bluuebunny/crossref_metadata_2025 huggingface dataset:
Postnatal development of the ipsilateral corticospinal component in rat spinal cord: A light and electron microscopic anterograde HRP study
Authors: Joosten Elbert A. J. , Schuitman R. L. , Vermelis M. E. J. , Dederen P. J. W. C.
Published: January 2005

Most developmental and regeneration studies using the corticospinal tract (CST) as a model are focussed on its major contralateral component in the ventralmost part of the dorsal funiculus. However, for a correct interpretation of the data in these and future studies, a complete anatomical description of the rat CST, including its ipsilateral uncrossed component, is a prerequisite. In this study we used anterograde horseradish‐peroxidase (HRP) tract‐tracing at the light and electron microscopic level to describe the development of the uncrossed ipsilateral CST component. In the far caudal portions of the medulla oblongata, most of the CST fibers decussate dorsally and medially to assume positions in the ventralmost part of the dorsal funiculus. However, a small number of labeled fibers continue uncrossed in a position just lateral to the ventral median fissure. Labeled ipsilateral CST fibers caudally extend into the ventral funiculus of the third thoracic segment at postnatal day 1 (P1), into the seventh thoracic segment at P3, and into the first lumbar segment at P5 and P7. After the first postnatal week labeled ipsilateral CST fibers gradually disappear from upper lumbar, lower‐, and mid‐thoracic spinal cord levels, respectively. From P14 through adulthood the ipsilateral CST projection can not be visualized below upper thoracic spinal cord levels. Quantitative analysis of the amount of label along the length of the outgrowing ipsilateral CST revealed a characteristic staggered pattern of outgrowth: a small number of fibers take the lead and additional fibers are successively added. The outgrowth of labeled ipsilateral CST fiber is mainly restricted to spinal cord white matter. Occasionally a few outgrowing fibers into the adjacent cervical spinal gray can be observed, however, only between P3 and P7. Electron microscopic observations at the cervical enlargement (fifth cervical segment) demonstrate that the first labeled ipsilateral CST fibers, at P1, are characterized by the presence of growth cone‐like enlargements at their distal endings. The process of myelination of labeled ipsilateral CST axons starts at about day P14. Although myelination seems to be largely completed at P28, labeled unmyelinated axons are still present in the adult ipsilateral CST component. © 1992 Wiley‐Liss, Inc.
Timing and duration of dihydrotestosterone treatment affect the development of motoneuron number and morphology in a sexually dimorphic rat spinal nucleus
Authors: Goldstein L. A. , Sengelaub D. R.
Published: January 2005

The spinal nucleus of the bulbocavernosus (SNB) is a sexually dimorphic motor nucleus in the rat lumbar spinal cord. SNB motoneurons and their perineal target muscles are present in adult males, but reduced or absent in adult females. This dimorphism is due to the presence of androgens during development. Perinatal treatment of females with testosterone (T), or a combination of dihydrotestosterone (DHT) and estrogen (E + D females) from embryonic (E) day 16 through postnatal (P) day 5, results in a masculine number of SNB motoneurons and the retention of the target muscles. Perinatal treatment with estrogen alone does not masculinize the SNB; prenatal treatment with DHT alone from E17–E22 results in a feminine number of SNB motoneurons and a significantly altered motoneuron morphology and connectivity. To determine if masculinization of the SNB involves the interaction of estrogen and DHT or results from a longer exposure to DHT alone, the number, morphology, and connectivity of SNB motoneurons in females treated with DHT both pre‐ and post‐natally (from E16–P5) were examined.

At E22, DHTP (E16–P5) females have SNB motoneuron numbers identical to E+D and normal females, but far fewer than normal males, thus indicating that T is essential for prenatal masculinization. After E22, SNB motoneuron number declines precipitously in normal females but remains stable in DHTP (E16–P5) females and E+D females, which do not differ from normal males at P10. These results demonstrate that DHT can completely masculinize SNB motoneuron number without any synergistic actions with estrogen, and suggest that the development of SNB motoneuron number is strictly an androgen‐mediated event.

In adulthood, horseradish peroxidase histochemistry reveals that the connectivity, dendritic length, and soma size of SNB motoneurons in DHTP (E17–P5) females are identical to those of normal males but differ significantly from those of DHTP (E17–E22) females. These data suggest that the altered connectivity in DHTP (E17–E22) females is not simply a hormone‐specific effect, but the result of a truncated hormone exposure. Thus, DHT can fully masculinize SNB morphology and connectivity if given during the appropriate period of development. It is suggested that while T may be required to masculinize the SNB prenatally, DHT may be involved in masculinizing postnatal aspects of SNB development. © 1992 Wiley‐Liss, Inc.
Course of the fiber pathways to pons from parasensory association areas in the rhesus monkey
Authors: Schmahmann Jeremy D. , Pandya Deepak N.
Published: January 2005

