bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of microglia in the albino rabbit retina
Authors: Ashwell Ken
Published: January 2005

In this study the development of ameboid microglia and resting microglia in the retina of the albino rabbit has been examined by means of a lectin derived from Griffonia simplicifolia. Ameboid microglia are present in the retina as early as E12, when the optic fissure is in the process of closure, and appear to be concentrated initially at the vitreal surface. At E14 many ameboid microglia can be seen to extend processes to the ventricular surface of the cytoblast layer, but in subsequent ages these cells are rare and ameboid microglia are largely confined to the ganglion cell layer, inner plexiform layer, and occasionally the developing inner nuclear layer. By adult life, mature (or resting) microglia are confined to the inner plexiform and ganglion cell layers. Numbers of microglia increase steadily throughout fetal life from a mean of 400 at E14, the earliest age quantified, to a peak of 28,600 at E30. There is a small postnatal drop in numbers to 17,150 at P9. Microglia could only be labelled faintly in animals older than P11, but analysis of two adult (P130) retinas with adequate labelling suggested that numbers rise to a value of about 23,800 at this age. Ameboid microglia thus appear in the retina 11 days prior to the onset of axon loss in the optic nerve (about E23) and 14 days prior to the beginning of the period of reduction of retinal ganglion cell numbers (about E26). The present findings indicate that while some microglial precursors may enter the retina in response to debris generated during the natural retinal ganglion cell death period, most enter the retina well before this period. Also, microglia present a uniform density distribution with apparently regular spacing as early as E16, so the uniform regular distribution cannot simply be the consequence of regularly distributed pyknotic figures as previously suggested.
Vasopressin and oxytocin systems in the brain and upper spinal cord of Macaca fascicularis
Authors: Caffé A. R. , Van Ryen P. C. , Van Der Woude T. P. , Van Leeuwen F. W.
Published: January 2005

This paper describes the vasopressin (VP) and oxytocin (OXT) immunoreactive structures in the brain and upper spinal cord of the adult male and female Macaca fascicularis.

Immunocytochemistry following intraventricular application of colchicine displayed VP neurons in the diagonal band of Broca (DBB), bed nucleus of the stria terminalis (BST), medial amygdaloid nucleus, dorsomedial hypothalamic nucleus, area of the locus coeruleus (LC), solitary tract nuclei (NTS), and the dorsal horn of the cervical spinal cord in addition to those known to exist in the paraventricular, supraoptic, and suprachiasmatic hypothalamic nuclei. Furthermore, a dense accumulation of VP fibers was observed in areas such as the DBB, medial septum, BST, amygdala, hippocampus, ventral tegmental area, periaquaductal gray, dorsal and ventral raphe, area of Forel, LC region, parabrachial nuclei, and NTS. The lateral septum and lateral habenula displayed no and very few VP fibers, respectively.

No extrahypothalamic OXT neurons were found in the brain of this macaque monkey. Dense concentrations of OXT fibers were demonstrated in the amygdala, NTS and marginal layer of the cervical spinal cord.

No sexual dimorphism was found in this primate VP or OXT system.

The results show a distribution of the central VP and OXT systems in this primate which is quite different from that in the rat. However, in various aspects it agrees with current data on the VP and OXT systems of the human brain. The present results suggest, therefore, that this monkey might serve as a better model for the human VP system than the rat.
Alterations in catecholamine neurons of the locus coeruleus in senile dementia of the Alzheimer type and in Parkinson's disease with and without dementia and depression
Authors: Chan‐Palay V. , Asan E.
Published: January 2005

The present study provides qualitative and quantitative investigations of the norepinephrine (NE) neurons in the locus coeruleus (LC) in two neurodegenerative disorders, the senile dementia of the Alzheimer type (SDAT) and Parkinson's disease (PD). The group of PD subjects was subdivided into cases without dementia (P − D), cases with dementia, L‐dopa responsive (P + D), and cases with fulminant dementia whose motor disorder symptoms were L‐dopa nonresponsive (P + D/L‐dopa non‐responsive). NE neurons were demonstrated by immunocytochemistry against tyrosine hydroxylase (TH). Quantitations of neuronal parameters and cell numbers and three‐dimensional reconstructions of the LC were carried out with a computer‐assisted system.

In SDAT cases, the rostrocaudal LC length (13 ± 2.2 mm) is shorter than in controls (14.9 ± 1.4 mm). The four basic LC neuron classes found in the normal human brain (large multipolar, large “bipolar,” small multipolar, and small “bipolar” neurons; Chan‐Palay and Asan: J. Comp. Neurol. This issue) are recognizable, but many cell somata are swollen and misshapen with foreshortened, thick, and less branched dendrites. LC neuron numbers are reduced (between − 3.5% and −87.5%). Neuron loss is greatest in the rostral part, less in the middle, and least in the caudal part.

