bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin of ascending projections to inferior colliculus in the mustache bat, Pteronotus parnellii
Authors: Zook J. M. , Casseday J. H.
Published: January 2005

The origins of pathways to the inferior colliculus of the mustache bat were identified by retrograde transport of horseradish peroxidase (HRP). A specific goal of this study was to obtain evidence that would help determine whether the nuclei, shown in the previous paper to have unusual cytoarchitectural features, are unique to bats, or whether they are homologous to areas that are not well differentiated in other mammals. The auditory pathways in the lower brain stem of Pteronotus appear to conform to the same basic organization as in other mammals: After injection of HRP into one inferior colliculus, labeled cells are located contralaterally in the cochlear nucleus, ipsilaterally in the medial superior olive, bilaterally in the lateral superior olive, ipsilaterally in the ventral and intermediate nuclei of the lateral lemniscus, and bilaterally in the dorsal nucleus of the lateral lemniscus. These patterns of labeling provide a basis for understanding how the specialized auditory areas of the bat may be organized within a basic plan of mammalian auditory systems. In the anteroventral cochlear nucleus the unusually small spherical cells seem to be homologous to stellate cells in the anteroventral cochlear nucleus of the cat. In the superior olive, differences in patterns of labeled cells distinguish the medial from the lateral superior olive. In the lateral lemniscus the pattern of labeled cells shows clear differences between the two special parts, intermediate and ventral nuclei, as well as between these and the dorsal nucleus of the lateral lemniscus. The results are consistent with the hypothesis that the unusual auditory nuclei of the bat have homologues in mammals whose auditory systems are not specialized for echolocation.
Neuropeptide proctolin (H‐Arg‐Try‐Leu‐Pro‐Thr‐Oh): Immunocytochemical mapping of neurons in the central nervous system of the cockroach
Authors: Bishop Cynthia A. , O'shea Michael
Published: January 2005

Proctolinlike immunoreactivity was mapped in the central nervous system of the cockroach, Periplaneta americana, by using whole‐ganglion immunoreacted preparations. The procedure for this immunohistochemical staining of whole‐mounts is described. Immunoreactivity was confined to neuronal cell bodies and processes. These were found in all ganglia of the CNS. The cells varied in the consistency and intensity of their staining. The occurrence and variability of staining is described in detail.

Cell bodies were found in the dorsal, ventral, and lateral regions of the ganglia. The highest number of cell bodies was found in the terminal ganglion and the lowest number in the cerebral ganglion. Those in the cerebral ganglion occurred mainly in the tritocrebral lobes. The distribution of immunoreactive cell bodies correlated with results previously obtained by radioimmunoassay. Immunoreactive processes were detected in all interganglionic connectives and many ganglionic nerve roots. Dense ramifications of immunoreactive processes and variocosities were detected in many of the ganglia. The widespread presence of immunoreactivity suggests that proctolin has diverse central and peripheral functions. The mapping of immunoreactive neuronal somata provides a valuable step in the identification of putative proctolin‐containing neurons suitable for further biochemical, anatomical, and physiological analysis.
Ascending lateral line pathways to the midbrain of the clearnose skate, Raja eglanteria
Authors: Boord Robert L. , Northcutt R. Glenn
Published: January 2005

Efferent projections of the electroreceptive dorsal and the mechanoreceptive intermediate octavolateralis nuclei were revealed, in the brain of the clearnose skate Raja eglanteria, by means of silver degeneration and autoradiographic methods. Efferents from each nucleus give rise to ipsilateral and contralateral lemnisci and commissural components. Commissural fibers terminate within their respective nuclei of the opposite side. The lemnisci from each nucleus parallel each other as they course from medullary to mesencephalic levels; those from the dorsal nucleus assume a lateral position and terminate within the lateral part of the nucleus of the lateral line lemniscus and the lateral nucleus of the midbrain; those from the intermediate nucleus assume a medial position and terminate within the medial part of the lateral line lemniscal nucleus and the dorsomedial mesencephalic nucleus. A substantial number of fibers of each class course through the mesencephalic nuclei and terminate bilaterally within the central tectal zone. The segregation of electroreceptive and mechanoreceptive information is maintained from medullary to mesencephalic levels although there probably is convergence within the central tectal zone and the magnocellular nucleus, the only octaval center to receive terminals from secondary lateral line fibers.
Crossed connections of the substantia nigra in the rat
Authors: Gerfen Charles R. , Staines William A. , Fibiger Hans C. , Arbuthnott Gordon W.
Published: January 2005

The existence of crossed multisynaptic pathways that allow for the interdependent control of activity in one substantia nigra and its contralateral counterpart has been inferred from a number of recent biochemical and neurophysiological investigations. This prompted a reexamination of the connections of the substantia nigra with an emphasis on crossed inputs to and crossed projections from that nucleus. Male albino rats received 20–50‐nl pressure injections of a 1% wheat germ agglutinin‐conjugated horseradish peroxidase (WGA‐HRP) solution into the substantia nigra or into surrounding areas as controls. Following a 24‐hour survival period the animals were processed according to the tetramethylbenzidine protocol for the visualization of HRP.