The course of the fiber pathways to pons from parasensory association areas in the rhesus monkey was investigated by injection of tritiated amino acids and the technique of autoradiography. Results confirm the projection to pons from parasensory association areas in the temporal, parietal, and occipital lobes and extend these observations to include the posterior parahippocampal gyrus. The findings reveal that the white matter of the posterior limb of the internal capsule above the midpoint of the lateral geniculate nucleus, and at the medical aspect of the lateral geniculate nucleus, comprise common regions through which these corticopontine fibers lead to the basis pontis. The fibers demonstrate a certain degree of topographic organization in the posterior limb of the capsule above the lateral geniculate nucleus and also in the cerebral peduncle. Taken together with previous observations concerning the termination patterns of these associative corticopontine projections, it would appear that the corticopontine system consists of segregated and partially overlapping pathways, which are to some extent distinguishable anatomically at each stage of their trajectory from origin to destination. Furthermore, the existence of a common area through which all parasensory associative input to pons is transmitted suggests that a precisely located lesion in this part of the corticopontocerebellar circuit may disrupt the cerebellar access to higher order information derived from the parasensory associative regions. © 1992 Wiley‐Liss, Inc.
Topographic organization of cardiovascular responses to electrical and glutamate microstimulation of the parabrachial nucleus in the rat
Authors: Chamberlin Nancy L. , Saper Clifford B.
Published: January 2005

We examined the functional organization of the parabrachial complex (PB) by mapping the cardiovascular and respiratory responses to PB microstimulation in anesthetized rats. The PB was explored with 100 m̈m resolution, at threshold doses of electrical current (5 m̈A) and glutamate (10‐500 pmols), and the locations of stimulation sites were identified by small iontophoretic or pressure injections of biocytin or Phaselous vulgaris leucoagglutinin. Threshold doses of either L‐glutamate or electrical current pulses caused pressor‐tachycardic responses that mapped to the outer edge of the external lateral subnucleus while depressor bradycardic responses were elicited from stimuli near the dorsal lateral subnucleus. Pressor responses persisted in paralyzed, ventilated animals and were thus not dependent upon concomitant respiratory changes. Cardiac arrhythmias sometimes occurred during large pressor responses and during augmented breaths that occurred during or following PB stimulation. These observations indicate that the PB contains at least two distinct neuronal systems that are potently and opposingly involved in cardiovascular control. The locations of the sites giving the most potent responses implicate specific ascending and descending pathways as substrates for the cardiovascular responses. © 1992 Wiley‐Liss, Inc.
Postnatal development of tyrosine hydroxylase immunoreactive amacrine cells in the rabbit retina: II. Quantiative analysis
Authors: Casini Giovanni , Brecha Nicholas C.
Published: January 2005

Tyrosine hydroxylase (TH)‐immunoreactive (IR) amacrine cells of the rabbit retina mature during the first four postnatal weeks, and their cellular development is described in the preceding paper (Casini, G., and N.C. Brecha, J. Comp. Neurol. 326:283–301, 1992). The present investigation is a quantitative analysis of the postnatal development of the TH‐IR amacrine cell population. TH‐IR amacrine cells gradually increase in size from birth (soma area of 44.7 ± 12.4 ± μm2, mean ± standard deviation) to adulthood (144.2 ± 28.0 μm2). Cell density slightly increases from postnatal day (PND) O (41.9 ± 9.5 cells/mm2) to PND 6 (47.2 ± 7.2 cells/mm2), then markedly decreases from PND 6 to adulthood (17.8 ± 5.3 cells/mm2) as a consequence of retinal growth. TH‐IR cell number almost doubles from PND O (about 4, 100 cells/retina) to adulthood (about 7,850 cells/retina). The increase in the total number of TH‐IR amacrine cells can be explained by the generation of new TH‐IR cells in the inner nuclear layer, a delay in the expression of the TH phenotype after neurogenesis by cells committed to be dopaminergic, or the acquisition of this dopaminergic phenotype by uncommitted cells. The development of the TH‐IR amacrine cell mosaic was assessed by an evaluation of the distribution of nearest neighbor distances of TH‐IR cells. There is a poor correlation between this distribution and a theoretical nonrandom distribution before PND 12. After this age, the nearest neighbor distance distribution shifts towards a nonrandom distribution, and is similar to that of the TH‐IR amacrine cell population in the adult retina. The establishment of the TH‐IR amacrine cell population mosaic is likely to be achieved through different interacting events, including intrinsic (e.g., genetic) factors, environmental influences, and nonuniform retinal growth. Overall, the population parameters analyzed in the present study approach adult values about the time of eye opening (PND 12) and they reach adult values by PND 26. © 1992 Wiley‐Liss, Inc.
Thalamic connections of the vestibular cortical fields in the squirrel monkey (Saimiri sciureus)
Authors: Akbarian S. , Grüsser O.‐J. , Guldin W. O.
Published: January 2005

The afferent thalamic connections to cortical fields important for control of head movement in space were analysed by intracortical retrograde tracer injections. The proprioceptive/vestibular area 3aV, the neck‐trunk region of area 3a, receives two thirds of its thalamic projections from the oral and superior ventroposterior nucleus (VPO/VPS), which is considered as the proprioceptive relay of the ventroposterior complex (Kaas et al., J. Comp. Neurol. 226:211–240, 1984). The parieto‐insular vestibular cortex (PIVC, area retroinsularis, Ri) receives its main thalamic input from posterior parts of the ventroposterior complex and from the medial pulvinar. Anatomical evidence is presented that the posterior region of the ventroposterior complex is a special compartment within this principal somatosensory relay complex. The parietotemporal association area T3, mainly involved in visual‐optokinetic signal processing, receives a substantial input from the medial, the lateral, and the inferior pulvinar.