In PD cases, the rostrocaudal length (12.4 ± 1.5 mm) is shorter than in SDAT and controls. The neuronal morphology is more severely altered than in SDAT. The basic neuron classes are hardly distinguishable. Most cell bodies are swollen; they frequently contain Lewy bodies; and the dendrites are short and thin with absent or reduced arborizations. Neuron numbers are more reduced than in SDAT (between − 26.4% and −94.4%). Alterations are as severe caudally as rostrally in P − D, and P+D/L‐dopa nonresponsive cases. P+D cases are more severely affected rostrally. The presence of depression in SDAT and Parkinson's patients is accompanied by the greatest loss of LC neurons. On the basis of morphological alterations of the TH‐immunoreactive neurons, and the degree and topographical distribution of neuron loss, a differentiation is possible between the LC in normal brain and that in SDAT and PD for diagnostic purposes.
Posterior parietal cortex in rhesus monkey: II. Evidence for segregated corticocortical networks linking sensory and limbic areas with the frontal lobe
Authors: Cavada Carmen , Goldman‐Rakic Patricia S.
Published: January 2005

We have examined the circuitry connecting the posterior parietal cortex with the frontal lobe of rhesus monkeys. HRP‐WGA and tritiated amino acids were injected into subdivisions 7m, 7a, 7b, and 7ip of the posterior parietal cortex, and anterograde and retrograde label was recorded within the frontal motor and association cortices. Our main finding is that each subdivision of parietal cortex is connected with a unique set of frontal areas. Thus, area 7m, on the medial parietal surface, is interconnected with the dorsal premotor cortex and the supplementary motor area, including the supplementary eye field. Within the prefrontal cortex, area 7m's connections are with the rostral sector of the frontal eye field (FEF), the dorsal bank of the principal sulcus, and the anterior bank of the inferior arcuate sulcus (Walker's area 45). In contrast, area 7a, on the posterior parietal convexity, is not linked with premotor regions but is heavily interconnected with the rostral FEF in the anterior bank of the superior arcuate sulcus, the dorsolateral prefrontal convexity, the rostral orbitofrontal cortex, area 45, and the fundus and adjacent cortex of the dorsal and ventral banks of the principal sulcus. Area 7b, in the anterior part of the posterior parietal lobule, is interconnected with still a different set of frontal areas, which include the ventral premotor cortex and supplementary motor area, area 45, and the external part of the ventral bank of the principal sulcus. The prominent connections of area 7ip, in the posterior bank of the intraparietal sulcus, are with the supplementary eye field and restricted portions of the ventral premotor cortex, with a wide area of the FEF that includes both its rostral and caudal sectors, and with area 45. All frontoparietal connections are reciprocal, and although they are most prominent within a hemisphere, notable interhemispheric connections are also present.

These findings provide a basis for a parcellation of the classically considered association cortex of the frontal lobe, particularly the cortex of the principal sulcus, into sectors defined by their specific connections with the posterior parietal subdivisions. Moreover, the present findings, together with those of a companion study (Cavada and Goldman‐Rakic): J. Comp. Neurol. This issue have allowed us to establish multiple linkages between frontal areas and specific limbic and sensory cortices through the posterior parietal cortex. The net‐works thus defined may form part of the neural substrate of parallel distrib‐uted processing in the cerebral cortex.
Anterograde tracing of the rat olivocerebellar system with phaseolus vulgaris leucoagglutinin (PHA‐L). Demonstration of climbing fiber collateral innervation of the cerebellar nuclei
Authors: van der Want J. J. L. , Wiklund L. , Guegan M. , Ruigrok T. , Voogd J.
Published: January 2005

The olivocerebellar climbing fiber system was investigated in the rat with anterograde Phaseclus vulgaris leucoagglutinin (PHA‐L) tracing. The specific objective of the study was to find morphological evidence of climbing fiber collaterals innervating the cerebellar nuclei.

Small iontophoretic injections of PHA‐L were placed in different parts of the inferior olivary complex, and labelled olivocerebellar fibers could be traced to their termination as climbing fibers in sagittal zones of the contralateral cerebellar cortex. Reaching the cerebellum via the restiform body, the labelled olivocerebellar axons entered the deep cerebellar white matter anterior to the cerebellar nuclei. Most of these thicker, nonterminal axons continued dorsally around the nuclei, but some ran through them. Bundles of fibers could be followed into the folial white matter toward their cortical zones of termination.

Depending on which part of the olivary complex that was injected with PHA‐L, labelled axons were seen to converge on different regions of the cerebellar nuclei, where dense plexuses of thin varicose terminal fibers appeared. Quantitative estimates of the innervation ranged from 1.7 to 4.3 million boutons per mm3 in the fastigial (FN), interposed, and main parts of the lateral cerebellar (LCN) nuclei, whereas the parvicellular portion of LCN demonstrated 15–20 million varicosities per mm3. Frequently, thicker olivocerebellar axons, which seemed directed toward the cerebellar cortex, were seen to send a fine collateral branch toward these areas of nuclear innervation.

As controls, PHA‐L was injected into the degenerated olivary complex of 3‐acetylpyridine‐treated rats. Neither cortical climbing fiber terminals nor nerve terminal plexuses in the nuclei appeared in these experiments. In cases with injection sites extending into the reticular formation, substantial mossy fiber labelling was present bilaterally in the cortex, but the cerebellar nuclei were devoid of labelled innervation or demonstrated only a few larger diameter fibers.