The pattern of anterograde transport of WGA‐HRP after substantia nigra injections, confirming for the most part previous reports, demonstrated ipsilateral nigral efferent projections to the striatum; globus pallidus; subthalamic nucleus; the lateral dorsal, paralamellar mediodorsal, ventromedial, and parafascicular thalamic nuclei; central gray, midbrain reticular formation; superior colliculus; and peribrachial area, including the pedunculopontine nucleus. Additionally, the nigral projections to the paralamellar mediodorsal and ventromedial thalamic nuclei and to the superior colliculus were demonstrated to be bilateral. Most of these connections were confirmed by the complementary retrograde experiment.

In accordance with previous reports, intranigral WGA‐HRP injections retrogradely labeled neurons located in the ipsilateral prefrontal cortex, motor cortex, striatum, globus pallidus, central nucleus of the amygdala, anterior hypothalamic area, subthalamic nucleus, and dorsal raphe. Additionally, labeled perikarya were observed in the ipsilateral parafascicular thalamic nucleus, in the contralateral posterior lateral hypothalamic area, and in the ipsilateral and contralateral peribrachial‐pedunculopontine area. These latter nigral afferents were confirmed with complementary WGA‐HRP injections into each of the regions of origin. While bilateral peribrachial‐pedunculopontine innervation of the substantia nigra has been reported in the cat there has been no previous demonstration of a crossed nigral afferent system from the contralateral posterior lateral hypothalamic area. The results are discussed with reference to the pathways that may mediate the interdependent control of the activity of neurons in the left and right substantia nigra. Additionally, the association of the substantia nigra with a variety of neuronal circuits, including the cerebellofugal, tectothalamic, thalamocortical, thalamostriatal, and basal ganglia pathways, are discussed.
The morphological relationships between substance P immunoreactive processes and ventral horn neurons in the human and monkey spinal cord
Authors: De Lanerolle Nihal C. , Lamotte Carole C.
Published: January 2005

The distribution of substance P (SP)‐containing neural processes in the ventral horn region of the human and monkey spinal cord was studied by staining for SP by the indirect antibody peroxidase‐antiperoxidase technique and by light and electron microscopic examination of stained material. Immunoreactive fibers and terminals were found in all major cell columns of the ventral horn in the human and monkey spinal cord, with the immunoreactive profiles in close apposition to motoneurons. The immunoreactivity was contained in synaptic knoblike (bouton) structures, in which the label was associated with small agranular vesicles, dense‐core vesicles, and mitochondria. The immunoreactive synaptic knobs formed synaptic junctions predominantly with dendrites. The labeled knobs were similar to “S” (agranular spheroid vesicles) and “G” (dense‐core vesicles) type bulbs described previously in the monkey ventral horn. Their location, mainly on the neuron dendrites and soma supports the physiological evidence that SP‐produced membrane depolarization is mediated primarily by a direct action of the neurochemical on the neuron rather than by a transynaptic mechanism.
Tonotopic organization in the central auditory pathway of the mongolian gerbil: A 2‐deoxyglucose study
Authors: Ryan Allen F. , Woolf Nigel K. , Sharp Frank R.
Published: January 2005

The uptake of 2‐deoxyglucose (2‐DG) was employed to map functional activation of the central auditory pathway in the mongolian gerbil, during 85 dB SPL stimulation with pure tonal stimuli at frequencies of 0.75, 3.0, or 12.0 kHz. Pure tones produced foci of very high 2‐DG uptake, when compared to adjacent tissue, in the cochlear nucleus, superior olivary complex, and inferior colliculus. Less distinct areas of elevated 2‐DG uptake were seen in the dorsal and ventral nuclei of the lateral lemniscus, medial geniculate nucleus, and auditory cortex. Little or no change in the distribution of 2‐DG uptake was noted in the nucleus of the trapezoid body. The location of discrete regions of relatively high 2‐DG uptake varied systematically with stimulus frequency. The tonotopic organization demonstrated by 2‐DG mapping agreed well with the results of previous electrophysiological studies for most structures. However, in the inferior colliculus, stimulus‐evoked increases in 2‐DG uptake were found to occur in a fixed pattern of three to four bands across the central nucleus, which did not correspond to any previously reported anatomical or physiological organization. Pure tonal stimuli activated discrete portions of this banding pattern. Also, a small area at the ventromedial edge of the colliculus was more broadly tuned than other regions of the nucleus. It is concluded that 2‐DG uptake is well suited to theinvestigation of tonotopic organization. This technique reveals patterns ofactivation which have not been observed with other methodologies.
Morphology and laminar distribution of nonpyramidal neurons in the auditory cortex of the rabbit
Authors: McMullen Nathaniel T. , Glaser Edmund M.
Published: January 2005

