bluuebunny/crossref_metadata_2025 huggingface dataset:
Embryonic development of the chick primary trigeminal sensory‐motor complex
Authors: Covell David A. , Noden Drew M.
Published: January 2005

The objective of this study is to define the development of all components in the chick embryonic trigeminal primary sensory‐motor complex, from their first appearance through the formation of central and peripheral axonal projections up to stage 34 (8 days of incubation). This was accomplished by two labeling procedures: application of the monoclonal antibody HNK‐1, which binds to the precursors of all these components except the placode‐derived neurons, and application of HRP to axons cut immediately distal to the trigeminal ganglion.

Single immunopositive motor neuron precursors are present at stage 12. These accumulate in the transient medial motor column, whose neurons initiate axon outgrowth by stage 13–14, concomitant with the onset of translocation of their somata to form the definitive trigeminal lateral motor column (LMC). Intiially these translocating somata accumulate on the medial margin of the LMC. Beginning on incubation day 5, axons growing from newly formed motor neurons pass beside the lateral margin of the LMC, and the nuclei of these cells subsequently follow this pathway. These events follow a rostral‐to‐caudal sequence, and this phase of motor nucleus formation is complete by day 8. The lateral translocation of some caudally located nuclei is arrested beginning on day 5. This cessation, which proceeds rostrally, demarcates neurons that form the dorsal motor nucleus of the trigeminal complex.

Sensory neurite formation is intiated in ophthalmic placode‐derived cells at stage 14.5, one stage later by maxillomandibular neurons, and from mesencephalic V cells at stage 15. Neural crest cells do not initiate axon formation until at least day 4 to 5. Following application of HRP distal to the condensing ganglion at stage 16, labeled ophthalmic nerve projections appear in contact with the wall of the hindbrain centrally and overlying the optic vesicle peripherally. Fibers forming the descending tract elongate rapidly, reaching the level of the VIIth nerve root (200 m̈m caudal to the trigeminal root) by stage 18 and the cervical cord by stage 22. Labeled terminal arborizations of descending trigeminal afferents are first visible at stage 22 and are evident along the entire descending and proximal ascending tracts by stage 27. Later‐developing descending axons grow in close association with existing trigeminal fibers, though a few growth cones are consistently evident superficial to the other fibers. No projections different from those reported in adult birds are seen, nor are there any contralateral afferent projections.

Peripheral axons from neurons in the mesencephalic trigeminal nucleus emerge from the trigeminal ganglion beginning at stage 21. These cells are labeled only when tracer is applied to the mandibular nerve.
Effect of fetal infraorbital nerve transection upon trigeminal primary afferent projections in the rat
Authors: Rhoades Robert W. , Chiaia Nicolas L. , MacDonald Gordon J. , Jacquin Mark F.
Published: January 2005

Transganglionic tracing with a combination of horseradish peroxidase (HRP) and wheat germ agglutinin–conjugated HRP (WGA‐HRP) was employed to compare the trigeminal (V) innervation of the brainstem in adult rats that sustained transection of the infraorbital nerve (ION) on either the day of birth or just prior to the beginning of the 17th embryonic day (E‐17). The same methods were also employed to assess the effects of such lesions upon the innervation of the brainstem by the lingual, inferior alveolar, mylohyoid, and auriculotemporal V branches. Previous experiments (Chiaia et al.: Dev. Brain Res. 36:75–88, '87) showed that application of HRPand WGA‐HRP to the ION in normal adult rats (N = 3) labelled 12,553 ± 1,455 (mean ± s.d.) V ganglion cells while application of these tracers to the regenerated ION after neonatal transection (N –9) labelled 5,001 ± 1,287 ganglion cells. Application of HRP and WGA‐HRP to the regenerated ION in adulthood (N = 6) after fetal transection labelled 5,476 ± 3,056 ganglion cells. Thus, the numbers of ganglion cells giving rise to the regenerated ION after fetal and neonatal transection were equivalent (P >.05).

The central projections of the ION after fetal transection were qualitatively different from those observed after neonatal injury. After neonatal transection, the central terminal field of regenerated ION fibers in adulthood is almost completely restricted to layers I and II of subnucleus caudalis (SpC; Jacquin and Rhoades: Brain Res. 269:137–144, '83; Chiaia et al.: Dev. Brain Res. 36:75–88, '87). After fetal transection, regenerated ION axons terminate heavily in all portions of the V brainstem complex.

After neonatal ION transection, we (Jacquin and Rhoades: J. Comp. Neurol. 235:129–143, '85) have been unable to detect central sprouting of undamaged V mandibular axons by means of transganglionic tracing with HRP and WGA‐HRP. Such sprouting was evident in both V subnucleus interpolaris (SpI) and SpC after fetal ION transection.

