bluuebunny/crossref_metadata_2025 huggingface dataset:
Serotoninergic system in the brainstem of the marmoset: A combined immunocytochemical and three‐dimensional reconstruction study
Authors: Hornung Jean‐Pierre , Fritschy Jean‐Marc
Published: January 2005

The distribution and morphology of serotoninergic neurons in the marmoset (New‐World monkey) brainstem were studied by immunocytochemistry and computer‐assisted threevdimensional reconstruction. The cytoarchitectonic localization of serotoninergic neurons was ascertained in series of adjacent immunostained and Nissl‐stained sections, and the extent and shape of the serotoninergic nuclei were visualized by computer reconstruction. The overall distribution of the immunoreactive neurons is comparable to that already described for several species of primates. The serotoninergic nuclei are spatially well segregated into an anterior and a posterior group. The anterior group, in the mesencephalon and the rostral pons, contains the largest population of serotoninergic neurons. These neurons are not confined to the raphe nuclei near the midline, but rather expand laterally in the reticular formation. This expanded distribution of the neurons in the anterior group results in a partial fusion of the nuclei. In some nuclei, particularly the median raphe, subdivisions can be clearly delineated on the basis of the distinct morphology of the neurons and of their clustering. The neurons of the posterior group, in the caudal pons and the medulla, are almost all contained within the limits of the raphe nuclei. The serotoninergic neurons located in the reticular formation form a lateral column, which is clearly separated from the serotoninergic neurons found near the midline.

Immunoreactive axons are distributed throughout the brainstem, but they innervate certain motor and sensory nuclei more densely. It was consistently found in newborn animals that the overall immunoreactive axonal network was richer than in juveniles or adults, suggesting that there may be a major modification in the function of the serotoninergic system around birth.
Regeneration of adult dorsal root axons into transplants of embryonic spinal cord
Authors: Tessler A. , Himes B. T. , Houle J. , Reier P. J.
Published: January 2005

Transplants of the embryonic rat spinal cord survive and differentiate in the spinal cords of adult and newborn host rats. Very little is known about the extent to which these homotopic transplants can provide an environment for regeneration of adult host axons that normally terminate in the spinal cord. We have used horseradish peroxidase injury filling and transganglionic transport methods to determine whether transected dorsal roots regenerate into fetal spinal cord tissue grafted into the spinal cords of adult rats. Additional transplants were examined for the presence of calcitonin gene‐related peptidelike immunoreactivity, which in the normal dorsal horn is derived exclusively from primary afferent axons. Host animals had one side of the L4‐5 spinal cord resected and replaced by a transplant of E14 or E15 spinal cord. Adjacent dorsal roots were sectioned and juxtaposed to the graft. The dorsal roots and their projections into the transplants were then labeled 2–9 months later. The tracing methods that used transport or diffusion of horseradish peroxidase demonstrated that severed host dorsal root axons had regenerated and grown into the transplants. In addition, some donor and host neurons had extended their axons into the periphery to at least the midthigh level as indicated by retrograde labeling following application of tracer to the sciatic nerve. Primary afferent axons immunoreactive for calcitonin gene‐related peptide were among those that regenerated into transplants, and the projections shown by this immunocytochemical method exceeded those demonstrated by the horseradish peroxidase tracing techniques. Growth of the host dorsal roots into transplants indicates that fetal spinal cord tissue permits regeneration of adult axotomized neurons that would otherwise be aborted at the dorsal root/spinal cord junction. This transplantation model should therefore prove useful in studying the enhancement and specificity of the regrowth of axons that normally terminate in the spinal cord.
Reorganization of primary afferent nerve terminals in the spinal dorsal horn of the primate caudal to anterolateral chordotomy
Authors: Bullitt Elizabeth , Stofer William D. , Vierck Charles J. , Perl Edward R.
Published: January 2005

A primate model has been used to explore the possibility that anterolateral chordotomy may produce intraspinal sprouting or rearrangement of primary afferent nerve terminations that could account for delayed postoperative recovery of sensory function. Monkeys were trained to limit the duration of an electrical stimulus, and the vigor and frequency of their escape responses were used to differentiate painful from nonpainful levels of stimulation. Behavioral testing after chordotomy revealed: (1) contralateral hypalgesia in all animals, with sensory recovery in half of the group, and (2) bilateral decreases in reflexive force in all animals, with reflex recovery in the majority of monkeys. At the terminal experiment, dorsal rootlets caudal to the spinal lesion were labeled bilaterally with HRP, and the distribution of labeled synaptic complexes was determined within the dorsal horn. When compared to controls, animals undergoing chordotomy showed a loss of terminals in the superficial dorsal horn and an increase of synaptic enlargements in deeper layers. These effects were bilateral, but were most pronounced on the side contralateral to chordotomy. Animals with diffuse spinal lesions showed a completely different change in the distribution of primary afferent terminals. Animals with sensory recovery demonstrated a more normal terminal distribution pattern than persistently hypalgesic monkeys, but there was considerable variability in the data, and analysis by different statistical tests yielded varying results.
FMRFamide‐ and adipokinetic hormone‐like immunoreactivity in the nervous system of the mosquito, Aedes aegypti
Authors: Brown Mark R. , Lea Arden O.
Published: January 2005