A study of the morphology and laminar distribution of nonpyramidal neurons in Goldi‐Nissl prepartions of electrophysiology verified auditory cortex was carried out in the adult rabbit. Nonpyramidal neurons were located primarily within laminae I‐IV and were only infrequently seen in lamina V and Vi. In lamina I, four nonpyramidal cell types were observed: (1) small, spine‐free horizontal neurons, (2) small, sparserly spined multipolar neurons with radiate dendrites, (3) large, multipolar neurons with fusiform somata and vertically aligned, sparsely spined dendrites, and (4) small, spine‐free neurogliform neurons. The horizontal and small multipolar neurons had tagentially running axons confined to lamina I. The large, fusiform cells had descending axons which arborized in lamina II and occasionally reached lamina III. In lamina II and the upper part of lamina III, seven nonpyramidal cell types were observed: (1) spine‐free bipolar neurons with vertically alined denddrites and axonal arbors; (2) large, (3) medium, and (4) small, spine‐free and sparsely spined multipolar neurons, all with locally ramifying axons; (5) pear‐shaped cells with highly oriented dendrites which branched toward the pial surface and vertically arborizing axons; (6) multipolar cells with tangentially and vertically oriented dendrites and ascending axons which entered lamina I, and (7) tufted cells with local axons. Three types of nonpyramidal cells were observed in lamina IV and the lower part of lamina III: (1) large, multipolar cells with radiate, spine‐free dendrites and stout axons which arborized locally, (2) spiny multipolar cells with vertically aligned dendrites and ascending axons which arborized in lamina II and III via long horizontal collaterals, and (3) spine‐free bipolar cells with vertical dendrites and axons which arborized in a narrow vertical column adjacent to the dendrites. Nonpyramidal neurons in lamina V and VI were primarily multipolar cells with sparsely spined and spine‐free dendrites. A comparison of these data with those of other species indicates that the neuronal organization of the rabbit auditory cortex is similar to the of the sensory cortex of the rodent butis strikingly differnt from that of cernivores and primates.
Ontogeny of the neurotensin‐containing neuron system of the rat: Immunohistochemical analysis. I. Forebrain and diencephalon
Authors: Hara Yoshinobu , Shiosaka Sadao , Senba Emiko , Sakanaka Masahiro , Inagaki Shinobu , Takagi Hiroshi , Kawai Yuriko , Takatsuki Kenichi , Matsuzaki Takashi , Tohyama Masaya
Published: January 2005

The ontogeny of the neurotensin (NT) neuron system in the forebrain and diencephalon of the rat was investigated by means of indirect immunofluorescence. NT‐positive structures first appear in the primordium of the olfactory bulb, anterior amygdaloid area, piriform cortex, amygdaloid complex, nucleus tractus diagonalis, lateral preoptic area, and lateral hypothalamus, etc., of the fetus of gestational day 16. From this day, NT‐positive structures appear gradually in various areas of the forebrain and diencephalon and reach their maximum content on postnatal day 7. In contrast, NT‐positive structures decrease slightly in number as the rat grows. However, even in adult rats, numerous NT‐positive structures are still identifiable in various areas of the forebrain and diencephalon.
A golgi study of the medial geniculate body in the tree shrew (Tupaia glis)
Authors: Oliver Douglas L.
Published: January 2005

The subdivisions of the medial geniculate body in Tupaia recognized in previous connectional and cytoarchitectural studies are identified in Golgi‐impregnated material. They may be distinguished by the organization of the neuropil, especially the dendrites, and, in many cases, by differences in the neurons. The ventral nucleus contains tufted cells with disc‐shaped dendritic fields which are aligned to form laminae. The caudomarginal and deep dorsal nuclei have less tufted, less precisely arranged cells with longer, thin appendages. Neurons in the suprageniculate and dorsal nuclei are similar except that they apparently are arranged more randomly and tend to have more spherically shaped dendritic fields. The medial division is characterized rostrally by the presence of stellate cells and caudally by large cells which appear to be the neurons, observed in previous studies to have widespread connections.

