bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional (14C) 2‐deoxyglucose uptake during forelimb movements evoked by rat motor cortex stimulation: Cortex, diencephalon, midbrain
Authors: Sharp Frank R.
Published: January 2005

The caudal forelimb region of right “motor” cortex was repetitively stimulated in normal, conscious rats. Left forelimb movements were produced and (14C) 2‐deoxyglucose (2DG) was injected. After sacrifice, regions of increased brain (14C) 2DG uptake were mapped autoradiographically.

Uptake of 2DG increased about the stimulating electrode in motor (MI) cortex. Columnar activation of primary (SI) and second (SII) somatosensory neocortex occurred. The rostral or second forelimb (MII) region of motor cortex was activated.

Many ipsilateral subcortical structures were also activated during fore‐limb MI stimulation (FLMIS). Rostral dorsolateral caudate‐putamen (CP), central globus pallidus (GP), posterior entopeduncular nucleus (EPN), sub‐thalamic nucleus (STN), zona incerta (ZI), and caudal, ventrolateral substantia nigra pars reticulata (SNr) were activated. Thalamic nuclei that increased (14C) 2DG uptake included anterior dorsolateral reticular (R), ventral and central ventrolateral (VL), lateral ventromedial (VM), ventral ventrobasal (VB), dorsolateral posteromedial (POm), and the parafascicular‐centre median (Pf‐CM) complex. Activated midbrain regions included ventromedial magnocellular red nucleus (RNm), posterior deep layers of the superior colliculus (SCsgp), lateral deep mesencephalic nucleus (DMN), nucleus tegmenti pedunculopontinus (NTPP), and anterior pretectal nucleus (NCU).

Monosynaptic connections from MI or SI to SII, MII, CP, STN, ZI, R, VL, VM, VB, POm, Pf‐CM, RNm, SCsgp, SNr, and DMN can account for ipsilateral activation of these structures. GP and EPN must be activated polysynaptically, either from MI stimulation or sensory feedback, since there are no known monosynaptic connections from MI and SI to these structures. Most rat brain motor‐sensory structures are somatotopically organized. However, the same regions of R, EPN, CM‐Pf, DMN, and ZI are activated during FLMIS compared to VMIS (vibrissae MI stimulation). Since these structures are not somatopically organized, this suggests they are involved in motor‐sensory processing independent of which body part is moving. VB, SII, and MII are activated during FLMIS but not during VMIS.
Laminar origin and septotemporal distribution of entorhinal and perirhinal projections to the hippocampus in the cat
Authors: Witter Menno P. , Groenewegen Henk J.
Published: January 2005

The Projections o the entorhinal and perirhinal cortices to the hippocampus in the cat have been studied with retrograde and anterograde tracing techniques. Retarogradely transported tracers, which were injected at different levels along the septotemporal longitudinal hippocampal axis, result in labeled neurons in superficial entorhinal cortical layers II and III. Occasionally, labeled cells were also observed in the deepest entorhinal layer as well as in the superficial layers of the perirhinal area 35. It could further be shown that labeled neurons located superficially in the entorhinal cortex corresponds to a septotemporal gradient along the longitudinal axis of the hippocampus. This topographical organization of the entorhinal‐hippocampal projection system could be substantiated by the use of anterograde tracing of radioactively labeled amino acids. Injections in the entorhinal cortex produce labeled fibers in the hippocampus. Injections in the perirhinal area 35 result also in labeling over the hippocampus, whereas area 36 does not seem to distribute fibers to the hippocampus. As anticipated from the results of the retrograde tracing experiments, injections located laterally, in or close to the posterior rhinal sulcus, produce prominent labeling over the septal pole of the hippocampus, whereas progressively more medially located injections result in progressively more temporally located labeling. This topographical distribution of perforant path fibers along the septotemporal axis of the hippocampus, which is related to a lateromedial axis in the entorhinal cortex, has been observed following injections in the lateral entorhinal area (LEA) as well as in the medial entorhinal area (MEA). The present observations are discussed in regard of other connectional and putative functional differences between the septal and temporal hippocampus.
Collateral innervation of the medial and lateral prefrontal cortex by amygdaloid, thalamic, and brain‐stem neurons
Authors: Sarter Martin , Markowitsch Hans J.
Published: January 2005

The distribution of the afferents to the rat's prefrontal cortex originating in the thalamic mediodorsal nucleus and the amygdala was investigated with two fluorescent tracers. Special emphasis was laid on detecting the loci of neurons which project via axonal collaterals into both lateral and medial portions of the prefrontal cortex.

It was found that a high number of neurons of the anterior portion of the basolateral amygdaloid nucleus terminate via collaterals in both the medial and lateral subfields of the prefrontal cortex. On the other hand, only a small number of mediodorsal thalamic cells were found to project to both sides of the prefrontal hemisphere via bifurcating axonal collaterals. These cells were situated exclusively in the lateral part of the medial segment of the mediodorsal nucleus. The majority of both thalamic and amygdaloid neurons with bifurcating axons originate from subregions whose cells innervate primarily the medial prefrontal cortex. In brain‐stem, neurons of the nucleus raphé dorsalis also project via collaterals to the medial and lateral prefrontal regions. Furthermore, neurons of the dorsal and ventral premamillary nuclei, the lateral mamillary nucleus, the ventral tegmental area of Tsai, and the ventral tegmental nucleus of Gudden were found to project to the medial prefrontal cortex.