As demonstrated with immunocytochemistry, specific cells and axons in the nervous system of female Aedes aegypti contain antigens immunologically related to FMRFamide (phenylalanine‐methioninevarginine‐phenylalaninevamide) and locust adipokinetic hormone I (AKH). In the supravesophageal ganglion, including some medial neurosecretory cells, and in all ganglia of the ventral nerve cord, there are 100–120 cells immunoreactive to a FMRFamide antiserum. The same cells cross‐react with a bovine pancreatic polypeptide antiserum, but when the latter antiserum is preabsorbed with FMRFamide, immunoreactivity is lost. However, immunoreactivity is maintained when FMRFamide antiserum is preabsorbed with pancreatic polypeptide, suggesting that the immunoreactive peptide is more closely related to FMRFamide.

There are 6–12 cells in the supra‐ and subesophageal ganglia immunoreactive to an AKH antiserum, and some of the same cells are reactive to the FMRFamide antiserum. As well, unpaired cells in each of the abdominal ganglia are positive for both AKH and FMRFamide.

Although the function of the FMRFamidev and AKH‐like peptides in mosquitoes is unknown, this study, combined with previous reports on the localization of FMRFamidevlike peptides in midgut endocrine cells, supports the concept of a brain‐midgut neuroendocrine axis in this insect.
Immunohistochemical studies of cholecystokininlike peptides and their relation to 5‐HT, CGRP, and bombesin immunoreactivities in the brainstem and spinal cord of lampreys
Authors: Brodin Lennart , Buchanan James T. , Hökfelt Tomas , Grillner Sten , Rehfeld Jens F. , Frey Peter , Verhofstad Albert A. J. , Dockray Graham J. , Walsh John H.
Published: January 2005

The distribution of cholecystokinin (CCK)‐like immunoreactivity in the brainstem and spinal cord of lampreys was studied by using CCK antisera with different properties. In the spinal cord, three separate systems reacted with CCK antisera: (1) A ventral and lateral fiber system descending from a group of neurons in the posterior reticular nucleus of the rhombencephalon was labeled by both a C‐terminal‐directed CCK antiserum and a monoclonal CCK antibody. (2) A dorsal root–dorsal column system of fibers originating from cell bodies in the dorsal root ganglia was labeled only by the C‐terminal CCK antiserum. This CCK immunoreactivity could be abolished by preabsorption with calcitonin‐gene‐related peptide (CGRP), suggesting that it was due to cross‐reactivity with a CGRP‐like peptide. This system also contained 5‐hydroxytryptamine (5‐HT)‐, bombesin‐, and CGRP‐like immunoreactivities. (3) An intraspinal system of 5‐HT neurons was labeled with an antiserum to the midportion of CCK‐33 but not by the other CCK antisera. The CCK labeling of this system was difficult to reduce by preabsorption with CCK peptide and thus appeared to be nonspecific.

Groups of cell bodies in the middle reticular nucleus of the rhombencephalon, the reticular nucleus of the mesencephalon, and the hypothalamus were labeled by both the C‐terminal and the monoclonal CCK antisera. The gut contained two types of CCK‐like immunoreactivity, one of which appeared to be due to cross‐reactivity with CGRP.

A biochemical analysis showed that the content of CCK was low in the spinal cord compared to the brain, and these results agreed with the immunohistochemical findings.
Neuronal microtubule‐associated proteins in the embryonic avian spinal cord
Authors: Tucker Richard P. , Binder Lester I. , Matus Andrew I.
Published: January 2005

We have used monoclonal antibodies to study the distribution of three developmentally regulated microtubule‐associated proteins–MAP2, MAP5, and tau–during the morphogenesis of the thoracic spinal cord and peripheral nervous system in the quail. MAP5 is the only one of the three that is present in growing motor neuron processes in the day 3 embryo. The lowmolecular weight form of MAP2, MAP2c, is found in motor neuron cell bodies at embryonic day 3. At later stages MAP2c appears in axons and in glia; it decreases in abundance between embryonic days 5 and 7. High‐molecular weight MAP2 appears in motor neuron cell bodies and spinal cord gray matter at embryonic day 4, and is never encountered in axons. Tau is found in axons, but only at embryonic day 3.5, after they have commenced active extension. The molecular form and patterns of intracellular compartmentalization of each of the microtubule‐associated proteins studied is conserved in mammalian and avian neurons. We conclude that MAP5 may be involved in the active growth of neuronal processes, whereas MAP2 and tau are not, and that high‐molecular weight MAP2 and tau may stabilize dendritic and axonal processes, respectively.
Central projections of intracellularly labeled auditory nerve fibers in cats: Morphometric correlations with physiological properties
Authors: Ryugo D. K. , Rouiller E. M.
Published: January 2005

The central arborizations and endings of type I spiral ganglion neurons were labeled with intracellular injections of horseradish peroxidase (HRP) after their characteristic frequency (CF) and spontaneous discharge rate (SR) were physiologically determined. A fiber‐by‐fiber analysis was conducted and the morphological data compared with the fiber's response properties. The total number of branch points was correlated with total fiber length, a relationship that remained relatively constant when analyzing the ascending and descending branches together or separately. On the other hand, the ascending branches of four out of five fibers having CFs below 0.5 kHz bifurcated and gave rise to a pair of terminal endbulbs of Held.