The results of this Golgi study suggest that the subdivisions of the medial geniculate body might be grouped differently than in previous reports. When combined with data from previous studies of connections, the results show that the medial geniculate body of even distantly related species may follow a common plan. The ventral nucleus is the medial geniculate component of the central pathway which extends from the central nucleus of the inferior colliculus to the primary auditory cortex. Most of the other medial geniculate subdivisions participate in either pericentral pathways originating in the cortex and other nuclei which surround the central nucleus of the inferior colliculus or in the pathways of the lateral midbrain tegmentum. Pericentral and lateral tegmental pathways terminate in nonprimary auditory cortex. The widespread pathway involves only the caudal nucleus of the medial division. It receives afferents from most, if not all, of the midbrain regions that give rise to the other pathways and distributes to all parts of the auditory cortex where it terminates in layers other than layer III‐IV.
An HRP study of the relation between cell size and motor unit type in cat ankle extensor motoneurons
Authors: Burke R. E. , Dum R. P. , Fleshman J. W. , Glenn L. L. , Lev‐Tov A. , O'Donovan M. J. , Pinter M. J.
Published: January 2005

The dimensions of the somata and stem dendrites of 57 α‐ and three γ‐ motoneurons, identified as to motor unit type and labeled by intracelluar injection of horseradish peroxidase, were measured in the triceps surae and plantaris motor pools. The somata of type S motoneurons tended to be smaller (mean diameter 47.9 μm) than those of FF and FR units (52.5 and 53.1 μm, respectively) but these mean values were not significantly different and the data distributions showed considerable overlap between the unit types. The mean numbers and diameters of stem dendrites of stem dendrites exhibited somewhat larger differences related to motor unit type and some of these were statistically significant. The total membrane area (AN) of each cell was estimated from measurements of the soma and stem dendrites, by using recent data of Ulfhake and Kellerth ('81) to calculate the membrane area of a dendritic tree from stem dendrite diameter. Mean AN varied with motor unit type in the sequence FF > FR > S (average values: 369 × 1003 μm2, 323 × 1003 μm2, and 250 × 1003 μm2, respectively). There was covariation between AN and the conduction velocity of the motor axon, as well as with the force output from the muscle unit. Comparison of AN and motoneuron input resistance (RN) in 19 α‐motoneurons suggested that the specific resistivity of the cell membrane in type S motoneurons was systematically higher than that characteristic of type FF or FR motoneurons.
Topography between the entorhinal cortex and the dentate septotemporal axis in rats: I. Medial and intermediate entorhinal projecting cells
Authors: Ruth Russell E. , Collier Timothy J. , Routtenberg Aryeh
Published: January 2005

Retrograde tracing experiments were performed to clarify the topographic projection from medial (area 28m) and intermediate (area 28i) divisions of the entorhinal cortex to the dentate gyrus. Pipets filled with horseradish peroxidase (HRP) were positioned by electrophysiologic guidance at one of several septotemporal (S‐T) levels in the dentate molecular layer of anesthetized rats; the tracer was expelled iontophoretically to minimize its spread. Retrograde labeling of neurons within areas 28m and 28i was analyzed in relation to cytoarchitectonic as well as spatial features of the region (obtained by histologic reconstruction).

Regardless of the S‐T level, ejections of HRP which were confined to the dentate gyrus labeled only layer II neurons of each area. Following septal pole ejections, labeled neurons were located in the posterolateral, extreme posterior, and postermedial parts of both areas 28m and 28i. Mid S‐T ejections produced not only a ventral, but also an anteromedial, shift in the location of entorhinal projection cells; no cells were labeled posterolaterally. After temporal dentate ejections labeled neurons occupied the most anteromedial part of these entorhinal areas. For both areas, but especially for area 28i, convergence of entorhinal efferents upon a single S‐T level in the dentate gyrus occurred from neurons which lay in a dorsoventral (i. e., frontal), and to a lesser extent a rostrocaudal, plane.

The efferent axes of both areas 28m and 28i thus appear to be curved and are therefore best described in three dimensions. The entorhinal axes begin in a posterodorsolateral location, wrap around the posterior cortical convexity, and end in an anteroventromedial position. The results provide a useful map for in situ exploration of entrohinodentate connections in the rat, emphasize the parallel innervation of the dentate gyrus by distinct entorhinal fiber systems, and reflect the importance of the S‐T axis as a framework for interpreting hippocampal organization.
The distribution and origin of serotonin‐containing fibers in the septal area: A combined immunohistochemical and fluorescent retrograde tracing study in the rat
Authors: Köhler Christer , Chan‐Palay Victoria , Steinbusch Harry
Published: January 2005

