bluuebunny/crossref_metadata_2025 huggingface dataset:
Somatotopic organization of the primary sensory trigeminal neurons in the hagfish, Eptatretus burgeri
Authors: Nishizawa Hideo , Kishida Reiji , Kadota Tetsuo , Goris Richard C.
Published: January 2005

Primary sensory trigeminal projections were investigated in the hagfish following application of horseradish peroxidase (HRP) to the sensory branches. In our control preparations we were able to distinguish five sensory ganglia and their respective nerves. HRP application confirmed the almost exclusive relation of each of these nerves to their respective ganglia, with very little overlap. In normal frontal sections of the medulla oblongata, five columns of fibers surrounded by neuronal cell bodies could be clearly distinguished, but the number is probably fortuitous, for there was no one‐on‐one relationship with the five trigeminal ganglia. From their peripheral connections, we surmised that columns 1 and 3 handle general cutaneous sensation, columns 2, 4, and 5 handle taste sensation, and column 5 handles general mucous cutaneous sensation conveyed by utricular ganglion cells. Dorsally located columns received projections from nerves with dorsal peripheral connections, and more ventrally located columns received projections from nerves with ventral peripheral connections. This relation is the reverse of that seen in other vertebrates.
Neuronal death and synapse elimination in the olivocerebellar system: III. Cell counts in the inferior olive of developing rats X‐irradiated from birth
Authors: Geoffroy Brigitte , Shojaeian Hadi , Delhaye‐Bouchaud Nicole , Mariani Jean
Published: January 2005

The change with age of cell number in the developing inferior olivary nucleus (ION) of the normal rat, compared to the time course of the regression of the polyneuronal innervation of Purkinje cells by olivary axons (i.e., the climbing fibers), suggests that the involution of the redundant olivocerebellar contacts is caused by a reduction of axonal branching rather than by degeneration of the parent cells, this being also suggested by the normal size of the olivary population in adult rodents whose Purkinje cells retain polyneuronal innervation. However, the similar size of the adult ION population does not necessarily imply that the developmental history is the same in normal and multiply innervated adult rodents. Therefore, cell counts were performed in developing rats which had been repeatedly X‐irradiated from birth until postnatal day 14 and which retained polyneuronal innervation. The results show that, although less marked than during normal development, the evolution of the ION population is also characterized by a phase of cell loss followed by a slow increase. However, the number of cells in X‐irradiated rats is higher than in their controls from birth to postnatal day 15 but becomes identical at 20 days and later. These data confirm that cell death in the ION does not play a major role in the shaping of olivocerebellar connections.
Immunohistochemical localization of serotonin and choline acetyltransferase in sensory neurones of the locust
Authors: Lutz E. M. , Tyrer N. M.
Published: January 2005

Sensory neuronal cell bodies in the leg of locust, Schistocerca gregaria, were visualized with antibodies to locust choline acetyltransferase and with antibodies to serotonin by the avidin‐biotin peroxidase technique. Two groups of sensory cells react with the antibody to choline acetyltransferase: One group is associated with external mechanoreceptors (i.e., hair‐plate hairs and campaniform sensilla) and the other with internal proprioceptors (i.e., chordotonal organs and multiterminal receptors). Sensory cells which react with the antibody to serotonin are associated only with internal proprioceptors being found in both chordotonal organs and multiterminal receptors. In the metathoracic femoral chordotonal organ indirect evidence suggests that some sensory cells are reactive to both antibodies. Some multiterminal receptors react with anti‐choline‐acetyltransferase, while others react with antiserotonin. These results support the conclusion that most insect sensory neurones are cholinergic but some are serotoninergic.
Brainstem afferents to the magnocellular basal forebrain studied by axonal transport, immunohistochemistry, and electrophysiology in the rat
Authors: Semba K. , Reiner P. B. , McGeer E. G. , Fibiger H. C.
Published: January 2005

Brainstem afferents to the magnocellular basal forebrain were studied by using tract tracing, immunohistochemistry and extracellular recordings in the rat. WGA‐HRP injections into the horizontal limb of the diagonal band (HDB) and the magnocellular preoptic area (MgPA) retrogradely labelled many neurons in the pedunculopontine and laterodorsal tegmental nuclei, dorsal raphe nucleus, and ventral tegmental area. Areas with moderate numbers of retrogradely labelled neurons included the median raphe nucleus, and area lateral to the medial longitudinal fasciculus in the pons, the locus ceruleus, and the medial parabrachial nucleus. A few labelled neurons were seen in the substantia nigra pars compacta, mesencephalic and pontine reticular formation, a midline area in the pontine central gray, lateral parabrachial nucleus, raphe magnus, prepositus hypoglossal nucleus, nucleus of the solitary tract, and ventrolateral medulla. A similar but not identical distribution of labelled neurons was seen following WGA‐HRP injections into the nucleus basalis magnocellularis.

