata of both classes was uneven, persisting longer in temporal than in nasal retina. This extended growth of temporal cells establishes the marked nasotemporal differences in soma diameter apparent among TH‐IR cells in the adult (Mitrofanis and Stone, '86; Mitrofanis et al., '88b). The growth and adult size of ChAT‐IR somata, on the other hand, did not vary with retinal position; their diameters were similar to those of the adult cells from the time they first appeared.

The distribution of ChAT‐IR cells at P15 shared several features of the distribution of ganglion cells. The density of ChAT‐IR cells was greatest at the area of peak ganglion cell density and declined toward the periphery. In contrast, TH‐IR cells concentrated from the time they first appeared at the superior temporal margin, peripheral to the area of peak density of ganglion and ChAT‐IR cells.
Expansion of spinal cord primary sensory afferent projection following combined sciatic nerve resection and saphenous nerve crush: A horseradish peroxidase study in the adult rat
Authors: Molander Carl , Kinnman Erik , Aldskogius HåKan
Published: January 2005

Transganglionic transport of horseradish peroxidase was used to study the potential for collateral sprouting of saphenous nerve afferent fibers in the lumbar dorsal horn of the adult rat following (1) combined unilateral saphenous nerve crush and ipsilateral sciatic nerve resection, (2) unilateral saphenous nerve crush, and (3) unilateral sciatic nerve resection. The saphenous nerve on the nonlesioned contralateral side served as control. Eight weeks after the lesion(s) the animals were subjected to bilateral application of horseradish peroxidase to the saphenous nerves. The distribution of the ensuing labeling in the superficial dorsal horn was subsequently mapped.

Combined saphenous nerve crush and sciatic nerve resection resulted in expansion of the saphenous nerve projection area in the dorsal horn when compared to the nonlesioned control side (mean = 13%, P < 0.05). No expansion of the saphenous nerve projection was found following isolated saphenous nerve crush or sciatic nerve resection, respectively (P > 0.05). The findings indicate that in the adult rat, central processes of primary sensory neurons which are regenerating their peripheral processes can extend collateral sprouts into adjacent projection areas in the superficial dorsal horn subjected to previous deafferentation by peripheral nerve resection.
Immunocytochemical demonstration of dynorphin(PH‐8P)‐like immunoreactive elements in the human hypothalamus
Authors: Abe Jun , Okamura Hitoshi , Kitamura Tadahisa , Ibata Yasuhiko , Minamino Naoto , Matsuo Hisayuki , Paull Willis K.
Published: January 2005

PH‐8P (dynorphin[1–8])‐like immunoreactive neuronal perikarya, processes, and terminals located within the human hypothalamus were investigated by the avidin‐biotin peroxidase complex (ABC) immunocytochemical procedure. Immunopositive neurons were distributed throughout the hypothalamus. The distributional pattern was found to be similar to that in other mammalian species by the use of antisera against dynorphin. A large number of immunoreactive neuronal perikarya were detected in the supraoptic nucleus (SON) and the magnocellular portion of the paraventricular nucleus (PVN). Their processes appeared to project to the posterior pituitary via the internal layer of the median eminence and their distribution seemed to be less dense than in other mammalian species. PH‐8P and vasopressin were colocalized in the neuronal perikarya in the human SON unlike the colocalization of these peptides in the rat SON and PVN. There were a few immunoreactive terminals in the external layer of the median eminence; their immunoreactive substances may be released into the portal veins to act on anterior pituitary cells. In addition, PH‐8P‐like immunoreactive neurons in the human hypothalamus may project to the extrahypothalamic area.
Descending pathways to the spinal cord: A comparative study of 22 mammals
Authors: Nudo R. J. , Masterton R. B.
Published: January 2005

In order to estimate the qualitative commonalities and range of variation among major descending spinal pathways relevant to mankind's ancestral lineage, the supraspinal cell groups originating fibers descending directly to the spinal cord were examined in 22 mammalian species. In a standardized retrograde tract‐tracing procedure, flakes of raw HRP were applied directly to the freshly cut fibers of the spinal cord after it had been hemisected at the C1–C2 junction. After a 72‐hour survival period, brain and spinal cord tissues were processed by conventional HRP‐processing techniques.