Our results indicate a differential collateral organization of thalamic and amygdaloid afferents to prefrontal cortical fields. The anterior basolateral amygdala (which innervates via collaterals both the medial and lateral prefrontal subfields) may add a common input to either subfield, such as information on the significance of incoming stimuli to the animal's behavior, while the mediodorsal nucleus (whose segments are principally connected to only one prefrontal subfield) may add segment‐specific information, for example, of a spatial‐cognitive nature for the lateral segment and of an emotional nature for the central and medial segments.

The existence of a basolateral limbic circuit, composed of the amygdala, the thalamic mediodorsal nucleus, and the prefrontal cortex, is confirmed and knowledge on its interconnectivity is extended. From an anatomical point of view these data provide arguments for both unitary and diverging functions of the prefrontal cortex.
The morphological diversity and receptive fields of spiking local interneurons in the locust metathoracic ganglion
Authors: Burrows M. , Siegler M. V. S.
Published: January 2005

Twenty‐one types of spiking local interneurons are described in a segmental ganglion of the locust. All have their cell bodies in a group at the ventral midline of the metathoracic ganglion. The interneurons are characterized by their shape as revealed by intracellular injection of dye, and by their physiology as revealed by intracellular recording. Each interneuron conforms to a basic plan, but the characteristic shape of each is derived from the elaboration of branches in some regions of the neuropil and by their absence in other regions. Some interneurons have ventral branches that extend over most of one‐half of the metathoracic neuropil, whilst others have ventral branches restricted to a small region of neuropil. A few interneurons have dorsal branches that enter the first abdominal neuromere. Each type of interneuron is excited by a specific array of mechanoreceptors on the hind leg ipsilateral to its neuropilar branches. Some interneurons have a wide receptive field that encompasses most of the surfaces of the distal three parts of a leg, whilst others have a field limited to the spurs at the distal end of the tibia. The relationship between the shape of an interneuron and the size or orientation of its receptive field is discussed.
Replication and differentiation of olfactory receptor neurons following axotomy in the adult hamster: A morphometric analysis of postnatal neurogenesis
Authors: Samanen David W. , Forbes William B.
Published: January 2005

Regeneration of olfactory receptor neurons following unilateral olfactory nerve section was studied in Syrian golden hamsters by morphometric procedures. Characteristic structural and histochemical features of olfactory receptor neurons were compared on the sectioned and intact sides of the nasal septum at 6, 12, 18, 33, and 130 days following axotomy. The parameters measured were epithelial thickness and the numbers of nuclei, hematoxylin‐staining olfactory vesicles, olfactory marker protein (OMP)‐containing neuronal perikarya, and OMP‐containing olfactory vesicles. The olfactory receptor neuron population was severely depleted 6 days after axotomy. In the succeeding 12‐day period there was an initially rapid, then slower return of receptor neuron numbers. Though the regenerating olfactory epithelium appeared normal by gross inspection 33 days after the lesion, morphometric analysis revealed a substantial increase in the number of olfactory receptor neurons between 33 and 130 days postlesion. At our longest survival interval, all quantitative parameters had returned to 91–99% of control values. The numbers of OMP‐containing perikarya and olfactory vesicles on the sectioned side were unchanged between the sixth and 12th postlesion days, thus suggesting that neural turnover was depressed for several days following surgery. Marker protein developed in newly formed receptor neurons between 6 and 12 days after the formation of the olfactory vesicle. Consequently, the ratio between OMP‐containing olfactory vesicles and hematoxylin‐staining vesicles (O/H) was used as an index of neural differentiation. The O/H ratio on the sectioned side was minimal 12 days following axotomy when stem‐cell division was well under way but OMP antigenicity had not yet been expressed in newly formed neurons. At 33 days postlesion, O/H ratios were slightly but significantly greater than the control value, reflecting a degree of synchrony in the regenerating receptor neuron population. The average O/H ratio on the unlesioned side was 0.667. This value, together with our other observations, was used to derive an estimate of the life span of hamster olfactory receptor neurons, approximately 25–35 days.
Distribution of enkephalin, substance P, tyrosine hydroxylase, and 5‐hydroxytryptamine immunoreactivity in the septal region of the rat
Authors: Gall Christine , Moore Robert Y.
Published: January 2005

