bluuebunny/crossref_metadata_2025 huggingface dataset:
Long ascending projections to the midbrain from cells of lamina I and nucleus of the dorsolateral funiculus of the rat spinal cord
Authors: Swett John E. , McMahon Stephen B. , Wall Patrick D.
Published: May 2005

Small volumes (5–40 nl) of an aqueous solution of wheat‐germ‐agglutinin‐conjugated horseradish peroxidase (WGA‐HRP) were injected unilaterally into midbrain structures of 18 adult, albino rats. In 17 of these preparations cells of many types were found to be retrogradely labeled in cervical and lumbar spinal cord segments. The data reported here concern the number and location of labeled cells from injection sites in the midbrain that affected two distinct cell populations: neurons within the marginal layer (lamina I cells) and neurons of the nucleus of the dorsolateral funiculus (NDLF cells). In ten of the preparations, only nine of which are reported in detail here, a total of 1,831 labeled lamina I cells were identified. In the lumbar enlargement they reached a density of more than 60 cells/mm. Of these, 85% projected to medial portions of the caudal, contralateral midbrain. Injection sites that were centered in the caudal periaqueductal gray (PAG) and/or in the immediately adjacent region of nucleus cuneiformis labeled the largest numbers of lamina I cells. Cells of the NDLF were retrogradely labeled in all preparations in which lamina I cells were labeled but they were also observed in five cases in which lamina I cells were not labeled. A total of 1,914 NDLF cells were labeled from all injection sites. These cells were found to have essentially a bilateral distribution with 57% of the cells located in the contralateral DLF. Although there is substantial overlap between the terminal fields of lamina I and NDLF cells within the midbrain, NDLF cells had a more diffuse target area encompassing the reticular core of the midbrain and PAG, bilaterally, while the target area for lamina I cells was comparatively discrete, being largely restricted to the more medially situated midbrain structures, contralaterally. Whether the terminations of lamina I cells in and near the PAG are from collaterals of spinothalamic neurons originating in lamina I, or a subclass of lamina I neurons that project exclusively to the midbrain, is not known. It is significant, however, that lamina I cells, known to be activated by noxious stimuli to the skin, should project to a region of the brain stem from which analgesia can be produced by electrical stimulation or by local application of opiates.
A correlation between receptive field properties and morphological structures in the pretectum of the cat
Authors: Ballas I. , Hoffmann K. P.
Published: May 2005

Retinal terminals in the pretectum were labelled by anterograde axonal transport of horseradish peroxidase (HRP) after injecting the enzyme into one eye.

Pretectal neurons were retrogradely labelled by HRP‐injections into the dorsal cap of the inferior olive.

Electrophysiological recordings were performed in the same animal. This procedure showed that direction‐selective neurons in the nucleus of the optic tract (NOT) projecting to the dorsal cap of the inferior olive lie dorsal and lateral to the retinal terminal clusters. Direction‐unselective neurons sensitive to high stimulus velocities (jerk‐neurons) were localized within the areas of retinal terminal clusters. Both jerk‐neurons and retinal terminal clusters never overlapped with retrogradely labelled neurons.

Latency measurements to stimulation of the optic chiasm (OX) confirmed a monosynaptic W‐cell projection to the direction‐selective NOT cells and indicated a predominantly monosynaptic Y‐cell projection to the jerk‐neurons.
Organization and postnatal development of callosal connections in the visual cortex of the rat
Authors: Olavarria Jaime , van Sluyters Richard C.
Published: May 2005

The distribution of callosal cells and terminals was studied in the posterior neocortex of pups whose ages ranged from 3 to 16 days and in adult rats 2 months of age or older. Callosal cells and terminations were revealed using retrograde (horseradish peroxidase) and anterograde (horseradish peroxidase; tritiated proline) tracing techniques, respectively, and the distribution of callosal connections was analyzed in tangential or coronal histological sections.

In agreement with previous studies, we observed that the pattern of callosal connections in areas 17 and 18 of adult rats contains the following features: (1) a dense band of callosal cells and terminations separating the interiors of areas 17 and 18a, (2) a ringlike configuration anterolateral to area 17, (3) a region of dense labeling lateral to area 18a, (4) several narrow bands of labeling that bridge area 18a at different anteroposterior levels, and (5) one or more labeled regions in area 18b. In all these callosal regions, labeled cells and terminations are densely aggregated in layers II–III, Va, and Vc–VIa, and less densely in layer IV and the remaining portions of layers V and VI. High densities of isotope‐labeled fibers are also observed in the lower half of layer I. Throughout the interiors of areas 17 and 18a, a significant number of labeled cells are observed in layers Vc–VIa.