Low‐ and medium‐SR fibers gave rise to more endings than did high‐SR fibers, especially on the ascending branch. This difference was accounted for by small endings, a category composed of terminal boutons, string endings, and small complex endings. The categories of modified endbulbs, and endbulbs of Held did not vary in number with respect to fiber SR. The mean area of each ending type within the small ending category was statistically smaller for low‐ and medium‐SR fibers than for high‐SR fibers, whereas the mean area of modified endbulbs and endbulbs of Held was not correlated with fiber SR. Total ending area per fiber appeared independent of either CF or SR. These results are discussed in relation to issues of conservation of axon arborizations and terminals, and convergence of input from the different SR groups.
Morphological and physiological development of olfactory receptor cells in rainbow trout (Salmo gairdneri) embryos
Authors: Zielinski Barbara , Hara Toshiaki J.
Published: January 2005

The morphological and functional differentiation of the olfactory receptor cells were investigated in developing rainbow trout (Salmo gairdneri) embryos by means of light and electron (transmission and scanning) microscopy and electrophysiology. Ciliated receptor cells first appeared when the olfactory placode was folded to form a groovelike structure rostrad to the eye at stage 24 (day 18; 18 days postfertilization). Ciliated receptor cells predominated until immature microvillar receptor cells developed in stage 28 (day 26) embryos. At stage 29, the day of hatching, the anterior edge of the olfactory epithelium contained only ciliated receptor cells, and the midregion contained both ciliated and microvillar receptor cells. Spontaneous neural firing activity was recorded from the olfactory mucosa as early as stage 25. The neural responses to amino acids were initially recorded from stage 26 embryos, containing sparse ciliated receptor cells with a few short cilia. The D‐enantiomers of amino acids were less effective. From these results we concluded that in rainbow trout the olfactory receptor cell has two separate morphological forms, ciliated and microvillar. These are ontogenetically distinct; the ciliated receptor cells preceded the microvillar. The ciliated receptor cells respond to amino acid stimulation.
Distribution of serotonin immunoreactivity in the forebrain and midbrain of the lizard Gekko gecko
Authors: Smeets Wilhelmus J. A. J. , Steinbusch Harry W. M.
Published: January 2005

The distribution of serotonin (5‐hydroxytryptamine, 5‐HT) in the forebrain and midbrain of the lizard Gekko gecko was studied by means of antibodies against serotonin. In the diencephalon, serotonin‐immunoreactive (5‐HTi) cell bodies were found in the hypothalamic periventricular organ and the ependymal wall of the infundibular recess. In the midbrain, 5‐HTi cells were observed in the nucleus raphes superior and the lateral portion of the nucleus reticularis superior. In addition, 5‐HTi cell bodies were found lateral to the ventral interpeduncular nucleus and around the ventral aspect of the medial longitudinal fasciculus. Serotonin‐immunoreactive fibers and varicosities are present throughout the forebrain and the midbrain, but particularly in the nucleus accumbens, the septal area, the dorsal cortex, the dorsal thalamus, the lateral geniculate body, the ventromedial hypothalamic nucleus, the pretectal nucleus, and the basal optic nucleus. The medial habenular nucleus contains a dense 5‐HTi plexus that shows a patchlike pattern. A laminar organization of 5‐HTi fibers and varicosities is present in the midbrain tectum. When compared with data obtained in other vertebrates, the present study has confirmed that in the phylogenetic series fishes‐amphibians‐reptiles‐birds‐mammals there appears to be (1) a gradual decrease in the number of cerebrospinal‐fluid‐contacting serotoninergic cells in the hypothalamic periventricular layer and (2) a remarkable increase in number of serotoninergic cells in the midbrain tegmentum. As in mammals, a strong serotoninergic innervation of structures related to sensory, in particular visual, pathways could be recognized.
Vestibular Projections to the thalamus of the pigeon: An anatomical study
Authors: Wild J. Martin
Published: January 2005

In a series of retrograde tracing studies involving the injection of WGA‐HRP into the thalamus of the pigeon, labeled neurons were consistently observed in anterior regions of the vestibular nuclei. Following small dorsal thalamic injections, labeled neurons were located predominantly in rostroventrolateral regions of te superior vestibular nucleus, less numerously within the ventral part of the lateral vestibular nucleus, and least numberously within the medial vestibular nucleus. Following large dorsal thalamic injections, many more vestibular neurons were labeled, and these were distributed more extensively throughout anterior parts of the superior, lateral, and medial nuclei. No labeled neurons were found in the descending nucleus. Injections of tritiated amino acids into vetibular nuclei revealed a terminal field within the dorsal thalamic nucleus: dorsolateralis posterior, pars rostralis. The location of this field between auditory, somatosensory, and paleostriatally and neostriatally projecting nuclei suggests a general similarity to the organization of vestibulothalamic projections in mammals.
Ultrastructural localization and characterization of sensory nerves in the rat kidney
Authors: Ferguson Meredith , Bell C.
Published: January 2005

