bluuebunny/crossref_metadata_2025 huggingface dataset:
Organization of the ascending projections from the ventral tegmental area: A multiple fluorescent retrograde tracer study in the rat
Authors: Albanese Alberto , Minciacchi Diego
Published: January 2005

The projections from the ventral tegmental area of Tsai (VTA) to the frontal cortex (FC), lateral septum (LS), nucleus accumbens (Acc), caudateputamen (CPu), and lateral habenula (LH) were investigated in the rat by means of the double retrograde fluorescent tracer technique.

True blue and fast blue were used in combination with nuclear yellow as retrograde tracers. After combined injections placed into two different terminal fields, many singly and some doubly labeled neurons were seen in the midbrain. In all cases the labeled cells were observed in the ipsilateral VTA, while after injections placed into the LS and Acc some fluorescent neurons were also seen in the contralateral VTA. The patterns of distribution of the labeled neurons showed a topographic organization of the VTA efferent pathways. However, some degree of overlapping was evident in the distribution of cells retrogradely labeled from different terminal fields. The number of the doubly labeled neurons varied according to the sites of combined injections, but in each experiment it never exceeded 10% of the total number of labeled perikarya. Doubly labeled neurons were particularly numerous after combined injections placed into the FC, LS, or LH; on the contrary, very few doubly labeled cells were observed after combined injections placed into the CPu and LS or LH.

The organization of the ascending VTA projections suggests that they are probably integrated into different anatomical sets.
The primary vestibular projection to the cerebellar cortex in the pigeon (Columba livia)
Authors: Schwarz Irmgard E. , Schwarz Dietrich W. F.
Published: January 2005

The cerebellar cortex of the pigeon receiving direct vestibular afferents was delineated by anterograde transport of [3H]‐amino acids injected the vestibular nerve. Labelled mossy fiber rosettes in the granular layer were concentrated in lobule X (nodulus) and to a lesser extent, in the ventral portion of lobule IXd (uvula and paraflocculus). A few solitary labelled rosettes were also found in more dorsal portions of lobule IX, as well as in the anterior lobe between lobule II and IV. The lingularernainedunlabelled. Dis‐crete injections of [3H]‐leucine into the cristae of each of the three semicircu‐lar canals or the utricular macula yielded a similar distribution of fewer labelled rosettes. A few primary mossy fiber terminals labelled after cochlear injections are attributed to afferents from the lagenar macula. Since effective diffusion of label from the injection site was excluded by controls, it is concluded that projection of individual canal and macula nerves to the ves‐tibulocerebellar cortex is not topographically separated. It is proposed that this extensive convergence of various afferents is required by the cerebellum to compute precise and directionally specific control signals during head rotation in all conceivable planes.
Subnuclear organization of the dorsal motor nucleus of the vagus nerve in the pigeon, Columba livia
Authors: Katz David Miles , Karten Harvey J.
Published: January 2005

The present study is the first of two papers describing the cytoarchitec‐tural and functional organization of the dorsal motor nucleus of the vagus nerve (DMN complex) in the pigeon. This paper describes the distribution of vagal motoneurons within the pigeon brainstem, and the cytoarchitectural organization of the DMN complex. Our description is based on studies of Nissl‐stained tissue from normal animals and on experimental studies using retrograde tracing techniques. Cells within the DMN complex were classified according to size, morphology, location, and staining characteristics.

These studies demonstrate that vagal motoneurons are localized to (1) the DMN complex, (2) the region of the nucleus ambiguus, and (3) the region of the reticular formation extending between the dorsal motor nucleus and the nucleus ambiguus. Our cytoarchitectural studies indicate that the DMN complex is composed of at least 11 cytoarchitecturally distinct subnuclei. These subnuclei are evident in normal tissue and are especially prominent in cases where HRP backfilling produces a Golgi‐like staining of the motoneu‐rons. The subnuclei can be distinguished by their positions within the DMN complex and by the size, shape, and staining chracteristics of their constituent neurons. Comparison of these data with studies in other species indicates similar patterns of cytoarchitectural organization in the DMN com‐plex of some mammals. The diversity of nuclear subgroups within the DMN complex may be related to the heterogeneity of target organs innervated by these cells.
Postembryonic growth of the macula neglecta auditory detector in the ray, Raja clavata: Continual increases in hair cell number, neural convergence, and physiological sensitivity
Authors: Corwin Jeffrey T.
Published: January 2005

Quantitative scanning electron microscopy in an age series demon‐strated that the macula neglecta auditory epithelium of the ray, Raja clavata, produces and accumulates sensory cells perpetually at 1–3 cells/ day, so that the total increases from approximately 500 cells at birth to 6,000 at 7 years of age. The shape of the macula also changes with growth, and changes in the marginal zones of small and intermediate size hair cells are consistent with this differential growth and their proposed role as hair cell production sites. The neurons contacting the epithelium do not increase in number as animals age; instead they hypertrophy, increasing axon diame‐ter and terminal field size. A hypothetical double‐gradient interaction be‐tween the growing nerves and new hair cells is proposed to explain the devel‐opment of synaptic connections and the continual production of individually oriented, functional hair cells. Electrophysiological recordings from the neu‐rons demonstrated best sensitivities between 40 Hz and 200 Hz, directional receptive fields, and little or no effect of changes in the ear's position relative to gravity. The convergence ratio from sensory cells to neurons increases because of their unequal patterns of growth, and physiological sensitivity improves 500‐fold and more as these animals age. These results contrast with current information on mammalian ears, where it appears that sensory cells are not produced at any time after birth.
Neocortical projections of the suprageniculate and posterior thalamic nuclei in the marsupial brush‐tailed possum, Trichosurus vulpecula(phalangeridae), with a comparative commentary on the organization of the posterior thalamus in marsupial and placental mammals
Authors: Neylon L. , Haight J.R.
Published: January 2005