In contrast to adult rats, in neonates no distinct tangential pattern of callosal connections is apparent. Instead, labeled cells are densely aggregated in two continuous horizontal bands located in cortical layers Va and Vc–VIa, and callosal axons are largely restricted to white matter. During the first 2 postnatal weeks there is a progressive loss of callosal cells in regions that normally have few callosal cells in the adult (e.g., interiors of areas 17 and 18a) and an increase in the number of cells in layers II–IV in regions that are densely callosal in the adult (e.g., callosal regions at the 17/18a border, lateral border of area 18a, and in area 18b). The decrease in the number of callosal cells in the interiors of areas 17 and 18a is more severe in the upper than in the lower band of the immature labeling pattern, and our data from tangential sections indicate that this loss of callosal neurons occurs synchronously across the interiors of these areas. During this period there is also a localized invasion of labeled callosal axons into those regions of gray matter where they will be found in adult life. By 7 days of age, all major features of the mature callosal pattern can be clearly recognized, and by 12 days of age—a few days before eye opening—the pattern appears virtually mature.
A correlated light and electron microscopic study of identified cholinergic basal forebrain neurons that project to the cortex in the rat
Authors: Ingham C. A. , Bolam J. P. , Wainer B. H. , Smith A. D.
Published: May 2005

Cholinergic neurons in the basal forebrain which project to the frontal cortex were studied by combining the retrograde transport of a conjugate of horseradish peroxidase and wheat germ agglutinin with choline acetyltransferase immunohistochemistry. Neurons that were both retrogradely labelled and immunoreactive were found on the medial, lateral, and ventral borders of the globus pallidus, within the globus pallidus, as well as in the substantia innominata and ventral pallidum region.

The cell bodies averaged 31 by 19 μm in size and had sparsely branching dendrites. Cells which were labelled by both techniques were first characterised in the light microscope and then studied in the electron microscope. The perikarya had large amounts of cytoplasm with abundant organelles. The nuclei were indented, were usually eccentrically placed, and contained prominent nucleoli. The synaptic input onto the cell bodies and their dendrites was studied in serial sections. The synaptic input onto the perikarya and proximal dendrites was sparse but the density increased on more distal regions of the dendrites. Subjunctional bodies were associated with the postsynaptic membrane in 20–30% of the synaptic contacts and these were classified as asymmetrical; the remaining contacts could not be classified because of an association of the immunoreaction product with the postsynaptic membrane. The synaptic input to these cells was distinctly different from that onto typical globus pallidus cells, the perikarya and dendrites of which were characteristically ensheathed in synaptic boutons.
Dendritic arbors and dendritic excrescences of abnormally positioned neurons in area CA3c of mice carrying the mutation “Hippocampal lamination defect”
Authors: Nowakowskl R. S. , Davis T. L.
Published: May 2005

BALB/cJ and BALB/cByJ mice are homozygous for the autosomal gene “hippocampal lamination defect” (provisional gene symbol: Hld) which produces an abnormality in the lamination of the pyramidal cell layer of area CA3c of the hippocampus such that early‐generated neurons are superficial and late‐generated neurons are deep. Other inbred strains of mice are wild‐type (+/+) at the Hld locus and do not have this inversion in cell position in area CA3c. The Golgi method was used to analyze the dendritic arbors of the abnormally positioned pyramidal cells and to compare the distribution of dendritic excrescences (i.e., the termination sites of the mossy fibers) in +/+ and Hld/Hld mice. It was found that in +/+ mice the late‐generated pyramidal cells (whose cell bodies are positioned just below the suprapyramidal mossy fiber layer) have one set of dendritic excrescences on their apical dendrites as they extend through the suprapyramidal mossy fiber layer and a second set on their basal dendrites as they pass through the infrapyramidal mossy fiber layer. In contrast, in Hld/Hld mice the late‐generated pyramidal cells (whose cell bodies are abnormally positioned just below the intrapyramidal mossy fiber layer) have two sets of dendritic excrescences on their apical dendrites, as they pass through the intrapyramidal and suprapyramidal mossy fiber layers, and none on their basal dendrites. In addition, in the vicinity of the apparent point of contact of the intrapyramidal mossy fibers, the apical dendrites of some of the abnormally positioned pyramidal cells have several fine‐caliber branches. These data indicate that (1) the apical dendrites of hippocampal pyramidal cells can form normally even though the cells never reach their normal position and (2) the dendritic excrescences are induced by contact from the mossy fibers. The anatomical differences produced by the Hld/Hld genotype provide some interesting clues as to the relationship between defects in neuronal migration and the subsequent establishment of axonal connections and could be the basis for some of the behavioral differences reported to exist between BALB/cJ and other inbred strains of mice.
The morphology and ultrastructure of common inhibitory motor neurones in the thorax of the locust
Authors: Watson A. H. D. , Burrows M. , Hale J. P.
Published: May 2005

The morphologies of three common inhibitory motor neurones which innervate muscles of a hind leg and the homologous three neurones which innervate muscles in a middle leg are described in relation to known commissures, tracts, and areas of neuropile in their ganglia. The neurones were stained individually by the intracellular injection of cobalt, and the ultra‐structure of common inhibitor 1 (CI1) in the metathoracic ganglion was revealed by the intracellular injection of herseradish peroxidase. Homologous inhibitory motor neurones in the meso% and metathoracic ganglia have similar shapes. CI1 has axons in nerves 3, 4, and 5, but common inhibitors 2 and 3 (CI2, CI3) have only a single axon in nerve 5. They nevertheless all share many features in common. All have large (60 70 μm diameter) cell bodies in the ventral cortex near the midline, well separated from those of the excitatory leg motor neurones. Their primary neurites run dorsally and laterally and send many fine branches into the dorsal and lateral neuropile, and some fine branches medially. None enter the ventral neuropile. CI1 and CI2 have a small branch that arises close to the cell body and arborises on either side of the midline. When examined with the electron microscope, CI1 was not found to make any output synapses, even though some of its fine branches are varicose and end in bulbous swellings. These were seen to be packed with mitochondria but not vesicles. Input synapses tend to be grouped together on the secondary neurites and, more especially, on the finer branches and their spines. The majority of processes presynaptic to CI1 contain round agranular vesicles.
Stimulation of photoreceptor disc shedding and pigment epithelial phagocytosis by glutamate, aspartate, and other amino acids
Authors: Greenberger Lee M. , Besharse Joseph C.
Published: May 2005