The distribution of 5‐hydroxytryptamine (serotonin, 5‐HT)‐containing nerve fibers and terminals in the septal area of the rat was studied by using immunohistochemistry with specific antibodies to 5‐HT in combination with fluorescent retrograde tracing methods. The 5‐HT innervation of the septum is heterogeneous with regard to both the morphology of individual processes and the density of distribution in different parts of the septum. Three major classes of 5‐HT like immunoreactive processes can be distinguished: (1) thin, convoluted fibers with small, round or elongated varicosities; (2) thick and relatively straight fibers with few varicosities; and (3) pericellular plexuses with large varicosities in close association with perikarya in the lateral septum. Three areas of the septum receive a prominent innervation by 5‐HT processes: the diagonal band of Broca, the ventral part of the lateral septum, and and area bordering the medial edge fo the islands of Calleja (insula magna). Whereas the two latter areas contain dense terminal networks, the diagonal band of Broca is occupied primarily by 5‐HT fibers en route to other parts of the septum. Intraseptal injections of HRP or fluorescent dyes (granular blue, propidium iodide) resulted in retrograde labeling of neuronal cell bodies in several nuclei of the brainstem which are known to contain 5‐HT neurons: the dorsal raphe, the median raphe, the nucleus reticularis tegmenti pontis, the raphe pontis, and the raphe magnus. Where fluorescent retrograde tracing was performed with 5‐HT immunohistochemistry on the same tissue section, a prominent 5‐HT containing pathway and a non‐5‐HT‐containing pathway from the raphe nuclei to the septum were revealed. Finally, double retrograde fluorescent labeling after injections of granular blue or propidium iodide into the septum and entorhinal area respectively of the same rat revealed extensive branching of the raphe efferents. Thus, individual raphe neurons may simultaneously connect with septum and the entorhinal area, two structures essential for normal hippocampal function.
The efferent connections of the nucleus of the optic tract and the superior colliculus in the rabbit
Authors: Holstege Gert , Collewijn Han
Published: January 2005

3H‐leucine injections were made in tectal and pretectal areas in the rabbit. After injections in the nucleus of the optic tract (NOT) labeled fibers were distributed bilaterally to the superior colliculus, the dorsal part of the medial geniculate nucleus (MGd), and the pulvinar nucleus, and ipsilaterally to the external layer of the ventral lateral geniculate nucleus (LGv), the dorsal geniculate nucleus (LGd) pars β, the reticular thalamic nucleus, and the lateral and medial terminal nucleus (LTN, MTN). Many labeled fibers were distributed to the lateral and some to the medial parts of the pontine nuclei. More caudally, coarse labeled fiber bundles descended ipsilaterally, distributing fibers to the prepositus hypoglossi and abducens nucleus and to the caudally adjoining medial reticular formation. Many labeled fibers were also present in the inferior olive, especially ipsilaterally in the dorsal cap and the ventrally adjoining pars β, and a few in the contralateral dorsal cap area. Contralaterally, some descending fibers terminated in the dorsal part of the facial nucleus, in which motoneurons are located innervating the orbicularis oculi muscle.

The superficial layers of superior colliculus distributed fibers bilaterally to the internal layer of the ventral lateral geniculate nucleus (LGv), the LGdα (lateral part), the MGd, the pulvinar, and more caudally to the ipsilateral parabigeminal and lateral pontine nuclei.

The deep collicular layers distributed fibers ipsilaterally to MG (internal division), pulvinar, and the internal layer of LGv. Furthermore, ascending connections were found to the suprageniculate nucleus, the zona incerta, the mediodorsal nucleus, and some intralaminar and midline nuclei. Descending fibers terminated in the mesencephalic lateral tegmentum, pontine nuclei, and ventrally in the pontine and high medullary reticular formation. Contralaterally fibers were distributed to the nucleus reticularis tegmenti pontis (NRTP), the medial reticular formation, and the inferior olive just lateral to the nucleus β. In one case fibers were also distributed to the lateral part of the contralateral facial nucleus in which motoneurons are located innervating the upper lip muscles.
Organization of nucleus rotundus, a tectofugal thalamic nucleus in turtles. III. The tectorotundal projection
Authors: Rainey W. T. , Ulinski P. S.
Published: January 2005

Nucleus rotundus is the primary thalamic recipient of projections from the optic tectum in pond turtles. Although the projection of the retina to the optic tectum is known to be topographically organized, earlier studies suggest that the tectorotundal projection is not topographically organized. Three types of analyses are used in this paper to characterize the organization of the projection of the optic tectum to nucleus rotundus.

First, large iontophoretic injections of horseradish peroxidase into the optic tectum anterogradely fill axons with reaction product after the use of a cobalt‐enhanced diaminobenzidine procedure. These preparations show that shafts of axons in the tectothalamic tract give rise to thinner, primary collaterals that enter nucleus rotundus from its caudolateral aspect and form sparsely branching arbors within the nucleus. Very thin secondary collaterals branch from these collaterals bear terminal collaterals with frequent varicosities. Although the total size of such arbors is unknown, the evidence suggests that each arbor is large in relation to the size of nucleus rotundus. Thus, injection sites restricted to central tectum label axons throughout nucleus rotundus. Second, subtotal lesions of the tectum produce degeneration throughout nucleus rotundus in silver degeneration preparations. Finally, analysis of electron microscopic degeneration material indicates that tectal boutons are distributed along the full lengths of the dendrites of rotundal neurons, but not on their somata. These boutons form asymmetric synaptic junctions and contain round synaptic vesicles.