Axonal transport methods were used to determine the extent and organisation of neocortical projections from the Suprageniculate (SG) and posterior (PO) thalamic nuclei in the brush‐tailed possum. Our findings show that SG projects extensively to the auditory cortex, overlapping the cortical projection field of the modial geniculatc nucleus, and to the immediately neighbouring association cortex. Though the input relationships of SG appear similar to those reported for other mammals, placental and marsupial, a strong SG projection to auditory cortex has not been reported previously. Neocortical relationships of PO are characterised by an orderly point‐to‐point projection to all but the most rostral parts of the motor‐somaesthetic cortex. There is also a substantial projection to the entire posterior parietal association cortex. The PO‐neocortex projection is reciprocally organised. The PO‐neocortical projection in the possum is similar to that reported in the Virginia opossum, rat, and several other mammals. There is a major difference in organisation in comparison with certain monkeys where the PO projection is much more restricted and does not involve the motor and som‐aesthetic cortex. We conclude that PO is similarly organised in many, though not all, mammals, including the marsupials, rodents, insectivores, and prosimian primates. The possum SG, on the other hand, is clearly distinct from other mammals in its extensive projection to auditory cortex, though we cannot say at present whether this a general property of marsupial mammals or a peculiarity restricted to this species and possibly its close relatives.
Visceral representation within the nucleus of the tractus solitarius in the pigeon,Columba livia
Authors: Katz David Miles , Karten Harvey J.
Published: January 2005

This study describes the distribution of organ‐specific populations of vagal afferent fibers within the nucleus of the solitary tract (nTS) in the pigeon. The central projections of vagal sensory neurons were visualized by the centripetal and trans‐ganglionic transport of horseradish peroxidase from either the central cut ends of peripheral vagal branches or from HRP injection sites in peripheral vagal target tissues. This paper also includes a detailed description of the cytoarchitectural organization of the nTS in the pigeon based on studies of Nissl‐stained material.

Vagal afferent fibers that innervate different peripheral target organs are partially segregated within cytoarchitecturally distinct subnuclei of the nTS. Gastrointestinal afferents, for example, project primarily to medial subnuclei. On the other hand, pulmonary, and on the basis of earlier studies, cardiovascular afferents, project primarily to lateral subnuclei, Moreover, the rostral to caudal distribution of gastrointestinal afferents corresponds to the rostrocaudal topography of the gastrointestinal tract. In addition, our data demonstrate a projection of gastrointestinal afferents to the lateral descending tract of the trigeminal nerve that appears to terminate in the external cuneate nucleus.

The cytoarchitectural organization of visceral representations within the pigeon nTS corresponds closely to recent descriptions of this cell group in mammals. Comparison of our results with studies of the central connections of nTS neurons suggests that the subnuclear distribution of organ‐specific vagal afferents within nTS plays a critical role in the organization of ascending and descending visceral afferent pathways.
The islands of Calleja complex of rat basal forebrain. III. Histochemical evidence for a Striatopallidal system
Authors: Fallon James H. , Loughlin Sandra E. , Ribak Charles E.
Published: January 2005

The characteristics of the islands of Calleja complex (ICC) in the basal forebrain of the rat were studied with immunohistochemistry, histofluorescence, acetylcholinesterase staining, India ink vascular perfusions, electron microscopy, and steroid autoradiography. The ICC contains clusters of granule cells and associated medium‐sized and large cells in the surrounding neuropil of the olfactory tubercle and septum‐nucleus accumbens interface. The ICCs were found to contain monoamine fibers (dopamine and norepi‐nephrine), neuroactive peptide fibers (leu‐enkephalin, met‐enkephalin, substance P, cholecystokinin, luteinizing hormone‐releasing hormone), acetyl‐cholinesterase‐containing somata and dendrites, and medium‐sized and large cells that concentrate [3H] estradiol.

The specific overlap and combination of putative neurotransmitters in separate compartments of the ICC suggest that these structures contain striatum‐ and pallidumlike components. Striatumlike regions are defined as the zone in the rim regions of the ICC and are innervated predominantly by dopamine and cholecystokinin inputs. Pallidumlike regions are defined as the synaptic zone near the medium‐sized and large cells of the cap and core regions of the ICC and they are innervated predominantly by enkephalin, substance P, and gamma aminobutyric acid inputs. The morphology, connections, and neurotransmitter relationships of the ICC, therefore, resemble classical Striatopallidal systems.