The ultrastructural localization of sensory nerves in the rat kidney was examined by using the chromaffin reaction to distinguish sympathetic catecholaminergic fibres from sensory fibres. The sensory fibres were further characterized by use of an immunoperoxidase staining method to identify nerves immunoreactive for substance P and for calcitonin‐gene‐related peptide. Sympathetic fibres were observed in the renal cortex, medulla, and pelvis, but sensory fibres were seen only in the renal pelvis. Immunostaining for substance P labelled 40% of the sensory fibres. Following incubation in calcitonin‐gene‐related peptide antiserum, 53% of the sensory nerves were positively stained. Simultaneous immunostaining for substance P and calcitonin‐gene‐related peptide resulted in immunoreactivity in 82% of the sensory fibres, a percentage of axons significantly lower than that expected if the axons containing each peptide had been entirely separate populations. The results indicate that sensory nerves in the rat kidney are located entirely in the renal pelvis. On the basis of their neuropeptide content, there appear to be at least four separate populations of sensory axons present: two large groups containing substance P or calcitonin‐gene‐related peptide alone and two small groups containing both peptides and containing neither.
Synaptic organization of serotonin‐immunoreactive fibers in primary visual cortex of the macaque monkey
Authors: de Lima Ana D. , Bloom Floyd E. , Morrison John H.
Published: January 2005

The macaque neocortex is very densely innervated by serotonin‐containing fibers. The highest density of these fibers is in primary sensory regions such as the primary visual cortex. By using an antibody against serotonin, we analyzed the distribution and morphology of serotonin‐immunoreactive fibers and synapses in the primary visual cortex of the adult cynomolgus monkey. In addition, we quantified the laminar distribution of labeled varicosities and the distances between varicosities in single fibers. While serotonin‐immunoreactive fibers are found in all cortical layers, at least three bands of heightened density of innervation were readily recognized that were coincident with (1) layer IIIB to IVCα, (2) layer VA, and (3) layer VIB. Layer IVCα of area 17 contained more varicosities per unit area than any other sublayer. There was a high degree of variability in the intervaricosity distances along single fibers; more than half were longer than 10 μm.

At the electron microscopic level, synaptic contacts were also observed throughout the entire thickness of area 17, with the highest frequency in layer IV. The labeled varicosities were packed with electron‐lucent synaptic vesicles and formed synaptic complexes with small, but conspicuous, postsynaptic densities. Dendritic shafts were the most common postsynaptic target of the labeled synapses. Among these characteristically slender postsynaptic shafts, profiles with structural features of both spiny and smooth dendrites were observed. The small diameter of most of the postsynaptic dendrites indicated that distal dendrites were preferentially contacted by serotonin‐immunoreactive varicosities. Although direct identification of the postsynaptic neurons will be required for complete characterization of this circuitry, the distribution of serotonin‐immunoreactive varicosities suggests that serotoninergic interactions in the primary visual cortex of the cynomolgus monkey are directed predominantly at the distal dendrites of granular and infragranular neurons rather than at targets in the supragranular layers.
Ultrastructural localization of immunoreactivity in the developing piriform cortex
Authors: Westenbroek R. E. , Westrum L. E. , Hendrickson A. E. , Wu J.‐Y.
Published: January 2005

The purpose of this study was to determine the ultrastructural basis for the immunoreactivity patterns in synaptic structures during development in layers I and II of the piriform cortex (PC) of rats. Antisera to cholecystokinin (CCK) and glutamic acid decarboxylase (GAD) were used at several different postnatal days (PN) and in adults to describe the distribution, characteristics, and relative frequency of labeled profiles–especially axons and terminals–with emphasis on details of the synaptic contacts. GAD‐positive terminals occur from PN 2 to adulthood but only form contacts in deeper sublayers (Ib and II) initially. Contacts increase in layer I after PN 6 and are reduced in layer II after PN 21 when the GAD‐labeled terminals and synapses take on adult features with flattened vesicles and symmetric contacts. CCK‐labeled terminals are present in deeper sublayers at PN 2 but are few and rarely form contacts. Both terminals and contacts increase between PN 2 and 9, taking on distinctive shapes and vesicle morphology by PN 13. At PN 21 and older, CCK terminals have mainly flattened vesicles and mostly form symmetric contacts onto dendrites and somata in deeper layers (Ib and II). Superficial sublayer Ia has very few CCK‐labeled synapses and axons. Thus immunoreactivity occurs in terminals prior to synapse formation; labeling of the presynaptic specializations precedes subsequent maturation; synaptic vesicle morphology and membrane specializations are similar for the vast majority of both CCK and GAD terminals; inhibitory (GABA) synapses are established sooner than the possibly excitatory CCK synapses; a deep to superficial gradient of synaptogenesis is associated with GAD‐positive terminals in the PC; and the labeling patterns may be related to critical developmental or synaptogenic periods.
Normal and regenerating optic fibers in goldfish tectum: HRP‐EM Evidence for rapid synaptogenesis and optic fiber‐fiber affinity
Authors: Hayes William Pär , Meyer Ronald L.
Published: January 2005

