bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of met‐enkephalin, dynorphin a, and neurotensin immunoreactive neurons in the cat and rat spinal cords: II. Segmental differences in the marginal zone
Authors: Miller Kenneth E. , Seybold Virginia S.
Published: January 2005

This study examined the number of met‐enkephalin, dynorphin A 1–8, and neurotensin immunoreactive (IR) neurons in the marginal zone (lamina I) at one thoracic (T8:cat,T9:rat), one midlumbar (L5:cat,L4:rat), and one lower lumbar or sacral (S1:cat,L6:rat) spinal cord segment in the cat and rat. Marginal zone IR neurons ranged 10–70 μm in diameter in cats and 10–50 μm in rats and were flattened, pyramidal, fusiform, or polygonal in morphology. Immunoreactive neurons for each peptide in both species were found in the marginal zone at all spinal levels, but with a differential segmental distribution. The average number of IR neurons per 50‐:μm section generally was lowest in thoracic cord and greatest in lower lumbar/sacral cord for all peptides. For enkephalin and dynorphin, the estimated total number of IR neurons per segment and number of IR neurons per volume (mm3) generally were lowest in the midlumbar segments and highest in the thoracic and lower lumbar/sacral cord. For neurotensin, the estimated total number of neurons per segment remained lowest in the thoracic and largest in the lower lumbar/sacral cord. The number of neurotensin IR neurons per volume was equal in the thoracic and midlumbar cord, but remained highest at lower lumbar/sacral levels. The IR neurons quantified in this study may be interneurons or may serve as supraspinal projection neurons. The large number of IR neurons observed in segments receiving a relatively large visceral afferent input suggests that some of these neurons may be involved in visceral sensory processing. In addition, the segmental distribution of the IR neurons indicates that physiological and pharmacological studies on the effects of opioid and/or neurotensin peptides should be interpreted in light of the spinal segment(s) investigated.
Dopamine‐like immunoreactivity in the brain and suboesophageal ganglion of the honeybee
Authors: Schäfer Sabine , Rehder Vincent
Published: January 2005

The distribution of dopamine in the brain and suboesophageal ganglion of the honeybee Apis mellifera was investigated by means of immunocytochemistry with a well‐characterized antiserum against dopamine. The binding of the antiserum in paraffin serial sections was studied with the peroxidase‐antiperoxidase method. Dopamine‐like immunoreactive neurons are present in most parts of the brain and in the suboesophageal ganglion. Only the optic lobes are devoid of label. There are ca. 330 dopamine immunoreactive somata in each brain hemisphere plus respective suboesophageal hemiganglion, which is less than 0.1% of the entire neuronal population. Most of the labelled somata are situated within three clusters: one below the lateral calyx and two in the anterior‐ventral protocerebrum. Other labelled somata lie dispersed or in small groups around the protocerebral bridge, below the optic tubercles, proximal to the ventral rim of the lobula, and in the lateral and ventral somatal rind of the suboesophageal ganglion. Similar to neurons that react with an antiserum against serotonin, the fine processes of dopamine immunoreactive fibers have a varicose appearance which is typical for aminergic neurons. In addition to the neuronal staining, dopamine‐like immunoreactivity is also present in the sheath surrounding the brain and in the retina, where it is not restricted to any particular cell type.

A detailed account is given for those neurons and groups of neurons that could be traced and reconstructed in some detail. A common feature of all dopamine immunoreactive fibers is that each fiber invades large volumes of neuropil, suggesting that dopamine is more important in mediating distant rather than local neural interactions.
Morphologies of rabbit retinal ganglion cells with concentric receptive fields
Authors: Amthor Franklin R. , Takahashi Ellen S. , Oyster Clyde W.
Published: January 2005

Rabbit retinal ganglion cells with concentric receptive fields were intracellularly recorded and stained in the isolated superfused eyecup preparation to relate specific physiological response properties to dendritic morphology. Concentric ganglion cells, as traditionally defined, were those that had On or Off centers with antagonistic surrounds but lacked complex response properties such as direction or orientation selectivity. Concentric cells were classified into different groups by extracellular recordings of their On‐ or Off‐center response sign, excitatory receptive field center size, linearity of spatial summation, and brisk vs. sluggish and transient vs. sustained responses to step changes in light intensity. The cells were then impaled, confirmed in identity during intracellular recording, and iontophoretically injected with horseradish peroxidase for histological analysis. Twenty‐three concentric ganglion cells were recovered and morphometrically analyzed. Their physiological response properties were found to be related to a number of underlying two‐ and three‐dimensional attributes of the cell's dendritic branching patterns. The dendrites of all 20 brisk concentric cells and two of the three sluggish cells were found to ramify narrowly in either the proximal or distal half of the inner plexiform layer, corresponding to whether they are On center or Off center, respectively. One of the sluggish concentric cells was found to have a more complex, partially bistratified ramification. Physiologically identified brisk‐sustained‐linear, brisk‐transient‐nonlinear, brisk‐transient‐linear, and at least two classes of sluggish concentric ganglion cells were stained. Each of these physiological classes appears to exhibit a distinct and identifiable dendritic branching pattern.
Morphologies of rabbit retinal ganglion cells with complex receptive fields
Authors: Amthor Franklin R. , Takahashi Ellen S. , Oyster Clyde W.
Published: January 2005