This procedure was performed on 94 individual animals. Of this total, 41 individual cases were eliminated by a rigorous culling procedure. The results are based on 53 individuals representing 15 species selected for their successive kinship with mankind and seven species in two other lineages selected for the convergence of their visual or sensorimotor systems with anthropoids. The 22 species represent 19 genera, 14 families, eight orders, and two subclasses of Mammalia.

The results show that at least 27 supraspinal cell groups, each containing intensely labeled cells, can be readily identified in each of the species. Despite vast quantitative differences in cell number and cell size, this qualitative uniformity among the relatively large number of diverse taxa suggests that the same pathways were probably present in the extinct ancestors throughout mankind's mammalian lineage and are probably still present in extant viviparous mammals as well. If so, these pathways are as old in phylogenetic history as the last common ancestor of marsupial and placental mammals—dating from the late Jurassic to early Cretaceous, perhaps 145–120 million years ago.

Further comparison of the results with similar experimental findings in members of other vertebrate classes supports the notion that several of these same pathways can be traced to even more remote ancestry, with some possibly as old as the entire vertebrate subphylum—dating from the early Devonian or before, perhaps 430 million years ago. Within mankind's ancestral lineage, from the appearance of vertebrates to the appearance of mammals, there seems to have been an irregular stepwise augmentation of the set of descending pathways until the full mammalian complement was finally attained with the appearance of the corticospinal tract.
Kinesthetic cortical area anterior to primary somatic sensory cortex in the raccoon (Procyon lotor)
Authors: Feldman Sanford H. , Johnson John I.
Published: January 2005

Extracellular microelectrode recording of cortical unit activity, with subsequent histological examination, was used to determine the extent, organization, and cytoarchitecture of the zone of muscle afferent projections (kinesthetic cortex) anterior to the primary somatic sensory cortex in anesthetized raccoons. Activity was evoked in response to mechanical stimulation of muscles from which the overlying skin had been dissected away. Most kinesthetic responses were elicited in a contiguous cortical area, which included: the anterior bank of the lateral arm, and the fundus and posterior bank of the medial arm of the medial central sulcus; and the anterior two‐thirds of the interfundic rise within the interbrachial sulcus. Some responses were recorded in a separate small area of the anterior bank at the medial end of the lateral central sulcus. Somatotopy was evident with forelimb represented lateral to hindlimb. Proximal limb muscles were represented in the center of the medial central sulcus; distal muscle projections were medial (hindlimb) or lateral (forelimb) in the same sulcus. Most representations were of flexor and extensor muscles of the contralateral carpus and forepaw digits. Activity at a given recording locus in the kinesthetic area could be elicited by both flexor and extensor muscles, which acted about a common joint. Low amplitude units evoked by cutaneous stimulation of the dissected skin were recorded in the kinesthetic area; these were from receptive fields of skin that normally overlay the muscles whose higher‐amplitude evoked kinesthetic units were represented in that same recording locus. The kinesthetic zone was anterior to primary somatic sensory cortex, where the outer stripe of Baillarger and granular layer IV become attenuated. In the hindlimb muscle representation area, the additional criterion of area 3a (large pyramidal cells in layer V) was seen. However, no cytoarchitecture could be identified that was consistently associated with the kinesthetic cortex.
Immunohistochemical study of the telencephalon of the spiny dogfish, Squalus acanthias
Authors: Northcutt R. Glenn , Reiner Anton , Karten Harvey J.
Published: January 2005

The paucity of experimental data and the differences in telencephalic organization between sharks and other jawed vertebrates have complicated telencephalic comparisons. The distribution of neuropeptides has been extremely useful in recognizing and comparing major subdivisions of the telencephalon among vertebrates. Immunohistochemical techniques were therefore used to study the distribution of substance P (SP), leucine‐enkephalin (LENK), and serotonin (5HT), as well as tyrosine hydroxylase (TH), an indicator of catecholamines, in the telencephalon of the spiny dogfish.