The projection of the inferior olivary complex to the cerebellar nuclei was strictly topographically organized and agreed in principle with the organization described in the cat by Groenewegen et al. ('79). The caudal medial accessory olive (MAO) projected to FN, the rostral MAO to the posterior interposed nucleus (NIP), the rostral part of the dorsal accessory olive (DAO) to the anterior interposed nucleus (NIA), and the principal olive (PO) to LCN. Smaller injections into olivary subnuclei resulted in labelled innervation in restricted sectors of individual cerebellar nuclei, suggesting the existence of a more detailed topographical organization.
Glutamate and aspartate immunoreactivity in corticospinal neurons of rats
Authors: Giuffrida R. , Rustioni A.
Published: January 2005

A combination of retrograde tracers and immunostaining was employed to test whether corticospinal tract (CST) neurons in rats may use amino acid excitatory neurotransmitters. CST neurons were identified following injections of either Diamidino Yellow (DY) or colloidal gold‐labeled enzymatically inactive horseradish peroxidase conjugated to wheat germ agglutinin (WGAapoHRP‐Au) in the spinal cord. As retrograde tracers, the two substances seemed to be equally effective, but WGAapoHRP‐Au was better suited than DY as a tracer to use in combination with immunocytochemistry. Sections through the primary sensorimotor cortex, which contained the bulk of identified CST neurons, and the secondary somatosensory cortex were processed with antisera raised in rabbits against glutamate (Glu) or aspartate (Asp) conjugated by glutaraldehyde to hemocyanin. In rats with DY injections, about 60–75% of the CST neurons were Glu‐immunopositive, with higher ratios in SI and MI than in SII. Similar results were obtained in all areas examined from the rats with injections of WGAapoHRP‐Au. Only sections from rats with injections of WGAapoHRP‐Au were processed for Asp immunostaining. In this material, between 65 and 75% of the CST neurons were Asp‐immunopositive, with a slightly higher ratio in SI and MI than in SII.

The possibility that these results might reflect limited penetration of the antiserum and/or staining of the same population of CST neurons by either antiserum was addressed in sections processed with both the Glu and Asp antisera. In sections incubated in a mixture of the two antisera, the percentage of immunostained CST neurons was higher, about 90%, than in sections processed for only one of the two antisera. Furthermore, in rats in which Glu and Asp antibodies were visualized by two distinguishable immunostainings, four populations of CST neurons were identifiable: (1) neurons only immunopositive for Glu, (2) neurons only immunopositive for Asp, (3) neurons likely to be stained by both, and (4) neurons immunonegative for both antisera. Twenty‐five to 30% of CST neurons were positive for only one antiserum, and about 50% were positive for both. No preferential distribution was evident for any one of these populations of neurons. However, perikaryal cross‐sectional areas were larger for the double‐stained than for the single‐stained CST neurons.

Glutamergic and aspartergic transmission in CST neurons has been proposed in several publications in which methods other than immunocytochemistry were employed. While the present observations support previous results and conclusions, it remains to be demonstrated conclusively that these amino acids, and not di‐ or oligopeptides, possibly recognized by the same antisera raised against Glu and Asp, are the natural transmitters in CST neurons.
Spino‐olivary termination on spines in cat medial accessory olive
Authors: Molinari Helen H. , Starr Kathy A.
Published: January 2005

Three functional regions of the inferior olive, the caudal medial accessory olive (cMAO) and the caudal and rostral dorsal accessory olive (DAO) receive input from the spinal cord. The present study determined how spinal inputs to cMAO interact with olivary neurons. These inputs were labeled by injections in cat lumbosacral of wheat germ agglutinin conjugated to horseradish peroxidase. The tracer was visualized with tetramethylbenzidine. The morphology of the labeled spino‐olivary terminals and the relationship between these terminals and postsynaptic elements were determined.

Spino‐olivary terminals in cMAO displayed the morphological characteristics classically associated with excitatory synapses. Almost three quarters synapsed on spines, most of which contacted other spines, forming spine clusters. The majority of postsynaptic spines also received convergent input from apparently excitatory, nonlumbosacral afferents. This postsynaptic organization provides several possible benefits for the putative role of cMAO in the control of posture.

An earlier study demonstrated that in DAO, almost three quarters of lumbosacral, spino‐olivary terminals synapse on dendrites (Molinari: Neuroscience 27:425–435, 1988). Thus, lumbosacral afferents appear to differ fundamentally in the way in which they interact with neurons in cMAO and DAO. These results suggest that the way information is processed may be as important in determining the functional differences between olivary regions as what information is received.
Metabolic anatomy of brain: A comparison of regional capillary density, glucose metabolism, and enzyme activities
Authors: Borowsky Iris Wagman , Collins Robert C.
Published: January 2005

Regional variations in capillary density, glucose utilization rate, and activities of the glycolytic enzyme lactate dehydrogenase and the mitochondrial enzyme cytochrome oxidase were compared in the rat brain. The distributions of capillaries and enzymes were studied by means of histochemical staining techniques, and glucose metabolism was measured by means of [14C]2‐deoxyglucose autoradiography. Analysis of 18 gray and five white matter regions revealed a positive correlation between capillary density and glucose utilization rate. A negative correlation was found between capillary density and lactate dehydrogenase among gray matter structures. Analysis of capillaries and enzymes was also performed within laminated histological fields: hippocampus, olfactory bulb, and olfactory cortex. In general, this revealed reciprocal patterns of staining for lactate dehydrogenase and cytochrome oxidase. Capillary density paralleled cytochrome oxidase activity. The zones of intense staining for lactate dehydrogenase and cytochrome oxidase corresponded to the synaptic terminal fields of different input pathways. These findings demonstrate distinct distributions of a glycolytic and an oxidative enzyme within the brain which are at least partly associated with pathway specificity.
Compartment‐specific changes in the density of choline and dopamine uptake sites and muscarinic and dopaminergic receptors during the development of the baboon striatum: A quantitative receptor autoradiographic study
Authors: Lowenstein P. R. , Slesinger P. A. , Singer H. S. , Walker L. C. , Casanova M. F. , Raskin L. S. , Price D. L. , Coyle J. T.
Published: January 2005