It has been reported that aspartate and glutamate selectively impair the structure (Olney, '82) and function (e.g., Furakawa and Hanawa, '55) of second‐ and third‐order retinal neurons while leaving the photoreceptor unaffected. Either amino acid may mimic the endogenous photoreceptor neurotransmitter (Ehinger, '82). We report here that excitatory amino acids also induce massive rod photoreceptor disc shedding in eyecups of Xenopus laevis maintanined in vitro. Disc shedding is the process whereby photoreceptors eliminate effete discs. It involves interaction between the distal outer segment and pigment epithelium. Millimolar L‐asparate and L‐glutamate, as well as micromolar kainic acid, a glutamate analog, stimulate disc shedding three‐to fivefold higher than normal light‐evoked shedding levels and result in extensive inner retinal damage. Fifty‐millimolar KC1, 1.0 μM ouabain, and replacement of sodium with choline also stimulate disc shedding and alter retinal structure. Extensive neurotoxicity appears unrelated to disc shedding since other amino acids having no significant or marginal effects on retinal structure also stimulate shedding. While the site and mechanism of action of these effectors, and in particular the excitatory amino acids, is now undefined, the data show that amino acids thought to act directly and specifically on inner retinal neurons can also markedly alter photoreceptor and pigment epithelial metabolism.
Organization of the filum terminale in the frog
Authors: Chesler Mitchell , Nicholson Charles
Published: May 2005

The histological organization of the filum terminale of the spinal cord in Rana catesbeiana and Rana pipiens was characterized to determine if this region possessed an organized neuropil or whether it was merely a glial remnant that persisted after absorption of the larval tail.

The excised filum was maintained in vitro. Intracellular electrophysiological recording was performed with horseradish peroxidase injection. Tyrosine hydroxylase and serotonin distribution were revealed by immunocytochemical methods.

Astroglia were the dominant cell type and displayed an elaborate variety of forms. The mean membrane potential was logarithmically related to the extracellular potassium concentration but displayed a sub‐Nernstian slope. Oligodendroglia were also seen, as well as ependyma that extended from the central canal to the pial surface.

Neuronal activity was revealed by occasional intracellular penetration of elements that displayed spontaneous excitatory postsynaptic or action potentials. The major evidence for the presence of neurons was the demonstration of tyrosine hydroxylase (TH) immunoreactivity in a large population of cerebrospinal fluid‐contacting neurons that abutted the ventral half of the central canal. The axons of these cells entered a ventral bundle and ascended the cord; some fibers left this tract and apparently terminated on large arcuate neurons within the filum. Serotoninergic fibers were primarily confined to a subpial location at the dorsal midline.

We conclude that the filum terminale of the frog has a sparse but functional neuropil that is organized around the central canal and supported by a profusion of elaborate glial forms.
Auditory neurons expand their terminal arbors throughout life and orient toward the site of postembryonic hair cell production in the macula neglecta in elasmobranchs
Authors: Corwin Jeffrey T.
Published: May 2005

The population of sensory hair cells in the macula neglecta auditory epithelium in skates increases from 500 to more than 3,000 postembryonically, but during the same time period the number of neurons innervating the epithelium changes by a much smaller amount, if at all. Morphometric analyses of the peripheral terminal arbors of these neurons demonstrate that the arbors expand in area through intussusceptive growth, so that each neuron contacts more hair cells as the epithelium grows by appositional addition of new hair cells at its outer edge. The synaptic contacts that these neurons make with hair cells may not be permanent. Many of the neurons that innervate the growing macula appear to shift their terminal arbors, breaking synaptic contacts with older hair cells in the center of the sensory epithelium as they branch to form new contacts with younger hair cells that are located in the periphery of the epithelium. Over 80% of the terminal branches of these auditory neurons are directed toward the outer edge of the macula, the site where new hair cells are produced. This suggests that the growth cones of these continually growing neurons are guided to newly produced hair cells by an active attraction mechanism.
Connections of area 2 of somatosensory cortex with the anterior pulvinar and subdivisions of the ventroposterior complex in macaque monkeys
Authors: Pons T. P. , Kaas J. H.
Published: May 2005

The principal goal of the present study was to determine the thalamic connections of area 2 of postcentral somatosensory cortex of monkeys. The placement of injections of anatomical tracers (horseradish peroxidase, wheat germ agglutinin, or 3H‐proline) was guided by extensive microelectrode maps of cortex in the region of the injection site. These maps identified the body parts represented in the cortex included in the injection site, and provided information about the physiological boundaries of area 2, which was related later to the cortical architecture. Most injections were placed in the representation of the hand in area 2, which was highly responsive to cutaneous stimuli and could be mapped in detail. Injections were also placed in other parts of area 2, area 1, or area 5, and some injections involved more than one area.