The distribution of SP and LENK provides a clear distinction between pallial and subpallial portions of the telencephalon. Two regions of the ventrolateral telencephalon, area superficialis basalis and area periventricularis ventrolateralis, exhibit histochemical similarities to the pallidal and striatal subdivisions, respectively, of the basal ganglia in amniotes.

Lower densities of LENK+ and SP+ perikarya and fibers occur in the medial pallium and the pars centralis of the dorsal pallium. Similar histochemical traits characterize the sensory thalamorecipient telencephalic structures in amniotes. The lateral pallium in dogfishes is distinguished by the presence of large numbers of TH+ neurons with radially oriented processes. The presence of these distinctive cells also in the medial wall of the rostral telencephalon suggests that the lateral pallium has a medial extension that is situated ventral to the medial pallium. Neurons containing TH were widely distributed in the telencephalon of spiny dogfish and were particularly abundant in the dorsal pallium, olfactory pallium, and area superficialis basalis. It is currently unclear whether these TH+ telencephalic neurons are, in fact, catecholaminergic or merely contain a TH‐like substance unrelated to catecholamine synthesis.
Basal forebrain cholinergic and noncholinergic projections to the thalamus and brainstem in cats and monkeys
Authors: Parent A. , Paré D. , Smith Y. , Steriade M.
Published: January 2005

The projections of basal forebrain neurons to the thalamus and the brainstem were investigated in cats and primates by using retrograde transport techniques and choline acetyltransferase (ChAT) immunohistochemistry. In a first series of experiments, the lectin wheat germ‐agglutinin conjugated with horseradish peroxidase (WGA‐HRP) was injected into all major sensory, motor, intralaminar, and reticular (RE) thalamic nuclei of cats and into the mediodorsal (MD) and pulvinar‐lateroposterior thalamic nuclei of macaque monkeys. In cats numerous neurons of the vertical and horizontal limbs of the diagonal band nucleus and the substantia innominata (SI), including its rostromedial portion termed the ventral pallidum (VP), were retrogradely labeled after WGA‐HRP injections in the rostral pole of the RE complex, the MD, and anteroventral/anteromedial (AV/AM) thalamic nuclei. Fewer retrogradely labeled cells were observed in the same areas after injections in the ventromedial (VM) thalamic nucleus, and none or very few after other thalamic injections. After RE, MD, and AV/AM injections, 7–20% of all retrogradely labeled cells in the basal forebrain were also ChAT positive, while none of the retrogradely labeled neurons following VM injections displayed ChAT immunoreactivity. The basal forebrain projection to the MD nucleus was shown to arise principally from VP in both cats and macaque monkeys. In a second series of experiments performed in cats, injections of WGA‐HRP in the brainstem peribrachial (PB) area comprising the pedunculopontine nucleus led to retrograde labeling of a moderate number of neurons in the lateral part of the VP, SI, and preoptic area (POA), only a few of which displayed ChAT immunoreactivity. In addition, a large number of retrogradely labeled cells were observed in the bed nuclei of the anterior commissure and stria terminalis after PB injections. In a third series of experiments, the use of the retrograde double‐labeling method with fluorescent tracers in squirrel monkeys allowed us to identify a significant number of basal forebrain neurons sending axon collaterals to both the RE thalamic nucleus and PB brainstem area, while no double‐labeled neurons were disclosed after injections confined to the ventral anterior/ventral lateral (VA/VL) thalamic nuclei and PB area or following injections in the cerebral cortex and PB area. Our findings reveal the existence of cholinergic and noncholinergic basal forebrain projections to the thalamus and the brainstem in both cats and macaque monkeys. We suggest that these projections may play a crucial role in the control of thalamic functions in mammals.
Coexistence of glutamate and substance P in dorsal root ganglion neurons of the rat and monkey
Authors: Battaglia G. , Rustioni A.
Published: January 2005

Antisera to a glutamate (Glu) conjugate, to glutaminase (GLN), and to substance P (SP) have been used to investigate the issue of putative glutamergic neurons in the dorsal root ganglia (DRG) and the possible coexistence in these neurons of Glu and SP. The Glu antiserum, characterized by immunoadsorption and immunoblot tests, is highly selective for Glu out of a number of other amino acids including aspartate. Quantitative data were gathered from consecutive 4‐μm‐thick paraffin sections from cervical ganglia of rats with or without spinal injections of colchicine and from one monkey not treated with colchicine. Neurons containing more than one antigen could be identified on adjacent sections tested with the three different antisera.