We carried out one additional experiment to determine whether ION ganglion cells that survived fetal axotomy were more resistant to axonal damage than the population of neurons that normally contribute to this nerve on theday of birth. Rats (N = 9) sustained transection of the ION on E‐17 and again on the day of birth. The regenerated ION was then labelled with HRP and WGA‐HRP when the animals reached adulthood. Anaverage of 1,798 ± 1,050 ganglion cells were labelled in these rats and the transganglionic labelling was restricted to layers I and II of SpC. Thus, V ganglion cells that sustain axotomy on E‐17 respond to damage on the day of birth in the same manneras primary afferent neurons that have not been subjected to previous injury.
Anatomical study of the connections of the primary auditory area in the rat
Authors: Roger Michel , Arnault Patricia
Published: January 2005

The aim of the present study was to identify in the rat the overall input‐output pattern of connections of the primary auditory field, with special attention to the topographical organization of the geniculocortical auditory projection. By using cytoarchitectural criteria, three temporal cortical fields were distinguished in the rat: Te1, Te2, and Te3. The primary auditory field Te1 is characterized by a relatively specific differentiation of its layers when compared with other temporal fields. The afferent and efferent connections of Te1 were identified by using the retrograde and anterograde transport of wheat germ agglutinin conjugated with horseradish peroxidase (WGA‐HRP).

The results indicate that Te1 is connected by a dense and reciprocal system of fibers with the auditory thalamus. Based on the nomenclature of Morest ('64) in the cat, five cytoarchitectural subdivisions of the medial geniculate complex (MG) were identified in the rat: ventral (MGv), dorsal (MGd), medial (MGm), suprageniculate (Sg), and peripeduncular (PPA). The major rostrocaudal extent of the MGv is connected to Te1. The surrounding cortical fields Te2 and Te3 do not receive a projection from the MGv, except from its most caudal pole. The MGv projection is topographically organized. When the deposit area of the tracer is shifted from dorsal to ventral upon Te1, the corresponding labeled zone within the MGv moves from rostral to caudal, whereas a cortical displacement of the deposit area of the tracer from rostrodorsal to caudoventral leads to a medial to lateral shift of the labeled zone in the MGv. In addition, more dorsal parts of the MGv project on more dorsal sectors of Te1.

Te1 receives a sparser, topographically organized projection from the deep dorsal subdivision of the MGd. The MGm and the lateral part of the posterior group of thalamic nuclei (Pol) also distribute fibers to the primary auditory field.

Te1 is reciprocally connected by a system of callosal fibers with the contralateral homotypic cortex. Finally, Te1 sends fibers to the dorsal and, to a lesser extent, external cortices of the inferior colliculus, caudomedial caudateputamen complex, and caudoventral thalamic reticular nucleus.
Localization of immunoreactive alpha‐bag‐cell peptide in the central nervous system of Aplysia
Authors: Painter Sherry D. , Kalman Vivian K. , Nagle Gregg T. , Blankenship James E.
Published: January 2005

The bag cells of the marine mollusc Aplysia are well‐characterized neuroendocrine cells that initiate egg laying, but the natural stimulus triggering bag‐cell activity has not been determined. As a first step toward identifying central neurons that might provide synaptic or neurohormonal input onto the bag‐cell network, antibodies specific for alpha‐bag‐cell peptide (α‐BCP) were generated. This peptide belongs to a small family of structurally related peptides that can elicit bag‐cell activity in vitro. Antibody specificity was established by immunodot assay and preabsorption studies: immunocytochemical labeling was abolished in each ganglion when the antibodies were preincubated with either α‐BCP‐thyroglobulin conjugate or α‐BCP‐(1–8) but was not affected by preincubation with thyroglobulin or thyroglobulin‐thyroglobulin conjugate. The antibodies specifically labeled the bag cells in the abdominal ganglion and ectopic bag cells in both the abdominal and right pleural ganglia. The ectopic bag cells were similar to conventional bag cells in size and morphology, but varied in number and location among preparations. In the cerebral ganglion, the antibodies labeled a bilaterally symmetrical pair of cell clusters, containing approximately ten cells each, on the dorsal surface of the ganglion. The cerebral cells were smaller than bag cells, were constant in location, and sent their processes into the neuropil rather than the connective tissue sheath. Immunoreactive processes were observed in the neuropils of the cerebral, pleural, and pedal ganglia and among the axons of the cerebropedal, cerebropleural, and pleurovisceral connectives. No immunoreactive cell bodies were observed in the buccal or pedal ganglia. Identical patterns of labeling were observed in Aplysia californica, A. Brasiliana, and A. Dactylomela. The distribution of immunoreactive cell bodies within the circumesophageal ganglia of all three species thus parallels the distribution of receptive sites for the in vitro induction of bag‐cell activity by atrial gland peptide B, a peptide structurally related to α‐BCP. These observations suggest that the immunoreactive cells identified in these studies, or a subset of them, may be involved in the physiological induction of bag‐cell activity. Since low doses of α‐BCP have additional inhibitory actions on the bag cells, however, it is possible that the identified cells could play a more complex role in the regulation of bag‐cell activity.
Ontogeny of cholinergic neurons in the mouse forebrain
Authors: Schambra U. B. , Sulik K. K. , Petrusz P. , Lauder J. M.
Published: January 2005