Immunocytochemical methods were used to define the distribution of enkephalin (ENK), substance P (SP), tyrosine hydroxylase (TH), and serotonin (5‐hydroxytryptamine: 5HT) in the rat septum. A dense plexus of axons containing enkephalin‐like immunoreactivity is found in the intermediate lateral septal nucleus. This is surrounded laterally by SP‐containing cell bodies and axons and medially by ENK‐containing cell bodies. Both SP‐ and ENK‐immunoreactive axons form pericellular and peridendritic terminal arbors around lateral septal neurons. TH‐positive axons are distributed throughout the septum and form dense pericellular terminal baskets around scattered neurons in the medial half of the intermediate lateral septal nucleus and in the extreme lateral septum. Very few SP and TH immunoreactive axons are present in the ENK immunoreactive plexus zone. 5HT‐immunoreactive axons are most dense at the lateral edge of the ventral and intermediate lateral septal nuclei but form pericellular terminal arbors only in the dorsal lateral septal nucleus, in the septofimbrial nucleus, and in the dorsal cap of the medial septal nucleus. These results indicate that the dorsal and intermediate lateral septal nuclei include three histochemically distinct laminated subfields: (1) an ENK immunoreactive axonal plexus within the lateral aspect of the intermediate lateral septal nucleus, (2) a more medial region of scattered ENK immunoreactive perikarya and similarly scattered TH immunoreactive pericellular baskets, and (3) a dorsolateral zone occupied by SP neurons and 5HT‐containing pericellular baskets. Thus, the data suggest that SP‐ and ENK‐containing neuronal populations in the lateral septum receive different monoaminergic inputs. Further, the somewhat exclusive laminated pericellular termination of peptide‐ and catecholamine‐containing axons in the lateral septum predicts very different functional and pharmacological properties among zones.
Distribution of serotonin‐containing neurons and their pathways in the supraoesophageal ganglion of the cockroach Periplaneta americana (L.) as revealed by immunocytochemistry
Authors: Klemm Nikolai , Steinbusch Harry W. M. , Sundler Frank
Published: January 2005

The distribution of serotonin (5‐HT)‐containing neurons in the supraoesophageal (cerebral) ganglion of the cockroach Periplaneta americana was studied using immunocytochemistry and the formaldehyde histofluorescence method (Klemm, ′83). In this material immunocytochemistry was more sensitive than the formaldehyde histofluorescence procedure. A relatively small number of 5‐HT‐immunoreactive cell bodies (220–280) were found. For the first time, their processes could be followed. They highly arborize and innervate many brain regions. Three patterns of monoamine innervation have been demonstrated: (1) 5‐HT and catecholamine fibres (Klemm, ′83) occurring in the same region (e.g., outer lateral protocerebral neuropil, stratum caudale, mushroom body, fan‐shaped body, olfactory lobe), but having certain differences with respect to the organization of their projection fields; (2) 5‐HT fibres innervating a region lacking catecholamine‐containing fibres (pons); and (3) catecholamine neurons innervating a region lacking 5‐HT fibres (ellipsoid body). In the mushroom body only the extrinsic neurons contain 5‐HT immunoreactivity. They form a commissural fibre system linking the left‐ and right‐hand mushroom bodies and other brain regions. The pons is part of a 5‐HT‐neuron fibre system innervating many areas including the mushroom bodies. The present study demonstrates novel, complex, and widely distributed connections within the insect brain.
The organization of retinal maps within the dorsal and ventral lateral geniculate nuclei of the rabbit
Authors: Holcombe V. , Guillery R. W.
Published: January 2005

The cytoarchitectonic subdivisions in the rabbit's dorsal and ventral lateral geniculate nuclei have been related to the several retinal maps that can be defined in terms of the distribution of retinal axons within these nuclei. Destruction of different retinal sectors was combined with intravitreal injections of 3H‐proline, so that the distribution of fiber degeneration and autoradiographic label in the geniculate nuclei could be used to define the retinal maps in each nucleus, and to compare the two nuclei with each other. The two nuclei show surprisingly similar patterns of organization. Each is made up of a laminated alpha sector that curves around a relatively cell‐sparse beta sector. Two morphologically distinct layers of each alpha sector receive contralateral retinal afferents and between these there is a small region in receipt of ipsilateral afferents. In each nucleus, the lines of projection that represent single points in visual space pass perpendicular to the layers of the alpha sector and continue an almost straight course into the beta sector. Quantitative comparisons of the retinal maps show that the relative volumes devoted to the representation of segments of the visual field are approximately the same in the two nuclei.
Sexual differentiation in the terminal ganglion of the moth Manduca sexta: Role of sex‐specific neuronal death
Authors: Giebultowicz Jadwiga M. , Truman James W.
Published: January 2005

In the insect Manduca sexta the genitalia on the terminal abdominal segments are sexually dimorphic structures but they arise during metamorphosis from segments that are monomorphic in the larva. The motoneurons in the terminal ganglion that innervate these structures were examined by cobalt backfills of peripheral nerves. In the larval stage the population of motoneurons innervating the terminal segments was identical in both sexes. By contrast, the motoneuron populations in the terminal ganglia of adult males and females were strikingly different. No new motoneurons were produced during metamorphosis. Rather, this difference was the result of sex‐specific cell death which occurred primarily during the early stages of adult differentiation. Possible mechanisms underlying this sex‐specific degeneration of neurons are discussed.
Dendritic distribution of motoneurons innervating the three heads of the trapezius muscle in the cat
Authors: Vanner S. J. , Rose P. K.
Published: January 2005

The organization of the nuclei and dendritic architecture of motoneurons innervating the three heads of the trapezius muscle, clavotrapezius (CT), acromiotrapezius (AT), and spinotrapezius (ST), have been examined by using intracellular staining techniques. CT, AT, and ST motoneurons were found in the spinal accessory nucleus and were arranged in three overlapping subnuclei. CT motoneurons were primarily found in C2 and C3. In contrast, most AT motoneurons were found in C3, C4, and C5 and ST motoneurons were found in C4, C5, and the rostral parts of C6.