The possible neurotransmitter content of some of these afferents to the HDB/MgPA was examined by combining retrograde Fluoro‐Gold labelling and immunofluorescence. In the mesopontine tegmentum, many retrogradely labelled neurons were immunoreactive for choline acetyltransferase. In the dorsal raphe nucleus, some retrogradely labelled neurons were positive for serotonin and some for tyrosine hydroxylase (TH); however, the majority of retrogradely labelled neurons in this region were not immunoreactive for either marker. The ventral tegmental area, substantia nigra pars compacta, and locus ceruleus contained retrogradely labelled neurons which were also immunoreactive for TH. Of the retrogradely labelled neurons occasionally observed in the nucleus of the solitary tract, prepositus hypoglossal nucleus, and ventrolateral medulla, some were immunoreactive for either TH or phenylethanolamine‐N‐methyltransferase.

To characterize functionally some of these brainstem afferents, extracellular recordings were made from antidromically identified cortically projecting neurons, mostly located in the HDB and MgPA. In agreement with most previous studies, about half (48%) of these neurons were spontaneously active. Electrical stimulation in the vicinity of the pedunculopontine tegmerital and dorsal raphe nuclei elicited either excitatory or inhibitory responses in 21% (13/62) of the cortically projecting neurons.

These findings indicate that neurons in the magnocellular basal fore‐brain receive afferents from widely distributed brainstem neurons that contain acetylcholine, serotonin, dopamine, noradrenaline, adrenaline, and some unknown neurotransmitters. Through their actions on magnocellular basal forebrain neurons, these brainstem neurons may indirectly regulate the activity of neurons throughout the cerebral cortex.
Role of visual experience in promoting segregation of eye dominance patches in the visual cortex of the cat
Authors: Swindale N. V.
Published: January 2005

Transneuronal autoradiography was used to study the role of visual experience in the development of ocular dominance patches in the cat. In order to assess quantitatively the effects of visual deprivation, image analysis was used to measure the profiles of grain density in layer IV. Fourier power spectra of these profiles were computed to give a measure of the amplitudes and frequencies of the fluctuations in grain density that were present.

Deprivation of normal patterned vision by binocular lid suture or by rearing in total darkness from shortly after birth abolished the dominant periodicity (of about 1.1 mm) in the distribution of left and right eye afferents in layer IV of area 17. A dominant periodicity of about 2.2 mm was, however, present in area 18 of both normal and dark‐reared animals.

Visual deprivation was not able to reverse segregation. One animal reared normally for 6 weeks was placed in the dark for a further 28 weeks and showed normal periodicities in the distribution of geniculate inputs to area 17. Another animal given 128 hours of experience and kept in the dark for the rest of the time until it was 12 weeks old also showed normal segregation.

To determine the minimum amount of visual experience necessary for segregation to occur, four animals were given 8‐, 24‐, 48‐, and 128‐hour periods of visual experience and were studied at 12 weeks of age. Eight hours of experience had no detectable effect on segregation; periodicities of intermediate amplitude were present in animals that received 24 and 48 hours of experience, while 128 hours of experience resulted in periodicities of normal amplitude.

Recovery from visual deprivation was studied by rearing kittens from birth in the dark for varying periods and then returning them to the normally lit colony room for periods of 6 to 22 weeks. Recovery from 6 weeks of dark rearing was found to be complete; much less recovery occurred following periods of 8 to 25 weeks of intial deprivation, and no recovery at all occurred after 30 weeks of deprivation.

It is concluded that the spontaneous activity present in the geniculocortical afferents of dark‐reared and lid‐sutured cats is not adequate to drive normal periodic segregation in area 17, though it can do so in area 18. Between 48 and 128 hours of visual experience, given before 8 weeks of age, appears to be necessary and sufficient for normal periodic segregation of geniculate afferents in area 17 of the cat.
Development of somatostatin immunoreactive neurons in the rat occipital cortex: A combined immunocytochemical‐autoradiographic study
Authors: Cavanagh Marion E. , Parnavelas John G.
Published: January 2005

The postnatal development of somatostatin (SRIF)‐immunoreactive neurons, previously labeled with [3H]thymidine on embryonic days E14–E22, has been studied in the rat occipital cortex. Immunocytochemistry combined with autoradiography showed an “inside‐out” maturation pattern. Only SRIF neurons generated at E14 were present in layer VI in newborn rats. Later generated SRIF neurons appeared progressively higher in the cortex until about postnatal day 12 when SRIF neurons from E21 appeared in layer II. At 2 weeks of age, therefore, all SRIF neurons from E14–E21 were present. Most of these had been generated between E15 and E17 with a moderate number at E14 and rapidly diminishing numbers from E18 to E21. Although an overall layered distribution was apparent at peak production, there was a tendency for diffuse distribution most noticeable at E17. Diffusely distributed neurons were more likely to be below their appropriate layer than above it, thus contributing extra SRIF neurons to layer VI. At 3, 4, and 5 weeks, progressively fewer SRIF neurons were seen with a consequent reduction in the number of double‐labeled neurons. It is suggested that the transient population of SRIF neurons thus revealed plays a role in cortical development.
Spinal origins of preganglionic B and C neurons that innervate paravertebral sympathetic ganglia nine and ten of the bullfrog
Authors: Horn John P. , Stofer William D.
Published: January 2005