The development of cholinergic neurons in the mouse forebrain was studied by immunocytochemistry with a monoclonal antibody to choline acetyl‐transferase (ChAT), the rate‐limiting enzyme for acetylcholine synthesis. Since this antibody stained dividing cells in ventricular germinal zones as well as differentiating neurons, likely routes of migration could be inferred on the basis of the location of immunoreactive (IR) cells at different gestational ages. Germinal zones for cholinergic cells were observed in all ventricular zones of the forebrain with the ventral zones generating the earliest cells by gestational day 13.5 (GD13.5). On GD14, ChAT IR cells were visible in the germinal zones of the eye, olfactory ventricle, anterior horn, and dorsolateral aspect of the lateral ventricle, lateral ganglionic eminence, ventro‐ and dorsolateral third ventricle, and in the pineal anlage (epiphysis). ChAT IR neurons continued to develop in these and additional germinal zones on GD15, including the medial, dorsal, and dorsomedial walls of the lateral ventricle, and the medial and dorsal ganglionic eminence. On GD16, ChAT IR neurons were located in the prelimbic, pyriform, and parietal cortices and the lamina terminalis, and a cluster of IR cells was observed in the ventricular zone of the caudatopallial angle. On GD17–18, neurons in the anterior olfactory nucleus, olfactory tubercle, horizontal and vertical nucleus of the diagonal band, and medial septal nucleus stained more darkly and were multipolar, whereas immature bipolar neurons appeared to continue their migration into the hippocampus and along major fiber tracts, such as the corpus callosum, external capsule, fornix and anterior commissure.

This study provides a comprehensive view of the zones of origin, probable routes of migration, and final destination of cholinergic neurons in the mouse forebrain.
Prodynorphin peptide distribution in the forebrain of the syrian hamster and rat: A comparative study with antisera against dynorphin A, dynorphin B, and the C‐terminus of the prodynorphin precursor molecule
Authors: Neal Charles Richard , Newman Sarah Winans
Published: January 2005

The neuroanatomical distribution of the prodynorphin precursor molecule in the forebrain of the male Syrian hamster (Mesocricetus auratus) has been studied with a novel antiserum directed against the C‐terminus of the leumorphin [dynorphin B (1–29)] peptide product. C‐peptide staining in sections from colchicine‐treated hamsters is compared to staining in sections from untreated animals. In addition, the pattern of C‐peptide immunostaining in hamster brain is compared to that in the rat brain. Finally, the C‐peptide immunolabeling patterns in hamsters and rats are compared to those obtained with antisera to dynorphin A (1–17) and dynorphin B (1–13).

Areas of heaviest prodynorphin immunoreactivity in the hamster include the hippocampal formation, lateral septum, bed nucleus of the stria terminalis, medial preoptic area, medial and central amygdaloid nuclei, ventral pallidum, substantia nigra, and numerous hypothalamic nuclei. Although this C‐peptide staining pattern is similar to dynorphin staining reported previously in the rat, several species differences are apparent. Whereas moderate dentate gyrus granule cell staining and no CA4 cell staining have been reported in the rat hippocampal formation, intense immunostaining in the dentate gyrus and CA4 cell labeling are observed in the hamster. In addition, the medial preoptic area, bed nucleus of the stria terminalis, and medial nucleus of the amygdala stain lightly for prodynorphin‐containing fibers and cells in the rat, compared to heavy cell and fiber staining in the hamster in all three of these regions.

In the rat there is no differential staining between tissues processed with the C‐peptide, dynorphin A, and dynorphin B antisera, but numerous areas of the hamster brain show striking differences. In most hamster brain areas containing prodynorphin peptides, the C‐peptide antiserum immunolabels more cells and fibers than the dynorphin B antiserum, which in turn labels more cells and fibers than dynorphin A antiserum. However, exceptions to this hierarchy of staining intensity are found in the lateral hypothalamus, substantia nigra, arcuate nucleus, and habenula. The differences in staining patterns between rat and hamster are greatest when C‐peptide antiserum is used; apparent species differences are present, though less pronounced, in dynorphin B– and dynorphin A–immunostained material.
Reorganization of visual pathways following posthatching removal of one retina in pigeons
Authors: Bagnoli P. , Casini G. , Fontanesi G. , Sebastiani L.
Published: January 2005

Organization of visual pathways was studied in 2‐month‐old pigeons that underwent unilateral retinal removal on either the day of hatching (ERA, i.e., early retinal ablated) or the 9th day after hatching (LRA, i.e., late retinal ablated).

A general size reduction of visual areas contralateral to the removed retina was found in ERA pigeons, which additionally showed an altered differentiation of thalamic visual targets as well as a different cytoarchitectonic arrangement of the superficial layers of the optic tectum. No comparable modification were found in LRA pigeons.

The retinal projections of the remaining eye were studied following intraocular injections of 3H‐proline. Both in ERA and LRA pigeons, the distribution of retinofugal afferents to primary visual regions contralateral to the injected eye was similar to that of control pigeons. Anomalous ipsilateral projections from the remaining retina to primary retinorecipient regions were found in ERA pigeons only.

Effects of early ablation of one retina on second‐order visual connections were also studied. Following injections of wheat germ agglutinin‐conjugated horseradish peroxidase (WGA‐HRP) into the visual Wulst contralateral to the operated eye, a smaller number of ipsilateral projecting thalamo‐Wulst neurons was found as compared with control pigeons. In contrast, the contralateral thalamo‐Wulst projections were increased. No changes in thalamo‐Wulst projections were found following tracer injections into the opposite Wulst, i.e., ipsilateral to the operated eye.