The distribution of normal and regenerating retinal fibers and synapses was studied on tectum in goldfish by light (LM) and electron microscopy (EM). Since labeling of the early regenerating fibers was previously reported to be difficult, a new “cold‐fill” HRP labeling protocol was developed, which labeled regenerating optic fibers and terminals on tectum as early as 14 days after nerve crush when they first arrive on tectum. In order to characterize the laminar distribution of optic afferents in normal fish and in fish regenerating for 14–240 days, EM photomontages of areas 14 μm wide by 160 μm deep through the HRP‐labeled primary optic innervation layer (S‐SO‐SFGS) were constructed. The time points in regeneration that were examined spanned the period in which others have shown that an initially diffuse retinotopic map becomes spatially restricted.

At the LM level regenerating optic fibers were restricted to the optic lamina. They reinnervated tectum in an anterior to posterior sequence as previously seen with autoradiography. In addition, at 14 days, some “pioneer” optic fascicles were found to have already grown to posterior tectum where they gave rise to branches with boutonlike terminations and growth‐cone‐like processes.

From the ultrastructural analysis it was clear that optic fibers and terminals observed strict laminar boundaries as they partitioned themselves in the optic laminae (S, SO and SFGS) in both normal and regenerating fish. The behavior of optic fibers was lamina specific with respect to synapse formation and the orientation of fiber outgrowth. As early as 14 days regeneration, optic fibers made synapses onto the four types of postsynaptic profiles observed in normal fish. Numerous optic terminals were labeled at 14 days, and there appeared to be no waiting period between fiber ingrowth to the SO and synapse formation in the S and SFGS. At 14–60 days, atypical synaptic contacts which appear to be nascent synapses were made by labeled optic fibers in fascicles and by growth‐cone‐like processes. By 21–30 days, the density of optic terminals was high and there were many more fasciculated optic fibers in the SFGS than normal as late as 240 days.

These findings suggest that optic fiber lamination is highly constrained by tectal cues, that fibers rapidly regenerate many synaptic terminals before retinotopic map refinement is complete, and that fibers have a strong affinity for each other.
Metabolic activity in striate and extrastriate cortex in the hooded rat: Contralateral and ipsilateral eye input
Authors: Thurlow G. A. , Cooper R. M.
Published: January 2005

The extent of changes in glucose metabolism resulting from ipsilateral and contralateral eye activity in the posterior cortex of the hooded rat was demonstrated by means of the C‐14 2‐deoxyglucose autoradiographic technique. By stimulating one eye with square wave gratings and eliminating efferent activation from the other by means of enucleation or intraocular TTX injection, differences between ipsilaterally and contralaterally based visual activity in the two hemispheres were maximized. Carbon‐14 levels in layer IV of autoradiographs of coronal sections were measured and combined across sections to form right and left matrices of posterior cortex metabolic activity. A difference matrix, formed by subtracting the metabolic activity matrix of cortex contralateral to the stimulated eye from the ipsilateral “depressed” matrix, emphasized those parts of the visual cortex that received monocular visual input. The demarcation of striate cortex by means of cholinesterase stain and the examination of autoradiographs from sections cut tangential to the cortical surface aided in the interpretation of the difference matrices. In striate cortex, differences were maximal in the medial monocular portion, and the lateral or binocular portion was shown to be divided metabolically into a far lateral contralaterally dominant strip along the cortical representation of the vertical meridian, and a more medial region of patches of more or less contralaterally dominant binocular input. Lateral peristriate differences were less than those of striate cortex, and regions of greater and lesser monocular input could be distinguished. We did not detect differences between the two hemispheres in either anterior or medial peristriate areas, thus indicating either completely binocular input (which seems unlikely given the retinotopic organization of these regions), or a greater dependence than in the lateral peristriate on inputs that were not affected by the visual manipulations.
The lateral giant fibers of the tubificid worm, Branchiura sowerbyi: Structural and functional asymmetry in a paired interneuronal system
Authors: Zoran Mark J. , Drewes Charles D. , Fourtner Charles R. , Siegel Alan J.
Published: January 2005

Neuroanatomical and ultrastructural studies of the paired lateral giant nerve fibers (LGFs) in posterior segments of the tubificid worm, Branchiura sowerbyi, demonstrate that the fibers are (1) segmental in origin (two cell bodies per segment), (2) joined longitudinally and transversely to form an intersegmental syncytial network, and (3) surrounded by a myelinlike sheath. The LGFs are unique among paired giant fiber systems because of their extreme asymmetry, the diameter of the left fiber being several times greater than that of the right. Electrophysiological studies demonstrate that the small, right fiber has a high input resistance and, during mechanosensory stimulation, functions as the locus for LGF spike initiation. The larger, left fiber contributes by enhancing the speed of LGF spike conduction along the animal. One physiological benefit of this asymmetric arrangement may be optimization of escape reflex sensitivity to mechanosensory inputs.
Development of acetylcholinesterase activity in the lateral geniculate nucleus
Authors: Hutchins James B. , Casagrande Vivien A.
Published: January 2005

The pattern of acetylcholinesterase activity in the tree shrew (Tupaia belangeri) lateral geniculate nucleus (LGN) undergoes a number of striking changes during postnatal development. The adult tree shrew LGN is made up of six cellular layers divided by relatively cell‐free interlaminar zones. At birth, however, the nucleus appears unlaminated when processed with conventional Nissl‐staining techniques. The cellular lamination appears during the first postnatal week. The eyes open much later, typically at the end of the third week after birth.