The additional presence of substances involved in the reproductive neuroendocrine systems (luteinizing hormone‐releasing hormone, estradiol‐binding cells), especially in the medial ICC, suggest that some ICC are involved in an endocrine corticostriatopallidal system. These endocrine systems resemble other neocortically and allocortically originating corticostriatopallidal systems in terms of their cell types, connections, and neurotransmitter systems. A functional role for the ICC in extrapyramidal motor systems is proposed.
Nongeniculate afferents to striate cortex in macaques
Authors: Doty Robert W.
Published: January 2005

Horseradish peroxidase (HRP) was injected in relatively massive amounts to cover most, or portions, of opercular striate cortex in four macaques. Absence of transcallosal or circumventricular labelling, plus discrete and consistent retrograde labelling in other areas in the four cases, assured the validity and specificity of the observations. Numerous labelled cells in regions directly bordering striate cortex, however, were excluded from the analysis because of the possibility of uptake consequent to physical diffusion. With this exception, all labelled cells were counted at roughly 2‐mm intervals for one case with extensive unilateral injection of HRP. Even excluding the closely circumstriate population, the totals indicate that more than 30% of the afferent input to striate cortex arises from nongeniculate sources. Four areas of neocortex together make up about one‐fourth of the total afferents: superior temporal sulcus 17.1%;inferior occipital area, 6.1%; intraparietal sulcus, 0.4%;and parahippocampal gyrus, 0.3%. Other areas projecting to striate cortex include claustrum, pulvinar, nucleus paracen‐ tralis, raphe system, locus coeruleus, and the nucleus basalis of Meynert. Cells of the latter were particularly striking with their very heavy uptake of HRP, and, even in cases of minimal effective injection, were scattered throughout an extensive area from the posterior edge of the globus pallidus passing rostrally beyond the chiasm and into the nucleus of the diagonal band. On the basis of their distribution and known cholinergic affinity, it is argued that this group also includes the cells labelled in and around lateral hypothalamus and cerebral peduncle, and that as a whole the group constitutes a cholinergic counterpart of the diffusely projecting monoaminergic systems. It seems possible that the basalis projection at first follows a forni cal‐subcallosal pathway to reach striate cortex via callosoperforant fibers.
Growth of segmental nerves to the developing rat diaphragm: Absence of pioneer axons
Authors: Noakes P. G. , Bennett M. R. , Davey D. F.
Published: January 2005

A study has been made of the growth of cervical nerves C3‐C6 to the ral diaphragm. At 11 days of embryonic age these cervical nerves first project out of the spinal cord toward the cardinal veins and later form the left and right phrenic nerve trunks. During the next 2 days, the phrenic nerves grow caudally in close association with the cardinal veins toward the diaphragm. At the growing tips of these nerve trunks the growth cones of axons were observed every 1–2 μm. The last axon did not project more than 2 μm ahead of any neighbouring axons. At 14 days the phrenic nerves reach the level of the developing diaphragm and converge into pools of premuscle cells. Previous studies have suggested that the phrenic nerve enters the premuscle masses of the diaphragm at an early developmental stage when the premuscle masses; are at approximately the segmenlal levels C3‐C6 This study shows that the phrenic nerves must grow to more caudal levels in order to reach the premuscle cells of the diaphragm. Furthermore, the leading axons of the phrenic nerve trunk do not project in a pioneering fashion, far in advance of the trailing axons.
Cytoarchitecture and topographic projections of the gustatory centers in a teleost, Carassius carassius
Authors: Morita Yasuhiro , Murakami Takeshi , Ito Hironobu
Published: January 2005

The neuronal connections in the central gustatory system of the crucian carp were examined by means of degeneration and HRP methods. Cell morphology in the primary gustatory lobes was studied in Golgi‐impregnated material.

Medium‐sized neurons of the facial lobe emit axons which project to the secondary gustatory nucleus. The nucleus intermedius facialis of Herrick ('05) projects bilaterally. Large neurons send axons through the spinal trigeminal tract to terminate in the spinal trigeminal nucleus and in the medial funicular nucleus. In the vagal lobs, second‐order neurons for the ascending projections are located in the superficial part of the sensory zone. These neurons project exclusively to the ipsilateral secondary gustatory nucleus. Neurons located in the deeper part of the sensory zone send axons to the motor zone and to the brainstem reticular formation to form short reflex arcs. The glossopharyngeal lobe has similar neuronal connections to the vagal sensory zone.

Both facial and vagal lobes receive afferent projections from the following central structures: nucleus posterioris thalami, nucleus diffusus lobi inferioris, optic tectum, motor nucleus of the trigeminal nerve, medullary reticular formation, and the gray matter of the upper spinal cord. The facial lobe has an additional afferent from the mesencephalic reticular formation. The major sources to the medullary gustatory lobes are the nucleus posterioris thalami and nucleus diffusus lobi inferioris.