In the fetal and young primate neostriatum, cholinergic and dopaminergic markers show patches of high density surrounded by a lower‐density matrix. In the adult, the same markers display the opposite pattern, a lower density in striosomes, surrounded by a higher‐density matrix. In order to understand the developmental sequences leading to the adult compartmental organization of the primate neostriatum, a quantitative technique was used to study the ontogeny of pre‐ and postsynaptic components of cholinergic and dopaminergic neurons in baboon caudate nucleus and putamen. The development of specific uptake mechanisms for choline and dopamine and receptors was studied by means of quantitative autoradiography of the specific binding of [3H]‐hemicholinium‐3 ([3H]‐HC3) and [3H]‐mazindol ([3H]‐MAZ) to the choline and dopamine uptake systems, respectively. [3H]‐pirenzepine ([3H]‐PIR) was used to label M1 muscarinic receptors and [3H]‐spiroperidol ([3H]‐SPI) was used to label striatal dopamine D2 receptors. Serial sections were used for each ligand to determine the precise anatomical relationships between the binding patterns of the different markers. Our aim was to determine whether the adult striosomal distribution of the binding sites studied was due to (1) a selective decrease in patch/striosomal binding density or (2) a selective increase in matrix binding density. Our studies show that a postnatal decrease in the density of [3H]‐HC3 sites in the patch/striosomes and an increase in the matrix density of [3H]‐MAZ sites are the primary, but not the sole, changes in the compartmental distribution of these sites leading to the adult striosomal organization of the striatal cholinergic and dopaminergic innervation. D2 receptors follow the general developmental pattern of [3H]‐MAZ and [3H]‐HC3, changing their density of distribution in both compartments during the developmental period examined. In addition, M1 muscarinic receptors already display their adult pattern in the newborn baboon striatum, and therefore represent one of the first neurochemical markers to adopt its mature organization.
Thalamocortical connections of the rostral intralaminar nuclei: An autoradiographic analysis in the cat
Authors: Royce G. J. , Bromley S. , Gracco C. , Beckstead R. M.
Published: January 2005

In this study the pattern of projections from the rostral intralaminar thalamic nuclei to the cerebral cortex was examined in the cat by autoradiography. Injections of tritiated proline and leucine were placed into the central lateral, paracentral, central medial, and para‐stria medullaris nuclei.

After injections into the central lateral nucleus, label is present on the lateral side within the presylvian sulcus, in most of the suprasylvian gyrus, including the adjacent lateral and suprasylvian sulci, and in the posterior corner of the ectosylvian gyrus. On the medial side, label is present in the orbitofrontal (Of), precentral agranular (Prag), anterior limbic (La), retrosplenial (Rs), and postsubicular (Ps) areas, as defined by Rose and Woolsey ('48a). The cingulate gyrus also contains label throughout (part of which was defined as the “cingular area,” Cg, by Rose and Woolsey, '48a). Label is also found on both banks of the splenial and cruciate sulci. In addition, label is present within the lateral gyrus, on both its lateral and medial sides.

The paracentral projections are similar to the central lateral input. On the lateral side, label is found within the presylvian sulcus, suprasylvian gyrus and adjacent lateral and suprasylvian sulci, and posterior ectosylvian gyrus. Medially, label is present in the Of, Prag, La, Cg, Rs, and Ps areas, and within the cruciate and splenial sulci, and in portions of the lateral gyrus.

Following injections of the central medial nucleus, label is present in the presylvian sulcus; but in contrast to the central lateral and paracentral projections, the suprasylvian gyrus is labeled only in its posterior part. The central medial nucleus also projects to the posterior lateral gyrus, both laterally and medially. Also, the central medial nucleus projects heavily to rostral cortical zones, which include the Of, Prag and La areas, cruciate sulcus, and the rostral cingulate gyrus.

The para‐stria medullaris nucleus projects only to the presylvian sulcus and orbitofrontal cortex laterally, but, medially, has an extensive input similar to the central lateral and paracentral projections in that label is present in the Of, Prag, La, Cg, Rs, and Ps areas, in the cruciate and splenial sulci, and in the posterior lateral gyrus.