The present study demonstrates a substantial anatomical reorganization of both primary and secondary visual pathways following unilateral retinal removal immediately after hatching, when maturation of the visual system is not yet completed.
Evidence for the stability of positional markers in the goldfish tectum
Authors: Busse Ursula , Stuermer Claudia A. O.
Published: January 2005

Positional markers in the tectum, which are thought to guide growing axons to their target sites, have been proposed to be induced by axons, to be only transiently associated with the tectal cells, and then lost after long‐term denervation periods (Schmidt: J. Comp. Neurol. 177: 279–300, '78). To further investigate this concept, retinal axons were induced to regenerate into ipsilateral tecta which had been deprived of their retinal afferents for shorter (0–4 months) and longer periods (4–8 months). The paths of HRP‐labeled regenerating axons of known retinal origin were traced and used as an operational test to decide whether the axons might navigate under the influence of positional markers. Two different kinds of experiments were performed:

The axons from a subpopulation of all ganglion cells in the retina were labeled by applying a small crystal of HRP at defined retinal regions. Independent of the denervation period of the tectum, the labeled regenerating axons traveled in abnormal but nonrandom routes. In early regeneration stages, axons exhibited signs of exploratory growth. They extended branches equipped with growth cones and filopodia into various regions of the tectum. In late regeneration stages, the axons lost these branches, exhibited U‐turns and bends, and ended in terminal arbors in the retinotopic target region. These findings suggest that the axons travel under the influence of tectal positional markers and that these markers are not transient.

Axons from a surgically created temporal hemiretina were labeled by application of HRP to the optic nerve to test whether the temporal axons might expand into the caudal tectum in long‐term‐denervated tecta. The HRP‐labeled axons coursed over rostral and midtectal regions. Instead of invading the caudal tectum they bent and terminated in the rostral tectal half. These results add further support for the conclusion that the path of regenerating retinal axons is governed by long‐lasting positional markers.
Localization of L‐glutamic acid decarboxylase mRNA in monkey and human retina by in situ hybridization
Authors: Sarthy P. Vijay , Fu Marlene
Published: January 2005

Immunocytochemical studies with γ‐aminobutyric acid (GABA) antibodies and glutamic acid decarboxylase antibodies have shown that the primate retina contains GABAergic amacrine, interplexiform, and displaced amacrine cells. In addition, subpopulations of photoreceptors and horizontal cells have also been suggested to be GABAergic in this retina. In the present study, we have used in situ hybridization to localize GABAergic neurons in human and monkey retinas. In situ hybridizations were carried out with 35S‐labeled DNA and RNA probes derived from human and cat glutamic acid decarboxylase cDNA clones. In the monkey retina, labeled cells were present in the inner nuclear and ganglion cells layers. The outer nuclear layer or the inner segment layer had only background levels of labeling. In the inner nuclear layer, all labeled somata were located in the vitread‐half bordering the inner nuclear layer/inner plexiform layer boundary. These cells constituted ∼83% of all labeled cells. Labeled cells were also seen in the ganglion cell layer.

In the human retina, labeled somata were observed only in the inner nuclear and the ganglion cell layers. In the inner nuclear layer, the majority of labeled cells were located close to the inner nuclear layer/inner plexiform layer boundary although a minor population of labeled somata (∼20%) were found deeper in the inner nuclear layer. The distribution of glutamic acid decarboxylase mRNA–containing cells we observed is in good agreement with the known location of GABAergic neurons. We, however, did not find glutamic acid decarboxylase mRNA in either horizontal cells or photoreceptors in monkey and human retina.
Cell death in the inner and outer nuclear layers of the developing retina in the wallaby setonix brachyurus (quokka)
Authors: Harman A. M. , Snell L. L. , Beazley L. D.
Published: January 2005

We have examined the number and distribution of dying cells in the developing inner (INL) and outer (ONL) nuclear layers of sectioned quokka retinae (N = 31) from embryonic day (E)24 to postnatal day (P)192.

Before birth, dying cells were seen in the optic fissure. Thereafter two major phases of cell death took place in the INL. The first phase was more pronounced within the vitread part with peak numbers of dying cells at P50. By contrast, during the second phase, cell death was more extensive in the sclerad portion; peak numbers of dying cells were recorded at P85 and P100 for the vitread and sclerad parts respectively. At these stages, photoreceptors were seen in the INL suggesting that these ectopic cells contribute to the pool of dying cells. The pattern of cell death broadly followed a central to peripheral sequence in the first phase but, in the second, was seen initially in midtemporal retina and then became panretinal. Dying cells were seen in the ONL but in smaller numbers than in the INL. There was a peak of cell death at P26 which may represent death of mitotic cells at the ventricular surface.