These experiments were designed to characterize the distribution, morphology, and number of spinal preganglionic neurons that selectively innervate the B‐ and C‐type sympathetic neurons in paravertebral ganglia 9 and 10 of the bullfrog. For this purpose, horseradish peroxidase (HRP) was applied to the anterior end of the sectioned sympathetic chain between ganglia 8 and 9. Subsequent retrograde axonal transport of the HRP labeled ipsilateral spinal neurons whose cell bodies form a column having rostral and caudal boundaries that are, respectively, just caudal to the level of spinal nerve 4 and midway between the entry zones of spinal nerves 7 and 8. In all segments, the labeled preganglionic somata were found in the lateral half of the spinal gray and slightly dorsal to the central canal; a position analogous to that of the intermediolateral cell column in mammals. Most labeled preganglionic neurons were multipolar in shape, and the cell bodies lying between spinal nerves 4 and 5 were, on average, larger than those found between spinal nerves 7 and 8. In transverse sections that were cut near spinal nerve 5, the axons of preganglionic neurons could be seen to exit the cord through ventral roots.

Counts of labeled preganglionic neurons indicate that an average ± S.D. of 338 ± 89 cells innervate ganglia 9 and 10. Selective labeling of preganglionic B neurons, by cutting spinal nerves 7 and 8 central to their rami communicantes at the time of HRP application, revealed an average ± S.D. of 137 ± 31 cells that lie exclusively between spinal nerves 4 and 6. By contrast, selective labeling of preganglionic C neurons, by cutting the sympathetic chain rostral to ganglion 7 at the time of HRP application, revealed an average ± S.D. of 187 ± 77 cells in an adjacent portion of the preganglionic column that is bounded by spinal nerve 6 and by a point midway between spinal nerves 7 and 8. These results thus demonstrate a clear segmental segregation between the preganglionic B and C neurons that innervate ganglia 9 and 10.
Central distribution of trigeminal and upper cervical primary afferents in the rat studied by anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin
Authors: Pfaller Kristian , Arvidsson Jan
Published: January 2005

Injections of WGA‐HRP were made in the rat trigeminal ganglion and C1–3 dorsal root ganglia (DRGs) to study the central projection patterns and their relations to each other. Trigeminal ganglion injections resulted in heavy terminal labeling in all trigeminal sensory nuclei. Prominent labeling was also observed in the solitary tract nucleus and in the medial parts of the dorsal horn at C1–3 levels, but labeling could be followed caudally to the C7 segment. Contralateral trigeminal projections were found in the nucleus caudalis and in the dorsal horn at C1–3 levels. The C1 DRG was found to be inconstant in the rat. When it was present, small amounts of terminal labeling were found in the external cuneate nucleus (ECN) and the central cervical nucleus (CCN). No dorsal horn projections were seen from the C1 DRG. Injections in the C2 DRG resulted in heavy labeling in the ECN, nucleus X, CCN, and dorsal horn, where it was mainly located in lateral areas. Labeling could be followed caudally to the Th 7 segment. C2 DRG projections also appeared in the cuneate nucleus (Cun), in all the trigeminal sensory nuclei, and in the spinal, medial, and lateral vestibular nuclei. A small C2 DRG projection was observed in the ventral cochlear nucleus. C3 DRG injections resulted in heavy labeling in both medial middle and lateral parts of the dorsal horn, in the ECN, and in nucleus X, whereas the labeling in the CCN was somewhat weaker. Smaller projections were seen to trigeminal nuclei, Cun, and the column of Clarke. Comparisons of the central projection fields of trigeminal and upper cervical primary afferents indicated a somatotopic organization but with a certain degree of overlap.
Catecholamine‐containing neurons in Drosophila melanogaster: Distribution and development
Authors: Budnik Vivian , White Kalpana
Published: January 2005

The development of catecholamine‐containing neurons (CA neurons) in the fruit fly Drosophila melanogaster was studied. Glyoxylic‐acid‐induced histofluorescence and antibodies against dopamine and tyrosine hydroxylase were used to describe catecholamine distribution in the larval central nervous system (CNS). The three techniques gave rise to a similar pattern of distribution of putative CA neurons. At all developmental stages CA neurons were distributed widely throughout the CNS but represented only a small fraction of all CNS neurons. Catecholamine‐containing processes were confined to the CNS. The CA neurons are first discerned at about 18 hours of embryonic development. We suggest that these larval CA neurons are maintained throughout the ontogeny of the fly and that the adult CA pattern is composed of embryonic neurons and neurons that differentiate during metamorphosis.
Structural correlates of functionally distinct X‐cells in the lateral geniculate nucleus of the cat
Authors: Humphrey Allen L. , Weller Rosalyn E.
Published: January 2005

In the companion paper (Humphrey and Weller, '88), we demonstrated 2 physiologically different groups of X‐cells (XL and XN) in the A‐laminae of the cat lateral geniculate nucleus. In order to investigate their possible morphological correlates, we iontophoresed horseradish peroxidase intracellularly into physiologically identified XL‐ and XN‐cells and examined their light microscopic appearance.

The 11 HRP‐labeled XL‐cells constituted the smallest relay neurons in the A‐laminae, and were similar morphologically. All had small somata (mean soma size = 236 μm2), very thin (< 1.0 μm) axons, few primary dendrites, and narrow, sinuous distal dendrites, which usually formed trees that were oriented perpendicular to laminar borders. The dendrites could be smooth or display beadlike varicosities, hairlike appendages, and/or occasional complex stalked appendages, but their most consistent feature was numerous clusters of grapelike dendritic appendages located at or near dendritic branch points.