Most dendrites of CT motoneurons, located in rostral C2, extended dorsally and many of these dendrites spread medially and laterally to encompass all of lamina VIII and the dorsolateral part of lamina VII. When viewed in the horizontal plane these motoneurons had a stellate appearance. The dendritic tree structure of CT motoneurons changed abruptly between rostral C2 and mid‐C2. The majority of dendrites of CT motoneurons located in the central and caudal parts of C2 projected rostrally and caudally to form a complex bundle of dendrites in the motoneuron nucleus. Small numbers of dendrites were also found ventromedial and dorsal to the soma. The dendritic trees of CT motoneurons in C3 and C4 and AT and ST motoneurons located in C4 and the rostral parts of C5 also followed this fusiform distribution pattern. The dendritic trees of AT and ST motoneurons in caudal C5 were not fusiform but instead had a complex distribution pattern which consisted of dendrites projecting in several directions. Many dendrites projected rostrally and caudally, and in addition, there were major dendritic projections ventrolateral and dorsolateral to the soma.

These results indicate that each head of the trapezius muscle is innervated by two structurally dissimilar groups of motoneurons which occupy different spinal segments. Trapezius motoneurons at the same segmental level, regardless of which head of the trapezius muscle they innervate, have similar dendritic trees whose structure differs from those of neighbouring dorsal neck muscle motoneurons in C2, C3, and C4. Thus, the organization of motoneuron dendritic trees appears to be governed by several factors including the muscle innervated by the motoneuron and the transverse and segmental position of the motoneuron's soma.
Distribution of neurotensin‐immunoreactivity within baroreceptive portions of the nucleus of the tractus solitarius and the dorsal vagal nucleus of the rat
Authors: Higgins Gerald A. , Hoffman Gloria E. , Wray Susan , Schwaber James S.
Published: January 2005

We have examined the distribution of neurotensin immunoreactivity within subnuclear regions of the nucleus of the tractus solitarius (NTS) and the dorsal motor nucleus of the vagus nerve (DVN) in the rat. In order to determine which regions of the NTS were involved in the regulation of baroreceptor reflexes, we mapped the central distribution of the aortic branch of the vagus nerve using transganglionic transport of horseradish peroxidase. Comparison of the pattern of aortic nerve innervation with that of the distribution of neurotensin‐immunoreactive cells and fibers shows the dorsomedial nucleus of the NTS both to be the primary site of aortic baroreceptor termination and to contain the highest concentration of neurotensin‐immunoreactive elements within the NTS. Neurotensin‐immunoreactive fibers are also present in medial regions of the NTS adjacent to the area postrema where they may be involved in the modulation of vagal gastric afferents.

Double‐label experiments, in which, on the same tissue sections, neurotensin immunohistochemistry was combined with retrograde horseradish peroxidase labeling of DVN neurons, reveal a topographic innervation of vagal preganglionic motoneurons by neurotensin‐immunoreactive fibers. The heaviest innervation is of lateral portions of the DVN and adjacent ventral portions of the NTS at the level of the obex, an area which may contain cardiac motoneurons. In this region neurotensin‐immunoreactive fibers can be observed in close proximity to retrogradely labeled cells.

The concentration of neurotensin elements in a region of the NTS which is involved in the control of baroreceptor reflexes provides a morphological basis for the cardiovascular effects produced by central administration of the peptide. Additional control may be exerted at the level of the motoneuron, as evidenced by apparent neurotensin fiber innervation of presumptive cardiac preganglionic neurons. Similarly, the distribution of neurotensin fibers suggests that the peptide may be acting in gastric regulatory areas of the NTS or on vagal secretomotor neurons to regulate gastric acid secretion.
The monocular and binocular subfields of the rat's primary visual cortex: A quantitative morphological approach
Authors: Zilles Karl , Wree Andreas , Schleicher Axel , Divac Ivan
Published: January 2005

Primary visual cortex in the rat was studied by a variety of methods: transsynaptic transport of labelled amino acids, 2‐deoxyglucose, and staining for perikarya, myelin, and acetylcholinesterase. The analysis was aided by a computer‐controlled television image analyzer. The results obtained with different methods agree with one another in describing the position and extent of the entire primary visual cortex as well as its monocular (medial) and binocular (lateral) subareas.
Substance P, neurotensin, enkephalin, and catecholamine‐synthesizing enzymes: Light microscopic localizations compared with autoradiographic label in solitary efferents to the rat parabrachial region
Authors: Milner T. A. , Joh T. H. , Miller R. J. , Pickel V. M.
Published: January 2005

The immunocytochemical localizations of substance P, neurotensin, enkephalin and the catecholamine‐synthesizing enzymes tyrosine hydroxylase and dopamine‐β‐hydroxylase were examined in the rat parabrachial region. The immunoreactivity for each marker was compared with the distribution of superimposed autoradiographic labeling of parabrachial afferents after unilateral injection of 3H‐amino acids into the caudal portion of the medial nucleus of the solitary tract (m‐NTS). Substance‐P‐ and neurotensinlike immunoreactivity (SPLI and NTLI, respectively) were localized primarily in varicose processes in the ventrolateral quadrant of the parabrachial region. The SPLI and NTLI were differentially localized with respect to each other; however, both peptides were detected in regions of the parabrachial containing dense autoradiographic label. In contrast, enkephalinlike immunoreactivity (ELI), tyrosine hydroxylase, and dopamine‐β‐hydroxylase were detected in processes and a few perikarya located outside the ventrolateral parabrachial region. The ELI was primarily in the dorsolateral, and the catecholamine‐synthesizing enzymes were primarily in the medial parabrachial regions which contained sparse autoradiographic labeling of transported amino acids. We conclude that in the rat parabrachial region, SPLI and NTLI are contained within two distinct populations of afferents which may originate from perikarya in the caudal m‐NTS, whereas ELI and the cate‐cholamines are more likely to be found in other afferents or possibly in intrinsic neurons.
Postnatal development of the serotonin innervation of the hippocampus and dentate gyrus following raphe implants
Authors: Holets Vicky R. , Cotman Carl W.
Published: January 2005