In the quokka, retinal cell genesis takes place in two phases (Harman and Beazley: Neuroscience 28:219–232, ′89). The two major phases of cell death described here peak approximately 40 days after episodes of maximal cell genesis. These findings, together with data for the mouse, suggest that a biphasic pattern of cell genesis and cell death may be a feature of eutherian as well as marsupial retinal development.
Topological link‐vertex analysis of the growth of purkinje cell dendritic trees in normal, reeler, and weaver mice
Authors: Sadler M. , Berry M.
Published: January 2005

The growth of Purkinje cell dendritic trees in normal, reeler, and weaver mice has been defined by using Link‐Vertex Analysis. Growth probably occurs in three phases in normal and cortically located reeler trees. Phase I, completed by 7 days postnatum (dpn), establishes a rudimentary tree of 100 segments by random terminal branching. Phase II lasts from 7 to 20 dpn when some 690 and 450 segments are generated in normal and cortical reeler trees respectively. Phase II is initiated by an inductive stimulus mediated by a finite number of parallel fibres. Thereafter, dendritic trees develop a similar topology in normal and cortical reeler Purkinje cells through random interactions between parallel fibres and dendritic growth cones. We have defined this process with the aid of computer simulation techniques. Interactions appear to be restricted to a narrow growth front occupied by the highest centrifugally ordered terminals behind which adhesions occur at a greatly reduced frequency. The cortical reeler tree thus has fewer segments than normal because fewer parallel fibres are available, but it is surprisingly normal in most other respects. Phase III is a period of remodelling and extends from 20 dpn into adulthood when high‐ordered terminals are eroded and middle‐ordered terminals are added, with no change in total segment number in both normal and cortical reeler trees.

Weaver and deeply placed reeler Purkinje cell dendritic trees are not influenced by parallel fibres. Accordingly, their growth is arrested at the end of Phase I, when both types of mutant tree have generated 100 segments by unrestrained random terminal branching. In the absence of parallel fibres, Phase II is not induced and remodelling, characteristic of Phase III, does not occur.
Frog sympathetic ganglion cells have local axon collaterals
Authors: Forehand Cynthia J. , Konopka Lukasz M.
Published: January 2005

Amphibian autonomic ganglia have been used as simple models for studies involving the physiology of synaptic transmission. These models assume an anatomical simplicity where the ganglion is a simple relay for central nervous system output to peripheral autonomic targets. Cholinergic preganglionic fibers innervate the soma and proximal axon of the unipolar ganglion cells, which were thought to relay the information to the periphery with little ganglionic processing. However, several different types of synaptic potentials occur in response to preganglionic stimulation. Also, a variety of neuropeptides are found in both preganglionic fibers and ganglion cells; at least one of the peptides found in preganglionic fibers is known to act as a neurotransmitter in the ganglion. Finally, there may be communication between ganglion cells.

In the present study, we have explored the morphology of lumbar sympathetic chain ganglion cells by intracellular injection with horseradish peroxidase to determine whether an anatomical substrate exists for processing information within these ganglia. We have shown that 39% of these cells have axons that branch within the ganglion. While both major classes of ganglion cells (B cells and C cells) had intraganglionic axon collaterals, there was a marked difference in the frequency: 65% of the C cell axons had collaterals while only 19% of the B cell axons collateralized within the ganglion. Ultrastructural examination of labeled axon collaterals indicated that these collaterals receive synaptic input; whether the collaterals also make synapses has not been definitively established.
Arborisation pattern and postsynaptic targets of physiologically identified thalamocortical afferents in striate cortex of the macaque monkey
Authors: Freund T. F. , Martin K. A. C. , Soltesz I. , Somogyi P. , Whitteridge D.
Published: January 2005

The monosynaptic targets of different functional types of geniculocortical axons were compared in the primary visual cortex of monkeys. Single thalamocortical axons were recorded extracellularly in the white matter by using horseradish‐peroxidase‐filled pipettes. Their receptive fields were mapped and classified as corresponding to those of parvi‐ or magnocellular neurons in the lateral geniculate nucleus. The axons were then impaled and injected intraaxonally with horseradish peroxidase. Two magnocellular (MA) and two parvicellular (PA) axons were successfully recovered and reconstructed in three dimensions. The two MA axons arborised mainly in layer 4Cβ, as did the two PA axons in layer 4Cβ. Few collaterals formed varicosities in layer 6. Both MA axons had two large, elongated clumps of bouton (approx. 300–500 × 600–1,200 μm each) and a small clump. One PA axon had two clumps (each with a core appr. 200 μm in diameter); the other had only one (appr. 150–200 μm in diameter). The PA axon with two clumps had 1,520 boutons; the other PA axon had 1,380; one MA axon had 3,200 boutons; and those of the more extensive MA axon were not counted. The distribution of postsynaptic targets as well as the number of synapses per bouton has been established for a sample of 150 PA boutons and 173 MA boutons from serial ultrathin sections. The MA axons made on average 2.1 synapses per bouton compared to 1.79 for one PA axon and 2.6 for the other. The sample of boutons taken from the two physiological types of axons contacted similar proportions of dendritic spines (52–68%), shafts (33–47%), and somata (0–3%). The postsynaptic elements were further characterized by immunostaining for GABA. All postsynaptic perikarya and some of the dendrites (4.5–9.5% of all targets) were positive for the amino acid. Near the thalamic synapse GABA‐negative dendritic shafts frequently contained lamellar bodies, an organelle identical in structure to spine apparatus. Dendritic shafts and spines postsynaptic to the thalamocortical boutons frequently received an adjacent synapse from GABA‐immunoreactive boutons.