The 14 labeled XN‐cells were structurally more heterogeneous, and they included relay neurons and interneurons. Eight of 11 XN‐relay cells differed markedly from the XL‐cells. These XN‐cells were multipolar neurons with medium to large somata (mean soma size = 365 μm2), small to medium‐size axons (1.0–2.0 μm), numerous primary dendrites, and straight distal dendrites that formed radially symmetric trees. The dendrites of the cells were largely smooth, except for occasional spines and/or hairs, and they were devoid of grapelike and other complex appendages. The three other XN‐relay neurons had morphologies either similar to XL‐cells or intermediate between XL‐cells and more simple, multipolar XN‐relay cells, but two of these cells had larger somata and axons than most XL‐cells. Finally, three XN‐cells were intrageniculate interneurons, which possessed small somata (mean soma size = 174 μm2), fine sinuous dendrites covered with beadlike varicosities on stalked appendages, and no obvious axon.

These results reveal that, despite minor overlap, there are marked structural differences between XL‐ and XN‐cells. Among the relay cells, these differences relate to soma and axon diameter, dendritic orientation, and the presence or absence of grapelike dendritic appendages. Our finding that interneurons were strongly excited at short latencies by spot onset supports the hypothesis (Mastronarde, '87a; Humphrey and Weller, '88) that such interneurons provide the major inhibitory input to XL‐cells, and that this input is important in generating the spot‐induced early dips in XL‐cell discharge.
Anatomical consequences of neonatal infraorbital nerve transection upon the trigeminal ganglion and vibrissa follicle nerves in the adult rat
Authors: Klein Bradley G. , Renehan William E. , Jacquin Mark F. , Rhoades Robert W.
Published: January 2005

A large body of experimental literature has demonstrated that neonatal infraorbital nerve damage in rodents produces anatomical and/or functional alterations of the normal whisker representation in central trigeminal structures. Less is known about the organization of primary afferent components of the trigeminal system following this manipulation. Such information provides an important basis for interpreting the central changes observed following damage of infraorbital nerve fibers at birth. We have therefore examined the composition and order of peripheral innervation in the pathway from the trigeminal ganglion to the vibrissa follicles in adult rats subjected to unilateral neonatal infraorbital nerve transection

Electron microscopy was used to determine the number and diameter of myelinated and unmyelinated fibers in vibrissa follicle nerves of these animals. Wheat germ agglutinin‐horseradish peroxidase and fluorescent retrograde tracers were employed to examine the number and diameter, as well as the topographic organization and branching, of ganglion cells innervating the vibrissae in these rats.

The data presented below indicate that neonatal infraorbital nerve transection has the following consequences within the adult trigeminal nerve and ganglion: (1) an alteration of the gross morphology of vibrissal nerves, (2) a significant reduction in the average number (85.4%) and diameter (32.6%) of myelinated, but not unmyelinated, follicle nerve axons, (3) a significant decrease in the average number (36.8%) of trigeminal ganglion cells innervating vibrissa follicles, (4) no significant change in the distribution of ganglion cell diameters, (5) an increase in peripheral branching (1.8‐fold) of these ganglion cell axons, and (6) an alteration of somatotopic order within the trigeminal ganglion.

Taken together, these data indicate that neonatal infraorbital nerve transection produces a profound reorganization of the primary afferent component of the trigeminal neuraxis.
Morphological and electrophysiological identification of gigantocellular tegmental field neurons with descending projections in the cat: I. Pons
Authors: Mitani Akira , Ito Keihachiro , Mitani Yuko , McCarley Robert W.
Published: January 2005

Two different descending projections from the pontine gigantocellular tegmental field (PFTG) were denned by the use of intracellular recording and intracellular horseradish peroxidase (HRP) techniques in the cat. Type I neurons (reticulospinal neurons) had antidromic spike potentials produced by stimulation of the ipsilateral medial longitudinal fasciculus (MLF) and sent axons to the ipsilateral MLF. Most type I neurons had large ellipsoidpolygonal somata (mean, 59.7 μm), thick axons (average diameter, 3.33 μm), and slightly oblate large dendritic fields. The mean anteroposterior extent of the dendritic field was 1,492 μm, the mean mediolateral extent was 1,784 μm, and the mean dorsoventral extent was 1,562 μm. There were no type I neurons with axon collaterals. In contrast, type II neurons (reticuloreticular neurons) had antidromic spike potentials produced by stimulation of the bulbar reticular formation (BRF) and sent axons directly to the BRF. In comparison with type I neurons, most type II neurons had smaller ellipsoid‐polygonal somata (mean, 40.2 μm), thinner axons (average diameter, 2.32 μm), and smaller, slightly oblate dendritic fields. The mean anteroposterior extent of the dendritic field was 1,264 μm; the mean mediolateral extent was 1,511 μm; and the mean dorsoventral extent was 1,226 μm. Also in contrast to type I neurons, 36% of type II neurons had axon collaterals.
Descending projections from the gigantocellular tegmental field in the cat: Cells of origin and their brainstem and spinal cord trajectories
Authors: Mitani Akira , Ito Keihachiro , Mitani Yuko , McCarley Robert W.
Published: January 2005