Dual tracer experiments revealed that about 5% of the thalamic neurons projecting to 3aV were spatially intermingled with neurons projecting to areas PIVC or T3. This spatial intermingling was distributed over small but numerous, circumscribed thalamic regions, called “common patches,” which were found mainly in the intralaminar nuclei, the posterior group of thalamic nuclei, and the caudal parts of the ventroposterior complex. The “common patches” may indicate a functional coupling of area 3aV with the PIVC or area T3 on the thalamic level.

In control experiments thalamic projections to the granular insula Ig and the anterior part of area 7, two cerebral structures connected with the vestibular cortical areas, were studied. Some overlap in the thalamic relay structures projecting to these areas with these areas with those projecting to the vestibular cortices was found. A quantitative evaluation of thalamic regions projecting to different cortical structures was performed by constructing so‐called “thalamograms.” A scheme was developed that describes the afferent thalamic connections by which vestibular, visual‐optokinetic, and proprioceptive signals reach the vestibular cortical areas PIVC and 3aV. © 1992 Wiley‐Liss, Inc.
Transneuronal transfer of herpes simplex virus type 1 (HSV 1) from mixed limb nerves to the CNS. I. Sequence of transfer from sensory, motor, and sympathetic nerve fibres to the spinal cord
Authors: Ugolini G.
Published: January 2005

The time course of transneuronal transfer of Herpes simplex virus type 1 (HSV 1) from sensory, motor, and sympathetic nerve fibres to connected spinal neurones was examined. After injection of a constant number of infectious units into distal forelimb or hindlimb nerves of inbred rats of the same age, the extent of viral transfer was strictly dependent on the survival time postinoculation (p.i.). Retrograde transport to somatic motoneurones occurred at 28–29 hours p.i. (stage 1), in synchrony with anterograde transneuronal transfer via small cutaneous afferents (to laminae I–II). At 36–43 hours p.i. (stage 2), retrograde transneuronal transfer from sympathetic nerve fibres first labelled sympathetic preganglionic neurones. At 48–51 hours p.i. (stage 3), transfer via sensory and sympathetic axons became more extensive, labelling laminae III7ndash;IV and other preganglionic neurones. Transneuronal transfer from large muscle afferents and motoneurones (to Clarke's columns and the spinal intermediate zone) occurred only at 66–78 hours p.i. (stage 4). Further increases in distribution (stages 5–6) obtained between 78 and 97 hours p.i. may reflect both specific labelling of second and third order neurones and a gradual local loss of specificity. These results indicate that transfer of HSV 1 occurs through all main classes of peripheral axons, but that both anterograde and retrograde transneuronal transfer from small(unmyelinated and fine myelinated) cutaneous and sympathetic axons precedes transfer from large (myelinated) cutaneous and muscle afferents and motor axons. Analysis of viral transfer at sequential intervals is required to distinguish serially connected neurones, determine the route of labelling, and ensure its specificity. © 1992 Wiley‐Liss, Inc.
A quantitative study of the human cerebellum with unbiased stereological techniques
Authors: Andersen Birgitte Bo , Korbo Lise , Pakkenberg Bente
Published: January 2005

Estimates of total number of different neuron and glial cell types in the dentate nuclei and the four major regions of the human cerebellum were obtained by new stereological methods. With the optical disector and Cavalieri methods, the total number of neurons and glial cells in the human cerebellum of five elderly men was estimated to be 105,000 × 106 (coefficient of variation, CV = 0.13). Of this total, the granule cells comprised 101,000 × 106 (CV = 0.13) and the Purkinje cells comprised 30.5 × 106 (CV = 0.13) of the neurons. The mean of the total number of neurons in the dentate nucleus was 5.01 × 106 (CV = 0.28). The average surface area of the human cerebellum was estimated to be 1160 cm2 (CV = 0.29).

The rationale for the different sampling schemes used to quantify the various cell types is described. © 1992 Wiley‐Liss, Inc.
PHA‐L analysis of projections from the supramammillary nucleus in the rat
Authors: Vertes Robert P.
Published: January 2005

The projections of the supramammillary nucleus (SUM) were examined in the rat by the anterograde anatomical tracer Phaseolus vulgaris leucoagglutinin (PHA‐L). The majority of labeled fibers from SUM ascended through the forebrain within the medial forebrain bundle. SUM fibers were found to terminate heavily in the hippocampal formation, specifically within the granule cell layer and immediately adjoining molecular layer of the dentate gyrus. In addition, SUM fibers were shown to distribute densely to several structures with strong connections with the hippocampus, namely, the nucleus reuniens of the thalamus, the medial and lateral septum, the entorhinal cortex, and the endopiriform nucleus.

SUM fibers were also shown to project significantly to several additional subcortical and cortical sites. The subcortical sites were the dorsal raphe nucleus, the midbrain central gray, the fields of Forel/zona incerta, the dorsomedial hypothalamic area, midline/intralaminar nuclei of the thalamus (posterior paraventricular, rhomboid, central medial, intermediodorsal, and mediodorsal), the medial and lateral preoptic areas, the bed nucleus of the stria terminalis, the substantia innominata, the vertical limb of the diagonal band nucleus, and the claustrum. The cortical sites were the occipital, temporal, parietal, and frontal cortices.

Some notable differences were observed in projections from the lateral as compared to the medial SUM. For example, fibers originating from the lateral SUM distributed heavily to the hippocampal formation and parts of the cortex, whereas those from the medial SUM projected sparsely to these two regions.