Each type of neuron classified by morphology and location in the facial, glossopharyngeal, and vagal Jobes was correlated with its particular destination. Topographic projections were demonstrated in the secondary and tertiary gustatory centers.
Postnatal development of caudate input neurons in the cat
Authors: Fisher Robin S. , Levine Michael S. , Gazzara Russell A. , Hull Chester D. , Buchwald Nathaniel A.
Published: January 2005

Lectin‐bound horseradish peroxidase (WG‐HRP) was pressure‐injected into the caudate nucleus (Cd) of neonatal (< 24 hours of age) and adult cats in order to assess the postnatal development of monosynaptic Cd input neurons. Tissue was processed for peroxidase activity with a benzidine dihydrochloride chromagen. The injection of WG‐HRP produced relatively similar labelled zones of marker uptake in the caudate nuclei of both neonates and adults. Similar axonal projections were also labelled in both age groups. While many characteristics of retrogradely labelled Cd input neurons were apparently constant throughout postnatal life, each of these features had a particular developmental modification. (1) Regardless of age, neuronal somata that projected to the Cd were located in the neocortex, thalamus, substantia nigra, mesencephalic raphe nuclei, and globus pallidus. In each of these brain sites, labelled Cd input neurons appeared to migrate postnatally. (2) The Cd afferent axons originated from the same neuronal lines in neonates and adults‐small‐to‐medium‐sized cortical neurons and medium‐sized‐to‐large fusiform cells in all other brain sites. In each of the brain sites, labelled neurons displayed marked postnatal somatic growth. (3) In both age groups, there was a characteristic intrasomatic reaction product density in the labelled neurons located in each brain site (substantia nigra > thalamus = raphe = globus pallidus > cortex). In each of these brain sites, the intrasomatic reaction product density was less in neonates than in adults.
The inferior olive of a prosimian primate Galago senegalensis. I. conformation and spino‐olivary projections
Authors: Whitworth R. H. , Haines D. E.
Published: January 2005

Spino‐olivary projections to inferior olive (10)in a prosimian primate, Galago senegalensis, were studied by using a modification of the Fink and Heimer ('67) technique. Prior to examining the arrangement of spinal axons within 10, its conformation was determined from a series of cresyl violet acetate sections. Galago I0 is composed of typical medial accessory (MAO), dorsal accessory (DAO), and principal (PO) olivary nuclei. The MA0 is divisible into subgroups a, b, c, d, a ventrolateral outgrowth (VLO), and a dorsomedial cell column (DMCC). Cytoarchitectural and experimental data indicate that DAO is subdivided into lateral (DAOI) and medial (DAO,) parts. The PO of Galago consists of dorsal and ventral lamellae connected by a lateral bend.

Following hemisections of the spinal cord at cervical, thoracic, and lumbar cord levels, degeneration is present in essentially identical subgroups of Galago 10. The preponderance of degeneration is found throughout the ros‐ trocaudal extent of ipsilateral DAO1. Moderate amounts of axonal debris are located in caudal parts of subgroup a of ipsilateral MAO, and only a few degenerated fibers extend into adjacent subgroup b after cervical lesions. A distinct contralateral component is evident only following a C1 hemisection. The moderate numbers of degenerated axons found in contralateral DAOM arise exclusively from cervical levels C1 to C3. Spinoalivary fibers terminating in MAO appear to ascend in the ventral funiculus while the majority of those to DAOlcourse through the lateral funiculus.
Cytoarchitecture and ultrastructure of nucleus prethalamicus, with special reference to degenerating afferents from optic tectum and telencephalon, in a teleost (Holocentrus ascensionis)
Authors: Ito Hironobu , Vanegas Horacio
Published: January 2005

Histological structure and neuronal geometry of the nucleus prethalamicus of holocentrid teleosts, which is homologous to the nucleus rotundus of reptiles and birds and to the nucleus lateralis posterior‐pulvinar complex of mammals, were studied by means of the Bodian, Nissl, toluidine blue, and Golgi methods. Synaptic terminals were classified electron microscopically, and terminal types originating from the telencephalon and the optic tectum were determined by electron microscopy in degeneration experiments.

The nucleus prethalamicus is composed of four layers, in the following order from medial to lateral: a small‐cell layer, a plexiform layer, a large‐cell layer, and a marginal layer. Six types of terminals (U, L, Sp, Sd, F, and P) were distinguished in the nucleus, and the distribution pattern for each type of terminal was determined by counting its relative number in each layer. Sp terminals make synaptic contacts with small‐cell dendrites or somata in the small‐cell layer, and degenerate after telencephalic ablations. Sd terminals synapse exclusively with spines of large‐cell dendrites in both marginal and large‐cell layers, and degenerate after tectal ablations.

Because only large neurons have been labeled after HRP injections into the telencephalon (Ito et al., '80, '82; Ebbesson, '80; Murakami et al., '83), it is considered that these neurons relay visual information from the optic tectum onto the telencephalon. It is hypothesized that the small neurons in the nucleus, which receive telencephalic input, might modulate the large neurons' relay function.
Organization of the efferent projections of the medial superior olivary nucleus in the cat as revealed by HRP and autoradiographic tracing methods
Authors: Henkel Craig K. , Spangler Kevin M.
Published: January 2005

Features of the organization of the efferent axonal projections from the medial superior olivary nucleus (MSO) in the cat were studied. In order to determine the origin and distribution of projections from MSO, the retrograde horseradish peroxidase (HRP) and autoradiographic tracing methods were used. The results showed that (1) in both HRP and autoradiographic studies the projection to the inferior colliculus was largely ipsilateral, although a contralateral component was present; (2) the projection field of MSO was confined to the ventral division of the central nucleus of the Inferior colliculus, and within this field the labeling was heavier in the rostral and dorsolateral parts of the ventral division; (3) the projection to the inferior colliculus was topographic with ventral parts of MSO projecting ventrally and dorsal parts of MSO projecting dorsolaterally; (4) the projection field in the central nucleus formed successive laminae oriented from ventro‐lateral to dorsomedial; (5) the axonal course was via the medial or internal segment of the lateral lemniscus; and (6) some fibers in this course ended additionally within the dorsal nucleus of the lateral lemniscus. This latter projection was also topographically organized. These observations supported previously described features of lamination and tonotopic order for afferents of the inferior colliculus, as well as recent suggestions that functional segregation of afferent connections exists within the laminated portion of the central nucleus of the inferior colliculus.
Separate origins for the dynorphin and enkephalin immunoreactive fibers in the inferior mesenteric ganglion of the guinea pig
Authors: Dalsgaard C. J. , Vincent S. R. , Hökfblt T. , Christensson I. , Terenius L.
Published: January 2005