The trajectories and the cells of origin of the pontobulbar gigantocellular tegmental field descending pathways were studied in the cat using anterograde WGA‐HRP and retrograde HRP techniques. Four main descending pathways and cells of origin were delineated: (1) Predominantly large neurons in the pontine gigantocellular tegmental field (average soma diameter = 43.4 μm) and rostral bulbar gigantocellular tegmental field (41.3 μm) gave rise to reticulospinal fibers descending in the ipsilateral medial longitudinal fasciculus and ventral funiculus and distributed in laminae V‐X with an ipsilateral predominance. These were primarily large‐diameter fibers. (2) Predominantly large neurons (46.9 μm) in the bulbar gigantocellular tegmental field gave rise to reticulospinal fibers descending in the contralateral medial longitudinal fasciculus and ventral funiculus. These were mainly large‐diameter fibers. (3) Neurons of predominantly medium size (29.5 μm) in the pontine gigantocellular tegmental field gave rise to reticuloreticular fibers descending directly to and distributed bilaterally in the bulbar reticular formation. These were small‐diameter fibers. (4) Neurons of predominantly medium size (28.9 μm) in the bulbar gigantocellular tegmental field gave rise to reticulospinal fibers descending in the ipsilateral reticular formation and lateral funiculus. These were small‐diameter fibers.
Monosynaptic transmission of respiratory drive to phrenic motoneurons from brainstem bulbospinal neurons in rats
Authors: Ellenberger Howard H. , Feldman Jack L.
Published: January 2005

The termination patterns in the rat phrenic nucleus of neurons within two respiratory cell groups of the ventrolateral medulla (Bötzinger Complex and the rostral ventral respiratory group) were determined. The plant lectin, Phaseolus vulgaris leuco‐agglutinin, was used as an anterograde tracer to label presynaptic processes of bulbospinal neurons, and horseradish peroxidase was used simultaneously to label phrenic motoneurons. Labeled bulbospinal axons ended with dense terminal arborizations within the phrenic cell column and on radial phrenic motoneuron dendrite bundles, which represented the exclusive site of termination of Bötzinger Complex and rostral ventral respiratory group neurons in the lower cervical spinal cord. Terminals of these descending axons formed presumptive synaptic contacts within longitudinal and radial dendrite bundles, and on the cell somata of phrenic motoneurons.
Development of the dopaminergic innervation in the prefrontal cortex of the rat
Authors: Kalsbeek A. , Voorn P. , Buijs R. M. , Pool C. W. , Uylings H. B. M.
Published: January 2005

The pre‐ and postnatal development of the dopaminergic innervation in the prefrontal cortex (PFC) of the rat is described from embryonic day 14 through postnatal day 90. By embryonic day 15 the dopamine (DA)‐containing fibers reach the anlage of the lateral neocortex; 2 days later the first fibers have reached the subplate of the future prefrontal cortex. The process of entering the cortical plate starts just before birth. Prenatally, some dopaminergic fibers can be observed in the marginal zone of both the lateral and the medial wall of the hemisphere. Within 48 hours after birth a large number of dopaminergic fibers can be observed in the marginal zone, i.e., the future layer I, in some subareas of the PFC. A transient appearance of DA‐positive fibers is noticed in the late embryonic and early postnatal periods especially in the marginal zone and possibly in the superficial layers of the pregenual cingulate cortex. Changes in the morphology of DA fibers at P4 suggest that the actual DA innervation starts at this age. From postnatal day 6 the different subareas of the PFC can be recognized according to the characteristics of the topographical distribution of the dopaminergic fibers. Until postnatal day 60 the density of the dopaminergic fibers continues to increase. No difference in density and topography was observed between postnatal days 60 and 90.
Autoradiographic studies of cerebellar histogenesis in the premetamorphic bullfrog tadpole: II. Formation of the interauricular granular band
Authors: Uray Nandor J. , Gona Amos G. , Hauser Kurt F.
Published: January 2005

This study examines the origin of cells in the interauricular granular band (iagb) in the cerebellum of the frog tadpole during early stages of development by means of histological and autoradiographic methods.

Premetamorphic bullfrog tadpoles were exposed to multiple doses of 3H‐thymidine (10 μCi/g body weight per exposure) at developmental stages ranging from 1 week to 1 year and were killed at either 6 or 12 months of age. The autoradiographic data were examined to determine the time when cells of the iagb were generated.