As other investigators have determined, regions of retrograde and anterograde thalamic label overlapped, demonstrating that connections with cortex are reciprocal. Injections completely confined to area 2 consistently produced label in two locations: the anterior pulvinar (Pa) and a dorsal capping zone of the ventroposterior complex that we term the ventroposterior superior nucleus (VPS). Single restricted injection sites resulted in one region of label in VPS, and multiple foci of label in Pa. In some cases where the injection was confined to the representation of the hand in area 2, label was also found more ventrally in the ventroposterior complex in ventroposterior nucleus proper (VP). Thus, area 2 receives input from Pa, VPS, and, at least in some locations and individuals, VP. Injections of tracers into area 1 confirmed previous findings that area 1 is densely interconnected with VP. In addition, there appear to be sparse connections with VPS. There was no evidence of connections with Pa. Evidence from injection sites that extended from area 2 into areas 5 and 7, and from injection sites in area 5, indicates that the lateral posterior nucleus (LP) projects to rostral areas 5 and 7.

The results support the conclusion that area 2 is a functionally distinct subdivision of somatosensory cortex, and indicate that area 2 has thalamic connections that are characteristic of both “sensory” (VP and VPS) and “association” (Pa) cortical fields.
Substantia nigra transplants into denervated striatum of the rat: Ultrastructure of graft and host interconnections
Authors: Mahalik Thomas J. , Finger Thomas E. , Stromberg Ingrid , Olson Lars
Published: May 2005

A number of recent experiments suggest that grafted dopaminergic neurons provide functional input to a host caudoputamen which previously had been deprived of its dopaminergic input. The purpose of the present study was to determine whether tyrosine hydroxylase immunoreactive processes which originate in the graft participate in morphologically identifiable synapses in the host neuropil.

Prior to transplantation, adult Sprague‐Dawley rats received unilateral injections of 6‐hydroxydopamine into the medial forebrain bundle. Animals were screened for the success of striatal denervation by a test of apomorphine‐induced rotation. Transplants of fetal substantia nigra then were placed into cavities in the caudoputamen. After a 6–8 month survival period, animals were perfused and prepared for tyrosine hydroxylase immunocytochemistry. No evidence of sprouting of the host catecholoaminergic system was observed, even after long survival times.

Both pre‐ and postsynaptic immunoreactive elements were clearly present in the host caudoputamen. Immunoreactive axons made synaptic contact with unlabeled dendrites; immunoreactive dendrites were postsynaptic to unlabeled axon terminals. The present results suggest that both host‐to‐graft and graft‐to‐host synapses are present in the host caudoputamen.
Segmental distribution of peptide‐ and 5HT‐like immunoreactivity in nerve terminals and fibers of the thoracolumbar sympathetic nuclei of the cat
Authors: Krukoff Teresa L. , Ciriello John , Calaresu Franco R.
Published: May 2005

The distribution of leucine‐enkephalin, methionine enkephalin, neurotensin, somatostatin, substance P, oxytocin, vasopressin, neurophysin II, and serotonin in nerve terminals and fibers of sympathetic autonomic areas of the thoracolumbar (T‐L) spinal cord was studied immunohistochemically in cats. Densities of these immunoreactive terminals and fibers were estimated in the intermediolateral nucleus pars principalis (IMLp) and pars funicularis (IMLf), the nucleus intercalatus (IC), and the central autonomic area (CA). Results for leucine‐ and methionine‐enkephalin‐like immunoreactivity (ENK) were similar and immunoreactivity for vasopressin was not observed.

The greatest numbers of terminals and fibers in the IMLp region contained ENK, neurotensin‐(NT), and serotonin‐like immunoreactivity (5HT); terminals and fibers containing substance P‐(SP) and neurophysin II‐like immunoreactivity (NP2) were intermediate in number, and those containing somatostatin‐(SS) and oxytocin‐like immunoreactivity (OXY) were generally sparse. In the IC and CA, terminals and fibers containing ENK and NT were dense, those containing SP were moderate, and those containing OXY, NP2, and 5HT were sparsely represented. In the IMLp, where the largest proportion of sympathetic preganglionic neurons (SPN) is found, the greatest concentration of terminals and fibers containing ENK was found in segments T1–T8; for NT these segments were T1–T5 and T11–L1, for SP–C8–T2 and T11–L1, for NP2–T4–T7 and L2 to L3, and for 5HT–T1–T5. Terminals and fibers containing SS and OXY were present in segments C8–T10 and segments C8, T2–T8, T13, and L2 to L3, respectively. These results indicate that while ENK, NT, SP, NP2, and 5HT fibers and terminals are widely distributed throughout the T‐L cord, they may influence to a greater degree the SPN in segments where they are present in greater numbers. As SS and OXY were not found at all levels of the IMLp, their functions may be more organ specific.
Distribution and immunoreactivity of glia in the retina of the rabbit
Authors: Schnitzer Jutta
Published: May 2005

Glial markers, namely antibodies to glial fibrillary acidic protein (GFAP), vimentin, galactocerebroside (GC), and 08 antigen, were used to study the occurrence and location of neuroglial cells in adult rabbit retinae. Müllerian glia were vimentin‐positive, lacked detectable amounts of GFAP, and were found in all parts of the rabbit retina. The neuronal A‐type horizontal cells were labeled by vimentin antibody only in the superior retina and at the medullary rays but not in the inferior retina. They lacked GFAP in all regions. Astroglia showing GFAP and vimentin immunoreactivity were absent from most of the superior and inferior retina, being found only in the myelinated area of the ganglion cell axon bundles, the medullary rays. Thus the rabbit retina differs from the retinae of all mammals studied to date by this restriction of astroglia to just one area. The medullary rays, which are known to be myelinated, were labeled by the antibodies to GC and 08 antigen.