By different denervation procedures the origin of dynorphin‐(1–17) and enkephalin immunoreactive fibers in the guinea pig inferior mesenteric ganglion was investigated. It was found that the dynorphin‐(1–17)‐positive fibers reached the ganglion predominantly via the colonic nerves and to a lesser extent via the hypogastric and intermesenteric nerves whereas the enkephalin‐positive fibers reached the ganglion via the lumbar splanchnic nerves. These findings show that the dynorphin‐(1–17) and enkephalin systems are separate in this ganglion.
Projections of the amygdala to the thalamus in the cynomolgus monkey
Authors: Aggleton J. P. , Mishkin M.
Published: January 2005

The projections of the amygdala to the thalamus in cynomolgus monkeys (Macaca fascicularis) were studied with both anterograde and retrograde axonal tracing techniques. Horseradish peroxidase (HRP) was injected into medial and midline thalamic sites in five animals, and tritiated amino acids were injected into selected amygdaloid regions in a total of 13 hemispheres in ten animals. The findings from the two types of tracer experiments demonstrated the origins, course, and terminal pattern of amygdaloid projections to two thalamic nuclei – medialis dorsalis (MD) and reuniens. Almost all of the amygdaloid nuclei contribute projections to MD, though the greatest proportion arise from the basal group and terminate in discrete, interlocking patches within the medial, magnocellular portion of MD. In addition to this major projection, the central and medial amygdaloid nuclei send a lighter projection to the lateral portion of nucleus reuniens. The amygdalothalamic projections took a variety of routes out of the amygdala before the large majority joined the interior thalamic peduncle and entered the rostral head of the thalamus where they turned caudally toward their targets. A small number of amygdalothalamic fibers may also run in the stria terminalis.
Tritiated 2‐deoxy‐D‐glucose: A high‐resolution marker for autoradiographic localization of brain metabolism
Authors: Hammer Ronald P. , Herkenham Miles
Published: January 2005

The technique for autoradiographic localization of 2‐deoxy‐D‐glucose (2DG) uptake has become a useful method for observing alterations of functional brain activity resulting from experimental manipulation. Autoradiographic resolution is improved using tritiated ([3H]) rather than carbon‐14 ([14C])2DG, due to the lower energy and shorter path of tritium emissions. In addition, lower 2DG uptake by white matter relative to gray matter is exaggerated in the [3H]2DG autoradiographs due to the greater absorption of tritium emissions by lipids. Using [3H]2DG, it is possible to observe differential metabolic labeling in various individual nuclei or portions of nuclei that is unresolvable using [14C]2DG in the awake, normal animal. Heterogeneous patterns of 2DG uptake seen only with [3H]2DG are found in the nucleus accumbens, the anterior portion of the basolateral nucleus of the amygdala, specific nuclei of the inferior olivary complex, various hypothalamic regions, and a region straddling the border of the medial and lateral habenular nuclei. The lamination of differential 2DG uptake in the hippocampus is better localized using [3H]2DG. Autoradiographic resolution of labeled 2DG is further improved when the brain is perfused prior to frozen sectioning, due perhaps to selective fixation and retention of intracellular labeled 2‐deoxy‐glycogen. A series of [3H]2DG autoradiographs are presented together with views of the Nissl‐stained sections that produced the autoradiographs.
Effects of monocular deprivation on geniculocortical synapses in the cat
Authors: Tieman Suzannah Bliss
Published: January 2005

In monocularly deprived (MD) cats, many cells in the lateral geniculate nucleus (LGN) but few cells in the visual cortex respond to input from the deprived eye, suggesting that the connections to visual cortex from the deprived geniculate laminae may have been disrupted. I have examined these connections in MD cats by using electron microscopic autoradiography of visual cortex after injections of tritiated lysine into single laminae of LGN. After injections into either deprived or experienced laminae, there was label over terminals that contained mitochondria and round synaptic vesicles and that made asymmetric contacts with dendritic profiles. However, the terminals of deprived afferents differed from those of experienced afferents: They were 25% smaller, contained 33% fewer mitochondria, were more likely to make synapses that were presynaptically convex (and thus, perhaps, immature), and synapsed onto smaller spines. These morphological changes were greater for afferents to upper layer IV than for afferents to lower layer IV. The geniculocortical synapses from deprived laminae were also reduced in number. To correct for variations in injection size and for a probable reduction in protein synthesis by cells in the deprived laminae, I computed the ratio of labeled synaptic terminals to labeled myelinated axons. Injections into the deprived laminae labeled 43% fewer synaptic terminals per labeled myelinated axon than did injections into the experienced lamina. The finding that the synaptic terminals of deprived afferents are both abnormal morphologically and fewer in number can help to explain the reduced effectiveness of the deprived eye in driving cortical cells.
Anatomy and innervation of the anterior aorta of Aplysia and the ultrastructure of specialized neuromuscular junctions on vascular smooth muscle
Authors: Price Christopher H. , Fowle William , Rittenhouse Ann R.
Published: January 2005