In view of the relatively large size of the dendritic fields of rotundal neurons, these data suggest that the tectorotundal projection is both strongly convergent on individual neurons and strongly divergent from single tectorotundal axons. This type of organization is consistent with physiological evidence that rotundal neurons have receptive fields that cover at least one‐half of the contralateral visual field and often include the entire hemifield. It seems unlikely that nucleus rotundus can be involved in neuronal transactions that preserve detailed spatial information, but it may be involved in processing information on other visual parameters such as stimulus velocity or color.
Exteroceptive and proprioceptive afferents of the trigeminal and facial motor nuclei in the mallard (Anas platyrhynchos L.)
Authors: Arends Joseph J. A. , Dubbeldam Jacob L.
Published: January 2005

Central pathways converging upon the trigeminofacial motor nuclei of the mallard were studied in order to elucidate neuroanatomically the presumed influence of primary sensory trigeminal afferents upon jaw muscle activity. The techniques used included the Fink‐Heimer I method after lesions, and axonal transport labeling following injections of 3H‐leucine or of HRP for retrograde identification of the neurons of origin.

A general description is given of the trigeminofacial motor complex. Jaw closer muscles are innervated by trigeminal motor neurons, and facial motor neurons innervate the jaw depressor muscles. Two afferent premotor systems, one including the mesencephalic trigeminal nucleus (MesV) and the other the rhombencephalic reticular formation, are distinguished. The proprioceptive neurons of the mesencephalic trigeminal nucleus project upon the ipsilateral trigeminal motor nucleus and upon the nucleus supratrigeminalis. The latter cell group bilaterally projects upon the dorsal and intermediate parts of the facial motor nucleus and upon part of the trigeminal motor nucleus. Exteroceptive information, relayed through the primary sensory trigeminal column (PrV and nTTD), ultimately reaches the motor nuclei via the reticular formation. The reticular formation forms the final link of three separate circuits: a telencephalic one entered through the principal trigeminal sensory nucleus, a cerebellar one via subnucleus oralis of the descending trigeminal system, and a direct one via subnucleus interpolaris. No direct connections between the principal trigeminal sensory nucleus or subnuclei of the descending trigeminal system and the motor nuclei of the trigeminal (NV) and facial (NVII) nerves have been observed, nor are such direct projections present in the outflow of the presumed telencephalic and cerebellar circuits, viz. of the archistriatum and the central cerebellar nuclei, respectively. The archistriatum projects via the occipitomesencephalic tract upon the lateral rhombencephalic reticular formation as far down as the rostral cervical cord, as well as upon the subnucleus interpolaris of the descending trigeminal system. Similarly, efferents from the central cerebellar nuclei reach the reticular formation, which in turn projects bilaterally upon the motor nuclei. Finally, commissural intermotor connections apparently are mediated by reticular cells surrounding the motor nuclei of NV or NVII, rather than emanating from these nuclei directly.
Light and electron microscopy of the photoreceptors in the retina of the red‐eared slider, Pseudemys scripta elegans
Authors: Kolb Helga , Jones Jill
Published: January 2005

The six different types of photoreceptor in the retina of the turtle Pseudemys scripta elegans have been studied by light and electron microscopy. Fresh whole‐mount retina, in which the oil droplet colors of the photoreceptors could be seen, was compared with fixed tissue cut in the vertical plane. The red single cone (large red oil droplet) is largest in diameter and, in electron microscopy (EM) views, has the least opaque oil droplet. It also has a vacuolated paraboloid and a cone pedicle that ends at the intermediate level of the outer plexiform layer (OPL). The green single cone (yellow medium‐size oil droplet) has a thinner inner segment and uniformly vacuolated paraboloid. Its cone pedicle ends at the same level as that of red cones. The blue cone (small colorless oil droplet) has an obliquely running axon joining cell body to cone pedicle that lies innermost in the OPL. Double cones are recognizable by their adherent cell bodies and inner segments. The accessory member (green cone) lacks an oil droplet but has a distinct large paraboloid while the principal member (red cone) has an oil droplet (orange) lying more distal than oil droplets of other cone types. The axons of the double cones are separated by glia but have closely apposed pedicles ending above those of the single cones in the outermost level of the OPL. Rod photoreceptors have a large outer segment, no oil droplet, and a lowlying cell body continuous with the pedicle, which ends, like those of the double cones, at the outermost level of the OPL.
Target regulation of synaptic number in the compressed retinotectal projection of goldfish
Authors: Murray Marion , Sharma Sansar , Edwards Michael A.
Published: January 2005

In order to determine the morphological consequences of the formation of a compressed retinotectal projection, the optic neuropil lamina (stratum fibrosum et griseum superficialis, SFGS) was examined in large goldfish 3 months to 4 years after ablation of the caudal half of the tectum, both with crush of the optic nerve (HTX) and without (HT). In semithin sections, the SFGS, as delineated with orthograde HRP labeling, shows a persistent hypertrophy of about 25% in HTX and HT groups. Comparison of ultrastructural stereological data with similar data on control and regenerated projections to intact tecta (Murray and Edwards, '82) indicates that this hypertrophy can be attributed largely to an increased number of axons and not to increases in terminal or dendritic compartments. A normal number of synaptic terminals per column through SFGS is conserved in HTX and HT groups. Planimetric analysis and observations using orthograde HRP labeling reveal no group differences in size and shape of terminal profiles. The same number of retinal ganglion cells project to a half‐tectum as to an intact tectum, as indicated by estimates of ganglion cell number and of the minimum percentage of them which project to the tectum using retrograde HRP labeling.