In the adult tree shrew, acetylcholinesterase (AChE) activity is found throughout the nucleus (both within and between the six cellular layers). In most sections examined, reaction product is slightly more intense in the lateral cell layers (4, 5, and 6).

This is in sharp contrast to the pattern at birth (postnatal day zero, or P0). The detectable AChE activity at this age is apparently found in inchoate layers 1‐2 and 4‐5. Within these pairs, areas innervated by the ipsilateral eye (i.e., incipient layers 1 and 5) appear to contain more reaction product. From P0 to P4, the density of AChE activity increases in layers 1‐2 and 4‐5 and becomes detectable in the barely evident layers 3 and (usually) 6 at this age. By the middle of the second postnatal week, after laminae are clearly apparent with a Nissl stain, AChE activity has increased and is mainly associated with each cellular layer in the nucleus. During the third week after birth this pattern undergoes a radical shift. The most intense AChE activity is now in the interlaminar zones. Finally, as the adult pattern emerges, AChE activity increases in the cellular layers and all areas of the nucleus exhibit relatively high levels of AChE activity.

Superimposed on this changing laminar pattern of AChE activity are changes related to the retinotopic map within the nucleus. Portions of the LGN representing central vision develop their characteristic pattern of activity several days ahead of the regions representing more peripheral visual field locations.

AChE activity is also found transiently in the optic tract near the LGN during the first 3 postnatal weeks. Two (possibly three) groups of AChE‐carrying fibers can be traced from the optic chiasm to their apparent sites of termination (or origin) in the parabigeminal nucleus, ventral lateral geniculate nucleus, and dorsal LGN. The activity present in the optic tract disappears shortly after eye opening.

These results suggest that AChE and/or its associated neurotransmitter, acetylcholine, may play a role in the sequential development of connections and lamination in the LGN. The observed shifting pattern of AChE activity is consistent with a morphogenetic role for the enzyme, as suggested by others. However, it may also simply reflect the establishment and neurochemical maturation of cholinergic synapses during development of the LGN.
Fine structure of identified neurons in the primate hippocampus: A combined Golgi/EM study in the baboon
Authors: Frotscher Michael , Kraft Jürgen , Zorn Uwe
Published: January 2005

The hippocampi of two 1‐year‐old female baboons (Papio anubis) were used for a combined Golgi/electron microscope (EM) study of characteristic cell types in the hippocampus proper and fascia dentata. Results were compared with previous Golgi/EM studies of hippocampal neurons in small laboratory animals.

Cell bodies of pyramidal neurons in CA1 were more loosely distributed than known from studies on the rat or guinea pig. Numerous basal and horizontal dendrites originating from the perikaryon filled in the space between neighboring cell bodies. Apical stem dendrites were varying in length, depending on the position of the parent cell body in outer or inner portions of the pyramidal layer. Dendrites were densely covered with spines which in the EM showed very complex synaptic contacts.

In contrast to our observations in rats and guinea pigs, CA3 pyramidal cells in the monkey hippocampus exhibited numerous large spines orexcrescences not only on apical dendrites but also on basal dendrites running through stratum oriens. These excrescences appeared to be more complex than in small rodents. They often branched, protruding deeply into presynaptic mossy fiber boutons, and formed multiple asymmetric synaptic contacts.

Granule cells of the monkey fascia dentata, in contrast to those of the rodent, occasionally had basal dendrites extending into the hilar region. In the EM, granule cells either with or without basal dendrites exhibited fine structural characteristics that were very similar to those described in Golgi/EM studies of granule cells in the rat fascia dentata.

Of the various types ofnonpyramidal neurons the horizontal cells in stratum oriens with dendrites parallel to the alveus were analyzed. As seen in rats, these cells exhibited large amounts of rough endoplasmic reticulum, indentations of the nuclear membrane, and nuclear inclusions. Numerous terminals formed synaptic contacts on dendritic shafts. In contrast to rodents, numerous spines arose from dendrites and cell bodies of these neurons. In the EM, often single spines were found to establish synaptic contacts with several presynaptic boutons.

In summary, our correlated light and EM study of four characteristic cell types, which are present in both nonprimates and primates, demonstrates a much more complex dendritic pattern and synaptic organization of these neurons in primates than in commonly studied small laboratory animals.
Synaptic analysis of amacrine cells with neuropeptide Y‐like immunoreactivity in turtle retina
Authors: Isayama Tomoki , Polak Julia , Eldred William D.
Published: January 2005

Neuropeptide Y‐like immunoreactivity has been localized previously within three classes of amacrine cells in the turtle retina. We have used the avidin‐biotin with horseradish peroxidase technique to label these neurons for examination at the ultrastructural level to answer the following questions. Where are the synaptic contacts of these neurons made? What types of neurons are involved pre‐ and postsynaptically? What is the intracellular distribution of the immunoreactivity?