The similarity between the magno‐ and parvicellular axons in their targeting of postsynaptic elements, including the GABAergic neurons, suggests that the structural basis of the physiological differences between 4Cα and 4Cβ neurons should be sought in other aspects of the circuitry of layer 4C, such as local cortical circuits, or in the far greater horizontal extent of the thalamocortical and GABAergic axons in layer 4Cα compared to those in the β subdivision.
Intracellularly labeled stapedius‐motoneuron cell bodies in the cat are spatially organized according to their physiologic responses
Authors: Vacher Sylvette R. , Guinan John J. , Kobler James B.
Published: January 2005

This study examines whether the locations of stapedius‐motoneuron cell bodies are correlated with their responses to sound. Single‐unit recordings and injections of horseradish peroxidase were made in axons of stapedius motoneurons in the fascicles which run from the facial nerve to the stapedius muscle in the cat. Single units were characterized physiologically by their responses to ipsilateral, contralateral, and binaural sounds. Labeled cell bodies (N = 28) were found in all of the brainstem regions previously identified as containing stapedius motoneurons. Motoneurons characterized as having similar response properties had cell bodies in relatively circumscribed locations. Most (eight of 12) motoneurons excited by sound in either ear had cell bodies in a narrow band around the facial nucleus. Most (seven of eight) motoneurons excited by ipsilateral but not contralateral sound had cell bodies in the cleft between the superior olivary complex and the facial nucleus. All four motoneurons excited by contralateral but not ipsilateral sound had cell bodies located ventromedial to the facial nucleus. The three motoneurons excited only by binaural sound had cell bodies located dorsal to the superior olivary complex. (Two of these were also in the cleft between the superior olivary complex and the facial nucleus.) The cell body of the one motoneuron showing activity in the absence of sound stimulation was located dorsolateral to the facial nucleus. These results show that the cell bodies of stapedius motoneurons with similar electrophysiologic properties tend to have similar locations in the brainstem. The results are consistent with the idea that the stapediusmotoneuron pool is divided into subgroups that are spatially segregated in terms of their patterns of input from the two ears.
Afferent connections of the valvula cerebelli in two teleosts, the common goldfish and the green sunfish
Authors: Wullimann Mario F. , Glenn Northcutt R.
Published: January 2005

The afferent connections of the valvula cerebelli were examined in one cypriniform teleost (Carassius auratus) and one perciform teleost (Lepomis cyanellus) with the use of horseradish peroxidase as a retrograde tracer. Both species have ipsilateral input to the valvula from the central pretectal and dorsal accessory optic nuclei, the dorsal and ventral tegmental nuclei, the lateral nucleus of the valvula, the perilemniscal nucleus, and nucleus isthmi and contralateral input from the inferior olivary nucleus. In addition, Carassius has ipsilateral valvulopetal projections from the eminentia granularis, the praeeminential nucleus, and the isthmic primary sensory trigeminal nucleus, whereas Lepomis has bilateral (stronger ipsilaterally) valvulopetal projections from the nucleus of the locus coeruleus and the rostral corpus cerebelli.

The topographical order of the cerebellopetal projections of the lateral nucleus of the valvula and inferior olive is also described, as are differential inputs to various subdivisions of the cerebellum in the two species.

Information on valvulopetal projections in teleosts has thus far been limited to electroreceptive mormyrids. The present study shows that many valvular inputs related to electroreception in mormyrids have no homologue in Carassius and Lepomis.

Finally, the present study indicates that the rostral part of the corpus cerebelli, but not the valvula cerebelli, in teleosts is the homologue of the anterior lobe of the corpus cerebelli in cartilaginous fishes. Thus, the valvula cerebelli is a shared derived feature (synapomorphy) of all ray‐finned fishes.
Immunocytochemical reactivity of Xenopus laevis retinal rods and cones with several monoclonal antibodies to visual pigments
Authors: Röhlich Pál , Szél ÁGoston , Papermaster David S.
Published: January 2005

Immunocytochemical reactions with several antibodies to visual pigments were used to study visual cells of the Xenopus laevis retina. Monoclonal antibodies to bovine opsin „E,”︁ 1D4, and 4B4 (reactive with the N‐ and C‐terminus and with the loop connecting transmembrane segments 5–6, respectively) and to chicken visual pigments COS‐1 and OS‐2 (binding to mammalian red/green and blue cones, respectively), as well as a rabbit antifrog opsin serum 11–7, were applied to semithin and thin sections of the retina. The bound antibodies were detected with the peroxidase technique at the light microscopic level; a three‐stage immunogold procedure was used for electron microscopic immunocytochemistry.