Serotoninergic (5‐HT) neurons derived from the embryonic raphe nuclear area (brainstem, embryonic days (E 16–18) were implanted into the entorhinal cortex of 6‐day‐old (P6) neonatal rat recipients which had received a fimbria lesion and entorhinal cortex ablation on P3. The hippocampus, dentate gyrus, and the raphe implant area were examined with 5‐HT immunohistochemistry 7, 14, 21, 30, and 60 days after implantation. The pattern of 5‐HT reinnvervation was compared to that of normal and lesioned animals, and to previous studies in which rats received septal or striatal implants. In the hippocampus adjacent to the implant 5‐HT‐immunoreactive fibers were first observed by 7 days postimplantation and increased in density and in their septotemporal and dorsoventral extent with increasing time postimplantation. Moderately dense fiber networks were diffusely distributed in the hippocampus and dentate gyrus at 30 and 60 days postimplant. Little, if any, indication of lamination was present. Retrogradely labeled neurons (the majority of which contained 5‐HT immunoreactivity) were observed in the raphe implant following injections of Fast Blue into the hippocampal formation. A few retrogradely labeled cells did not contain 5‐HT, methionine‐enkephalin (ME), or substance P (SP) immunoreactivity, although ME‐ and SP‐ immunoreactive neurons were observed in the implants. The lamination patterns and the increased density of 5‐HT‐immunoreactive fibers following a raphe implant into the entorhinal cortex clearly differ from the normal 5‐HT pattern and from the patterns of lamination following a striatal or septal implant.
The representation of the visual field in parvicellular and magnocellular layers of the lateral geniculate nucleus in the macaque monkey
Authors: Connolly Michael , Van Essen David
Published: January 2005

Two‐dimensional maps of individual layers of the dorsal lateral geniculate nucleus (LGN) in the macaque monkey were constructed and used as a basis for comparing laminar size, shape, and topographic organization. Topographical data from the electrophysiological investigation of the LGN by Malpeli and Baker ('75) were displayed on maps of all six layers. As known from previous studies, there is a significant over‐representation of central vision in the LGN. Unexpectedly, though, the visual representation is anisotropic over portions of most LGN layers. That is, the linear magnification factor (millimeters along the laminar surface per degree of visual field) is not equal for all directions from a given point in the visual field. Moreover, the visual representations in the parvicellular and magnocellular divisions of the LGN differ both in their emphasis on central vision and in their anisotropies.

To determine the degree of individual variability, laminar maps were prepared from the LGN of seven other hemispheres. The shapes of laminar maps varied considerably between LGNs, from nearly circular to highly elliptical, but the surface area was relatively constant for each layer. Topographical organization, determined by mapping the optic disc representation on the LGN laminae and by labeling from anterograde and retrograde tracer injections in striate cortex, showed significant individual variability.

Interestingly, the visual representations in the LGN and striate cortex are topologically inverted with respect to one another. This indicates that the establishment of geniculocortical connections involves a systematic crossing‐over of fibers.

Information on cell densities and magnification factors in striate cortex obtained from other studies was compared to the results of the present study in order to estimate ratios of cortical neurons to LGN neurons at different eccentricities. The total number of cortical neurons per LGN neuron is about 130 on average, but it extends over approximately a tenfold range, from less than 100 in the far periphery to nearly 1,000 in the fovea. The estimated number of cells in layers 4A and 4Cβ per parvicellular layer neuron is smaller and extends over a slightly narrower range, from 30 to 240, whereas the number of layer 4Cα neurons per magnocellular neuron varies more widely, from about 45 to 7,000.
Regulation of axonal ingrowth into area dentata as studied by sequential, double intraocular brain tissue transplantation
Authors: Goldowitz Dan , Seiger Årke , Olson Lars
Published: January 2005

The anterior eye chamber was used as a model environment to study, in isolation, the interaction of embryonic area dentata transplants with transplants of one of three important sources of in situ innervation: entorhinal cortex, locus coeruleus or septal nuclei. None of these brain regions significantly affected the morphogenesis or in oculo growth of area dentata transplants. All three brain regions innervated the area dentata transplant. Entorhinal cortical transplants sent nerve fibers into a limited, and apparently specific, region of area dentata that was adjacent to the entorhinal transplant. This light innervation contrasts to the predominant innervation of area dentata by entorhinal cortex in situ. The fluorescent, noradrenergic neurons of locus coeruleus provided the area dentata transplant with an abundance of fine varicose nerve fibers. Given about 100 noradrenergic neurons in the locus coeruleus transplant and 4 to 6 months joint survival, the area dentata transplant was noradrenergically hyperinnervated. The cholinergic neurons of the septal nuclei transplant had a prolific ingrowth of acetylcholinesterase (AChE)‐positive nerve fibers to the area dentata transplant. There appeared to be a mutual exclusion between the extrinsic AChE‐positive fibers and the intrinsic Timm's‐positive granule cell mossy fibers in the area dentata transplant.