The fine structure of the cellular layers and innervation of smooth muscle in the anterior aorta of Aplysia were examined. The inner layer of circular muscle is not innervated but its fibers may be electrically coupled. In contrast, longitudinal fibers in the outer layer are well separated and richly innervated by highly specialized neuromuscular junctions (NMJ). Three distinct types of NMJ are present on this smooth muscle, each identifiable by a set of quantitatively described morphological features including size, degree of contact with sarcolemma, density of active zones, number of mitochondria and vesicular content. The three types of NMJ are likely to arise from the identified serotonergic (RDAAE), cholinergic (RDAAI), and glycinergic (R14) neurons that provide the major known excitatory, inhibitory, and modulatory inputs to this vessel. Each longitudinal muscle fiber is separately innervated by one or more NMJ of each type. Since there are no intercellular junctions between longitudinal fibers, coordination of contractility is clearly a function of the pattern of neural activity. This report further characterizes the rapid and fine control of the vasculature in Aplysia and demonstrates the utility of this preparation for cellular‐level studies on the neural control of smooth muscle and neurochemical messengers mediating its activity.
The organization of projections from the cortes, amygdala, and hypothalamus to the nucleus of the solitary tract in rat
Authors: van der Kooy Derek , Koda Leonard Y. , McGinty Jacqeline F. , Gerfen Charles R. , Bloom Floy E.
Published: January 2005

Direct projections from the forebrain to the nucleus of the solitary tract (NTS) and dorsal motor nucleus of the vagus in the rat medulla were mapped in detail using both retrograde axonal transport of the fluorescent tracer True Blue and anterograde axonal transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP). In the retrograde tracing studies, cell groups in the medial prefrontal cortex, lateral prefrontal cortex (primarily ventral and posterior agranular insular cortex), bed nucleus of the stria terminalis, central nucleus of the amygdala, paraventricular, arcuate, and posterolateral areas of the hypothalamus were shown to project to the NTS and in some cases also to the dorsal motor nucleus of the vagus. The prefrontal cortical areas projecting to the NTS apparently overlap to a large degree with those cortical areas receiving mediodorsal thalamic and dopaminergic input. The retrogradely labeled cortical cells were situated in deep layers of the rat prefrontal cortex.

The anterograde tracing studies revealed a prominent topography in the mediolateral termination pattern of forebrain projections to the rostral part of the NTS and to the dorsal pons. The projections to the NTS were generally bilateral, except for projections from the central nucleus of the amygdala and bed nucleus of the stria terminalis which were predominantly ipsilateral. The prefrontal cortical projections to the NTS travel through the cerebral peduncle and pyramidal tract and terminate throughout the rostrocaudal extent of the NTS. Specifically, the prefrontal cortex innervates dorsal portions of the NTS (lateral part of the dorsal division of the medial solitary nucleus, dorsal part of the lateral solitary nucleus and the caudal midline region of the commissural nucleus), areas which receive relatively sparse subcortical projections. These dorsal portions of the NTS receive major primary afferent projections from the vagal and glossopharyngeal nerves. In contrast, the subcortical projections, which travel through the midbrain and pontine tegmentum, terminate most heavily in the ventral portions of the NTS, i.e., the area immediately dorsal and lateral to the dorsal motor nucleus of the vagus. Only the paraventricular hypothalamic nucleus has substantial terminals throughout the dorsal motor nucleus of the vagus. Hypothalamic cell groups innervate the area postrema and, along with the prefrontal cortex, innervate the zone subjacent to the area postrema.

We suggest that direct projections to the NTS and dorsal motor nucleus of the vagus are one criterion that can be used to define the visceral fore‐brain. The organization of the forebrain terminations in the solitary complex described here may eventually allow a better understanding of how the brain controls visceral function.
The development of photoreceptors in the zebrafish, Brachydanio rerio. II. Function
Authors: Branchek Theresa
Published: January 2005

The functional development of rod and cone photoreceptors in the zebrafish (Brachydanio rerio) was studied by electroretinographically measuring flicker fusion frequencies. Two to 3 days after fertilization, fish gave little or no response to high intensity stimuli. Increases in sensitivity and flicker resolution were observed after this time. Biphasic response curves typical of adults could be elicited from fish as young as 2 weeks postfertilization, thus indicating a functional divergence of rods and cones. The results are consistent with behavioral and anatomical analyses of zebrafish photoreceptor development.
Subcortical projections of the inferior parietal cortex (area 7) in the stump‐tailed monkey
Authors: Weber Joseph T. , Yin Tom C. T.
Published: January 2005