The laminar distribution of label is as follows: the central lateral, paracentral and para stria medullaris nuclei project primarily to layers I and III, whereas the central medial nucleus projects to layers I and VI. In addition, the central lateral projection has a patchy appearance in the retrosplenial and postsubicular cortices.
Quantitative study of glutamic acid decarboxylase‐immunoreactive neurons and cytochrome oxidase activity in normal and partially deafferented rat hindlimb somatosensory cortex
Authors: Warren R. , Tremblay N. , Dykes R. W.
Published: January 2005

Somatosensory cortex reorganizes following restricted deafferentation so that deprived neurons acquire new receptive fields. Electrophysiological data suggest that a decrease in inhibition might be one of the mechanisms contributing to these changes. This hypothesis was tested by evaluating quantitatively glutamic acid decarboxylase (GAD) immunoreactivity and cytochrome oxidase (CO) activity in normal and partially deafferented rat hindlimb somatosensory cortex. In normal animals, there were laminar differences in the frequencies of GAD+ cells that correlated with the levels of CO activity. Two weeks after transection of the sciatic nerve, CO levels were reduced in all layers of the hindlimb somatosensory cortex contralateral to the nerve transection whereas the frequencies of GAD+ cells were unchanged except in layer IV where a 16% decrease was observed. This observation is consistent with the hypothesis that the expression of GAD in layer IV is partially controlled by the amount of afferent input. The ability of novel inputs to develop stable patterns of excitation in deafferented somatosensory cortex may depend upon the reduction of GABAergic inhibition which follows deafferentation.
Localization of L‐glutamic acid decarboxylase mRNA in cat retinal horizontal cells by in situ hybridization
Authors: Sarthy P. Vijay , Fu Marlene
Published: January 2005

Retinal horizontal cells receive synaptic input from photoreceptors and provide a pathway for lateral interactions in the vertebrate retina. In nonmammalian retinas, the H1 horizontal cells appear to use γ‐amino butyric acid (GABA) as their neurotransmitter. The transmitter used by mammalian horizontal cells, however, remains to be identified. In the present study, we have employed in situ hybridization to examine whether cat retinal horizontal cells contain L‐glutamic acid decarboxylase (GAD) mRNA and hence might use GABA as their transmitter. In the cat retina, labeled cell bodies were found in the inner nuclear layer and the ganglion cell layer. No labeled cells were found in the photoreceptor layer. In the inner nuclear layer, labeled somata were present at two locations. The majority of them (∼72%) were located in the vitread side of the inner nuclear layer bordering the inner nuclear layer/inner plexiform layer boundary. A second class of labeled cells in the inner nuclear layer (∼20%) had larger somata and were present at the inner nuclear layer/outer plexiform layer boundary. Double labeling experiments with antisera to parvalbumin, a horizontal cell marker, showed that these perikarya belonged to horizontal cells. RNA blot analysis showed that cat retina contains a single species of GAD mRNA that is about 4 kb in size. These data show that in addition to GABAergic amacrine, displaced amacrine, and interplexiform cells described previously, horizontal cells contain GAD mRNA and may use GABA as their neurotransmitter. Hence, GABA may be a transmitter that is involved in lateral inhibition in both nonmammalian and mammalian retinas.
Structure of the starburst amacrine network in the cat retina and its association with alpha ganglion cells
Authors: Vardi N. , Masarachia P. J. , Sterling P.
Published: January 2005

To investigate indirect pathways to ganglion cells we studied the starburst amacrine cell network and its relationship to the alpha ganglion cell. Starburst cells were identified by an antiserum to choline acetyltransferase and alpha cells by injection of Lucifer yellow. The density of on and off starburst cells peaks at the area centralis and decreases with eccentricity by a factor of seven. The fine amacrine processes, interrupted by distinct varicosities, arborize in a planar fashion in the inner plexiform layer. The on network, at the junction of strata 3 and 4, and the off network, in stratum 2, have a similar appearance. Neighboring starburst processes run in intimate association to form a network of bundles. As bundles cross each other, loops of irregular size and shape are formed. The loops are smallest in the area centralis and increase by a factor of three towards the periphery; correspondingly, bundle length per unit area decreases with eccentricity. However, the number of varicosities/bundle length stays constant with eccentricity as does the number of processes per bundle. Segments of the starburst network associate over fairly long distances with dendrites of alpha ganglion cells. About 26% of the alpha ganglion dendritic tree shows such association, and this is significantly greater than would be expected if the alpha and starburst processes were independent. We conclude that the functional unit of the starburst cell is a linear bundle of processes and that the starburst network may connect synaptically to the alpha cell.
Cerebellar connections with the motor cortex and the arcuate premotor area: An analysis employing retrograde transneuronal transport of WGA‐HRP
Authors: Orioli Paul J. , Strick Peter L.
Published: January 2005

We have employed transneuronal transport to examine the anatomical relationships between the deep cerebellar nuclei and 2 cortical motor areas: the primary motor cortex and the arcuate premotor area (APA). In the same animals, we have also examined the patterns of labeling in the thalamus and the red nucleus to provide evidence for the potential routes of transneuronal transport to the cerebellum.

When the appropriate technical procedures were employed, cortical injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) resulted in transneuronal labeling within portions of the contralateral deep cerebellar nuclei. Injections into the primary motor cortex labeled neurons in the dentate and in the 2 subdivisions of the interpositus. Injections into the APA labeled neurons in the dentate and in only the posterior subdivision of the interpositus. In most instance, dentate neurons were more intensely labeled following the cortical injections than interpositus neurons.

The transneuronal labeling observed in the dentate nucleus was topographically organized. The dentate region that was labeled following injections into the “arm area” of the APA was caudal and ventral to the dentate region that was labeled following injections into the “arm area” of the primary motor cortex. This observation provides evidence for two “arm areas” in the dentate: one anatomically related to the APA, and the other related to the primary motor cortex.