Boycott and Hopkins ('84) found, using whole‐mounted rabbit retinae stained by the reduced silver method of Richardson, that all neurons in the ganglion cell layer of the rabbit retina have a cilium, while cells that have only a diplosome are either neuroglia or microglia. By using this criterion as a basis to differentiate between neurons and glia, the absence of neuroglia from the nerve fiber layer outside the medullary rays was confirmed in the same silver‐stained material. Thus, the data obtained from immunocytochemistry and conventional silver staining agree closely. It has been concluded that, at least in the adult, significant lengths of ganglion cell axons extend without astroglial sheaths.
The organization of the neonatal rat's brainstem trigeminal complex and its role in the formation of central trigeminal patterns
Authors: Bates Carolyn A. , Killackey Herbert P.
Published: May 2005

The present study delimits the relationship of primary trigeminal afferents to their targets, the brainstem trigeminal nuclei of the neonatal rat. Previously, the brainstem trigeminal complex of the rat has been subdivided on the basis of either cytoarchitectonics or patterns of succinic dehydrogenase activity into the principal sensory nucleus and the three subnuclei of the spinal trigeminal nucleus, oralis, interpolaris, and caudalis. In this paper, we demonstrate that each of these subdivisions can also be identified by its pattern of primary trigeminal afferents. In addition, we demonstrate that the terminations of these afferents are distributed in a punctate fashion which correlates with vibrissae‐related patterns of histochemical staining. Further, vibrissae removal in the neonatal rat at any age studied results in a corresponding deafferentation of both the principal sensory nucleus and all subnuclei of the spinal trigeminal nucleus. This same procedure has a graded, age‐dependent effect on the vibrissae‐related pattern of cytochrome oxidase staining in somatosensory cortex. On this basis, we conclude that vibrissae‐related pattern formation in the central trigeminal system can be best understood in terms of a single “sensitive” period for the entire system. We hypothesize that this is the period during which an interaction normally occurs between primary trigeminal afferents and target neurons of the principal sensory nucleus.
Golgi and Nissl studies of the visual cortex of the bottlenose dolphin
Authors: Garey L. J. , Winkelmann E. , Brauer K.
Published: May 2005

Nissl, Golgi and fibre preparations were made of the cerebral cortex of the lateral gyrus of the bottlenose dolphin (Tursiops truncatus)in the region where visual evoked potentials have been reported (Sokolov et al., '72; Ladygina et al., '78). In the adult the visual cortex is relatively thin (average about 1,300 μm) for so large a brain (fixed brain weight for a typical adult in our series was 1,330 g). Layers I, III, and VI are wide and represent three‐quarters of the total cortical thickness. Layer I contains few cell bodies, while III and VI have a variety of pyramidal and nonpyramidal neurons. Layers II and V are narrow and contain striking palisades of darkly staining pyramidal cells that are particularly large in layer V. No clearly demarcated layer IV is present in the adult dolphin visual cortex. Many of the neurons identified with the Golgi technique are typical of pyramids in other mammals, with a single apical dendrite and a bouquet of basal dendrites, mostly highly spiny. Others are unusual in having bifurcated or oblique apical dendrites. Typical large and small spiny and nonspiny stellates are also found, mainly in layers III and VI. In addition various forms of spindle‐shaped, bipolar and multipolar neurons are found in most layers.

An 18‐day‐old brain shows signs of immaturity in its visual cortex. It is thinner (970 μm) and on average its neurons are smaller, paler, and more densely packed. Especially the pyramids of layer V are much smaller than in the adult. Also, a distinct “granular” band occurs between layers III and V and seems to be a rudimentary layer IV. At 3 years of age most of the adult features have developed, but layer IV is still detectable.

No striking differences were observed in cell and fibre architecture between the cortex of the lateral gyrus and that of the so‐called “calcarine” area that has also been considered as “visual.”

We conclude that, although different in many respects from other mammalian visual cortices, that of the dolphin is apparently well developed and differentiated.
Morphology, central projections, and dendritic field orientation of retinal ganglion cells in the ferret
Authors: Vitek Dagmar J. , Schall Jeffrey D. , Leventhal Audie G.
Published: May 2005