The efferent projections of the neocortex on the lateral convexity of the inferior parietal lobe (area 7 of Brodmann) were examined using the anterograde transport of tritiated amino acids. Multiple injections of 3H‐leucine and 3H‐proline were placed within the three cytoarchitecturally distinct zones that lie along the exposed surface of the inferior parietal lobe (IPL). The subcortical projections resulting from these injections were studied. Prominent projections were seen in the thalamus (medial and lateral pulvinar), brainstem (dorsolateral and ventral pontine nuclei), and basal ganglia (caudate and putamen) with less dense label over the thalamic intralaminar nuclei, pretectal complex, superior colliculus, reticular nucleus of the thalamus, suprageniculate nucleus, lateral posterior nucleus, oral pulvinar, and claustrum. In many of these cases there was a topographical relationship apparent with regard to the injections placed along the rostral‐caudal dimension of the IPL. There is a striking reciprocal arrangement in the afferent and efferent projection systems of the IPL. The functional relevance of both the topography and the efferent projections of the IPL is discussed.
Torpedo electromotor system development: A quantitative analysis of synaptogenesis
Authors: Fox Geoffrey Q. , Kötting Dieter
Published: January 2005

Synaptogenesis in the electric organ of Torpedo marmorato has been studied quantitatively at the ultrastructural level of observation. In addition to establishing the normal developmental time course for this event we were interested in determining whether a gradient of synaptogenesis might be present because the electric organ produces several morphologically recognizable spatiotemporal gradients during its early ontogeny. These gradients genesis of electrocyte columns, both gradients of which are operative for periods of weeks. No gradient of synaptogenesis was found, indicating this to be a synchronous process. The idea is advanced that synaptogenesis in the electric organ is modulated by extrinsic influences, many of which may originate from the target electrocytes which, by this time, have became synchronized in their development.
Axons of the dorsal division of the medial geniculate body of the cat: A study with the rapid Golgi method
Authors: Winner Jeffery A. , Morest D. Kent
Published: January 2005

The arrangement of eight groups of axons afferent to the nuclei of the dorsal division of the medial geniculate body is described in rapid Golgi impregnations from young cats. Three kinds of axons travel predominantly in the brachium of the inferior colliculus and enter the medial geniculate body ventromedially: group I, thin axons resembling ivy tendrils ending along dendrites; group II, thicker axons with a sinuous course and few branches group IV, coarse thick axons with grumous collaterals and massive peridendritic terminals near principal cells and interneurons. Three kinds of axons enter from the parabrachial region and pass laterally group III, very thin axons with many collaterals forming dense terminal nests; group V, runcinate axons with sparse, thin collaterals; group VI, either medium‐sized (group VIa) or thin (group VIb) smooth axons, perhaps corticofugal, and ending near principal neuron dendrites; group VII, thick axons, entering from the auditory radiation, with large, grapelike terminal arbors and group VIII, thin and forming peridendritic festoons on principal cells after entering from the brachium of the superior colliculus.

There appears to be some, though not complete, segregation of axons in the dorsal division nuclei. Thus axons of groups I, III, IV, and VI are found in each nucleus, although group VI axons are conspicuous in the superficial dorsal nucleus, and group IV endings are much more elaborate in the dorsal and deep dorsal nuclei than in the superficial dorsal nucleus. Each axon type has a specific pattern of terminal branches, which contributes to the texture of the neuropil in each nucleus. Golgi type II axons accentuate these textural differences. Thus each nucleus has a specific pattern of neuropil by virtue of the relative proportions of the different groups of axons ending there and the density and architecture of the axonal plexus. For example, both the dorsal nucleus and the deep dorsal nucleus receive the same groups of afferent axons, but the axonal plexus is more diffusely and evenly distributed in the dorsal nucleus, whereas the neuropil of the deep dorsal nucleus is highlighted by aggregates of grumous endings, more irregularities in the distribution of the axonal plexus, and many more fibers of passage.

The extrinsic axons in the dorsal division come from the inferior and superior colliculi, the lateral tegmental system of the midbrain, and the cerebral cortex. Since there is variation in the density and diversity of input in the various parts of the dorsal division, as well as differences in the intrinsic organization of nuclei, there might also be functional distinctions between subdivisions. This hypothesis is supported by the existence in each nucleus of cell types unique to it, different patterns of cortical projections to and from each nucleus, and dissimilar midbrain inputs. The synaptic organization of the dorsal division suggests a functional heterogeneity in this part of the medial geniculate body.
Growth and death of cells of the mesencephalic fifth nucleus in Rana pipiens larvae
Authors: Kollros Jerry J.
Published: January 2005

Positions, numbers, and nuclear sizes of mesencephalic fifth nucleus M‐V) cells were determined in Rana pipiens lervae in stages XIII through the end of metamorphosis at stage XXV, in a few just postmetamorphic juveniles, and in adults. M‐V cells are found throughout the tectum, with the greatest concentrations just anterior to each optic ventricle, and along the medioanterior aspect of each ventricle. Some cells lie below these levels, ventricle; a very few cells occur in the anterior medullary velum and in the adjacent anterior cerebellum. Up to 879 M‐V cells were seen in single animals in stages XIV–XVIII, with mean values near 650 cells. Pyknotic M‐V cells appear in all stages from XVII through XXV, and possibly in the youngest juveniles. Peak rates of cell loss occur at stage XXI, some 4–5 days after the forelimbs have emerged. Mean postmetamorphic cell numbers are about 350, suggesting an average M‐V cells loss of 300 per animal. Nuclear cross‐sectional areas are 72 m̈m2 at stage XIII, slightly above the size of such cells in hypophysectomized tadpoles. Nuclear growth is progressive to 102–111 m̈m2 at stages XXI–XXV. Adult sizes increase to a mean of 121 m̈m2. Hypophysectomized animals display pyknotic cells only after the tadpoles have been strongly stimulated by thyroid hormone, as demonstrated by significant growth of the legs and of the M‐V cells themselves.
The morphology of two groups of spiking local interneurons in the metathoracic ganglion of the locust
Authors: Siegler M. V. S. , Burrows M.
Published: January 2005