Our findings show that initial generation of iagb cells begins at week 3 and that a peak in the formation of postmitotic neurons is reached at the age of 10 weeks. This is followed by other peaks of cell generation at the ages of 16 weeks, 10 months, and 11.5 months. The generation cycles of iagb cells are interrupted by periods of quiescence when label cannot be detected in any of the cells. These quiescent periods occur at the ages of 20–26 weeks, 7 months, and 12 months. These findings indicate that cells of the iagb are generated in a cyclical manner over the entire 1‐year period which was studied. Comparison of our present data on iagb cell formation with the generation of cells in the EGL shows that the production of these two groups of cells is overlapping, but cells of the iagb begin and cease production before those of the EGL. On the basis of our findings we propose that the cells of the iagb and the EGL belong in separate cell groups which are generated by distinct subpopulations of germinal cells in the neuroepithelial cap.
Do axons grow during adulthood? A study of caliber and microtubules of sural nerve axons in young, mature, and aging rats
Authors: Saitua Francisco , Alvarez Jaime
Published: January 2005

Calibers and microtubules of sural nerve axons were studied in young (6‐week‐old), mature (14‐week‐old), and aging (2‐year‐old) rats. The mean cross‐sectional area of nonmedullated fibers was about 0.50 μm2 (range: 0.47–0.52) in the three age groups. Their caliber spectra were also similar. In contrast, myelinated axons grew from 6.6 to 16.7 μm2 between the sixth and 14th week of age. The increase of cross‐sectional area was greater, the greater the initial caliber of axon (range 44–154%). No further change of caliber was observed in the aging rat. The cross‐sectional area of nerve allotted per myelinated fiber was 42, 66, and 97 μm2 in young, mature, and aging rats, respectively. The fraction of nerve tissue occupied by the axoplasm, though, did not change substantially; it was 20, 28, and 21%, respectively. The microtubules density of 3‐μm3 myelinated axons had a general average of 21 microtubules μm2. Differences between groups were not significant. In nonmedullated fibers, the microtubular density decreased as the size of the axon increased. No differences were observed between age groups. We conclude that nonmedullated fibers of the sural nerve stop growing before the sixth week whereas myelinated fibers keep growing until the 14th week of age. The correlation between microtubular content and axonal caliber is a lifelong feature of axons.
Cholinergic synaptic input to different parts of spiny striatonigral neurons in the rat
Authors: Izzo P. N. , Bolam J. P.
Published: January 2005

The postsynaptic targets of cholinergic boutons in the rat neostriatum were assessed by examination in the electron microscope of boutons that were immunoreactive for choline acetyltransferase, the synthetic enzyme for acetylcholine. These boutons formed symmetrical synaptic specializations with neostriatal neurons. Of 209 immunoreactive synaptic boutons observed in random searches of the neostriatum, 45% made contact with dendritic shafts, 34% with dendritic spines, and 20% with neuronal perikarya. Many of the postsynaptic structures had ultrastructural characteristics of the most common type of striatal neuron, the medium‐size densely spiny neuron. This was confirmed by the examination in the electron microscope of Golgi‐impregnated medium‐size spiny neurons from sections that had also been immunostained for choline acetyltransferase. Immunoreactive boutons formed symmetrical synaptic specializations with all parts of the neurons examined, i.e., perikarya, proximal and distal dendritic shafts, and dendritic spines. Two of the Golgi‐impregnated medium‐size spiny neurons that received input from the cholinergic boutons were also retrogradely labelled with horseradish peroxidase that had been injected into the substantia nigra, they were thus further characterized as striatonigral neurons. Similarly, seven retrogradely labelled perikarya of striatonigral neurons were found to receive input from the cholinergic boutons.

It is concluded that cholinergic boutons in the neostriatum form synaptic specializations and that one of their major targets is the medium‐size densely spiny neuron that projects to the substantia nigra. The topography of the cholinergic afferents of these cells is distinctly different from that of other boutons derived from local neurons and from boutons that form asymmetrical synaptic specializations, but it is similar to that of the dopaminergic boutons originating from neurons in the substantia nigra.
Connections of the primary auditory cortex in the common marmoset, Callithrix jacchus jacchus
Authors: Aitkin Lindsay M. , Kudo Motoi , Irvine Dexter R. F.
Published: January 2005

The afferent and efferent connections of the primary auditory cortex (AI) of common marmosets were traced following small injections of wheat germ agglutinin conjugated with horseradish peroxidase (WGA‐HRP) made at best frequency (BF)‐defined sites in the AI. After the injections the animals remained anesthetized for 15–23 hours; they were then perfused transcardially with fixative and the brains were processed for WGA‐HRP reaction product.

Examination of the disposition of labelled material revealed the following results. First, patches of terminal labelling, and to a lesser extent retrograde labelling, were found outside the injection site in the ipsilateral cortex rostral and caudal to the AI. Second, the region of the contralateral cortex corresponding to the injection site contained labelled terminals throughout the depth of the cortex; labelled neurons were found in the middle layers. Third, in each experiment a discrete region of the medial geniculate body (MG) contained retrogradely labelled neurons interspersed with anterogradely labelled terminals. These regions had a banded appearance, were found in the dorsal and rostral half of the MG, and shifted in location progressively dorsal and as the injection site BF increased.

The presence of projection zones rostral and caudal to the AI of marmosets, and the disposition of the MG sources of projection in relation to BF, are similar to observations made on other New World monkeys. The ipsilateral corticocortical projections confirm electrophysiological evidence suggesting the existence of auditory fields rostral and caudal to the AI. The thalamocortical auditory system of the marmoset appears relatively simple, with a comparatively undifferentiated MG projecting to a cortical auditory system dominated by a large AI.
Localization and characterization of angiotensin II receptor binding and angiotensin converting enzyme in the human medulla oblongata
Authors: Allen Andrew M. , Chai Siew Yeen , Clevers Jenni , McKinley Michael J. , Paxinos George , Mendelsohn Frederick A. O.
Published: January 2005

Angiotensin II receptor and angiotensin converting enzyme distributions in the human medulla oblongata were localised by quantitative in vitro autoradiography. Angiotensin II receptors were labelled with the antagonist analogue 125I‐[Sar1, Ile8] All while angiotensin converting enzyme was labelled with 125I‐351A, a derivative of the specific converting enzyme inhibitor, lisinopril.