Retinal ganglion cells were studied in pigmented ferrets that received small electrophoretic injections of horseradish peroxidase (HRP) into the dorsal lateral geniculate nucleus (LGNd) or optic tract. Ferret retina contains a number of types of retinal ganglion cells of which the relative cell body sizes, dendritic field structures, and central projections correspond closely to those of retinal ganglion cell types in the cat. Ferret retina contains about the same proportion of alphalike cells, a lower proportion of betalike cells, and thus a high proportion of other types of ganglion cells than cat retina. Ferret retina has a visual streak and somewhat weaker area centralis than cat retina. Changes in ganglion cell morphology associated with eccentricity are less pronounced in the ferret than in the cat. The adult ferret retina is about 12.5 mm in diameter, and the nasotemporal division is about 2.7 mm from the temporal margin. Interestingly, virtually all alpha cells in the pigmented ferrets studied projected contralaterally. Studies of infant ferrets indicate that 4 days after birth (P4) the area of ferret retina is 25% that of the adult. The neonatal ferret retina contains numerous small, densely packed cells in the presumptive ganglion cell layer. At P4 these cells appear to be uniformly distributed across the retina. The area centralis and visual streak are not obvious as late as 8 days after birth.
Catecholaminergic innervation of the septal area in man: Immunocytochemical study using TH and DBH antibodies
Authors: Gaspar P. , Berger B. , Alvarez C. , Vigny A. , Henry J. P.
Published: May 2005

The catecholaminergic innervation of the human septal area and closely related structures has been visualized by using tyrosine hydroxylase (TH) and dopamine‐β‐hydroxylase (DBH) as immunocytochemical markers. TH‐like immunoreactivity with no corresponding DBH labelling was considered to be indicative of dopaminergic fibers.

Catecholaminergic innervation offered the following similarities to that of rodents: (1) moderate innervation in the medial septal division, with predominant DBH immunolabelling; (2) dense dopaminergic innervation in the lateral septal nuclei, organized in a laminar pattern; (3) presence of dopaminergic pericellular arrangements in the dorsal septum and bed n. of the stria terminalis; (4) clustering of dopaminergic terminals in n. accumbens associated with a medioventral zone of DBH‐like immunoreactive fibers; (5) close overlap between dopaminergic fields and acetylcholinesterase‐reactive zones in both the lateral septum and the n. of the stria terminalis.

Differences with the catecholaminergic septal innervation of rodents consisted of (1) general caudal extension of the dopaminergic fields, possibly accounted for by the vertical stretching and caudal displacement of the septal nuclei in man; (2) complementary lateromedial. topography of dopaminergic and DBH‐immunoreactive inputs in the n. of the stria terminalis as opposed to their dorsoventral organization in rodents; (3) presence of TH‐immunolabelled cell group in the anterior olfactory nucleus and parolfactory cortex, which seems specific for primates.

Precise topographical mapping of the catecholaminergic structures in this central region of the limbic forebrain seems to be a prerequisite for accurate tissue sampling in the biochemical investigations of pathological cases and should help in the interpretation of aminergic dysfunction in a variety of human diseases.
Cerebellar external granule cells are attached to the basal lamina from the onset of migration up to the end of their proliferative activity
Authors: Hausmann Beate , Sievers Jobst
Published: May 2005

The development of cerebellar external granule cells in rats was studied from the time of demarcation of the cerebellar anlage on embryonal day 12 up to the time of their disappearance on postnatal day 20. Two types of cells were found. The first was orientated tangentially to the cerebellar surface and was characterized by a persistent contact to the basal lamina via an external process, with a lamellopodial tip and a cytoskeleton characteristic for migratory cells, and a retracting internal process featuring a single cilium. This cell type was the first to appear on embryonal day 14 in the caudolateral angle of the cerebellar anlage and, later, spread, over the whole cerebellar surface. It disappeared after the external granular layer was completely expanded over the cerebellum. The second cell type appeared for the first time on embryonal day 16 in the caudal part of the cerebellar anlage and disappeared on postnatal day 20. It was orientated radially and also had contact with the basal lamina either with its cell body or with one or two short, radial processes, whose morphology differed from that of the external process of tangential cells by the absence of a lamellopodium and a prominent cytoskeleton. After postnatal day 17 contacts of external granule cells with the basal lamina decreased rapidly in length and number and were absent on postnatal day 20.

We interpret these findings to indicate that tangential external granule cells are migrating before taking on a radial orientation characteristic for the mitotic cycle of proliferating external granule cells. In the light of increasing evidence implicating extracellular matrix in various developmental events of the nervous system we propose that the basal lamina of the cerebellum may be used as substrate and guidance structure by migrating external granule cells, and, furthermore, that the persistent contact with the basal lamina may mediate stimuli maintaining external granule cells in a proliferative state.
The trigemino‐olivary projection in the cat: Contributions of individual subnuclei
Authors: Huerta M. F. , Hashikawa T. , Gayoso M. J. , Harting J. K.
Published: May 2005

Anterograde autoradiographic methods were used to determine the projection of the principal sensory trigeminal nucleus and of each of the three spinal trigeminal subnuclei to the inferior olivary complex in the cat. Our data reveal that the principal sensory trigeminal nucleus does not contribute to the trigemino‐olivary pathway. Each spinal trigeminal subnucleus has a unique contribution to this pathway: pays oralis projects sparsely to the border between the dorsal accessory and principal olives (DAO‐PO), pars interpolaris projects mostly to the rostral medial DAO, and pays caudalis projects mostly to the rostral medial part of the ventral leaf of PO and slightly to the caudal medial accessory olive. In the light of recent physiological and anatomical findings, our data indicate that information from each spinal trigeminal subnucleus reaches a different segment of the contralateral inferior olivary complex, which in turn distributes differentially to the cerebellar cortex.
Anatomical organization of primary visual cortex (area 17) in the ferret
Authors: Rockland Kathleen S.
Published: May 2005