The SUM projections to the hippocampal formation and associated structures may serve as the substrate for a SUM involvement in the generation of the theta rhythm of the hippocampus and the gating of information flow through the hippocampal formation. © 1992 Wiley‐Liss, Inc.
Developmental expression of the prothoracicotropic hormone in the CNS of the Tobacco Hornworm Manduca sexta
Authors: Westbrook Anne L. , Regan Sheila A. , Bollenbacher Walter E.
Published: January 2005

The prothoracicotropic hormone is an insect neuropeptide released into the hemolymph to signal molting and metamorphosis through its stimulation of steroidogenesis. The only known source of the prothoracicotropic hormone in the tobacco hornworm, Manduca sexta, has been a group of lateral cerebral neurosecretory cells, the L‐NSC III. In this study, the developmental and spatial distribution of the prothoracicotropic hormone was examined throughout the life cycle of Manduca. In common with many vertebrates and invertebrates in which neuropeptides are located in several regions within the central nervous system (CNS), the prothoracicotropic hormone phenotype in Manduca is expressed by CNS neurons in addition to the L‐NSC III. These neurons are located in the brain, frontal ganglion, and subesophageal ganglion. One cerebral neurosecretory cell group, the ventromedial neurons, expresses the prothoracicotropic hormone phenotype and the behavioral neurohormone, eclosion hormone. Whereas the L‐NSC III and the ventromedial neurons express the peptide phenotype throughout the life cycle, the other neurons express the peptide only during the embryonic and larval stages. This precise spatial and temporal expression of the prothoracicotropic hormone by different groups of neurosecretory cells raises the possibility that in Manduca the peptide may, in addition to its known neuroendocrine function, play other physiological roles in different ways at different stages of the life cycle. © 1993 Wiley‐Liss, Inc.
Cholinergic innervation of the mediodorsal thalamic nucleus in the monkey: Ultrastructural evidence supportive of functional diversity
Authors: Schwartz Michael L. , Mrzljak Ladislav
Published: January 2005

The ultrastructural organization of association nuclei in the primate thalamus is largely unexplored. In the present study we have combined electron microscopy with immunocytochemistry for the acetylcholine synthesizing enzyme choline acetyltransferase (ChAT) to assess the cholinergic synaptic organization of the mediodorsal (MD) nucleus in macaque monkeys. The cholinergic innervation of the MD nucleus showed striking regional variations with the greatest density of immunoreactive axons and varicosities found within the parvicellular division. Electron microscopic examination revealed that these ChAT immunoreactive (ChAT‐IR) axons were primarily small and unmyelinated. The majority of immunoreactive synaptic profiles were found within the extraglomerular neuropil (80.5%), with the remainder present in glomerular regions. Within the glomerular and extra‐glomerular neuropil ChAT‐IR profiles made contact with both conventional, presumably relay cell dendrites (CD), as well as with synaptic vesicle containing dendrites (SVCD) of local circuit neurons. In the glomeruli the frequency of synapses was approximately equal for CDs and SVCDs while in the extraglomerular areas 75% of the synaptic contacts were with CDs. ChAT‐IR synaptic profiles had a diversity of junctional complex morphologies. Within glomeruli they made symmetric synapses with CDs and predominantly asymmetric with SVCDs. The majority of extraglomerular contacts (60%) were classified as asymmetric and these as well as the smaller number of symmetric synapses contacted both CDs and SVCDs.

In accord with results of physiological studies, these anatomical data indicate that cholinergic input to thalamic nuclei influences relay cell activity both directly and indirectly via local circuit neurons. © 1993 Wiley‐Liss, Inc.
Fine structure of the dorsal cap of the inferior olive and its GAB aergic and non‐Gabaergic input from the nucleus prepositus hypoglossi in rat and rabbit
Authors: De Zeeuw C. I. , Wentzel P. , Mugnaini E.
Published: January 2005

The dorsal cap of the inferior olive is involved in the control of eye movements and is excited by inputs from the midbrain. In the present study we attempted to determine the inhibitory input to this nucleus in rat and rabbit.

The projection from the nucleus prepositus hypoglossi to the dorsal cap was studied in the light microscope by anterograde tracing of Phaseolus vulgaris‐leucoagglutinin and lesioninduced depletion of glutamic acid decarboxylase immunoreactivity, and in the electron microscope by anterograde tracing of wheat germ agglutinin‐coupled horseradish peroxidase combined with GABA immunocytochemistry. We show that the nucleus prepositus hypoglossi projects bilaterally to the dorsal cap, contralaterally to the ventrolateral outgrowth, and ipsilaterally to the medial accessory olive. After lesioning of the nucleus prepositus hypoglossi, the caudal dorsal cap was depleted of most of its glutamic acid decarboxylase‐immunoreactive terminals while the rostral dorsal cap and the ventrolateral outgrowth were depleted of a minor part. Ultrastructural analysis indicates that the majority, but not all, of the terminals from the nucleus prepositus hypoglossi in the dorsal cap are GABA‐positive. These GABA‐positive and GABA‐negative terminals form predominantly symmetric and asymmetric synapses; most of them synapse on dendrites outside and inside glomeruli, frequently in association with dendrodendritic gap junctions, while a small minority are axosomatic. None of the terminals from the nucleus prepositus hypoglossi was found to form a crest synapse, although synapses of this kind were predominantly formed by GABAergic terminals.