Angiotensin II receptor binding and angiotensin converting enzyme are present in high concentrations in the nucleus of the solitary tract, the dorsal motor nucleus of vagus, the rostral and caudal ventrolateral reticular nucleus, and in a band connecting the dorsal and ventral regions.

In the rostral and caudal ventrolateral reticular nucleus, angiotensin II receptors are distributed in a punctate pattern that registers with neuronal cell bodies. The distribution and density of these cell bodies closely resemble those of catecholamine‐containing neurones mapped by others. In view of the known interactions of angiotensin II with both central and peripheral catecholamine‐containing neurons of laboratory animals, the current anatomical findings suggest similar interactions between these neuroactive compounds in the human central nervous system.

The presence of angiotensin II receptors and angiotensin converting enzyme in the nucleus of the solitary tract, dorsal motor nucleus of vagus, and rostral and caudal ventrolateral reticular nucleus demonstrates sites for central angiotensin II to exert its known actions on vasopressin release and autonomic functions including blood pressure control. These data also suggest a possible interaction between angiotensin II and central catechol‐eminergic systems.
Morphology of neurons in area 4γ of the cat's cortex studied with intracellular injection of HRP
Authors: Ghosh S. , Fyffe R. E. W. , Porter R.
Published: January 2005

Neurons in laminae II, III, V, and VI of area 4γ of the cat motor cortex were studied following intracellular penetration with an HRP‐filled microelectrode. Antidromic and synaptic responses produced by stimulation of the cerebral peduncles and/or of the ventrolateral nucleus of the thalamus were investigated. Horseradish peroxidase was then iontophoresed into the same neurons to allow examination of their detailed morphology.

The morphology of pyramidal neurons whose somata were located in a particular lamina was similar but differed from that of pyramidal neurons in other laminae. The modified pyramidal neurons of lamina II had a truncated apical dendrite or did not possess an obvious apical dendrite, even though the ascending dendritic branches were longer and more extensive than the “basal” branches. As was the case for the pyramidal cells in other laminae, the axons of these lamina II modified pyramidal cells descended toward the white matter; their somata were generally pyramidal in shape; and their dendrites were spiny.

All pyramidal neurons except some of lamina VI had ascending dendrites which terminated in a tuft in lamina I, subpially.

No intracortical collaterals were seen originating from the axons of lamina II or of lamina VI pyramidal neurons.

Lamina III pyramidal neurons had extensive short and long axon collaterals which contributed synaptic boutons to all laminae of the cortex. Pyramidal neurons of lamina V had fewer axon collaterals whose synaptic boutons were restricted to laminae V and VI.

All somata of pyramidal tract neurons (PTNs), identified by antidromic responses from peduncular stimulation, were located in lamina V, except for one which was located in lamina VI.

Recurrent collaterals of pyramidal neurons were activated by peduncular stimulation. Recurrent excitatory postsynaptic potentials (epsps) could be evoked in fast PTNs, slow PTNs, other pyramidal neurons of lamina V, and pyramidal neurons of lamina VI at latencies between 1.3 and 6.25 msec. In some slow PTNs, a recurrent inhibitory postsynaptic potential of long duration was the predominant response. Stimulation of the ventrolateral nucleus of the thalamus resulted in epsps in pyramidal neurons of lamina III, V, and VI at latencies between 1.0 and 5.0 msec.
Ultrastructure of mouse foliate taste buds: Synaptic and nonsynaptic interactions between taste cells and nerve fibers
Authors: Royer Suzanne M. , Kinnamon John C.
Published: January 2005

High voltage electron microscopy and conventional transmission electron microscopy were used to examine the ultrastructure of foliate taste buds of mice. Computer‐assisted, three‐dimensional reconstructions from serial sections were used to visualize regions of interaction between taste cells and nerve fibers.

Based on criteria previously established for murine vallate taste buds (Kinnamon et al., '85), foliate taste cells were classified as dark, light, or intermediate depending on their cytoplasmic content and the characteristics of their nuclei. Cells of foliate taste buds display a continuous range of morphologies, from “typical” dark cells to “typical” light cells. Cells of dark, intermediate, and light morphologies all make afferent synapses onto nerve processes, suggesting that cells of all 3 types are sensory in function. Synapses between taste cells and nerve processes may be either macular or fingerlike in shape. No efferent synapses were found.

In addition to conventional synapses, taste cells exhibit 2 other types of specializations at sites of apposition with nerve fibers: subsurface cisternae and atypical mitochondria. Subsurface cisternae are narrow sacs of endoplasmic reticulum that are closely apposed to the inner leaflet of the taste cell membrane. Possible functions of subsurface cisternae include synthesis of synaptic membrane components, modification of the electrical or adhesive properties of the taste cell membrane, and exchange of trophic factors with nerve processes. Atypical mitochondria are usually much larger than typical taste cell mitochondria, and their cristae often display a swollen, twisted configuration. These mitochondria are closely apposed to the inside of the taste cell membrane adjacent to nerve fibers. Atypical mitochondria may be providing unusual amounts of energy for metabolic reactions in their vicinities or participating in calcium buffering in the taste cell.