Neurons labeled by the Glu‐antiserum represent 15–30% of the DRG population in untreated rats. They include most of the small neurons (with mean perikaryal area around 300–400 μm) but also larger neurons (with perikaryal area greater than 600 μm). DRG neurons labeled by either the GLN or the SP antiserum are small (mean area 335–375 μm and 356–374 μm, respectively) and account for approximately 40 and 15%, respectively, of the sampled neurons. In colchicine‐treated rats the number of Glu‐positive neurons increases up to about 70%. The same tratment also increases the number of SP‐positive neurons but not that of GLN‐positive neurons. In the monkey about half of the DRG neurons are Glu positive and, as in rats, they are mostly small. GLN‐positive neurons in the same species account for about half of the DRG population and are only small.

In rats, about 60–80% of Glu‐positive neurons are also GLN‐positive and most GLN‐positive neurons are Glu positive. In colchicine‐treated rats, close to 90% of SP‐positive neurons are also positive for Glu and about 60% of SP‐positive neurons are triple labeled. In the monkey's DRGs, whose sections were not processed for SP, most Glu‐ or GLN‐positive neurons are also positive for the other antiserum used.

Several considerations argue against the possibility that, under the present experimental conditions, the Glu antiserum is a metabolic marker. It is therefore suggested that Glu‐positive neurons may use Glu as neurotransmitter. Coexistence of Glu and SP in some DRG neurons suggests that both agents may be released by terminals of primary afferents from the same DRG neuron. A role for SP as neuromediator in afferents that use another agent as a transmitter is thus supported by the present results. Our data also support previous electrophysiological data suggesting that the same primary afferent terminal may discharge dorsal horn neurons by way of a classical neurotransmitter and also induce in these a prolonged, peptidemediated, slow depolarization.
Spatial and temporal patterns of oligodendrocyte differentiation in rat cerebrum and cerebellum
Authors: LeVine Steven M. , Goldman James E.
Published: January 2005

Oligodendrocytes are largely generated postnatally during mammalian CNS development. We have used a variety of antibodies to label immature neuroectodermal cells and developing oligodendrocytes in several areas of the rat CNS. Antibodies included those to GD3 ganglioside, a characteristic glycolipid of immature cells; carbonic anhydrase (CA), contained primarily in oligodendrocytes; and galactocerebroside and myelin basic protein, myelin components. Several aspects of oligodendrocyte development were examined: changes in shapes of immature cells with respect to time and to location within the brain, the sequential acquisition of the various markers, and possible sites of origin and pathways of precursor cell migration. Our observations suggest that oligodendrocytes in the forebrain and cerebellum arise from cells of the subventricular zone (SVZ) adjacent to the ventricles and migrate into and through nearby white and gray matter. During maturation, there are distinct patterns of morphological changes that correlate with time, locations of the cells in the brain, and acquisition of specific markers.
Sharpening of topographical projections and maturation of geniculocortical axon arbors in the hamster
Authors: Naegele Janice R. , Jhaveri Sonal , Schneider Gerald E.
Published: January 2005

During specification of orderly neural maps, axons correctly navigate to their targets and form terminal arbors in topographically correct positions. To learn more about this mapping process, the patterns of geniculocortical topography were correlated with growth of axon arbors in the hamster visual cortex. Topography was studied by retrograde transport of WGA‐HRP from area 17 to the dorsal lateral geniculate nucleus (LGd) and visualized with TMB histochemistry. In separate experiments, geniculocortical axon arbors were filled with HRP deposited extracellularly into the optic radiations and stained with cobalt‐intensified DAB.