More than one route of transport may be responsible for the labeling of cerebellar neurons. We propose that the labeling observed in the dentate nucleus reflects the pattern of connections in the cerebellothalamocortical pathways that link the dentate with the cerebral cortex. Thus, our observations support the concept proposed by Schell and Strick (J. Neurosci. 4: 539–560, '84)—that the cortical targets of the dentate nucleus include both the primary motor cortex and the APA.
CNS connections with the median raphe nucleus: Retrograde tracing with WGA‐apoHRP‐gold complex in the rat
Authors: Marcinkiewicz M. , Morcos R. , Chrétien M.
Published: January 2005

In this work we examined the neuronal input to one of the serotoninergic centers in the brain, median raphe nucleus (MR). Special consideration is given to projections of the hypothalamus. To describe the afferents to MR, a retrograde transport technique was used after microinjection of WGA‐apoHRP‐Gold complex under pressure and subsequent gold‐silver intensification on formaldehyde‐fixed rat brain sections. Optimal conditions were obtained when the coordinates of the injection site were A ± 1.5, L ± 0.15, and H ± 2.7 according to Paxinos and Watson (The Rat Brain in Stereotaxic Coordinates. New York: Academic Press, '82). Results obtained under these conditions show a heterogeneous distribution of labeled neurons throughout the brain, including a large proportion (±65%) of hypothalamic neurons. Extrahypothalamic neurons projecting to MR were from the prefrontal cortex, lateral and medial habenular nuclei, the pontine area of the central grey, interpeduncular nucleus, dorsal raphe nucleus, oculomotor and trochlear nuclei, dorsal and laterodorsal tegmental nuclei, parabrachial nuclei, and lateral and interpositus cerebellar nuclei. Hypothalamic neurons connected to MR were found to be from medial and lateral preoptic areas, lateral hypothalamus, dorsomedian nucleus, the perifornical area, and the complex of mammillary bodies. Many other discrete regions contained different densities of labeled perikarya: the medial preoptic nucleus, paraventricular nucleus, retrochiasmatic area, arcuate nucleus, lateral magnocellular nucleus, and the posterior area. The MR appears as an integrative center receiving many neuroanatomically and functionally heterogeneous inputs from the whole brain.
Distribution and spatial geometry of dopamine interplexiform cells in the rat retina: I. Developing retina
Authors: Savy Claudine , Yelnik Jérôme , Martin‐Martinelli Elisabeth , Karpouzas Ioanis , Nguyen‐Legros Jeanine
Published: January 2005

The morphology and distribution of dopaminergic interplexiform cells were analyzed in 9‐day‐old rat retinas processed as wholemounts for tyrosine hydroxylase immunohistochemistry. The mean number of dopaminergic interplexiform cells was estimated as about half of the total number of dopaminergic neurons in the immature retina, with a higher density in the temporal retina. Four interplexiform cells were individually analyzed and reconstructed with a computer system. Their arborizations could be divided into three different regions based on both their morphological features and their position within the retinal layers: (1) an internal arborization, spreading at the margin between the inner nuclear layer and the inner plexiform layer, composed of long, thick, somatofugal dendrites branching at acute angles, (2) an external arborization in the middle of the inner nuclear layer, formed by short, thin, varicose, recurved axon‐like processes branching at right angles, (3) and one or more scleral process(es), originating either from the cell body or from the internal arborization, running toward the outermost cell row of the INL, some of which reached the outer plexiform layer. Finally, analysis of the arborization network by computer simulations based on the 4 digitalized cells was compared with a nearest‐neighbour analysis of cell body distribution. It showed that cell bodies are almost randomly distributed—at least in the inferior retina—but that an adjustment of dendritic growth and orientation probably occurs to ensure a homogeneous coverage of the retina with a constant degree of overlap in the adult. This report represents the first three‐dimensional computer reconstruction of chemically identified neurons in the retina.
Organization of the septal region in the rat brain: Cholinergic‐GABAergic interconnections and the termination of hippocampo‐septal fibers
Authors: Leranth Csaba , Frotscher Michael
Published: January 2005

This study deals with two characteristic cell types in the rat septal complex,

In this study the term “spetal complex” comprises the MSDB (medial septal nucleus and vertical limb of the nucleus of the diagonal band) and the lateral septum (LS) (lateral and dorsal septal nuclei).

i.e., cholinergic and GABAergic neurons, and their synaptic connections. Cholinergic elements were labeled with a monoclonal antibody against choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme. Antiserum against glutamate decarboxylase (GAD), the GABA synthesizing enzyme, was employed to identify GABAergic perikarya and terminals, by using either the peroxidase‐antiperoxidase (PAP) technique or a biotinylated second antiserum and avidinated gold or ferritin. With these contrasting immunolabels we have studied the cholinergic‐GABAergic interconnections in double‐labeled sections of intact septal regions and the GABAergic innervation of medial septal area cholinergic neurons in sections taken from animals 1 week following lateral septal area lesion. In other electron microscopic experiments we have studied cholinergic and GABAergic neurons in the septal complex for synaptic contacts with hippocamposeptal fibers, which were identified by anterograde degeneration following fimbria‐fornix transection. Our results are summarized as follows: (1) GAD‐positive terminals form synaptic contacts on ChAT‐immunoreactive dendrites in the medial septum/diagonal band complex (MSDB), (2) surgical lesion of the lateral septal area resulted in a dramatic decrease of the number of GABAergic boutons on MSDB cholinergic neurons, (3) cholinergic terminals establish synaptic contacts with GAD immunoreactive cell bodies and proximal dendrites in the MSDB as well as in the lateral septum (LS), (4) degenerated terminals of hippocampo‐septal fibers were mainly observed in the LS, where they formed asymmetric synaptic contacts on dendrites of GABAergic neurons and on nonimmunoreactive spines. We did not observe degenerated boutons in contact with ChAT‐positive dendrites or cell bodies in the MSDB.