Ganglion cells that had complex receptive field properties, namely, On‐Off and On direction‐selective cells, orientation‐selective cells, local edge detectors, and uniformity detectors (suppressed by contrast cells) were recorded in an isolated superfused rabbit eyecup preparation. Cells were first classified by their characteristic extracellular responses to manually controlled stimuli similar to those which have been used in previous in vivo studies. Ganglion cells were then impaled, confirmed in identity by intracellular recording, and iontophoretically injected with horseradish peroxidase for staining. Twenty‐two ganglion cells, which included members of all the major classes mentioned above, were recovered from the visual streak or near periphery. All recovered cells were drawn in camera lucida from flatmounted retinas and entered into a computer as two‐dimensional stick figures; nearly all were three‐dimensionally reconstructed to determine the level and manner of dendritic ramification in the inner plexiform layer (IPL). The location of ganglion cell dendrites in sublaminar regions of the IPL was found to be consistent with the hypothesis of a division of the IPL into excitatory On (promixal) and Off (distal) sublaminae, with some qualifications for particular classes. Each of the complex receptive field ganglion cell classes exhibited a distinctive three‐dimensional dendritic arborization pattern uniquely associated with that physiological class.
Peptidergic neurons in the basal forebrain magnocellular complex of the rhesus monkey
Authors: Walker Lary C. , Koliatsos Vassilis E. , Kitt Cheryl A. , Richardson Russell T. , Rökaeus Åke , Price Donald L.
Published: January 2005

The basal forebrain magnocellular complex of primates is defined by the presence of large, hyperchromic, usually cholinergic neurons in the nucleus basalis of Meynert and nucleus of the diagonal band of Broca. Because there is growing evidence for noncholinergic neuronal elements in the basal forebrain complex, five neuropeptides and the enzyme choline acetyltransferase were studied immunocytochemically in this region of rhesus monkeys. Galaninlike immunoreactivity coexists with choline‐acetyl‐transferase‐like immunoreactivity in most large neurons and in some smaller neurons of the primate nucleus basalis and nucleus of the diagnonal band. Four other peptides show immunoreactivity in more limited regions of the basal forebrain complex, usually in separate smaller, noncholinergic neurons. Numerous small, somatostatinlike‐immunoreactive neurons occupy primarily anterior and intermediate segments of the nucleus basalis, especially laterally and ventrally. Somewhat fewer, small neuropeptide Y‐like‐immunoreactive somata are found in the same regions. Neurons that show neurotensinlike immunoreactivity are slightly larger than cells that contain immunoreactivity for somatostatin or neuropeptide Y, but these neurons also occur mainly in anterior and intermediate parts of the nucleus basalis. Overall, the usually small, leucine‐enkephalin‐like‐immunoreactive neurons are infrequent in the basal forebrain complex and are most abundant in the rostral intermediate nucleus basalis. Thus, neurons that appear to contain somatostatin, neuropeptide Y, neurotensin, or enkephalin mingle with cholinergic/galaninergic neurons only in some subdivisions of the nucleus basalis/nucleus of the diagonal band, and their distributions suggest that some of these small neurons could be associated with structures that overlap with cholinergic neurons of the labyrinthine basal forebrain magnocellular complex. We also have found light microscopic evidence for innervation of basal forebrain cholinergic neurons by boutons that contain galanin‐, somatostatin‐, neuropeptide Y‐, neurotensin‐, or enkephalinlike immunoreactivity. The origins and functions of these putative synapses remain to be determined.
Studies on the cellular architecture of the bed nuclei of the stria terminalis in the rat: II. chemoarchitecture
Authors: Ju G. , Swanson L. W. , Simerly R. B.
Published: January 2005

In a companion paper (Ju and Swanson; J. Comp. Neurol. 280:587–602, '89) we described a parcellation scheme for the bed nuclei of the stria terminalis (BST) that was based on cytoarchitectonic criteria. In the work reported here, antisera to the neuropeptides corticotropin‐releasing hormone, neurotensin, galanin, substance P, and cholecystokinin were used to determine the extent to which immunostained neuronal cell bodies and presumed terminal fields are correlated with this cytoarchitectonic scheme in the adult male rat. The results confirm the validity of the cytoarchitectonic parcellation and provide additional chemoarchitectonic criteria for determining the (as yet still somewhat arbitrarily defined) border between the BST and the ventrally adjacent preoptic region, for distinguishing between the anterior and posterior divisions of the BST, and for identifying and distinguishing between the particular cell groups or nuclei within each division. The projections of each neuropeptide‐containing cell group in various parts of the BST remain to be determined, as do the precise origins of the localized immunoreactive terminal fields identified here.
Afferent and efferent projections of the VIIIth cranial nerve in the lamprey Lampetra japonica
Authors: Koyama Hiromichi , Kishida Reiji , Goris Richard C. , Kusunoki Toyokazu
Published: January 2005