On the day of birth (P0) and on P1–2, a crude topography was detected in the geniculocortical system. At these ages, geniculocortical axons coursed in the embryonic white matter of the visual cortex, parallel to the pia. During their passage, multiple short collaterals, with no terminal arbors, were extended into the subplate and deeper portions of the cortical plate. By P3–5, the topography was more precise and simple axonal arbors had now begun to be formed on some branches within the cortical plate. During the second postnatal week, branches in the white matter without terminals were eliminated and the ramifications of branches in the gray matter became more elaborate. The arbors continued to increase in complexity and resembled adult forms by P24.
Anatomy of glutamic acid decarboxylase immunoreactive neurons and axons in the rat medial geniculate body
Authors: Winer Jeffery A. , Larue David T.
Published: January 2005

This is a study of the form, density, and distribution of glutamic acid decarboxylase (GAD) immunoreactive neurons and puncta (axon terminals) in the adult rat medial geniculate complex. GAD‐positive elements were stained by either the peroxidase‐antiperoxidase or avidin‐biotin procedures. Thalamic architectonic subdivisions were defined independently in Golgi, Nissl, plastic‐embedded semi‐thin, and fiber‐stained preparations, and from investigations of medial geniculate connectivity.

GAD‐positive neurons represent only ∼1% of medial geniculate neurons. They occur in the three major medial geniculate subdivisions (ventral, dorsal, and medial). There is variability between subdivisions in the form and number of such neurons, and among the puncta. In the ventral division, immunopositive somata may have sparsely branched dendrites as long as 300–400 μm and capped with varicose expansions or bouton‐like sprays of appendages. These closely appose the somata or primary dendrites of other cells; the axons of these GAD‐positive neurons are also immunostained. In the dorsal division there are fewer GAD‐positive neurons and their structure is different. Their dendrites are rarely immunoreactive for more than 100–150 μm; nor can their immunostained axons be traced very far. In the medial division the number of GAD‐positive neurons, considering the relatively small size of this division, was high. These neurons rarely have immunostained dendrites, and more than one type of neuron is immunoreactive.

The average somatic diameter of GAD‐positive neurons is about 60% of that of non‐immunostained cells in semi‐thin material; however, the range of somatic area and the dendritic variability of these neurons suggest that cells representing more than one population are immunopositive and include all but the largest neurons.

The puncta also show regional differences. Small (0.5–2 Cm in diameter), medium (2–3 μm), or large (> 3 μm) puncta occur. In the ventral division, the predominantly medium‐sized puncta are about four times as numerous on a unit/area basis than in the dorsal division, where they are far smaller and more delicate; medial division puncta are as numerous as those in the ventral division, but are much larger and coarser, and may form perisomatic arrangements. Controls were devoid of specific immunostaining.

These data suggest that (1) there are significant local differences in the form and density of GABAergic neurons and puncta; (2) there is regional diversity in the form and size of such neurons; and (3) these local patterns might reflect differences in intrinsic organization, such as presynaptic dendrites in the ventral division and their probable absence in the medial division.
Organization of primary visual cortex (area 17) in the ferret
Authors: Law Margaret I. , Zahs Kathleen R. , Stryker Michael P.
Published: January 2005

Anatomical and electrophysiological mapping techniques were used to determine topographic organization and arrangement of ocular dominance columns in the primary visual cortex of ferrets. From its border with area 18 on the posterior lateral gyrus, area 17 extends around the caudal pole of the hemisphere and over the splenial gyrus to the caudal bank of the splenial sulcus. The visuotopic map is oriented with the isoazimuth lines approximately parallel to the long axis of the posterior lateral gyrus and the isoelevation lines approximately perpendicular to the isoazimuths. Central azimuths are represented on the posterior lateral gyrus and peripheral azimuths are represented on the splenial gyrus; the inferior visual field maps medially and the superior visual field maps laterally. As in other species, the representation of the central visual field is expanded.