The results suggest that the regenerating and sprouting optic axons participating in the formation of a compressed retinotopic projection compete for a limited accommodation in the SFGS and that this capacity to accept synaptic input becomes saturated at the control innervation density. The results are consistent with the formation of a smaller than normal number of terminals per optic axon, numerical estimates for which are given. If the percentage of terminals which are optic does not change, then the number of terminals per axon is reduced by about 40%.
Spinal cord development in anuran larvae: I. Primary and secondary neurons
Authors: Forehand Cynthia J. , Farel Paul B.
Published: January 2005

The spinal cord of the bullfrog (Rana catesbeiana) tadpole contains primary neurons, born during embryonic stages, and scondary neurons born for the most part during larval stages. Electrophysiological and anatomical characteristics of these two categories of neurons were examined during larval development to trace the development of secondary neurons and to determine whether primary neurons persist into adult life or are replaced by secondary neurons. Five classes of primary neuron were identified on the basis of their distinctive locations, morphologies, cytoplasmic melanin content, and presence at the earliest larval stages examined: primary motoneurons, Rohon‐Beard cells, commissural cells, dorsal marginal cells, and anterolateral marginal cells. Secondary neurons of the lateral motor column and dorsal root ganglia underwent extensive developmental changes during larval life manifested both in anatomical studies with horseradish peroxidase and electrophysiological experiments on the isolated spinal cord. Primary motoneurons that innervate the tadpole tail were not found in the adult, although those innervating thoracic musculature persisted, as did at least some primary neurons projecting to other spinal segments or brainstem. Primary neurons are thus replaced or maintained through metamorphosis depending on their class and location.
Influence of neonatal cochlear removal on the development of mouse cochlear nucleus: I. Number, size, and density of its neurons
Authors: Trune Dennis R.
Published: January 2005

Right cochleae were aspirated from 6‐day‐old mice to determine the influence of cochlear integrity on the development of cochlear nucleus (CN). At 45 days of age, cochlear destruction was confirmed histologically, and the CN of unilaterally deafferented and control animals were analyzed morphometrically. The molecular, fusiform, and polymorphic layers of deafferented dorsal CN were reduced in volume, and the polymorphic layer neurons were fewer, smaller, and less dense. The octopus and multipolar cell regions in deafferented ventral CN (VCN) were smaller, and their neurons were fewer, smaller, and more densely packed. The VCN globular and small spherical cell regions were also smaller with fewer, denser, but normal‐sized neurons. There were fewer VCN large spherical cells, but no change was measured in their size. The granule cell regions throughout CN were also reduced in volume. Overall, CN was reduced to 46% of its normal size and 34% of its normal neuronal numbers. These results in the mouse show that deafferentation before the onset of hearing causes more severe CN changes than those reported after adult deafferentation in other mammals and support the theory of a critical period in development when presynaptic integrity is much more important for neuronal maturation than it is for maintenance after the neuron is mature. This suggests that any congenital pathology that compromises the sensorineural structures of the cochlea may cause severe structural and functional abnormalities in the maturing central auditory nuclei.
Retinofugal pathways in juvenile and adult channel catfish, Ictalurus (Ameiurus) punctatus: An HRP and autoradiographic study
Authors: Rao P. D. Prasada , Sharma S. C.
Published: January 2005

The retinal projections of the juvenile and adult channel catfish, Ictalurus (Ameiurus) punctatus, were studied by using horseradish peroxidase (HRP) and autoradiography. The contralateral optic tract sends fibers to the suprachiasmatic nucleus (SCN) and divides into lateral (LOT) and medial optic tracts (MOT). In the adult fish, the former is thicker than the latter, whereas in the juvenile form, the reverse is true. The MOT curves laterally and divides into eight to 15 medial fascicles of the optic tract (MFOT). The contralateral optic fibers project to the nucleus opticus dorsolateralis, nucleus of the posterior commissure, nucleus geniculatus lateralis, pretectal nuclear complex, nucleus corticalis, stratum fibrosum et griseum superficiale (SFGS), and a few optic fibers extend into the stratum griseum centrale. The tractus opticus accessorius arises from the postero‐dorsal margin of the LOT and extends ventromedially to project to the nucleus opticus accessorius. At the optic chiasm a few fibers do not decussate, and these fibers project to almost all ipsilateral sites similar to those of the contralateral side, including the optic tectum. The autoradiographic observations substantiated the analysis of optic fiber projections provided by the HRP technique.
Parasympathetic preganglionic neurons and visceral primary afferents in monkey sacral spinal cord revealed following application of horseradish peroxidase to pelvic nerve
Authors: Nadelhaft I. , Roppolo J. , Morgan C. , de Groat W. C.
Published: January 2005