Anterograde and retrograde transport of horseradish peroxidase was used to examine the afferent and efferent projections of the VIIIth cranial nerve in the lamprey Lampetra japonica. Ganglion cells of the VIIIth nerve are classified into three types on the basis of their morphology. The central processes of these ganglion cells enter the medulla in two groups: the anterior group (mostly thick fibers) and the posterior group (mostly thin fibers). Afferent fibers mainly terminate within the ipsilateral ventral and octavomotor nuclei of the octavolateralis area and within the granular and molecular layer of the cerebellum. Some fibers terminate in the contralateral cerebellum, the medial and dorsal nuclei of the octavolateralis area, the descending nucleus of the trigeminal nerve, some cranial motor nuclei, and the lateral octavus nucleus, which has not been described previously. This small nucleus is located beneath the descending nucleus of the trigeminal nerve near the obex. Within the ventral nucleus, thin fibers occupy the dorsal part and thick fibers occupy the ventral part. The basic projection pattern of the primary afferents of the VIIIth nerve in the lampreys was similar to that of gnathostome fishes that have been studied to date. Cell bodies of the efferent vestibular neurons are located between the ipsilateral trigeminal motor nucleus and the facial motor nucleus. The lateral location of these cell bodies differs from that of all other fish species that have been studied.
Development of the thalamocortical system: Transient‐crossed projections to the frontal cortex in neonatal rats
Authors: Minciacchi Diego , Granato Alberto
Published: January 2005

The developmental remodeling of thalamic projections to frontal and prefrontal cortical fields was investigated in the rat by using a double retrograde tracing technique. Bilateral cortical injections of fluorescent tracers were made either in neonatal (first or second postnatal day) or in adult animals. In neonates, the cell populations retrogradely labeled from each cortical injection overlapped in a medial thalamic region that included the midline nuclei and the medial part of the mediodorsal nucleus, ventral medial nucleus, and nucleus gelatinosus. In adults, the overlap region was confined within the boundaries of the midline nuclei. Quantitative analysis showed that this overlap area was three times as wide in neonates as in adults. The neurons located in this region projected unilaterally both in neonatal and adult animals; bilaterally projecting cells were virtually absent.

In neonates, a second set of contralaterally projecting neurons was found in more lateral thalamic regions. This population consisted of cell clusters in the dorsal part of the central lateral nucleus and in the lateral part of the ventral medial nucleus; scattered cells were also observed throughout other nuclei. This second cell population was represented in part by neurons bifurcating bilaterally. In adult animals, neurons projecting contralaterally were observed only occasionally in the lateral thalamus.

The present results demonstrate that the bilaterality of thalamocortical projections undergoes a reduction during postnatal development. The mechanisms underlying this remodeling and the possible functional role of the transient‐crossed thalamocortical system are discussed.
Endogenous opioid systems and the regulation of dendritic growth and spine formation
Authors: Hauser Kurt F. , McLaughlin Patricia J. , Zagon Ian S.
Published: January 2005

The role of endogenous opioid systems (endogenous opioids and opioid receptors) in neuronal development was examined in 10‐ and 21‐day‐old rats by utilizing an opioid antagonist (naltrexone) paradigm. Throughout the first 3 weeks of life, Sprague‐Dawley rats were given daily subcutaneous injections of either 50 mg/kg naltrexone, a dosage that invoked a complete (24 hours/day) receptor blockade, or 1 mg/kg naltrexone, a dosage which intermittently blocked (4–6 hours/day) opioid receptors and exacerbated opioid action; animals injected with sterile water served as controls. Pyramidal cells from the frontoparietal cortex (layer III) and hippocampal field CA1, and cerebellar Purkinje cells, were impregnated by using the Golgi‐Kopsch method; total and mean dendrite segment length, branch frequency, and spine concentration were analyzed morphometrically. Perturbations of endogenous opioid systems caused region‐dependent alterations in dendrite complexity and/or spine concentration in all brain areas. Continuous opioid receptor blockade resulted in dramatic increases in dendrite and/or spine elaboration compared to controls at 10 days in all brain regions; however, these increases were only evident in the hippocampus at 21 days. With intermittent blockade, dendrite and/or spine growth were often subnormal, being predominant at day 21. Our results indicate that endogenous opioid systems are critical regulators of neuronal differentiation, and they control growth through an inhibitory mechanism. Considering previous findings demonstrating that neurobehavioral ontogeny is dependent on endogenous opioid‐opioid receptor interactions, the present results suggest an opioid‐dependent, structure‐function relationship between neuronal and behavioral maturation.
Distribution of proenkephalin‐derived peptides in the brain of Rana esculenta
Authors: Merchenthaler István , Lázár Gyula , Maderdrut Jerome L.
Published: January 2005

The immunocytochemical distribution of authentic proenkephalin‐containing perikarya and nerve fibers in the brain of Rana esculenta was determined with antisera directed toward different epitopes of preproenkephalin. The pattern of proenkephalinlike immunoreactivity was similar with antisera directed toward [Met5]‐enkephalin, [Met5]‐enkephalin‐Arg6, [Met5]‐enkephalin‐Arg6‐Phe7, [Leu5]‐enkephalin, and metorphamide; however, the intensity of the labelling varied depending on the target antigen.

Proenkephalin‐containing perikarya were located in all major subdivisions of the brain except the metencephalon. In the telencephalon, immunoreactive perikarya were detected in the dorsal, medial, and lateral pallium; the medial septal nucleus; the dorsal and ventral striatum; and the amygdala. In the diencephalon, immunoreactive perikarya were detected in the preoptic nucleus, in the dorsal and ventral caudal hypothalamus, and in an area that appeared to be homologous to the paraventricular nucleus. In the mesencephalon, numerous immunoreactive perikarya were detected in layer 6 of the optic tectum and a few scattered perikarya were detected in layer 4 of the optic tectum. Immunoreactive perikarya also occurred in the laminar nucleus of the torus semicircularis. In the rhombencephalon, immunoreactive perikarya were detected in the obex region and the nucleus of the solitary tract. Immunoreactive fibers of varying density were observed in all major subdivisions of the brain with the densest accumulations of fibers occurring in the dorsal pallium, the lateral and medial forebrain bundles, the amygdala, the periventricular hypothalamus, the superficial region of the caudolateral brainstem, and in a tract that appeared to be homologous to the tractus solitarius.