We conclude that isolated replicas of the coeruleo‐, septo‐, and entorhinal cortico‐dentate pathways can be made through sequential intraocular double grafting. The nature of the in oculo connectivity between these replicates offers clues as to the mechanisms that might account for the regulation of nerve growth.
The fine structure of the lateral superior olivary nucleus of the cat
Authors: Cant Nell Beatty
Published: January 2005

The synaptic organization of the lateral superior olivary nucleus of the cat was analyzed under the electron microscope. The predominant cell type, the fusiform cell, has dendrites that extend from opposite poles of the cell body toward the margins of the nucleus, where they terminate in spinous branches. The fusiform cells are contacted by three types of synaptic terminals that can be distinguished by the size and shape of their synaptic vesicles. The somatic and proximal dendritic surfaces are apposed by synaptic terminals containing small, flat synaptic vesicles. Further from the cell body, the dendrites form numerous synaptic contacts with terminals containing large round vesicles as well as with the terminals containing small, flat vesicles. The most distal dendritic branches and their spiny appendages appear to form synapses almost exclusively with the terminals with large, round vesicles. A relatively rare type of terminal that contains small, round vesicles may form synapses with either the somatic or dendritic surfaces. A few small cells are interspersed among the fusiform cells, but they are more commonly located around the margins of the nucleus. The small cells form few axosomatic contacts.

The simplest interpretation of the findings is that the terminals with small, flat vesicles arise in the medial nucleus of the trapezoid body and are inhibitory in function, whereas the terminals with large, round vesicles arise in the anteroventral cochlear nucleus and are excitatory; however, this remains to be demonstrated experimentally. In any case, the differential distribution of these two types of inputs on the somatic and dendritic surfaces must be an important determinant of the physiological response properties of the fusiform cells to binaural acoustic stimuli.
The effects of a lengthy period of environmental diversity on well‐fed and previously undernourished rats. II. Synapse‐to‐neuron ratios
Authors: Bhide P. G. , Bedi K. S.
Published: January 2005

Rats were undernourished from the 16th day of gestation until 25 postnatal days of age and then weaned on to an ad libitum diet. Around 35 days of age, 12 previously undernourished male rats were assigned to an enriched environmental condition (EC) and their littermates to an isolated environmental condition (IC). A parallel set of well‐fed rats was similarly assigned. After 80 days in these environmental conditions, all rats were killed by perfusion with 2% phosphate buffered glutaraldehyde.

Small pieces of tissue containing the entire depth of the right visual cortex were embedded in Spurr's resin. Semithin (0.5 μm) sections were cut from these blocks and stained with toluidine blue. Photomicrographs of these sections were used to estimate the numerical density of neurons in cortical layers II to III. Ultrathin sections (∼ 70 nm) of the same region of cortex were then prepared for electron microscopy. These were used to estimate the mean synaptic disc diameter and synaptic numerical density. From these estimates of neuronal and synaptic numerical density, synapse‐to‐neuron ratios were calculated.

The results of a two‐way analysis of variance test revealed that environment had significant effects on neuronal numerical density, mean synaptic disc diameter, and synapse‐to‐neuron ratios. Neither nutrition nor its interaction with environment had significant effects on any of the parameters analyzed. These results suggest that environmental diversity can produce alterations in certain neuronal and synaptic characteristics in the visual cortex of both well‐fed and previously undernourished rats.
Dendritic caliber and the 3/2 power relationship of dentate granule cells
Authors: Desmond Nancy L. , Levy William B.
Published: January 2005

A quantitative examination of granule cell dendritic caliber and knowledge of dendritic lengths allows assessment of the distribution of dendritic membrane and the 3/2 power relationship at branch points. This paper presents caliber data of Golgi‐impregnated rat dentate gyrus. We used camera lucida drawings of the dendritic trees of 15 dorsal leaf and 15 ventral leaf granule cells to quantify mean dendritic caliber, dendritic taper, the 3/2 power relationship of parent and sibling dendritic diameters at branch points, and surface area.

First‐order dendrites vary substantially in diameter. However, the mean caliber of all other dendrites is uniform across the proximal two‐thirds of the molecular layer for the dorsal and ventral leaves. The average diameter here is 1 μm. More distally, only mean ventral leaf dendritic caliber declines.

Granule cell dendritic taper is due primarily to caliber decreases at branch points and not to a gradual decline in diameter across the length of a dendritic segment.

Comparing the parent segment diameter raised to the 3/2 power with the sum of the 3/2 powers of the two sibling segment diameters reveals, for the dendritic tree located within the distal two‐thirds of the molecular layer, the desired 3/2 power relationship for the dorsal and ventral leaves. More proximally, where first‐, second‐, and third‐order dendrites branch sequentially across a 60–100‐μm extent, a 3/2 power relationship is not obtained.

For the average dorsal leaf granule cell, dendritic surface area (without spines) is 11,984 μm2. The ratio of dendritic to somatic surface area is 28:1.