Two bilaterally symmetrical groups of spiking local interneurons are described in a segmental ganglion of the locust. Interneurons in both groups are excited by specific sets of sensory receptors on one leg. The cell bodies of the anterior‐lateral group lie amongst approximately 40 small cell bodies at the anterior of the ganglion, close to the lateral edge of an anterior connective. Interneurons in this group have primary neuritis in Ventral Commisure I (VCI), and dorsoventral processes in the Oblique Tract, which divide the extensive neuropilar branches into distinct ventral and dorsal regions. Cell bodies of the midline group lie amongst a group of approximately 100 small cell bodies near the ventral midline. Interneurons in this group have primary neuritis in Ventral Commisure II (VCII), and dorsoventral processes in the Perpendicular Tract, which divide the neuropilar branches into dorsal and ventral regions. The ventral branches of interneurons in both groups are numerous and of uniform texture, whereas the dorsal branches are sparse and varicose. The ventral branches project to the same ventral areas of neuropil as the afferent from some hairs on the hind leg. The dorsal branches of midline interneuron and the branches of leg motor neuron that it affects project to the same dorsal area of neuropil. Some midline interneurons receive direct inputs from leg hair afferent and make direct connections with leg motor neurons.
Demonstration of a sexual dimorphism in the distribution of serotonin‐immunoreactive fibers in the medial preoptic nucleus of the rat
Authors: Simerly R. B. , Swanson L. W. , Gorski R. A.
Published: January 2005

The distribution of serotonergic fibers in the medial preoptic nucleus (MPN) and adjacent areas was evaluated with an indirect immunohistochemical method in the normal adult male and female albino rat. Sections through the MPN were processed for immunofluorescence with an antiserum directed toward serotonin and were counterstained with the fluorescent Nissl stain ethidium bromide. The distribution of serotonin‐immunoreactive fibers in the MPN was correlated with cytoarchitectonic features of the nucleus. On the basis of the results, we have subdivided the MPN into three parts: a medial cell‐dense part (MPNm), a lateral cell‐sparse part (MPN1), and a central very cell‐dense part (MPNc) that is embedded in the medial part. The MPNc corresponds to the sexually dimorphic nucleus of the preoptic area identified by Gorski et al. (′80). A marked sexual dimorphism was found in the relative size of each part of the MPN. In the male, the volumes of the cell‐dense MPNm and MPNc appear to be notably larger, while in the female more than half of the nucleus is occupied by the cell‐sparse lateral part. The MPN as a whole appears to be slightly larger in the male. Each subdivision contains a characteristic pattern of serotonin‐immunoreactive fibers. In each sex, the MPN is surrounded by a low to medium density of serotonin‐stained fibers, while the MPN1 is filled with a dense plexus of varicose immunoreactive fibers. In contrast, the MPNm contains a low density of stained fibers, and the MPNc is virtually devoid of serotonin‐stained fibers. Since both the MPNm and the MPNc are larger in the male, a correspondingly larger region of very low serotonin‐stained fiber density is found in the male. It appears then that the MPN is a sexually dimorphic complex composed of at least three cytoarchitectonically distinct subdivisions, each of which contains a characteristic density of serotonin‐immunoreactive fibers.
Light and electron microscopic evidence for a direct corticospinal projection to superficial laminae of the dorsal horn in cats and monkeys
Authors: Cheema S. S. , Rustioni A. , Whitsel B. L.
Published: January 2005

The anterograde transport of horseradish peroxidase (HRP) and wheat germ agglutin conjugated to horseradish peroxidase (WGA‐HRP) was employed in cats and monkeys to investigate, at both the light and electron microscopical levels, the contribution of the corticospinal tract (CST) to the superficial laminae of the dorsal horn.

At the light microscopic level, this approach not only confirmed the previously documented pattern of CST termination, but also revealed a sparse projection to laminae VIII and IX of the cat and a prominent projection to the most superficial parts of the brachial dorsal horn, i.e., laminae I and II. Discrete injections involving particular cytoarchitectonic areas (4, 3a, 3b, and 1–2) of monkeys showed that the superficial laminae receive their corticofugal inputs primarily from areas 3b, 1, and 2.

Electron microscopic observations were made on CST fibers and boutons which were labelled, after histochemical processing, with the reaction product of anterogradely transported WGA‐HRP. The labelled fibers in the superficial laminae were small (± 0.5 μm), and boutons established mainly axodendritic contacts, contained mostly clear, spherical, or pleomorphic vesicles, but sometimes also displayed dense core vesicles. These boutons were primarily in lamina I and outer lamina II, but not in inner lamina II.

The possible role of n direct monosynaptic pathway from the cerebral cortex to the superficial laminae of the dorsal horn is discussed in relation to the previous reports that laminae I and II play a significant role in nociception.