From these results and from data in the literature we conclude that excitatory hippocampo‐septal fibers activate GABAergic cells, and as yet unidentified spiny neurons in the LS, which may control the discharge of medial septal cholinergic neurons known to project back to the hippocampal formation.
Morphometric modifications associated with early sensory experience in the rat olfactory bulb: II. Stereological study of the population of olfactory glomeruli
Authors: Royet J. P. , Jourdan F. , Ploye H. , Souchier C.
Published: January 2005

The present study explores the local variations of size and number of olfactory glomeruli induced by the exposure of young rats to long‐term stimulation with a single odor. Three groups of 5 rats were used that were either: (1) stimulated with ethyl acetoacetate from birth to 1 month of age, (2) unilaterally deprived following early occlusion of one nare, or (3) normal animals of the same age. Areas and coordinates of all glomerular profiles were measured in 14 coronal sections uniformly distributed along the rostrocaudal axis of the olfactory bulb. A distribution‐free stereological method was applied to compute the size and number of glomeruli either along the bulbar rostrocaudal extent or in the bulbar coronal plane. Following complete sensory deprivation or longterm stimulation with ethyl acetoacetate, the mean diameter of glomeruli was significantly reduced everywhere, except in the ventrolateral and ventromedial regions of the posterior olfactory bulb in rats reared with a single odor. In both of these areas, the number of glomeruli was either significantly increased following long duration exposure or significantly reduced following unilateral deprivation. Thus these results show that selective modifications of the olfactory environment during postnatal maturation induce morphometric variations in specific areas of the glomerular layer. These data are discussed with respect to the concept of the topographical coding of odor quality at the level of the glomeruli and plasticity of the olfactory system during postnatal development.
Morphology of midlumbar interneurones relaying information from group II muscle afferents in the cat spinal cord
Authors: Bras H. , Cavallari P. , Jankowska E. , Kubin L.
Published: January 2005

The morphology of midlumbar interneurones with peripheral input from group II muscle afferents was analysed after intracellular injection of horseradish peroxidase (HRP). Twenty‐three interneurones were stained intrasomatically and five others intra‐axonally. The majority (10 of 13) of interneurones located in lamina VII (intermediate zone and ventral horn interneurones) were found to project ipsilaterally. They had medium‐sized somata and dendrites projecting radially over a distance of more than 1 mm. All of these neurones had axons that projected caudally within the ventral part of the lateral funiculus or in the lateral part of the ventral funiculus, although four had in addition an ascending secondary axonal branch. Numerous axon collaterals were given off from these axons, both before and after they left the grey matter. The collaterals arborized within laminae VII, VIII, and IX, where they covered the area of several motor nuclei. Intra‐axonal labelling of five neurones with similar input and axon trajectories revealed several axon collaterals given off between the cell body and the terminal projection areas in L7 or S1 segments. Only three of the labelled interneurones located in lamina VII and displaying the same kind of input had axons with different destinations; their axons crossed to the opposite side of the spinal cord and ascended within the contralateral ventral funiculus. These were large neurones with extensive dendritic trees, which had fairly thick axons with initial axon collaterals that branched primarily ipsilaterally (within laminae V‐VIII). Interneurones located in lamina V and in the bordering parts of laminae IV and VI (dorsal horn interneurones; n = 10) constituted a very nonhomogenous population. They projected either ipsilaterally or contralaterally and had either ascending or descending axons running in either the lateral or ventral funiculi. Generally, dorsal horn interneurones had cell bodies smaller than those of intermediate zone and ventral horn interneurones, and their dendrites extended less extensively and less uniformly around the soma. Their initial axon collaterals branched primarily in the dorsal horn, or in lamina VII, but not in or close to the motor nuclei. Our results support the conclusions of previous physiological studies that the intermediate zone and ventral horn midlumbar interneurones with group II input and that project to motor nuclei have collateral actions on other interneurones in the L4‐L6 segments, and that dorsal horn interneurones do not project to motoneurones, but have as their targets other interneurones or ascending cells. On the other hand, we have not found any projections of L4 interneurones with input from either group I or group I1 muscle afferents, to Clarke's column, in contrast to the projections of interneurones in reflex pathways from tendon organs from more caudal segments.
Development of the electrosensory nervous system in eigenmannia (gymnotiformes): I. The peripheral nervous system
Authors: Vischer H. A. , Lannoo M. J. , Heiligenberg W.
Published: January 2005

The nerves of the anterior lateral line system in embryonic and larval stages of the weakly electric gymnotiform fish Eigenmannia were visualized by injection of the fluorescent marker DiI into the primordium of the anterior (ALLN) and posterior (PLLN) lateral line nerves. Examination of developmental series reveals that the nerve fibers that innervate the electrosensory and mechanosensory components of the anterior lateral line system are present before the first mechanoreceptors and electroreceptors have differentiated. This suggests that nerve fibers might induce the formation of lateral line receptors. Whereas the innervation of the mechanoreceptive system is already established at an early stage, the afferent innervation of electroreceptors continues to arborize in the periphery, presumably by following pioneer axon pathways.