The extensive system of proenkephalin‐containing perikarya and nerve fibers in the brain of an amphibian showed many similarities to the distribution of proenkephalin‐containing perikarya and nerve fibers previously described for the amniote brain.
Cell production in the chicken cochlea
Authors: Katayama Akiko , Corwin Jeffrey T.
Published: January 2005

In the chicken cochlea, the structural features of the cilia bundles of individual hair cells vary systematically along the length of the sensory epithelium. As a first approach to understanding the developmental mechanisms that underlie this precise arrangement of structurally distinct hair cells, the spatiotemporal pattern of the terminal mitoses of their precursor cells was investigated by administering 3H‐thymidine, a radioactive precursor to DNA. This demonstrated that the first hair cells were produced during the sixth day of incubation and formed a longitudinal band that extended along most of the length of the sensory epithelium. The epithelium grew further through appositional addition of hair cells at the edges of this first band of cells, and the hair cell addition process expanded into the surrounding areas during the next 3 days. By the ninth day of incubation all the hair cells in the sensory epithelium except for those at the peripheral edges in the distal (apex) portion had been produced through terminal mitoses. Our results have demonstrated that hair cells that have similar stereocilia phenotypes do not all leave the mitotic cycle at the same time.
Changes in neuronal cell bodies in N. laminaris during deafferentation‐induced dendritic atrophy
Authors: Deitch Jeffrey S. , Rubel Edwin W.
Published: January 2005

N. laminaris dendrites begin to atrophy almost immediately after they are deafferented. Accompanying this rapid change in shape is a loss of microtubules and neurofilaments at the base of the dendrite, and a decrease in the density of the dendritic cytoplasm. However, degenerative changes in the dendritic plasma membrane were not evident until 2 days after deafferentation. Thus it was unknown what happened to the volume and membrane lost from the atrophying dendrites before this time. The soma was investigated in this study as a possible recipient of the volume of the atrophying dendrite. Soma size increased significantly by 2 hours after deafferentation and continued to increase for 1–8 days after deafferentation. The nucleus, which is normally concentric with the soma, moved continuously to the dorsal pole of the soma, toward the innervated side of the cell. The cytoplasm on the ventral side of the soma showed a decrease in density and loss of cytoskeleton similar to what was found in the initial portion of the ventral primary dendrites in the accompanying paper.

These changes are interpreted as indicative of a rapid resorption of the ventral dendrite back into the soma following deafferentation.
Gap junction protein in rat hippocampus: Correlative light and electron microscope immunohistochemical localization
Authors: Shiosaka S. , Yamamoto T. , Hertzberg E. L. , Nagy J. I.
Published: January 2005

Immunohistochemical techniques and an affinity‐purified antibody directed against the 27‐kD gap‐junctional protein (GJP) from rat liver were used to determine the ultrastructural localization of GJP in the rat hippocampus. At the light microscope level, dense GJP immunoreactivity having a stringlike appearance was seen in a very small percentage of medium‐sized neuronal somata located in the stratum pyramidale, and diffuse immunostaining was seen in many small cell bodies in the stratum pyramidale, stratum oriens, and the alveus. Abundant GJP‐immunoreactive (GJP‐IR) varicose fibers were observed in the strata pyramidale, radiatum, and oriens but were less concentrated in the alveus. Numerous punctate GJP‐IR elements were observed in all hippocampal layers. Upon EM analysis, GJP‐IR neuronal somata in the stratum pyramidale were found to be, without exception, nonpyramidal neurons as judged by such distinguishing features as their fusiform perikarya, indented nucleus, and well‐developed rough endoplasmic reticulum (RER). Immunostaining within these cells was largely localized to the Golgi apparatus and associated vesicular components. Small, diffusely GJP‐IR cells were identified ultrastructurally as protoplasmic and fibrous astrocytes. Immunostaining within these cells was localized to the Golgi apparatus, RER, and small, ribosomelike bodies 15–25 nm in diameter. Among neuronal processes GJP immunoreactivity was found within dendrites, axons, and axonal terminals. The latter structures contained numerous GJP‐IR vesicles having an average diameter of about 40 nm. A frequent observation indicating some degree of specificity of the anti‐GJP antibody employed here was immunostaining of typical gap junctions between dendrites and, more commonly, between processes of glial cells. Ocassionally, however, GJP‐IR dendrodendritic, axodendritic, and axoaxonic contacts were found that could be considered, at best, as being gap‐junction‐like (gj‐L). In these cases, asymmetric immunostaining of adjacent plasma membranes forming gj‐L structures was not uncommon.