The present report describes the intrinsic and extrinsic cortical connectivity of striate cortex (area 17) in the ferret. Injections of horseradish peroxidase demonstrate periodic intrinsic connections over an extent of 2.5–3.0 mm, mainly in the supragranular layers but also occurring secondarily in layer 5. These connections have a stripelike configuration, with a centerto‐center spacing of 0.5–0.7 mm. Their laminar distribution and stripelike configuration resemble the pattern in the cat (Gilbert and Wiesel,′83), another member of the carnivore family, but not that in monkeys. In both macaque and squirrel monkeys, these connections have a bilaminar distribution in layers 2–3 and 4B, and a more complicated latticelike geometry (Rockland and Lund,'83). Their interperiod spacing, of about 0.5 mm, however, is relatively constant across species. Extrinsic connections in the ferret link striate cortex with territories probably homologous to feline areas 18 and 19, and to the suprasylvian region. Callosal connections extend on the lateral surface about 1.5 mm into area 17 and 4.0 mm into area 18 beyond their common border. There are homotopical connections between striate cortices and heterotopical connections from at least areas 18 and 19 to contralateral area 17. In addition to gray matter connections, intracortical injections also result in labeled interstitial neurons in the subgriseal white matter. These occur both subjacent to an injection site in area 17, and below labeled foci in area 18 projecting back to area 17, as if interstitial neurons shared the connectivity of overlying layer 6.
Freeze‐fracture study of an invertebrate multiple‐contact synapse: The fly photoreceptor tetrad
Authors: Fröhlich A.
Published: May 2005

Bow‐shaped particle arrays on the P‐faces of the photoreceptor terminals R1–R6 in the lamina ganglionaris of the house fly represent the presynaptic sites of chemically mediated multiple‐contact synapses (Shaw and Stowe, '82, Saint Marie and Carlson, '82). A particle array consists of two polar patches of regularly arranged particles and a central patch of irregularly arranged ones. Corresponding to these P‐face arrays, the receptor E‐faces have lattices of pits opposite the polar patches, and pits and some particles at the center. The presynaptic particle array corresponds in its dimensions to the electron‐dense bar found in thin sections. The center‐to‐center spacing of the regularly arranged particles agrees with the spacing of striations found in the bar overlying the two polar elements of the postsynaptic tetrad. The elements in the two medial postsynaptic positions are hyperpolarizing monopolar cells Ll and L2, which show a strip of P‐face particles within an otherwise bare postsynaptic membrane enclosed by a ridge, and a bare Eface. Comparison with other invertebrate synapses reveals two types of organization of postsynaptic membranes. IMPs fracture with the postsynaptic P‐face in GABAergic and/or inhibitory synapses and with the E‐face in glutaminergic and/or excitatory synapses; the fly photoreceptor synapse thus fits in the former category.
Development of the rhesus monkey retina. I. Emergence of the inner plexiform layer and its synapses
Authors: Nishimura Yozo , Rakic Pasko
Published: May 2005

The emergence and differentiation of the inner plexiform layer (IPL) and the establishment of its synapses were analyzed in retinae of 18 rhesus monkeys ranging in age from the 55th embryonic day (E55) to 10 years. The IPL becomes recognizable by E65 as a thin acellular zone consisting of immature neurites and growth cones scattered within large extracellular spaces. In each specimen, apposing paired membrane specializations were classified as junctions without synaptic vesicles, conventional synapses, ribbon synapses, or gap junctions. Initially, at E65, the IPL consists of variety of immature cell processes that are interconnected exclusively by junctions without synaptic vesicles, at a density of 4.7/100 μm2. By E73, the IPL becomes more distinct and wider and contains 7.8 such junctions/100 μm2. Conventional synapses develop by the addition of vesicles to initially vesiclefree junctions. The first conventional synapses appear at E78. They increase in density from 1.5 to 3.2/100 μm2 between E78 and E84 and reach a density of 7.9/100 μm2 by E99. A rapid burst in synaptogenesis occurs in the IPL between E99 and E114; a density of 16.5/100 μm2 is reached, mainly due to accretion of conventional synapses.

Ribbon synapses first become recognizable at E99, almost 3 weeks after the emergence of conventional synapses. By E114 they account for about 7% of all synaptic contacts in the IPL. The rate of synaptogenesis slows down during the last quarter of gestation; the adult level of about 24 contacts/100 μm2 is reached between E130 and E149. Of these, 72.2% are of conventional type, 15.4% are ribbon synapses, and 12.4% are junctions without vesicles. However, in the adult the density of junction without vesicles is only about one‐half that found at E149. Gap junctions are absent during the initial and rapid phases of synaptogenesis; they appear abruptly, between E130 and E149, only after the density of chemical synapses in the IPL has reached the adult level.