This study shows that the dorsal cap receives a major inhibitory input from the nucleus prepositus hypoglossi, the terminals of which are located at strategic positions on the olivary neurons. © 1993 Wiley‐Liss, Inc.
Dorsal root and dorsal column mediated synaptic inputs to reticulospinal neurons in lampreys: Involvement of glutamatergic, glycinergic, and GABaergic transmission
Authors: Dubuc Réjean , Bongianni Fulvia , Ohta Yoshihiro , Grillner Sten
Published: January 2005

This study was aimed at characterizing the inputs from dorsal roots and dorsal columns to reticulospinal neurons within the posterior rhombencephalic reticular nucleus in the lamprey. The in vitro isolated brainstem and spinal cord preparation was used. Microstimulation of dorsal roots and columns on both sides induced, in identified reticulospinal neurons, synaptic responses which consisted of large IPSPs mixed with excitation, particularly from stimulation on the ipsilateral side. When the spinal cord was selectively exposed to kynurenic acid or to Ca2+, synaptic responses to stimulation of dorsal roots and columns were not modified, whereas the same responses were abolished when the brainstem was exposed selectively to kynurenic acid, thus suggesting that the responses were carried by long fibres ascending directly to the brainstem. The excitatory and inhibitory synaptic responses are relayed by interneurons located in the brainstem. The ascending excitatory inputs to inhibitory interneurons and, most likely, also to excitatory interneurons, use excitatory amino acid transmission. Inhibitory responses were abolished by adding the glycinergic antagonist strychnine (5 μM) to the physiological solution, thus suggesting that inhibitory interneurons use glycine transmission. The synaptic transmission was depressed by (−)‐baclofen, a GABAu agonist, probably acting at a presynaptic site.

Taken together, the present results suggest that dorsal root and dorsal column stimulations give rise to disynaptic inhibition and excitation of reticulospinal neurons mediated by excitatory and inhibitory amino acid transmission via brainstem interneurons. © 1993 Wiley‐Liss, Inc.
Ultrastructure of the circuit providing, input to the crayfish lateral giant neurons
Authors: Lee Sunhee C. , Krasne Franklin B.
Published: January 2005

Labeled or otherwise identified neurons of the crayfish lateral giant escape reaction circuit were examined electron microscopically and the findings compared to expectations from physiology.

Terminals of primary afferents contained clear, approximately 45 nm, irregularly round synaptic vesicles, while sensory interneuron terminals had slightly larger, 50 nm, more strictly round vesicles, permitting tentative classification based on anatomical criteria.

Excitatory synapses on the lateral giants, believed from physiology to be electrical, generally had some gap junctions, but these were almost invariably paralleled by more prominent chemical junctional regions of unknown function. There may also be a class of interneurons making purely chemical synapses on the lateral giants. Synapses from primary afferents to sensory interneurons, believed from physiology to be cholinergic, had purely chemical morphology.

Synapses with narrow elongated vesicles, similar to GABAergic vesicles seen in other neurons, frequently occurred on terminals of primary afferents. These synapses provide a basis for known presynaptic inhibition of afferent input. Consistent with physiology, such inhibitors sometimes also contacted the postsynaptic targets of the primary afferents and sometimes received input from other primary afferents. Afferent terminals also received some input from profiles richin large dense cored vesicles.

Presumptive inhibitory input found on proximal dendrites of lateral giants provides a basis for known recurrent inhibition. However, similar inhibitory synapses that sometimes received local input from excitors of the lateral giants were also found distally mixed with excitatory inputs. These provide a basis for recently discovered distal inhibitory input following excitation and for tonic inhibition. © 1993 Wiley‐Liss, Inc.
Vestibular primary afferent projection to the cerebellum of the rabbit
Authors: Barmack N. H. , Baughman R. W. , Errico P. , Shojaku H.
Published: January 2005

The vestibular primary afferent projection to the cerebellum of the rabbit was studied with retrograde and orthograde tracers. We injected individual lobules of the cerebellum with horseradish peroxidase (HRP) or wheat germ agglutinin‐HRP (WGA‐HRP). Following these injections the numbers of labeled and unlabeled cells in Scarpa's ganglion were counted. Approximately 64–89% of the cells in Scarpa's ganglion were labeled retrogradely following uvula‐nodular injections. About 2% of the cells in the ipsilateral Scarpa's ganglion were labeled after injections of the flocculus. Virtually no cells were labeled following injections of the ventral paraflocculus.

The vestibular primary afferent projection to the uvula‐nodulus is so extensive that it must be part of a collateral system that also innervates the vestibular nuclei. This collateral projection pattern was confirmed by using fluorescent tracers injected into the uvula‐nodulus and vestibular complex. Fluorogold was injected into the uvula‐nodulus and peroxidaserhodamine isothiocyanate was injected into the vestibular complex. More than 50% of the neurons in Scarpa's ganglion were double labeled by these subtotal injections.