These results confirm the existence of gap junctions between dendrites in the rat hippocampus and demonstrate that GJP immunoreactivity on cytoplasmic membranes is restricted either to typical neuronal and glial gap junctions or to gj‐L structures at circumscribed sites of contact between various types of neuronal elements where GJP may contribute to a novel mechanism of neural communication.
Cholinergic innervation of the monkey amygdala: An immunohistochemical analysis with antisera to choline acetyltransferase
Authors: Amaral David G. , Bassett Julia L.
Published: January 2005

The organization of the cholinergic innervation of the macaque monkey amygdaloid complex was investigated by means of immunohistochemical techniques and either a polyclonal antiserum or a monoclonal antibody directed against the specific synthetic enzyme choline acetyltransferase (ChAT). Adjacent series of sections were processed histochemically for the demonstration of the degradative enzyme acetylcholinesterase (AChE) or for cell bodies with thionin. The density of ChAT immunoreactivity differed substantially among the various nuclei and cortical regions of the amygdala. In general, the distribution of ChAT immunoreactivity paralleled the pattern of AChE staining. One notable exception was the presence of AChE containing cell bodies in addition to AChE positive fibers within nearly all of the nuclear and cortical regions. In contrast, ChAT immunoreactivity was associated only with fibers and terminals.

The highest density of ChAT immunoreactive fibers and terminals was consistently observed in the magnocellular subdivision of the basal nucleus. Staining was substantially less dense in the more ventrally situated parvicellular subdivision. Medially, in the adjacent accessory basal nucleus, immunoreactive fibers and terminals were densest in the magnocellular and superficial subdivisions and least prominent in the parvicellular subdivision. Of the deep nuclei, the lateral nucleus generally contained the least ChAT immunoreactive terminals and processes. Only its more densely cellular ventrolateral portion contained appreciable fiber and terminal staining.

One of the more distinctive patterns of ChAT immunoreactivity was seen in the nucleus of the lateral olfactory tract. Here, ChAT positive fibers formed pericellular basket plexuses around unstained cell bodies. This unique pattern of staining was used to delineate the boundaries of the nucleus and indicated that it is present for much of the rostrocaudal extent of the amygdala. Another region of conspicuous staining on the medial surface of the amygdala was the sulcal portion of the periamygdaloid cortex. This region, associated with the sulcus semiannularis and bordering the entorhinal cortex, consistently contained dense immunoreactivity. The central nucleus also presented a somewhat idiosyncratic pattern of ChAT staining. The lateral subdivision had a diffuse distribution of immunoreactivity in which focal patches of more densely stained terminals and occasional fine fibers were embedded. In contrast, the medial subdivision contained a larger number of thicker, stained fibers without diffuse background labeling. Of the remaining amygdaloid nuclei, the amygdalohippocampal area contained dense ChAT staining, whereas progressively lighter staining was seen in anterior amygdaloid, posterior cortical, anterior cortical, and medial nuclei.
Cortical connections of areas 17 (V‐I) and 18 (V‐II) of squirrels
Authors: Kaas J. H. , Krubitzer L. A. , Johanson K. L.
Published: January 2005

Connections of visual cortex in squirrels were investigated by placing WGA‐HRP injections, and in some cases fluorescent dyes, into area 17 (V‐I) or area 18 (V‐II). Results were related to architectonic fields determined in brain sections cut parallel to the surface of manually flattened cortex and to limited microelectrode mapping data. Injections in area 17 provided evidence for (1) a patchy pattern of horizontal intrinsic connections extending 1–2 mm form the injection site; (2) uneven, widely distributed connections with area 18 (V‐II) and adjoining occipital‐temporal (OT) cortex; and (3) callosal connections of large portions of area 17 with the 17/18 border zone. While restricted locations in area 17 had uneven interconnections over several mm of area 18, more rostral locations in area 17 related to more rostral locations in area 18, demonstrating a topographic tendency. Injections in area 18 revealed (1) zones of discontinuous connections with area 17 that followed a topographic pattern, (2) patches of intrinsic connections that spread over distances of up to 6–8 mm from the injection site; (3) two zones of uneven connections with OT cortex suggesting the locations of at least two visual areas, OTr and OTc; (4) connections with limbic cortex rostromedial to areas 17 and 18; (5) sparse connections with regions of temporal cortex lateral to OT; and (6) uneven callosal connections with area 18 and OT cortex. The widespread and unevenly distributed intrinsic callosal interconnection patterns of areas 17 and 18 contrast with the restricted excitatory receptive fields of neurons and the retinotopic patterns of representation in these fields. Although physiological evidence is presently lacking, the patchy connections suggest that areas 17 and 18 in squirrels are modularly organized.
Immunohistochemical localization of choline acetyltransferase in the chicken mesencephalon
Authors: Sorenson Eva M. , Parkinson David , Dahl June L. , Chiappinelli Vincent A.
Published: January 2005

Choline acetyltransferase, a specific marker for cholinergic neurons, has been immunohistochemically localized in the mesencephalon and in the caudal diencephalon of the chicken. A complete series of transverse sections through the mesencephalon is presented.