The overwhelming majority of rods were labeled by monoclonal antibodies „E,”︁ 4B4, 1D4, OS‐2, and serum 11–7. A small fraction (2–3%) of rods did not bind monoclonal antibodies „E”︁ and 4B4, but this minor population of rods was strongly reactive with 1D4 and to a lesser extent with OS‐2, indicating the presence of different visual pigment. These rods differ in shape from the major rod type; they are thinner, shorter, and may be comparable to the blue‐sensitive („green”︁) rods of other amphibia. Cones were morphologically heterogeneous: double cones, large single cones, and small single cones were found, and the large single and the double cones were occasionally duplicated. Double cones and large single cones (as well as their duplicated varieties) strongly bound monoclonal antibodies COS‐1 and were unlabeled by all other monoclonal antibodies, except OS‐2. The small single cone was remarkably unreactive with COS‐1 and „E,”︁ weakly labeled by 1D4 and 4B4, and most reactive with OS‐2 and 11–7. This unique pattern of immunocytochemical reactions in the small cone type indicates the uniqueness of its visual pigment from other cone types in the Xenopus retina. The present study shows the existence of two different opsins in morphologically distinct (thick and thin) rod types and at least two cone pigments in the heterogeneous cone population.
Connections and frequency representation in the auditory brainstem of the mustache bat, Pteronotus parnellii
Authors: Zook John M. , Leake Patricia A.
Published: January 2005

The goals of this study were to describe the cochlear frequency map of the mustache bat, Pteronotus parnellii, and to relate the organization of cochlear primary afferents to that of the second‐order projections from the cochlear nucleus to the superior olivary complex. Small deposits of horseradish peroxidase (HRP) were placed in the cochlear nucleus at sites that were physiologically characterized with respect to unit‐best frequency. From the deposits, labeled fibers were traced in the retrograde direction to the cochlea and in the anterograde direction to the superior olive.

Cochleas from both experimental and control animals were examined with light and electron microscopy. The peripheral axons of spiral ganglion neurons were counted in order to quantify the unusual variation in the innervation density along the cochlear spiral of the mustache bat. Regions of increased innervation density were found at the beginning and end of the basal turn of the cochlea. The highest cochlear innervation density consistently occurred in the upper basal turn. In horseradish peroxidase tracing experiments, this region contained labeled fibers only when HRP deposits were made at sites within the cochlear nucleus with unit‐best frequencies around 60 kHz. These findings support the suggestion (Kössl and Vater, '85) that the cochlear sites of increased innervation density are related to the neural and behavioral emphasis that this echolocating bat places upon the analysis of the 60 kHz frequency band.

The general arrangement of tonotopic maps within the cochlea, cochlear nucleus, and superior olive was consistent with previous observations in this bat and other mammalian species. At all three levels, there was evidence of a disproportionately large representation of frequencies around 60 kHz, similar to the enlarged representation reported within the inferior colliculus and auditory cortex of the mustache bat. In all cases there was a consistent relation between the size of the HRP deposit and the number and distribution of retrogradely labeled neurons in the cochlea. For most cases there was a similar relation between the size of the deposit and the terminal arborization field of anterogradely labeled fibers in the superior olive. However, in cases with deposits associated with the 60 kHz frequency band, the size of the labeled arborization field was more than twice as large as expected from the size of the deposits and from the extent of labeling in the cochlea. These cases suggest that the representation of frequencies around 60 kHz, already overrepresented in both the cochlea and cochlear nucleus, may be further expanded at the level of the superior olivary complex.
Intrinsic circuitry: Synapses involving the local axon collaterals of corticocortical projection neurons in the mouse primary somatosensory cortex
Authors: Elhanany Edith , White Edward L.
Published: January 2005

Pyramidal neurons in the mouse SmI cortex were labeled by the retrograde transport of horseradish peroxidase (HRP) injected into the ipsilateral MsI cortex. Terminals of the local axon collaterals of these neurons (CC terminals) were identified in SmI, and their distribution and synaptic connectivity were examined. To avoid confusion, terminals in SmI cortex labeled by the anterograde transport of HRP injected into MsI were eliminated by lesioninduced degeneration. Lesions of MsI were made 24 hours after the injection of HRP; postlesion survival time was 4 days.

Most CC axon terminals occurred in layers III and V where they formed asymmetrical synapses. Of 139 CC synapses in layer III and 104 in layer V, approximately 13% were formed with dendritic shafts. Reconstruction of 19 of these dendrites from serial thin sections showed them to originate from both spiny and nonspiny neurons. Most synapses of CC terminals (about 87%) were onto dendritic spines. In contrast, White and Keller (1987) demonstrated that terminals belonging to the local axon collaterals of corticothalamic (CT) projection cells synapse mainly with dendritic shafts of nonspiny neurons: 92% onto shafts, the remainder onto spines. The distribution of asymmetical synapses onto spines and dendritic shafts was analyzed for neuropil in layers III, IV, and V. Depending on the layer, from 34 to 46% of the asymmetrical synapses in the neuropil were onto dendritic shafts. Results showing that CC and CT terminals form proportions of axodendritic vs. axospinous synapses that differ from each other, and from the neuropil indicate that local axon collaterals are highly selective with regard to their postsynaptic elements.
Postnatal development of preproenkephalin mRNA containing neurons in the rat lower brainstem
Authors: Morita Yasuhiro , Zhang Jian‐Hua , Hironaka Takashi , Tateno Emiko , Noguchi Koichi , Sato Makoto , Kiyama Hiroshi , Tohyama Masaya
Published: January 2005

Postnatal developmental changes of preproenkephalin (PPE) gene expression in rat brainstem neurons were studied by in situ hybridization histochemistry. On the basis of PPE mRNA expression, brainstem neurons were categorized into three types: 1 type I neurons were characterized by constant or increasing expression of PPE mRNA during postnatal development; 2 type II neurons started to express PPE mRNA several days after birth and continued to do so thereafter; and (3) type III neurons showed transient expression of PPE mRNA or stopped expressing the mRNA during early postnatal development.