The dense vestibular primary afferent projection to the uvula‐nodulus was confirmed by using the C fragment of tetanus toxin (TTC) injected into the labyrinth as an orthograde tracer. With the TTC technique, the vestibular primary afferent projection to the uvula‐nodulus terminated exclusively in the ipsilateral granule cell layer of lobules 9d and 10. Much sparser vestibular primary afferent projections were found in the banks of major cerebellar sulci. A barely detectable projection was found to the flocculus and ventral paraflocculus. © 1993 Wiley‐Liss, Inc.
Localization of cardiac vagal preganglionic motoneurones in the rat: Immunocytochemical evidence of synaptic inputs containing 5‐hydroxytryptamine
Authors: Izzo P. N. , Deuchars J. , Spyer K. M.
Published: January 2005

The origin of cardiac vagal preganglionic motoneurones in the rat is still controversial and knowledge of the chemistry of synaptic inputs onto these neurones is limited. In this investigation vagal preganglionic motoneurones innervating the heart were identified by the retrograde transport of cholera toxin conjugated to horseradish peroxidase (CT‐HRP) combined with the immunocytochemical localization of 5‐hydroxytryptamine. Injection of CT‐HRP into the myocardium resulted in the retrograde labelling of neurones primarily in the ventral regions of the nucleus ambiguus (75.1%). Labelled neurones were also distributed in a narrow band through the reticular formation extending between the dorsal motor nucleus of the vagus nerve and the nucleus ambiguus (17.3%) as well as in the dorsal motor nucleus itself (7.6%).

A combination of retrograde labelling with immunocytochemistry for 5‐hydroxytrypta‐mine revealed that the neuronal perikarya and the dendrites of cardiac vagal motoneurones in the nucleus ambiguus were often ensheathed in 5‐hydroxytryptamine‐immunoreactive axonal boutons. Electron microscopic examination of this material confirmed that there were synaptic specializations between these boutons and the cardiac vagal motoneurones. The identification of 5‐hydroxytryptamine‐containing synaptic inputs to this population of vagal motoneurones provides further detail towards the understanding of the regulation of heart rate by the parasympathetic nervous system. © 1993 Wiley‐Liss, Inc.
Noradrenergic innervation of the hypothalamus of rhesus monkeys: Distribution of dopamine‐β‐hydroxylase immunoreactive fibers and quantitative analysis of varicosities in the paraventricular nucleus
Authors: Ginsberg Stephen D. , Hof Patrick R. , Young Warren G. , Morrison John H.
Published: January 2005

The distribution of noradrenergic processes within the hypothalamus of rhesus monkeys (Macaca mulatta) was examined by immunohistochemistry with an antibody against dopamine‐β‐hydroxylase. The results revealed that the pattern of dopamine‐β‐hydroxylase immunoreactivity varied systematically throughout the rhesus monkey hypothalamus. Extremely high densities of dopamine‐β‐hydroxylase‐immunoreactive processes were observed in the paraventricular and supraoptic nuclei, while relatively lower levels were found in the arcuate and dorsomedial nuclei and in the medial preoptic, perifornical, and suprachiasmatic areas. Moderate levels of dopamine‐β‐hydroxylase immunoreactivity were found throughout the lateral hypothalamic area and in the internal lamina of the median eminence. Very few immunoreactive processes were found in the ventromedial nucleus or in the mammillary complex. Other midline diencephalic structures were found to have high densities of dopamine‐β‐hydroxylase immunoreactivity, including the paraventricular nucleus of the thalamus and a discrete subregion of nucleus reuniens, the magnocellular subfascicular nucleus. A moderate density of dopamine‐β‐hydroxylase immunoreactive processes were found in the rhomboid nucleus and zona incerta whereas little dopamine‐β‐hydroxylase immunoreactivity was found in the fields of Forel, nucleus reuniens, or subthalamic nucleus. The differential distribution of dopamine‐β‐hydroxylase‐immunoreactive processes may reflect a potential role of norepineph‐rine as a regulator of a variety of functions associated with the nuclei that are most heavily innervated, e.g., neuroendocrine release from the paraventricular and supraoptic nuclei, and gonadotropin release from the medial preoptic area and mediobasal hypothalamus. Additionally, quantitative analysis of dopamine‐β‐hydroxylase‐immunoreactive varicosities was performed on a laser scanning microscope in both magnocellular and parvicellular regions of the paraventricular nucleus of the hypothalamus. The methodology employed in this study allowed for the high resolution of immunoreactive profiles through the volume of tissue being analyzed, and was more accurate than conventional light microscopy in terms of varicosity quantification. Quantitatively, a significant difference in the density of dopamine‐β‐hydroxylase‐immunoreactive varicosities was found between magnocellular and parvicellular regions, suggesting that parvicellular neurons received a denser noradrenergic input. These differential patterns may reflect an important functional role for norepinephrine in the regulation of anterior pituitary secretion through the hypothalamic‐pituitary‐adrenal stress axis. © 1993 Wiley‐Liss, Inc.
Fibronectin‐like immunoreactivity of the basilar membrane of young and aged rats
Authors: Keithley Elizabeth M. , Ryan Allen F. , Woolf Nigel K.
Published: January 2005