Discussion of these data includes their implications for electrotonic modeling of the dentate granule cell.
The distribution of afferent neurones in the mesencephalic nucleus of the fifth nerve in the cat
Authors: Gottlieb Sue , Taylor Anthony , Bosley Michael A.
Published: January 2005

The objective of this study was to examine anatomically the distribution of afferent neurones in the mesencephalic nucleus of the fifth nerve (Mes V). HRP was applied, in separate experiments, to the inferior alveolar, infraorbital, and masseter nerves, and injected into the masseter muscle and periodontal ligament. Following application of HRP to the masseter muscle and masseter nerve, labelled cells were found in the ipsilateral motor nucleus of the fifth nerve and in the ipsilateral Mes V. Labelled cells in Mes V, identified as belonging to proprioceptor afferents from jaw‐closing muscles, were distributed throughout the full extent of the nucleus. Following application of HRP to the inferior alveolar nerve, infraorbital nerve, and periodontal ligament, labelled cells were found in the ipsilateral trigeminal ganglion and Mes V, and the latter identified as belonging to periodontal receptor afferents. In contrast to the distribution of spindle afferent somata, they were restricted to the caudal region of Mes V. The differential distribution of afferent neurones within Mes V demonstrated in this study confirms previous electrophysiological findings, and its significance is considered.
Partial characterization of lectin binding sites of retinal photoreceptor outer segments and interphotoreceptor matrix
Authors: Wood John G. , Besharse Joseph C. , Napier‐Marshall Lynda
Published: January 2005

We have used cytochemistry together with exoglycosidase digestion and polyacrylamide gel electrophoresis to partially characterize lectin binding sites of the interphotoreceptor matrix and of photoreceptor outer segments. In order to obtain uniform access of reagents to all regions of the preparation, we have used a procedure in which plastic sections are etched with sodium ethoxide prior to cytochemical analysis. Neuraminidase pretreatment of plastic‐embedded sections of Xenopus laevis eyecups leads to a loss of wheat germ agglutinin binding and a concomitant appearance of Ricinus communis agglutinin binding to the interphotoreceptor matrix. In contrast, wheat germ agglutinin binding to the outer segments is not altered by the neuraminidase pretreatment. These results suggest that wheat germ agglutinin binding sites of interphotoreceptor matrix are sialoglyconjugates and that outer segment binding sites are not sialoglycoconjugates. Enzyme digestions followed by lectin cytochemistry of matrix polypeptides separated by polyacrylamide gel electrophoresis do not identify a likely candidate to give rise to the cytochemical staining patterns. Lectin cytochemistry of retinas from which the interphotoreceptor matrix has been extracted do not show a loss of wheat germ agglutinin binding sites to the matrix. These results suggest that the major wheat germ agglutinin binding sites in the interphotoreceptor matrix are to as yet unidentified sialoglycoconjugates.
The postnatal development of corticotrigeminal projections in the cat
Authors: Tolbert D. L. , Dunn R. C. , Vogler G. A.
Published: January 2005

The postnatal development of corticotrigeminal projections was studied in kittens following 3H‐amino acid injections into the face area of the primary somatosensory cortex. Corticofugal axons grow into the brainstem and form the pyramidal tract prenatally. Corticotrigeminal projections begin to develop at the end of the first postnatal week. The earliest corticotrigeminal axons grow out of the pyramidal tract caudally and project into laminae III–V of the spinal trigeminal (Vs) nucleus caudalis. During the second postnatal week, corticotrigeminal axons grow out of the pyramidal tract in a caudal to rostral sequence and project up to the ventromedial borders of Vs‐interpolaris, Vs‐oralis, and to the principal trigeminal nucleus. Corticotrigeminal axons pause at the periphery of these nuclei for 1–2 days before penetrating the trigeminal neuropil and forming terminal arborizations in a centripetal direction. Coincident with the development of cortical projections to the principal trigeminal nucleus, some of the labeled axons which were in lamina III of Vs‐caudalis project into lamina I and terminate. This sequence of development of corticotrigeminal projections closely parallels, albeit at a later time, the sequence of formation of the trigeminal nuclei, suggesting that the temporal sequence of cytogenesis of trigeminal neurons may be a factor which regulates their order of innervation by afferents.

Corticotrigeminal projections develop bilaterally and, during the second postnatal week, are relatively equal in density in the ipsilateral and contralateral nuclei. Many of the ipsilateral corticotrigeminal projections are lost, however, after the second postnatal week, so that by the fourth postnatal week, corticotrigeminal projections are mainly contralateral and adultlike in their distribution. It remains to be determined whether the transience of ipsilateral corticotrigeminal projections is due to selective elimination of axon collaterals or to neuronal death.
Afferents to the ventral tegmental nucleus of gudden in the mouse, rat, and cat
Authors: Irle Eva , Sarter Martin , Guldin Wolfgang O. , Markowitsch Hans J.
Published: January 2005