Type I PPE neurons were observed in diverse brainstem structures including the mesencephalic and pontine central gray matter, various reticular and raphe nuclei, the ventral tegmental area of Tsai, the interpeduncular nucleus, the nucleus of the brachium of the inferior colliculus, the ventral and dorsal tegmental nuclei of Gudden, the sphenoid nucleus, the laterodorsal tegmental nucleus, Barringtons nucleus, the parabrachial region, the lateral lemniscus and its related nuclei, the trapezoid nucleus, the rostral and ventromedial periolivary nuclei, the mesencephalic trigeminal and principal sensory trigeminal nuclei, the locus coeruleus, the subcoeruleus nucleus, the medial and spinal vestibular nuclei, the dorsal and ventral cochlear nuclei, the medial and lateral cerebellar nuclei, the Roller nucleus, and the intermedius nucleus of the medulla. Type II PPE neurons were found in the superior colliculus, the inferior colliculus, the central part of the dorsal tegmental nucleus, and as Golgi neurons in the granular layer of the cerebellum. Type III PPE neurons were located in the substantia nigra, the red nucleus, the superior olive, the motor trigeminal nucleus, the facial nucleus, the inferior olive, the dorsal motor nucleus of the vagus, and the hypoglossal nucleus.

Such region‐specific expression of the PPE gene during postnatal ontogeny suggests that rat brainstem PPE neurons may be involved in a variety of developmental events, such as cell proliferation, differentiation, and migration.
Developmental changes in the distribution of retinal catecholaminergic neurones in hamsters and gerbils
Authors: Mitrofanis John , Finlay Barbara L.
Published: January 2005

Although Syrian hamsters and Mongolian gerbils are closely related, they have quite different patterns of retinal ganglion cell distribution and different patterns of retinal growth that produce their distributions. We have examined the morphology and distribution of catecholaminergic (CA) neurones in adult and developing retinae of these species in order to gain a more general understanding of the mechanisms producing cellular topographies in the retina. CA neurones were identified with an antibody to tyrosine hydroxylase (TH), the rate limiting enzyme in the production of catecholamines.

In adult retinae of both hamsters and gerbils, most CA somata were located in the inner part of the inner nuclear layer (INL) and CA dendrites spread in a outer stratum of the inner plexiform layer (IPL). Their somata varied with retinal position, being largest in temporal and smallest in central retina. In hamsters, but not gerbils, a small number of CA interplexiform cells was also observed. In development, CA somata of hamster retinae were observed first in the middle and /or scleral regions of the cytoblast layer (CBL) at P (postnatal day) 8. By P12, CA somata were commonly located in the inner part of the INL and their dendrites spread into the outer region of the IPL. In developing gerbil retinae, CA somata were first observed at P6 in the middle of the CBL. Over subsequent days, they migrated into the inner part of the INL and spread their dendrites into the outer strata of the IPL.

In both hamsters and gerbils, CA cells were initially concentrated in the superior temporal margin of the retina. In hamsters, this supero‐temporal concentration persisted until adulthood, whereas in adult gerbils, the greatest density of CA cells was found just superior to the visual streak. These distributions were distinct from those of the ganglion cells in adult and developing retinae of each species. We discuss the role of maturational expression of TH, cell death, and retinal growth in the generation of the distinct distribution of the CA cells.
Vomeronasal and olfactory nerves of adult and larval bullfrogs: II. Axon terminations and synaptic contacts in the accessory olfactory bulb
Authors: Burton Paul R.
Published: January 2005

The ultrastructure of the accessory olfactory bulb (AOB) of the bullfrog tadpole and adult was examined, and the main difference between tadpole and adult is that the latter is more compact and shows more synapses. Except for vomeronasal (VMN) glomeruli, the AOB is not highly organized, with mitral cell neurons scattered throughout the neuropil. VMN axon terminals from asymmetric synapses with mitral cell dendrites in glomeruli; in VMN axon terminals, dense‐cored vesicles are seen along with the more abundant lucent vesicles 40–50 nm in diameter. Counts indicated that more than 90% of the dendro‐dendritic synapses between mitral cells and presumed granule cells are of the asymmetrical type, and reciprocal asymmetrical‐symmetrical synapses are not common. Lucent vesicles with round or slightly ellipsoidal profiles and less abundant dense‐cored vesicles 60–90 nm in diameter are found in pre‐ and postsynaptic dendrites; sometimes the dense‐cored vesicles lie against or near the presynaptic membrane. Microtubules were often seen to be closely associated with pre‐ and postsynaptic elements of dendro‐dendritic synapses. The most characteristic feature of mitral cell bodies, apart from their large size, is an extensive Golgi system that may extend well into their major dendritic extensions. Dense‐cored vesicles are associated with Golgi membranes, from which they probably originate. Centrioles are associated with the Golgi system, and some become basal bodies and give rise to cilia in some mitral cells.