Dysfunction of cochlear mechanics has been hypothesized to be a source of age‐related hearing loss and the basilar membrane mass and stiffness contribute to normal cochlear mechanics. Fibronectin, a large, extracellular matrix protein and a major component of the basilar membrane, may contribute to both the mass and stiffness of the membrane. Mesothelial cells underlying the basilar membrane may produce the fibronectin and also contribute to the mass of the membrane. Changes in either the fibronectin or the mesothelial cells might, therefore, have an effect on cochlear mechanics. In order to assess basilar membrane changes in aged animals, young adult (2–4 months) and aged (24–26 months) Sprague‐Dawley rats were evaluated for the presence of fibronectin‐like protein and mesothelial cells. The basilar membrane in the young animals had strong fibronectin‐like immunoreactivity throughout its length. The old animals, on the other hand, showed normal fibronectin immunoreactivity in the basilar membrane of the basal turn, but little or no reactivity in the apical cochlear turn. The number of mesothelial cells was reduced throughout the length of the membrane in aged animals, with the greatest loss in the basal turn (60% fewer cells). These two degenerative changes, which appear to be independent of each other, may contribute to the observed threshold shifts in aged cochleas. © 1993 Wiley‐Liss, Inc.
Functional organization of the ventral lateral geniculate complex of the tree shrew (Tupaia belangeri): I. Nuclear subdivisions and retinal projections
Authors: Conley Michael , Friederich‐Ecsy Beate
Published: January 2005

This is the first of two papers describing the organization and connections of the ventral lateral geniculate complex (GLv) in the tree shrew. Using a combination of Nissl, Golgi, histochemical, and immunocytochemical methods, we have identified two major divisions (lateral and medial) of GLv, both of which can be further subdivided. The lateral division contains three subdivisions, external, internal and intergeniculate leaflet. The medial division contains two subdivisions, medio‐rostral and medio‐caudal. All three lateral subdivisions receive input from the retina, the densest terminations being in the external subdivision and intergeniculate leaflet. These projections originate primarily from small retinal ganglion cells, although a feẁ large retinal ganglion cells also project to GLv by way of collateral branches. Each subdivision of GLv has a distinct cytoarchitectonic and immunocytochemical make‐up. In general, the level of immunoreactive endings for glutamic acid decarboxylase (GAD), leuenkephalin (ENK), and choline acetyltransferase (ChAT) parallels the distribution of retinal projections. Thus, all three markers are particularly dense in the external subdivision and the intergeniculate leaflet. Cell bodies immunoreactive for ENK are restricted to the external and intergeniculate leaflet subdivisions. The medial subdivisions stain relatively poorly for GAD, ENK, and ChAT, although each has other cytological features that differentiate them from the lateral subdivisions and the adjacent thalamic reticular nucleus. © 1993 Wiley‐Liss, Inc.
Regional and laminar organization of projections from the presubiculum and parasubiculum to the entorhinal cortex: An anterograde tracing study in the rat
Authors: Caballero‐Bleda Maria , Witter Menno P.
Published: January 2005

The regional and laminar organization of the projections from the presubiculum and the parasubiculum to the entorhinal cortex was analyzed in the rat with the anterograde tracer Phaseolus vulgaris‐leucoagglutinin (PHA‐L). The projections from the presubiculum were bilateral and confined to layers III and I of the medial entorhinal area (MEA). Both the ipsi‐ and the contralateral projections showed similar distributions and were almost of equal density. Projections to layer III of the entorhinal cortex arose predominantly from superficial layers of the presubiculum, whereas the fibers that reach layer I of the entorhinal cortex appear to originate preferentially from the deep layers of the presubiculum. These fibers also appeared to innervate weakly layer II of MEA. The parasubiculum distributed projections not only to MEA but also to the lateral entorhinal area (LEA), innervating layer II selectively. The innervation of LEA was quite dense and extensive. Very weak projections from the parasubiculum to the contralateral entorhinal cortex were observed in this study.

The position of the terminal plexus in the entorhinal cortex was determined by the point of origin along both the dorsoventral and transverse or proximodistal axes of the presubiculum and parasubiculum. Projections from the presubiculum and parasubiculum entered the entorhinal cortex at the level of the injection, or slightly ventral to it, and the main terminal field was always present ventrally to the injection site. The dorsoventral axis of origin thus corresponded to a similarly oriented axis of termination in the entorhinal cortex. The distribution in relation to the origin along the transverse axis was more complex, and differences between the presubiculum and parasubiculum were present. The proximal presubiculum, i.e., the part closest to the subiculum, projected to the most lateral part of MEA and the central part of the presubiculum sent fibers to the most medial part of MEA. The distal part of the presubiculum, i.e., the part that borders the parasubiculum, projected to the central part of MEA. Projections from the portion of the parasubiculum directly adjacent to the presubiculum, the so‐called proximal parasubiculum, reached medial parts of MEA, and those originating in the central part distributed preferentially to lateral parts of MEA and adjacent medial parts of LEA. The distal part of the parasubiculum that borders the entorhinal cortex projected mainly to almost the full mediolateral extent of LEA.

The regional and laminar organizations of the projections from the presubiculum and parasubiculum to the entorhinal cortex suggest that information is selectively conveyed not only to different cell layers but also to restricted dorsoventral and mediolateral parts of the entorhinal cortex. © 1993 Wiley‐Liss, Inc.
Early pattern of neuronal differentiation in the Xenopus embryonic brainstem and spinal cord
Authors: Hartenstein Volker
Published: January 2005