The ferret has a considerable degree of binocular vision. Receptive fields driven through the ipsilateral eye extended more than 20° into the contralateral visual field. Within the region of area 17 corresponding to the binocular portion of the visual field, tritiated proline injected into one eye transneuronally labelled an ipsilateral projection as a series of patchy bands roughly complementary to gaps in the labelled contralateral projection. Physiological ocular dominance columns were evident as well in that neurons and groups of neurons recorded in this region showed clustered ocular dominance preferences. Most single neurons studied were binocularly driven.
Laminar histochemical and cytochemical localization of cytochrome oxidase in the goldfish retina and optic tectum in response to deafferentation and during regeneration
Authors: Kageyama Glenn H. , Meyer Ronald L.
Published: January 2005

Cytochrome oxidase (C.O.) histochemistry and cytochemistry were used to examine the effects of optic denervation and subsequent optic fiber regeneration on oxidative metabolism in the retina and optic tectum of the goldfish. In the tectum, there was a dramatic and rapid decrease in C.O. activity within the optic layers 3–4 days after contralateral eye removal or optic nerve crush. At the E.M. level this was correlated with an initial decrease in mitochondrial reactivity within optic terminals followed by the subsequent degradation of mitochondria and phagocytosis of optic terminals.

By 1 month after optic nerve crush, the entire tectum was reinnervated. However, the normal dark reactivity of the stratum fibrosum et griseum superficialis (SFGS), the main optic innervation layer, was not restored until after 3–4 months postcrush. The normal intense reactivity of the largediameter optic axons and terminals at the bottom of the SFGS required an even longer period, about 7–8 months, for full recovery. The delayed restoration of C.O. reactivity was not due to a delay in synaptogenesis or in mitochondrial accumulation within optic terminals but to a delay in the maturation of mitochondrial reactivity. Following regeneration, the normal sublaminar stratification of C.O. bands was reestablished, suggesting that metabolically distinct classes of optic fibers may reinnervate at their original sublaminae. By using a distinct and persistent C.O. reactive sublamina, a of stratum griseum centrale (SGCa), just subjacent to the SFGS, it was possible to measure the thickness of the SFGS following optic denervation and subsequent reinnervation. At 1 week after optic nerve crush, the SFGS shrank by 35%. During regeneration, the thickness of the SFGS gradually increased to about 23% above normal at 2 months postcrush and this was maintained indefinitely.

In the retina, ganglion cells were hypertrophic by 1 month postcrush and exhibited elevated levels of C.O. during the same period of time when optic terminals were unreactive. This indicates that oxidative metabolic activity within perikarya and axon terminals of the same neuron may be locally and independently regulated. It also suggests that in spite of the well‐known elevation of axonal transport during the initial period of axon elongation and synaptogenesis, that oxidative metabolic energy production within the optic fibers is less than that of the mature projection. We hypothesize that the comparatively greater oxidative metabolism of the mature projection results from greater synaptic convergence of fibers having correlated activity and may be a target‐mediated metabolic response of optic axons having reached their topographically appropriate synaptic sites.
Dense‐cored vesicle‐containing components of the terminal nerve of sharks and rays
Authors: Demski Leo S. , Fields R. Douglas
Published: January 2005

This paper describes electron microscopic observations of dense‐cored vesicle‐containing axons, cell bodies, and endings of the terminal nerve in several elasmobranchs. The vesicles are found in two apparent cell types, one with a polymorphic nucleus and another with an oval nucleus. The types may correspond to cells producing one each of two neuropeptides (LHRH and FMRF‐amide) that have previously been localized in the nerve. Dense‐cored vesicles are found in many unmyelinated fibers in both the terminal nerve proper and its major ganglia. Some of these form complicated structures with interdigitation and wrapping of membranes. Vesicle‐containing fibers branch from the nerve, run along nearby blood vessels, and appear to end adjacent to endothelial cells which demonstrate vesicular activity. The observations suggest terminal nerve neurosecretion into the cerebral circulation. Synapses are found in and near the ganglia where they appear to be axodendritic, with multiple contacts in some cases.
Correspondence between high affinity 125I‐neurotensin binding sites and dopaminergic neurons in the rat substantia nigra and ventral tegmental area: A combined radioautographic and immunohistochemical light microscopic study
Authors: Szigethy E. , Beaudet A.
Published: January 2005