In the diencephalon, cholinergic fibers were found in the stria medullaris, the fasciculus retroflexus, and the ventral portion of the supraoptic decussation. The nucleus triangularis and the nucleus geniculatus lateralis, pars ventralis also contained cholinergic fibers. Small cholinergic cell bodies were found in the medial habenula. In the pretectum, cholinergic fibers innervated the nucleus lentiformis mesencephali and the tectal gray. The nucleus spiriformis lateralis also contained cholinergic fibers, while most of the cell bodies in the nucleus spiriformis medialis were cholinergic. In the mesencephalon, labelled fibers were found in the nucleus intercollicularis and in all layers of the optic tectum except the stratum opticum. The highest density of tectal cholinergic fibers was in the stratum griseum et fibrosum superficiale (SGFS), layer f. Radial cells located in SGFS, layer i were also cholinergic. In the isthmic nuclei, cholinergic fibers were found in the pars magnocellularis, while the pars parvicellularis and the nucleus semilunaris contained labelled cells. The oculomotor, Edinger‐Westphal, trochlear, and trigeminal motor nuclei all had cholinergic cell bodies. Cholinergic axons were present in the oculomotor and trochlear nerves. In the tegmentum, cell bodies were labelled in the nucleus mesencephalicus profundus, pars ventralis, while the nucleus interpeduncularis had dense cholinergic innervation.

Our localization of cholinergic cell bodies and fibers has been compared with earlier autoradiographic and anatomical studies to help define cholinergic systems in the avian brain. For example, the results indicate that the chicken may have a cholinergic habenulointerpeduncular system similar to that reported in the rat. Establishing the cholinergic systems within the avian midbrain is important for designing future neurophysiological and pharmacological studies of cholinergic transmission in this region.
Quantitative analysis of the number and distribution of neurons richly innervated by GABA‐immunoreactive axons in the rat superior cervical ganglion
Authors: Wolff J. R. , Kasa P. , Dobo E. , Wenthold R. J. , Joo F.
Published: January 2005

The superior cervical ganglion of rats contains a considerable number of nerve fibers with GABA‐like immunoreactivity which show a nonuniform distribution within the ganglion. The topography of these fibers has been analyzed by using antibodies raised against GABA‐BSA‐glutaraldehyde complexes. GABA‐postive axons and axon varicosities accumulated around a subpopulation of principal ganglion cells forming basketlike patterns. These neurons richly innervated by GABA‐positive axons (RIG‐neurons) in turn were aggregated in patches with strong immunoreactivity. The size and packing desity of the patches containing RIG‐neurons and GABA‐positive axons approaching them had rostral‐to‐caudal and medial‐to‐lateral gradients. Similar patterns were found in right and left ganglia. In five ganglia, a quantitative analysis revealed on average 1,344 RIG‐neurons per ganglion representing about 5% of the total neuron population, with small variations (standard deviation 122) despite the highly variable shape of the ganglia. The distribution of RIG‐neurons resembles that of neurons sending their axons into the internal carotid nerve. To check this possible correlation, HRP was injected into the eye and applied to the transected external carotid nerve. Double staining for the retrogradely transported peroxidase and GABA immunohistochemistry revealed that RIG‐neurons formed a small subpopulation of retrogradely labelled neurons in both experiments. This suggests that RIG‐neurons innervate various target organs. This conclusion is in agreement with the observation that RIG‐neurons also exist in other sympathetic ganglia. Data presented suggest that sympathetic ganglion cells can be classified on the basis of non‐uniform innervation patterns formed by axons that use different neurotransmitters.
Interstitial cells of the adult neocortical white matter are the remnant of the early generated subplate neuron population
Authors: Chun Jerold J. M. , Shatz Carla J.
Published: January 2005

The postnatal fate of the first‐generated neurons of the cat cerebral cortex was examined. These neurons can be identified uniquely by 3H‐thymidine exposure during the week preceding the neurogenesis of cortical layer 6. Previous studies in which 3H‐thymidine birthdating at embryonic day 27 (E27) was combined with immunohistochemistry have shown that these neurons are present in large numbers during fetal and early postnatal life within the subplate (future white matter), that they are immunoreactive for the neuron‐specific protein MAP2 and for the putative neurotransmitters GABA, NPY, SRIF, and CCK. Here, the same techniques were used to follow the postnatal location and disappearance of the early generated subplate neuron population.

At birth (P0), subplate neurons showing immunoreactivity for GABA, NPY, SRIF, or CCK are present in large numbers and at high density within the white matter throughout the neocortex, and the entire population can be observed as a dense MAP2‐immunoreactive band situated beneath cortical layer 6. Between P0 and P401 (adulthood), the MAP2‐immunostained band disappears so that comparatively few MAP2‐immunoreactive neurons remain within the white matter. There is a corresponding decrease in the number and density of neurons stained with antibodies against neurotransmitters. In each instance, these neurons could be double‐labeled by the administration of 3H‐thymidine at E27, indicating that they are the remnants of the early generated subplate neuron population. The major period of decrease occurs during the first 4 postnatal weeks, and adult values are attained by 5 months. Within the white matter of the lateral gyrus (visual cortex), the density of immunostained neurons decreases dramatically: MAP2, 82%, SRIF, 81%, and NPY, 96%. While SRIF‐immunoreactive neurons compose a nearly constant percentage of MAP2‐immunoreactive neurons in the white matter between P0 (22%) and P401 (23%), those immunoreactive for NPY decline from 18 to 4%. These changes occur during the same period in which there is less than a twofold increase in white matter area.