Wholemount antibody labeling techniques and horseradish peroxidase backfilling were used to analyze the pattern of neuronal differentiation in the embryonic Xenopus central nervous system between stages 22 and 35/36. In the spinal cord, the first neurons to differentiate are the Rohon‐Beard neurons; they are followed by ventral neurons with descending axons (descending interneurons, motoneurons) and lateral interneurons with commissural axons. The somata and axons of these primary neurons form dorsal, ventral, and lateral columns, respectively; the ventral and lateral columns uninterruptedly continue forward into the brainstem. The distribution and projection patterns of spinal neurons were analyzed quantitatively. Rohon‐Beard neurons, commissural interneurons, and primary motoneurons vary in number from segment to segment. Thus, these neurons are not distributed in a segmental pattern. In each segment, neurons of a given type project axons whose length varies over a wide range. The numerical distribution of length of axons formed by a population of neurons of a given type was calculated and expressed as the projection profile of these neurons. For each type of neuron and spinal segment, the projection profile is different. Furthermore, the projection profiles change in a systematic way along the spinal cord. For example, the fraction of Rohon‐Beard neurons with long ascending axons steadily increases if one moves towards caudal spinal levels. The findings suggest that suprasegmental cues with a graded distribution along the spinal cord determine the number and projection profile of a particular cell type in a given segment. © 1993 Wiley‐Liss, Inc.
Sensory innervation in the inner conical body of the vibrissal follicle‐sinus complex of the rat
Authors: Mosconi T. M. , Rice F. L. , Song M. J.
Published: January 2005

The innervation of the inner conical body of the vibrissal follicle‐sinus complex of the rat was examined by high‐voltage and conventional transmission electron microscopy of serial and semi‐serial sections. The inner conical body is innervated by axons supplied almost exclusively by several superficial vibrissal nerves that arise from the infraorbital branch of the trigeminal nerve and converge upon the neck of the follicle‐sinus complex. Each superficial vibrissal nerve contains a few Aδ myelinated axons and several bundles of 20–30 unmyelinated axons. These axons enter the inner conical body and distribute circumferentially within 7–10 ring‐like arrays that encircle the vibrissal follicle and are stacked through the superficial‐to‐deep extent of the inner conical body. Each ring consists of 1 or 2 myelinated axons and several small bundles of 2–15 unmyelinated axons enclosed in sheaves of parallel collagen fibrils. Myelinated axons provide exclusively lanceolate endings that may arise at the termination of the axon or at nodes of Ranvier. Within the small bundles, unmyelinated axons individually terminate in succession as abrupt cytoplasmic swellings referred to as cytoplasmic blebs, which contain mitochondria or clusters of clear or dense‐core vesicles. Because of their affiliation with collagen fibrils and the proximity of myelinated axons, the blebbed endings may have been misinterpreted as Ruffini endings in previous studies. Their structure, distribution, and origin from unmyelinated axons suggest that the blebbed endings may constitute a unique array of low‐threshold C‐mechanoreceptors. © 1993 Wiley‐Liss, Inc.
Cholinergic projection to the dorsal cap of the inferior olive of the rat, rabbit, and monkey
Authors: Barmack N. H. , Fagerson M. , Errico P.
Published: January 2005

The inferior olive is divided into several subnuclei that receive specific sensory information. The caudal dorsal cap of the medial accessory subdivision of the inferior olive receives horizontal optokinetic information from the nucleus of the optic tract. The immediately subjacent b̃‐nucleus receives vertical vestibular information mediated by a GABAergic pathway originating from the ipsilateral descending and medial vestibular nuclei. None of the transmitters to the dorsal cap have been identified.

Using choline acetyltransferase (ChAT) immunohistochemistry, we have identified a cholinergic pathway that terminates exclusively in the dorsal cap of rats and monkeys. No other division of the inferior olive received a significant cholinergic innervation. In the rabbit, immunostaining for ChAT reveals a weaker and more diffuse cholinergic innervation of both the dorsal cap and the subjacent b̃‐nucleus.

In rats and rabbits we injected iontophoretically the orthograde tracer Phaseolus vulgaris leucoagglutinin (PHA‐L) into the medial and descending vestibular nuclei (MVN, DVN) as well as the nucleus prepositus hypoglossi (NPH) in order to trace the possible origin of the cholinergic projection. PHA‐L injections into the NPH and medial aspect of the MVN labeled terminals within the contralateral dorsal cap. PHA‐L injections in the central and lateral aspects of the MVN as well as the DVN labeled the ipsilateral b̃‐nucleus.

Pressure injections of wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) in the caudal dorsal cap of the rabbit inferior olive demonstrated a predominantly contralateral projection to the dorsal cap from the lateral aspect of the NPH. However, pressure injections of HRP into the caudal dorsal cap combined with ChAT immunohistochemistry in the rabbit demonstrated that most of the neurons of the NPH that projected to the dorsal cap were not cholinergic, and that most of the ChAT‐positive neurons within the NPH occupied a more ventral location than the neurons within the NPH that were retrogradely labeled from the HRP injection into the contralateral dorsal cap.

In the rat, we made lesions in the MVN, DVN and NPH by injection of ibotenic acid (0.3–0.5 m̈l), in an attempt to deplete the dorsal cap of the inferior olive of its cholinergic input. Lesions confined to the NPH and medial aspect of the MVN of the rat caused a loss of ChAT staining in the contralateral dorsal cap. Lesions placed more laterally within the MVN or DVN failed to deplete ChAT‐positive terminals in the contralateral or ipsilateral dorsal caps.

The dorsal cap of the rat and monkey receives a discrete cholinergic projection. In the rat, this projection originates from the contralateral NPH. In the rabbit, the caudal inferior olive receives a weak cholinergic projection. The dorsal cap receives a projection from the contralateral NPH. However, this projection is mediated by a non‐cholinergic transmitter. © 1993 Wiley‐Liss, Inc.