Several lines of anatomical, biochemical, and pharmacological evidence have suggested that specific high affinity neurotensin binding sites are associated with dopamine‐containing neurons in the rat ventral tegmentum. In the present study we confirmed and quantified the extent of this association by combining monoiodinated neurotensin radioautography and tyrosine hydroxylase immunohistochemistry on adjacent 5–10μm‐thick midbrain sections. We found that 95–100% tyrosine hydroxylase‐immunoreactive neurons detected in all subdivisions of the substantia nigra (pars compacta, pars lateralis, and pars reticulata) exhibited intense 125I‐neurotensin labeling in adjacent light microscopic radioautographs. Tyrosine hydroxylase‐positive dendrites radiating downward from compacta neurons were also heavily labeled throughout the pars reticulata. In the paranigral subdivision of the ventral tegmental area, silver grains were evenly distributed over neuropil and perikarya and therefore could not be readily attributed to any given tyrosine hydroxylase‐positive element. In contrast, within the parabrachial pigmentous subdivision of the ventral tegmental area, 80–90% of the tyrosine hydroxylase‐immunoreactive somata and proximal processes were clearly in register with 125I‐neurotensin labeled cells. Finally, all tightly packed TH‐positive neurons in the interfascicular nucleus showed intense 125I‐neurotensin labeling. The vast majority of the neurotensin binding sites observed in the ventral midbrain tegmentum were of the high affinity, physiologically active receptor type since levocabastine, a selective blocker of the low affinity neurotensin binding component, had minimal effect on the binding density in any of the midbrain regions examined. The present results demonstrate an extensive overlap between specific, high affinity neurotensin binding sites and dopamine perikarya and dendrites in the rat ventral tegmentum, and thereby provide a direct anatomical substrate for observed neurotensin‐dopamine interactions in the mesocorticolimbic and nigrostriatal projection systems.
Axonal connections of a forebrain nucleus involved with vocal learning in zebra finches
Authors: Bottjer Sarah W. , Halsema Keri A. , Brown Sandra A. , Miesner Elizabeth A.
Published: January 2005

Connections of a telencephalic vocal‐control nucleus, the lateral magnocellular nucleus of the anterior neostriatum (lMAN), were studied in adult male zebra finches. Anterograde transport of horseradish peroxidase (alone or conjugated to wheat germ agglutinin) revealed that neurons in lMAN project to another forebrain song‐control nucleus, the robust nucleus of the archistriatum (RA). RA is known to project onto the hypoglossal motor neurons that innervate the vocal organ. Retrograde transport of HRP from lMAN labeled a large thalamic nucleus, the medial portion of the dorsolateral nucleus of the thalamus (DLM). DLM in turn receives input from another nucleus of the song‐control system, area X of the parolfactory lobe. We confirmed results of previous studies showing that area X receives a projection from the ventral area of Tsai (AVT) in the midbrain. In addition, we replicated results of previous experiments with canaries showing that the song‐control nucleus HVc (caudal nucleus of the ventral hyperstriatum) receives input from three sources: the medial magnocellular nucleus of the anterior neostriatum (mMAN), the interfacial nucleus (NIf), and the uvae‐form nucleus (Uva) of the thalamus. HVc neurons project to area X and to RA. In summary, there is a path from AVT in the midbrain, to area X, to DLM, and then to lMAN; HVc projects to X and hence indirectly to lMAN. We do not yet know the afferent connections of AVT. Thus, lMAN receives indirect input from a variety of other sources, including other regions known to be involved with vocal control.
Morphological types of spinomesencephalic neurons in the marginal zone (Lamina I) of the rat spinal cord, as shown after retrograde labelling with cholera toxin subunit B
Authors: Lima Deolinda , Coimbra Antonio
Published: January 2005