Afferents to the ventral tegmental nucleus of Gudden (VT) were investigated in mice, rats, and cats. Unilateral and bilateral injections or iontophoretical applications of horseradish peroxidase (HRP) were made into the region of the VT. The entire cerebrum was then screened for labeled neurons. Following injection situated principally within the VT, in all three species many retrogradely labeled neurons were observed in the mamillary bodies and the lateral habenular nuclei. Fewer labeled cells were observed in the prefrontal cortex, the basal forebrain, various hypothalamic nuclei, the interpeduncular nucleus, nucleus of the posterior commissure, nucleus of Darkschewitsch and interstitial nucleus of Cajal, vestibular nucleus, and nucleus praepositus hypoglossi. Scant but consistent labeling occurred in the cingular, retrosplenial, and insular cortices, within the medial forebrain bundle, fields of Forel, zona incerta, ventral tegmental area of Tsai, substantia nigra, pretectal area, periaqueductal gray, dorsal tegmental nucleus, locus ceruleus, and raphe complex. Our results show a high similarity in the distribution of afferent connections converging on the VT of mice, rats, and cats. They indicate furthermore that the VT is reached by a variety of cortical and subcortical afferents, which belong either to the limbic system or to brain stem regions related to motor, sensory, and autonomic functions. It is suggested that the VT subserves as a midbrain core structure of the limbic system, which is responsible for the transfer of motor, sensory, and autonomic informations arising within the brain stem to limbic forebrain structures.
Corticocortical connections among visual areas in the cat
Authors: Symonds Laura L. , Rosenquist Alan C.
Published: January 2005

The cortical interconnections of 17 visual areas in the cat were studied by making single injections through recording micropipettes of the neuroanatomical tracers 3H‐leucine and horseradish peroxidase (HRP) into the visual cortex of 40 adult animals. Coronal sections from each of the brains were analyzed for location of silver grains and HRP‐filled neurons. There are five main results: (1) all corticocortical connections among visual areas are reciprocal. (2) Each cortical visual area has a unique set of cortical connections; the cortical targets of no two cortical visual areas are identical. (3) There is a vast and complicated pattern of connections among the visual areas which implies that there are numerous parallel circuits which run through any one visual area. (4) The connections among the cortical visual areas link retinotopically similar loci and are consistent with the visuotopic maps which microelectrode recording experiments have provided. (5) The connections among visual cortical areas often originate from, or terminate in, discontinuous patches within each area; this result obtains not only for areas 17, 18, 19, and posteromedial lateral suprasylvian area (PMLS), but for at least 13 other areas as well.

The data reveal many parallel pathways and suggest multiple functional circuits interconnecting visual cortical areas. Since each visual area has multiple inputs and outputs it may have multiple functions, a different one for each of the circuits of which it is a part.
Extrinsic visual and auditory cortical connections in the 4‐day‐old kitten
Authors: Cornwell Paul , Ravizza Richard , Payne Bertram
Published: January 2005

The major extrinsic projections to and from the visual and auditory cortical areas were examined in 4‐day‐old kittens using axonal transport of horseradish peroxidase (HRP) and/or tritiated proline. Six different afferent and seven different efferent systems were studied; all 13 were present by postnatal day 4 as revealed by either HRP, or autoradiography alone, or these two techniques combined. Topographical projections were found for the corticopetal pathways from the thalamus and claustrum and for the corticofugal pathways to the thalamus, claustrum, striatum, and tectum, as well as for the inter‐ and intrahemispheric pathways. No topographical relations were seen in projections to the cortex from the basal ganglia or the lower brainstem.

The results of the present study indicate that most or all of the major extrinsic connections of the kitten's visual and auditory cortical areas are present neonatally, and that both the cells of origin and the axonal targets are arranged topographically much like those of adult cats. However, the origins of callosal projections from visual cortex are more widespread in newborn kittens than in adult cats. In addition, the laminar arrangements of the kitten's corticocortical connections differ from those of adult cats in a number of details. The results suggest that the sparing of some visual and auditory functions after neonatal lesions occurs despite the fact that the cortical areas removed have formed extrinsic connections.
The projection of the supramammillary nucleus to the hippocampal formation: An immunohistochemical and anterograde transport study with the lectin PHA‐L in the rat
Authors: Haglund Lena , Swanson Larry W. , Köhler Christer
Published: January 2005

The organization and possible neurotransmitter specificity of a projection from the lateral supramammillary nucleus to the hippocampal formation has been examined with immunohistochemical and axonal transport methods in the adult male rat. Experiments with the retrograde tracer true blue indicate that neurons throughout the rostrocaudal extent of the nucleus are labeled after injections in either dorsal parts of the dentate gyms and Ammon's horn, or the entorhinal area, although cells labeled by the entorhinal injections tended to occupy more ventral parts of the nucleus. Combined immunohistochemical‐retrograde transport studies showed that a small number (<5%) of cholecystokinin‐immunoreactive neurons in the caudal tip of the supramammillary nucleus project to, the hippocampal formation, as do some (5–10%) vasoactive intestinal polypeptide (VIP)‐immunoreactive neurons throughout the nucleus. Anterograde transport studies with the lectin phaseolus vulgaris leucoagglutinin (PHA‐L) indicate that fibers from the supramammillary nucleus innervate all parts of the hippocampal formation. Many varicose fibers with terminal boutons were observed in the granular and molecular layers of the dentate gyrus, throughout the molecular layer of field CA3 of Ammon's horn, and in the pyramidal layer and stratum oriens of subfield CA3a. Only scattered fibers were found in fields CA1 and CA2. Apparent terminal fields were also observed in superficial parts of the molecular layer, and deep parts of the pyramidal layer, of the subiculum, in the deepest layer of the presubiculum and parasubiculum, and in all layers of the entorhinal area.