Processes with neuropeptide Y‐like immunoreactivity were located primarily within three regions of the inner plexiform layer: stratum 1, stratum 3, and at the border between strata 4 and 5. In all three regions the processes with neuropeptide Y‐like immunoreactivity received synaptic contacts from both unlabeled amacrine and bipolar cells, but the majority of the synaptic input in all three regions was from unlabeled amacrine cells. Processes with neuropeptide Y‐like immunoreactivity were presynaptic to unlabeled amacrine cells in all three regions, but also formed contacts onto unlabeled bipolar cells in the region between strata 4 and 5.

The immunoreactivity within these cells gave rise to a diffuse reaction product that was distributed throughout the cytoplasm and within large vesicles. This localization of neuropeptide Y‐like immunoreactivity within large vesicles suggests that this peptide may play a neuromodulatory role. Such a role would be consistent with previous studies of neuropeptides in the turtle retina.
Feline islands of calleja complex: I. Cytoarchitectural organization and comparative anatomy
Authors: Talbot Konrad , Woolf Nancy J. , Butcher Larry L.
Published: January 2005

Cytoarchitectural analyses demonstrated that the islands of Calleja complex (ICC) is highly developed and discretely organized in the cat. The feline complex is clearly divided into morphological units, each containing a granular Callejal island and a population of satellite neurons. These ICC units change progressively in cytoarchitecture from the lateral to the medial edge of the olfactory tubercle. In particular, the islands flatten, sink into the tubercular molecular layer, and increase in cell density, while their satellite neurons increase in number and decrease in size. The lateromedial transformation was judged to take place in five stages, resulting in the successive appearance of lateral, lateral transitional, central, medial transitional, and medial ICC units. The first two unit types display prominently two additional components of the feline ICC‐‐‐namely, clusters of dwarf cells and small pyramidal‐like neurons constituting the densocellular layer cupping the base of lateral Callejal islands.

All of the various types of ICC units contact the tubercular molecular layer via their dwarf and/or granule cell components, raising the possibility of direct olfactory input to the entire Callejal complex (apart from the isla magna). Output from the complex is presumed to arise from the satellite neurons, which are distinguished from adjoining cell populations by their close association with Callejal islands, typical chromophilic character, and relatively large size (15‐42 μm in soma length). In the tubercular ICC, these neurons are most numerous immediately above Callejal islands in a fiberrich zone continuous with the supratubercular zone and hence with the ventral pallidum. In the accumbal ICC, satellite neurons are most conspicuous in granule‐cell‐poor spaces within the isla magna, where many nongranular neurons are uncharacteristically small and chromophobic. The isla magna itself is unusual not only for its large size but for lateral extensions encircling a group of accumbal neurons far caudally. Such extensions are one of several indications that the isla magna is intimately associated with the nucleus accumbens.

A comparative anatomical survey of the ICC in rats, cats, and macaque monkeys demonstrated a number of species differences. Of particular interest is the finding that the complex is unambiguously divided into discrete island‐satellite cell units only in cats and macaques. In these species, the complex is also distinguished by a predominance of superficial islands and an especially prominent isla magna. ICC units, however, were most conspicuous in cats.
Estrogen/progesterone treatment in adulthood affects the size of several components of the medial preoptic area in the male rat
Authors: Bloch G. J. , Gorski R. A.
Published: January 2005

The results of preliminary studies suggested that steroid and/or propylthiouracil (PTU) treatment of adult gonadectomized (Gxd) male rats significantly reduced the volume of the sexually dimorphic nucleus of the preoptic area (SDN‐POA). Therefore, we designed a study to examine this effect in detail. Groups of adult rats were sham Gxd (intact) or Gxd, then treated with multiple injections of oil (males and females), or estrogen and progesterone (males). Gonadectomized estrogen/progesterone‐treated males had a significantly smaller SDN‐POA volume, smaller volume of the medial division of the medial preoptic nucleus (MPNm), smaller volume of the anteroventral MPNm (MPNav), and larger volume of the anteroventral periventricular nucleus (AVPv). The volume of the central division of the medial preoptic nucleus (MPNc) or of the suprachiasmatic nucleus was not affected. There were no differences between Gxd estrogen/progesterone‐treated males vs the group that received PTU as well, indicating that the PTU treatment was unnecessary. The reduced volume of the SDN‐POA was due to a reduced volume of the MPNav and of the portion of the SDN‐POA located within the MPNm‐exclusive of the MPNav and MPNc. In conclusion, estrogen/progesterone treatment in adulthood caused significant changes in the volume of several medial preoptic structures in two separate groups of Gxd males. Because the steroids produced no significant effects in intact males, testicular hormones appear to “protect” these structures from the effects of the estrogen/progesterone treatment.
Hormonal modification of the number of total and late‐arising neurons in the central part of the medial preoptic nucleus of the rat
Authors: Dodson Robin E. , Shryne James E. , Gorski Roger A.
Published: January 2005