Retrogradely labelled lamina I neurons were studied after intramesencephalic injections of subunit B of cholera toxin. The tracer was visualized with a mixture of two monoclonal antibodies followed by the peroxidase‐antiperoxidase technique that produced Golgi‐like staining of the labelled cells. A morphological and morphometric analysis in the three anatomical viewing planes disclosed two structural neuronal types which were recognized as the fusiform and pyramidal cells of our Golgi‐based classification of rat marginal cells. Fusiform cells had a bipolar longitudinally elongated dendritic arbor, were located in the lateral third of lamina I, and appeared to project mainly to the contralateral parabrachial nuclei. It is asserted that these cells may convey the spinal input which elicits visceral responses generated in that area. Pyramidal cells were longitudinally oriented pyramids with the triangular base straddling the dorsal horn/white matter border and a dendritic arbor extending lateromedially and mainly rostrocaudally throughout superficial lamina I and the dorsal funiculus. These cells occurred along the entire mediolateral extent of lamina I and seemed to have a prevalent projection to the contralateral caudal ventrolateral periaqueductal gray. They may represent the ascending branch of the spinalmidbrain loop centered in that zone which controls nociceptive transmission postsynaptically in the dorsal horn.
Forebrain projections from cholecystokininlike‐immunoreactive neurons in the rat midbrain
Authors: Seroogy Kim B. , Fallon James H.
Published: January 2005

The purpose of the present study was to analyze the distribution of cholecystokininlike‐immunoreactive (CCK‐I) neurons within the rat ventral mesencephalon which project to several forebrain areas. The peroxidase‐antiperoxidase immunocytochemical technique was used to examine the anatomical localization of CCK‐I within the ventral midbrain and in the following forebrain regions: caudate‐putamen, nucleus accumbens, olfactory tubercle, bed nucleus of the stria terminalis, septum, amygdala, and prefrontal, anterior cingulate, and piriform cortices. CCK‐I perikarya were distributed throughout the substantia nigra, ventral tegmental area, and several midline raphe nuclei to a greater extent than previously reported, particularly in the substantia nigra pars compacta. Terminallike immunoreactivity for CCK was observed in all of the above forebrain sites. In addition, infrequent CCK‐I cell bodies were localized in the caudate‐putamen, nucleus accumbens, olfactory tubercle, septum, and bed nucleus of the stria terminalis.

To analyze forebrain projections of the ventral midbrain CCK‐I neurons, indirect immunofluorescence was combined with fluorescence retrograde tracing. CCK‐I neurons of the substantia nigra and/or ventral tegmental area were found to project, to varying extents, to all of the above CCK‐I forebrain terminal fields. The nucleus accumbens, olfactory tubercle, and septal and prefrontal cortical projections arose primarily from CCK‐I perikarya in the ventral tegmental area whereas the projections to the caudateputamen and anterior cingulate cortex arose predominantly from immunoreactive neurons in the substantia nigra pars compacta. The amygdala received innervation mainly from CCK‐I cell bodies located in the substantia nigra pars lateralis. CCK‐I afferents to the bed nucleus of the stria terminalis and piriform cortex originated from perikarya distributed approximately equally across the ventral tegmental area and substantia nigra pars compacta. The general topography of CCK‐I forebrain innervation observed in this study is similar to that previously reported for the ascending dopaminergic projections from ventral mesencephalic neurons. CCK‐I neurons of the midline raphe nuclei were found to provide relatively minor afferents to the caudate‐putamen, bed nucleus of the stria terminalis, septum, and prefrontal cortex and more substantial projections to the amygdala.

The results of this study demonstrate that CCK‐I neurons of the ventral midbrain supply a much broader innervation of forebrain regions than previously appreciated. Moreover, these data suggest that ventral mesencephalic CCK projections encompass the full range of the well‐known dopaminergic masolimbic. mesostriatal, and mesocortial projections. Thus, CCK may play a significant role in the ascending mesotelencephalic systems.