Within taste cells, presynaptic specializations, subsurface cisternae, and mitochondria are often clustered together to form “synaptic ensembles.” We hypothesize that the functions served by the subsurface cisternae and mitochondria, as well as synaptic transmission, may be important in interactions between taste cells and nerve fibers.
Afferent innervation of outer hair cells in adult cats: I. Light microscopic analysis of fibers labeled with horseradish peroxidase
Authors: Simmons D. D. , Liberman M. C.
Published: January 2005

Outer spiral fibers (OSFs), the afferent innervation of the outer hair cells (OHCs), were retrogradely labeled following horseradish peroxidase injections into the cat's auditory nerve. The peripheral branching patterns of 85 OSFs from adult cochleas were reconstructed. Fibers contacted OHCs via terminal or en passant swellings; however, the latter were seen exclusively in the apical half of the cochlea. Many OSFs also gave off branches ending on structures other than OHCs. Fibers in the cochlear apex were much more highly branched than in the base. Most fibers contacted only one row of OHCs, and more fibers contacted row 1 than row 2 or row 3 OHCs. Third‐row fibers were the most highly branched in all cochlear regions. These results are consistent with a growing body of morphological evidence that suggests that the peripheral branching patterns of OSFs may be fundamentally similar in all mammalian ears.
Ultrastructural study of large efferent neurons in the superior colliculus of the cat after retrograde labeling with horseradish peroxidase
Authors: Behan M. , Appell P. P. , Graper M. J.
Published: January 2005

The ultrastructure of large neurons in the stratum griseum intermedium of the cat superior colliculus was examined following injections of horseradish peroxidase (HRP) into the dorsal tegmental decussation. Four HRP‐labeled cells were selected, and the synaptology of their cell bodies and selected regions of proximal and distal dendrites was examined. The four neurons represent four morphologically distinct cell types: multipolar radiating, tufted, large vertical, and medium‐sized trapezoid radiating. These four neurons correspond with cell types X1, X2, X3, and T1 respectively, according to the recent classification of neurons in the superior colliculus of the cat by Moschovakis and Karabelas (J. Comp Neurol. 239:276–308, '85).

The three X type neurons are similar in having 83% of their somata and over 74% of their proximal dendrites contacted by synaptic profiles. Distal dendrites of the X type neurons, however, receive fewer synaptic contacts. In contrast, in the T1 cell, only 69% of the soma membrane is contacted by synaptic profiles, and the synaptic coverage on proximal and distal dendrites does not vary much from this. Of the eight types of synaptic terminals described in the stratum griseum intermedium of the cat superior colliculus by Norita (J. Comp. Neurol. 190:29–48, '80), only five are found in contact with the X and T type efferent neurons described here. There are some regional differences in terminal distribution, although each terminal is represented on each cell. Type III terminals (small, contain mostly pleomorphic vesicles, and make symmetrical contacts) are the most abundant on cell bodies and dendrites of all four cell types. Terminal types II (medium‐sized, containing round and flattened vesicles, and making asymmetrical contacts), and IV (medium to large in size, containing flattened vesicles, and making symmetrical contacts) are well represented. In general, terminal types I (small, containing densely packed round vesicles/and making asymmetrical contacts) and VI (small and irregular in shape, containing flattened vesicles and making symmetrical contacts) are found infrequently. The identity of different types of synaptic terminal is discussed.
Location of motoneurons supplying upper neck muscles in the chicken studied by means of horseradish peroxidase
Authors: Watanabe Tohru , Ohmori Yasushige
Published: January 2005

The distribution of motoneurons innervating the upper cervical muscles, biventer cervicis, splenius capitis, complexus, rectus capitis dorsalis, rectus capitis lateralis, and rectus capitis ventralis in the chicken was examined by retrograde transport of horseradish peroxidase. Labeled motoneurons supplying upper neck muscles ranged from 30 to 60 μm in diameter and were located within two subnuclei in the brainstem. The rostrocaudal distributions of motoneurons projecting to individual cervical muscles ranged from 3 to 9 mm in length, both rostral and caudal to the obex. Detailed analysis of the data showed that the more dorsally positioned subnucleus projected mainly to the hypaxial muscles, i.e., the rectus capitis ventralis and lateralis, whereas the ventral subnucleus supplied chiefly the epaxial muscles, i.e., the biventer cervicis and splenius capitis. The complexus and rectus capitis dorsalis were innervated by both of these subnuclei.

Historically these dorsal and ventral subnuclei, respectively, have been called the nucleus hypoglossus ventralis and the nucleus hypoglossus ventralis ventrolateralis. In view of the observation that these nuclei do not undergo retrograde degeneration following section of the hypoglossal nerves, this older nomenclature is misleading. In agreement with other authors, we suggest that these motoneuron groups should be collectively referred to as the nucleus supraspinalis.