The sexually dimorphic nucleus of the preoptic area (SDN‐POA) is larger in volume in males, is responsive to steroids developmentally, and contains a subpopulation of late‐arising neurons that can be specificially labeled with 3H‐thymidine on embryonic day 18 (E18). The cytoarchitecture of this region has been described, and one component, the central part of the medial preoptic nucleus (MPNc), shows considerable overlap with the SDN‐POA. One goal of the present study was to relate the two by determining if testosterone propionate (TP) exposure perinatally increases MPNc volume and neuronal number, and by characterizing the distribution of the late arising neurons of the SDN‐POA with respect to the MPNc. A second goal was to determine if these late‐arising neurons are a representative, hormone‐sensitive population. Finally, TP exposure was delayed past the time of the endogeneous testosterone surge in males and after the neurons have become postmitotic, to determine if female brain structure could still be sex‐reversed under these conditions. Pregnant rats were injected on E18 with 3H‐thymidine. Daily injections of 2.0 mg TP were given to the mothers starting on either E16 or E20 and continued through birth. The pups were injected daily with 100 μg TP from birth through postnatal day 10. Control rats, from mothers given oil from E16 until birth, were injected with oil from birth through postnatal day 10. Rats were sacrificed at 30 days of age and their brains processed for autoradiography. Neurons and labeled cells were counted in three areas: (1) the MPNc, (2) the region surrounding the MPNc, and (3) a region anterior to the MPNc within the SDN‐POA. Labeled cells composed approximately 16% of the neurons in the MPNc and only 3 to 4% in the control regions. Within the MPNc there were more neurons and labeled cells in males than in females. Testosterone treatment, regardless of the starting day, increased MPNc volume and its number of neurons and labeled cells to those of males. These data demonstrate that there is a sex difference in the number of late‐arising neurons at 30 days of age, that they are sensitive to steroids during development, and that they are localized to the MPNc. In addition, TP exposure is effective beyond the time of the endogeneous surge in males. Steroid injections in one group of animals were not started until neurons in this region had become postmitotic but still resulted in a sex‐reversal, suggesting that testosterone does not modify neurogenesis.
Efferent connections of the striatum and the nucleus accumbens in the lizard Gekko gecko
Authors: Russchen Fokje T. , Jonker Allert J.
Published: January 2005

The efferent connections of the striatum and the nucleus accumbens of the lizard Gekko gecko were studied with the anterograde tracer Phaseolus vulgaris‐ leucoagglutinin (PHA‐L). These structures were found to have segregated output systems. The striatum shows a major projection to the globus pallidus. Striatal fibers which are more caudally directed run through the lateral forebrain bundle and can be traced as far caudally as the pars reticularis of the substantia nigra where they exhibit many varicosities. Along its course, the lateral forebrain bundle issues fibers with varicosities to the anterior and posterior entopeduncular nuclei. The major recipient structure of the nucleus accumbens is the ventral pallidum. The nucleus accumbens, in addition, projects to the portion of the lateral hypothalamus in the path of the medial forebrain bundle and to the ventral tegmental area, which is its most caudal target.

Subsequently, the same technique was used in an attempt to study the efferents of the globus pallidus and the ventral pallidum, the major recipient structures of the striatum and the nucleus accumbens. The globus pallidus was found to project to the rostral part of the suprapeduncular nucleus in the ventral thalamus and, in addition, may distribute fibers to the same structures as does the striatum. The ventral pallidum distributes fibers to the ventromedial thalamic nucleus. It probably also projects diffusely to the hypothalamus, the habenula, and the mesencephalic tegmentum.
Anatomical and functional organization of the prepacemaker nucleus in gymnotiform electric fish: The accommodation of two behaviors in one nucleus
Authors: Kawasaki M. , Maler L. , Rose G. J. , Heiligenberg W.
Published: January 2005

The diencephalic prepacemaker nucleus (PPn) of gymnotiform electric fish projects to the medullary pacemaker nucleus and modulates its regular firing frequency. Each firing of the pacemaker, in turn, drives an electric organ discharge (EOD) Two types of PPn neurons were retrogradely labeled from the pacemaker with HRP in Eigenmannia and Apteronotus. In both species, smaller ovoidal cells were found in the dorsomedial part of the PPn (PPn‐G), and larger multipolar cells were found in the ventrolateral part of the PPn (PPn‐C). This morphological distinction between the two subnuclei in the PPn was paralleled by a functional dichotomy. Microiontophoresis of L‐glutamate in the PPn‐G of both species elicited slow and gradual accelerations of EOD frequency characterized by a time constant on the order of seconds. The elicited frequency modulations were similar to those observed during the jamming avoidance response and during courtship. Glutamate stimulation of the PPn‐C, in contrast, produced fast and abrupt frequency modulations characterized by a time constant on the order of milliseconds. These abrupt modulations resembled “chirps” observed during courtship and aggression. Similar behavior was produced by intracellular current injection into a PPn‐C neuron of Apteronotus, and intracellular labeling of this neuron with Lucifer Yellow revealed a multipolar PPn‐C neuron similar to those retrogradely labeled with HRP.