In the rhesus monkey, synaptogenesis begins several weeks later in the IPL than in its primary targets–the dorsal lateral geniculate nucleus and the superior colliculus (Hendrickson and Rakic, '77; Cooper and Rakic, '83). However, the rapid increase in density of conventional synapses in the IPL coincides with the segregation of retinal projections from right and left eyes in the geniculate nucleus (Rakic, '76) and with the elimination of the large surplus of retinal ganglion cell axons (Rakic and Reley, '83).
Patterns of primary afferent termination in the external cuneate nucleus from cervical axial muscles in the cat
Authors: Bakker D. A. , Richmond F. J. R. , Abrahams V. C. , Courville J.
Published: May 2005

Using the method of transganglionic transport of horseradish peroxidase (HRP), the distribution of primary afferent projections was examined in the external cuneate nucleus (ECN) from different muscle groups in the forequarter of the cat. The terminal zones of afferent fibers from three shoulder muscles–clavotrapezius, acromiotrapezius, and spinotrapezius–were compared to projections from suboccipital muscles, dorsal neck extensors, and muscles of the proximal forelimb. Each muscle group had a labelled terminal zone that occupied a different subvolume of the ECN. The zone labelled from trapezius muscles formed a continuous column in the ECN running from the caudal pole of the nucleus to a level 3.0 mm rostral to the obex. Terminal zones of suboccipital muscles and dorsal neck extensors formed longer columns that extended into the most rostral tip of the ECN, while those of proximal forelimb muscles formed shorter columns confined to the caudal two‐thirds of the ECN. At comparable cross‐sectional levels in the caudal and middle portions of the ECN, terminal zones from proximal limb muscles were located most dorsomedially, while those from shoulder muscles, dorsal neck muscles, and suboccipital muscles were located in progressively more ventral and lateral regions. The subvolume of the ECN occupied by projections from cervical axial muscles was estimated to be more than 40% of the volume of the nucleus, suggesting that the ECN has a major role in the transmission of sensory information from axial musculature to the cerebellum. Following exposure of all muscle nerves to tracer, a second labelled zone was also identified close to the ECN in the descending vestibular nucleus at transverse levels 2.0–3.0 mm rostral to the obex. Here, reaction product was concentrated around a circumscribed collection of medium‐sized, multipolar cells.
Efferent connections of the prelimbic (area 32) and the infralimbic (area 25) cortices: An anterograde tracing study in the cat
Authors: Room Peter , Russchen Fokje T. , Groenewegen Henk J. , Lohman Anthony H. M.
Published: May 2005

The projections from the caudal part of the medial frontal cortex, encompassing the prelimbic area (PL) and the infralimbic area (IL) (Brodmann's areas 32 and 25, respectively), were studied in the cat with the anterograde autoradiographic tracing technique. The results indicate that the projection fields of IL, in contrast to those of PL, are restricted almost exclusively to limbic structures.

Whereas the major thalamic projections from PL reach the mediodorsal, anteromedial, and ventromedial nuclei, the medial part of the lateral posterior nucleus, and the parataenial and reticular nuclei, and weak projections from this area are directed to the nucleus reuniens and other midline nuclei, the nucleus reuniens is the major thalamic termination field of fibers arising from IL. Cortical areas that are reached by fibers originating in PL and, to a lesser degree, also in IL, include more rostral prefrontal areas (areas 8, 6, and 12), the agranular insular, and the rostral perirhinal cortices. In contrast, cortical areas that are more strongly related to IL include the cingulate, retrosplenial, caudal entorhinal, and perirhinal cortices and the subiculum of the hippocampal formation. Another prominent output of PL concerns projections to an extensive medial part of the caudate nucleus and the ventral striatum, whereas fibers from IL only distribute most ventrally in the striatum. In the amygdaloid complex, fibers from PL were found to reach the basolateral, basomedial, and central nuclei, and fibers from IL to distribute to the medial and central nuclei. PL furthermore projects to the claustrum and the endopiriform nucleus. Other structures in the basal forebrain, including the medial septum, the nuclei of the diagonal band, the preoptic area, and the lateral and dorsal hypothalamus are densely innervated by IL and only sparsely by PL. With respect to more caudal parts of the brainstem, projections from PL and IL appeared to be essentially similar. They reach the ventral tegmental area, the periaqueductal gray, the parabrachial nucleus, and in cases of PL injections were followed as far caudally as the pons.
Peptidergic innervation of insect skeletal muscle: Immunochemical observations
Authors: Witten Jane L. , O'Shea Michael
Published: May 2005

Proctolin (Arg‐Tyr‐Leu‐Pro‐Thr) is a pentapeptide present in the hindgut or proctodeum of the cockroach Periplaneta americana where it may be a transmitter. Its widespread distribution among peripherally projecting neurons in the CNS (Bishop and O'Shea, '82) suggested that proctolin's motor function is not restricted to the hindgut, but has a variety of peripheral targets. This idea was further supported when proctolin was localized to an identified skeletal motoneuron, the slow coxal depressor, where it acts as a cotransmitter (O'Shea and Bishop, '82; Adams and O'Shea, '83). Our objective was to investigate the proctolinergic innervation of a variety of skeletal muscles of the cockroach Periplaneta americana. We used immunohistochemical and radioimmunochemical methods to map the distribution of proctolin immunoreactivity. This survey revealed that a subpopulation of skeletal muscles are innervated by proctolinergic motoneurons. The anatomical features of the peptidergic innervation and the levels of proctolin‐like immunoreactivity of one muscle group, the coxal depressor system, are here described in detail. The source of the proctolin innervation to the metathoracic coxal depressor group is identified as the slow coxal depressor motoneuron. The results of a survey of fast and slow skeletal muscles revealed that proctolin is associated with slow motor function. The functional implications of the association of a peptide with motoneurons are discussed in relationship to the organization of the insect motor pool.