The earliest recognizable stage of the anterior lateral line nerve ganglion (ALLNG) is evident 2 days after spawning. The ganglion shows two germinal cell masses that develop into the supraorbital‐infraorbital and the hyomandibular placodes. The supraorbital‐infraorbital placode forms the dorsal part of the ALLNG; the hyomandibular placode forms the ventral part of the ALLNG.

Counts of ALLNG cells in embryonic, larval, and adult stages of Eigenmannia show that, at each stage examined, the number of ganglion cells is always significantly larger than the number of mechanoreceptors and electroreceptor units in the periphery. During development, the distribution of ALLNG cell diameters shifts from a unimodal distribution in juveniles to a bimodal distribution in adults, peaking at 8 μm and 18 μm. These results suggest that tuberous electroreceptive organs, which are innervated by the large ALLNG cells, may not be functional prior to day 18. Our results further suggest that the number of ALLNG cells correlates with the rate of induction of lateral line receptors in the periphery.
Development and differentiation of early generated cells of sublayer VIb in the somatosensory cortex of the rat: A correlated Golgi and autoradiographic study
Authors: Valverde Facundo , Facal‐valverde Maria Victoria , Santacana Maria , Heredia Margarita
Published: January 2005

Autoradiographic and Golgi techniques are used to study the origin, developmental characteristics, and adult morphology of the cells of sublayer VIb in the somatosensory cortex of the rat. In the adult rat, this sublayer forms a stratum of two to three rows of cells located immediately above the white matter. It is clearly separated from the remaining cortical layers by a light plexus of fibers. The cortical plate begins to appear in the lateral wall of the brain hemisphere at embryonic day 15 (E15). By using tritiated thymidine autoradiography, we can see that cells generated between E12 and E14 become located in layers I, V, and VI in the adult. After injections on E12, heavily labeled cells were found almost exclusively in layer I and in sublayer VIb, indicating that these are the earliest generated cells in the neocortex of the rat. No labeled cells were found in sublayer VIb after injection on E15.

We describe the morphology of cells of layer VI from E15 to the adult using the Golgi technique. Our observations show the existence of different types of cells, among which we found horizontal bipolar cells very early during development. They transform into horizontal and inverted pyramidal cells, which are the predominant morphological types found in the adult. Horizontal cells lie at the lower part of sublayer VIb. Inverted pyramidal cells have descending apical dendrites penetrating the white matter. Their axons form ascending loops turning into projection fibers. A correlation with previous studies and some functional implications indicating the unique role of sublayer VIb in the rat during development and in the adult are discussed.
Topographical organization of the efferent projections of the medial prefrontal cortex in the rat: An anterograde tract‐tracing study with Phaseolus vulgaris leucoagglutinin
Authors: Sesack Susan R. , Deutch Ariel Y. , Roth Robert H. , Bunney Benjamin S.
Published: January 2005

The purpose of the present investigation was to examine the topographical organization of efferent projections from the cytoarchitectonic divisions of the mPFC (the medial precentral, dorsal anterior cingulate and prelimbic cortices). We also sought to determine whether the efferents from different regions within the prelimbic division were organized topographically. Anterograde transport of Phaseolus vulgaris leucoagglutinin was used to examined the efferent projections from restricted injection sites within the mPFC.

Major targets of the prelimbic area were found to include prefrontal, cingulate, and perirhinal cortical structures, the dorsomedial and ventral striatum, basal forebrain nuclei, basolateral amygdala, lateral hypothalamus, mediodorsal, midline and intralaminar thalamic nuclei, periaqueductal gray region, ventral midbrain tegmentum, laterodorsal tegmental nucleus, and raphe nuclei. Previously unreported projections of the prelimbic region were also observed, including efferents to the anterior olfactory nucleus, the piriform cortex, and the pedunculopontine tegmental‐cuneiform region. A topographical organization governed the efferent projections from the prelimbic area, such that the position of terminal fields within target structures was determined by the rostrocaudal, dorsoventral, and mediolateral placement of the injection sites.

Efferent projections from the medial precentral and dorsal anterior cingulate divisions (dorsomedial PFC) were organized in a similar topographical fashion and produced a pattern of anterograde labeling different from that seen with prelimbic injection sites. Target structures innervated primarily by the dorsomedial PFC included certain neocortical fields (the motor, somatosensory, and visual cortices), the dorsolateral striatum, superior colliculus, deep mesencephalic nucleus, and the pontine and medullary reticular formation. Previously unreported projections to the paraoculomotor central gray area and the mesencephalic trigeminal nucleus were observed following dorsomedial PFC injections.

These results indicate that the efferent projections of the mPFC are topographically organized within and across the cytoarchitectonic divisions of the medial wall cortex. The significance of topographically organized and restricted projections of the rat mPFC is discussed in light of behavioral and physiological studies indicating functional heterogeneity of this region.