These observations indicate that the interstitial neurons of the adult neocortical white matter are the oldest neurons of the cerebral cortex since most if not all are derived from the subplate neuron population. In addition, a quantitative analysis suggests that the postnatal decline in subplate neuron density cannot be accounted for solely through dilution by differential growth of the white matter and most likely reflects an absolute decrease in subplate neuron number. Thus, the adult interstitial neurons have survived a postnatal period during which many of their early generated cohorts have disappeared, probably via cell death.
Origin of ascending and spinal pathways from the nucleus tegmenti pedunculopontinus in the rat
Authors: Spann Bryan M. , Grofova Irena
Published: January 2005

The distribution and collaterlization of ascending and descending projections from neurons in the nucleus tegmenti pedunculopontinus (PPN) were studied in the rat by using retrograde transport of HRP, HRP/WGA, and fluorescent dyes. The PPN and its two subdivisions, the subnucleus compactus (PPNc) and subnucleus dissipatus (PPNd), were delineated on sagittal Nisslstained sections by using cytoarchitectural features as guidelines.

Large bilateral pressure injections of HRP and/or fluorescent dyes into the cervical cord retrogradely labeled moderate numbers of fusiform and polygonal PPN cells which ranged in size between 65 and 390 μm2. The labeled cells were scattered throughout the PPNd and were somewhat more numerous in the medial half of the subnucleus. The PPNc contained only occasional labeled cells in its ventralmost portion.

Following single unilateral HRP/WGA injections in the striatum, globus pallidus, entopeduncular nucleus, subthalamus, or the substantia nigra, the distribution of the labeled cells was similar to that of the spinal cord‐projecting PPN neurons. Multiple HRP injections were then made bilaterally in the substantia nigra and the entopeduncular nucleus and/or subthalamus in order to label the entire population of PPN neurons projecting to the basal ganglia. In this case, not only the PPNd but also the PPNc contained a substantial number of retrogradely labeled cells. The rostrally projecting PPN cells outnumbered 5.4 times those projecting to the spinal cord, and their somata were somewhat larger, ranging between 114 and 472 μm2. While both fusiform and polygonal shapes were encountered, the polygonal cell somata were more numerous.

In the double‐labeling experiments, Granular Blue and Diamidino Yellow Dihydrochloride were injected into the cervical cord and the entopeduncular nucleus or subthalamus. In general, these experiments confirmed the extensive overlap of forebrain‐ and spinal cord‐projecting neurons within the PPNd and the quantitative preponderance of ascending neurons. They also demonstrated that these two projection systems originate largely from separate cell populations since the double‐labeled cells always composed less than 5% of the labeled neurons.

The results confirm the existence of a direct PPN projection to the spinal cord. This pathway originates mainly in the PPNd and appears to be quantitatively weaker than the PPN projections to the forebrain. The spinal cord‐projecting cells are not spatially segregated from the cells projecting to the basal ganglia, but they represent a separate population of the PPN projection neurons.
Interganglionic dendrites constitute an output pathway from the procerebrum of the sanil Achatina fulica
Authors: Chase Ronald , Tolloczko Barbara
Published: January 2005

The procerebrum is an olfactory processing region that occupies approximately one‐third of the total brain area in pulmonate gastropod molluscs. It has many unusual features, including a development separate from the rest of the brain and the absence of axons belonging to its intrinsic neurons. We have investigated the input and output pathways of the procerebrum in the terrestrial snail Achatina fulica by using hexamminecobalt chloride as a selective label. Both the tentacle nerve and the cerebropedal connective nerve contribute to a fine neural plexus that is distributed throughout the neuropile region of the procerebrum. The fibers from the tentacle nerve are predominantly presynaptic, whereas those from the cerebropedal connective are predominantly postsynaptic. The postsynaptic fibers (dendrites) were traced to two groups of nerve cells (total number, 20–25) near the ventral surface of the ipsilateral pedal ganglion. No evidence was obtained for any other numerically significant output pathway from the procerebrum. Since locomotion is known to be controlled by the pedal ganglion, these results provide an anatomical substrate for the strong influence of olfaction on locomotor behavior in snails. The pathway is unusual in that the dendrites are interganglionic and can be as long as 5 mm.
Viscerotopic representation of the upper alimentary tract in the rat: Sensory ganglia and nuclei of the solitary and spinal trigeminal tracts
Authors: Altschuler Steven M. , Bao Xinman , Bieger Detlef , Hopkins David A. , Miselis Richard R.
Published: January 2005

The aim of this study was to map the viscerotopic representation of the upper alimentary tract in the sensory ganglia of the IXth and Xth cranial nerves and in the subnuclei of the solitary and spinal trigeminal tracts. Therefore, in 172 rats 0.5–65 μl of horseradish peroxidase (HRP), wheat germ agglutinin‐HRP, or cholera toxin‐HRP were injected into the trunks and major branches of the IXth and Xth cranial nerves as well as into the musculature and mucosa of different levels of the upper alimentary and respiratory tracts.

The results demonstrate that the sensory ganglia of the IXth and Xth nerves form a fused ganglionic mass with continuous bridges of cells connecting the proximal and distal portions of the ganglionic complex. Ganglionic perikarya were labeled in crude, overlapping topographical patterns after injections of tracers into nerves and different parts of the upper alimentary tract. After injections into the soft palate, pharynx, esophagus, and stomach, anterograde labeling was differentially distributed in distinct subnuclei in the nucleus of the tractus solitarius (NTS). Palatal and pharyngeal injections resulted primarily in labeling of the interstitial and intermediate subnuclei of the NTS and in the paratrigeminal islands (PTI) and spinal trigeminal complex. Esophageal and stomach wall injections resulted in labeling primarily of the subnucleus centralis and subnucleus gelatinosus, respectively.

The distribution of upper alimentary tract vagal‐glossopharyngeal afferents in the medulla oblongata has two primary groups of components, i.e., a viscertopic distribution in the NTS involved in ingestive and respiratory reflexes and a distribution coextensive with fluoride‐resistant acid‐phosphatase‐positive regions of the PTI and spinal trigeminal nucleus presumably involved in visceral reflexes mediated by nociceptive or chemosensitive C fibers.
Junction between parent and daughter axons in regenerating myelinated nerve: Properties of structure and rapid axonal transport
Authors: Chan H. , Smith R. S. , Snyder R. E.
Published: January 2005

The primary aim of this work was to investigate the properties of rapid axonal transport in regenerating myelinated axons in the sciatic nerve of Xenopus laevis, with particular attention to events at the junction between the proximal, intact axon (the “parent”) and the distal, newly formed axon (the “daughter”). Morphological studies indicated that all myelinated axons initiated regeneration and that at least 80% of these axons regenerated at a rate of 1 mm/day or greater (20°C). The ultrastructure of the junctional region was examined at regeneration times between 3 days and 20 weeks. The main qualitative change in the junctional axoplasm over this period was in its content of particulate organelles. At times up to 2 weeks regeneration, the junction contained abnormal numbers of 50 nm diameter vesicles and 10 nm granules. Between 2 and 5 weeks the junction showed in addition a peripheral rim of large membrane‐bounded organelles around a central core of microtubules and neurofilaments. At longer times the numbers of large membrane‐bounded organelles diminished and all junctions contained prominent accumulations of 10 nm granules. The rate of rapid axonal transport of protein was similar in parent and daughter axons. Compared to the parent axons, a 2–5 times greater amount of protein was deposited to a stationary phase in daughter axons. Specimens of nerve that were subjected to mechanical stress during the removal of the perineurium showed a large accumulation of rapidly transported protein in the region of the crush at regeneration times up to 40 days; some of the accumulated protein was subsequently transported retrogradely. Video microscopy of isolated axons supplied evidence that the transport deficit in mechanically stressed nerve was a partial block of anterograde vesicle transport, plus a reversal of anterograde transport, at the junction of parent with daughter axons. No structural changes were detected in mechanically stressed nerve. The results show that the junction between parent and daughter myelinated axons is a region with distinct morphology at which the dynamics of anterograde axonal transport may change dramatically.
Endocytosis and autophagy in dying neurons: An ultrastructural study in chick embryos
Authors: Hornung J. P. , Koppel H. , Clarke P. G. H.
Published: January 2005

In an effort to understand naturally occurring neuronal death in the developing isthmo‐optic nucleus, we have accentuated one of its most probably causes, failure to receive adequate trophic maintenance from the axonal terminal zone in the retina, and have studied the dying neurons ultrastructurally. Retrograde trophic maintenance was blocked by means of intraocularly injected colchicine, which caused all the isthmo‐optic neurons to die by just one of the two or more kinds of cell death that they undergo during normal development. The present paper deals with the very prominent cytoplasmic aspects of this kind of cell death, notably the uptake of exogenous horseradish peroxidase and autophagy. There were also nuclear changes, which are dealt with mainly in the accompanying paper (Clarke and Hornung, J. Comp. Neurol. 283: 438–449, '89).

Numerous cytoplasmic vacuoles occurred in both soma and dendrites, and they were of three main kinds, of which the smallest (less than 0.5 μm diameter) had unstructured contents, whereas the larger two (1–2 μm and 2–7 μm) were secondary lysosomes (mostly residual bodies).

Intravascularly injected horseradish peroxidase labeled all three kinds of vacuole but not the free cytoplasm, indicating that the uptake was by endocytosis rather than by leakage through holes in the membrane, as is confirmed by our failure to detect any such holes. We suspect that the smallest vacuoles are the primary endosomes, that these subsequently fuse with vacuoles of the intermediate kind, and that the largest vacuoles are formed by the fusion of these latter. The purpose of the endocytosis may be to channel the plasma membrane piecemeal into the lysosomes for destruction.
Changes in the nuclei of dying neurons as studied with thymidine autoradiography
Authors: Clarke P. G. H. , Hornung J. P.
Published: January 2005

Thymidine autoradiography has been used at light and electron microscopic levels to elucidate intracellular events during the death in chick embryos of isthmo‐optic neurons deprived of trophic maintenance from their axonal target organ, the retina. When the intense cytoplasmic vacuolization described in the accompanying paper (Hornung, Koppel, and Clarke, J. Comp. Neurol. 283: 425–437, '89) was beginning, the nuclei also underwent profound changes. They became more electron dense and shrank; their membranes became more sharply defined and convoluted; they sometimes contained pyknotic balls, but apparently only in the early stages of cell death; all lost more than half of their content of DNA, some of which was transferred to the largest kind of cytoplasmic vacuole. This transfer may have involved the budding off of nuclear regions containing pyknotic balls. The cells continued to survive for a day or 2 after these severe losses of nuclear DNA, sustaining intense endocytic activity. Pronounced unscheduled DNA synthesis occurred in the nuclei, but this was insufficient to replace the lost DNA.