Horseradish peroxidase (HRP) applied to the central stump of the transected pelvic nerve of rhesus monkeys labeled afferent and efferent neurons innervating the pelvic viscera. Preganglionic neurons forming the sacral parasympathetic nucleus (SPN) were located in a narrow band 150–200 μm wide on the border of the ipsilateral intermediate gray matter. The SPN contained an average of 820 neurons and characteristically extended over two or three sacral segments (average length: 14.5 mm) with the majority of cells in S2. It was composed of medium sized, elongated somata (15.7 × 30.7 μm) with their major axes in the transverse plane and oriented parallel to the lateral border of the gray matter. Dendrites extended deep into the lateral funiculus, horizontally into the medial dorsal gray commissure, and dorso‐laterally along the lateral edge of the dorsal horn. Preganglionic axons followed the lateral border of the ventral horn to the ventral rootlets.

Pelvic nerve afferent axons carried HRP to neurons in the dorsal root ganglia (DRG) and by transganglionic transport to the spinal cord. The average number of labeled DRG cells was 2, 992 (range: 2, 193–4, 363) with the largest fraction (80%) in S2. The numbers of DRG cells correlated with the numbers of SPN cells in corresponding spinal cord segments. Within the spinal cord labeled primary afferent fibers were prominent in the sacral segments and were also observed in decreasing numbers within two to three segments beyond the rostral and caudal limits of the SPN. In transverse sections, primary afferents were found throughout Lissauer's tract (LT) and in the lateral half of the dorsal columns. A prominent collateral fiber bundle from LT was located in lamina I along the lateral edge of the dorsal horn. This bundle extended into the SPN and a few collaterals continued medially into the dorsal gray commissure and the contralateral side of the cord. A much less prominent collateral fiber group from LT passed medially over the apex of the dorsal horn in lamina 1 and descended into the dorsal gray commissure. Horizontal sections revealed that these two collateral pathways were organized into periodically spaced bundles of fibers about 250 μm apart. HRP reaction product in terminal fields related to these afferent collateral projections were found in the lateral marginal zone and bilaterally in the dorsal gray commissure.
Direct projections from the cerebellar nuclei to the superior colliculus in the rabbit: An HRP study
Authors: Mizuno Noboru , Sugimoto Tetsuo , Itoh Kazuo , Kudo Motoi , Uchida Kuniko
Published: January 2005

Cerebellar projections to the superior colliculus in the rabbit were studied by the anterograde and retrograde HRP methods. Cerebellotectal fibers arise mainly from the anterior and posterior interpositus nuclei and terminate contralaterally in layer VII, layer VI, layer V, and the deep tier of layer IV of the superior colliculus. Cerebellotectal fibers from the posterior interpositus nucleus originate from the lateral part of the nucleus and end chiefly in the caudal part of the superior colliculus. Cerebellotectal fibers from the anterior interpositus nucleus arise from the ventral part of the nucleus and terminate mainly in the rostromedial part of the superior colliculus. Some neurons in the lateral cerebellar nucleus also send fibers contralaterally to the intermediate and deep layers of the superior colliculus, especially to its rostral and lateral parts. Few, if any, Cerebellotectal fibers arise from the medial cerebellar nucleus.
Pathways of the electric organ discharge command and its corollary discharges in mormyrid fish
Authors: Bell C. C. , Libouban S. , Szabo T.
Published: January 2005

The motoneurons which innervate the mormyrid electric organ are driven by a descending volley from the medullary relay nucleus. This nucleus does not initiate the electric organ discharge (EOD) but is driven in an obligatory manner by another center, a command nucleus. One goal of the present study was to identify this command nucleus anatomically. A second goal was to determine the pathways by which corollary discharges of the EOD motor command exert their effects on sensory input to the electrore‐ceptive lateral line lobe.

Horseradish peroxidase (HRP) was injected into the medullary relay nucleus and other EOD command‐related centers. Placement was guided by recording the electrical activity preceding the EOD.

A nucleus of smaller cells is found immediately beneath the large cells of the medullary relay nucleus. This nucleus, nucleus C, projects densely to the medullary relay nucleus and is hypothesized here to be the command nucleus. Nucleus C appears to receive input from the mesencephalon and from unspecified sources of input to the nearby reticular formation.

Nucleus C projects to the medullary relay nucleus and to a lateral nucleus, the bulbar command‐associated nucleus. This nucleus is probably the source of the corollary discharge signals. It projects to the medullary relay nucleus and to the paratrigeminal and mesencephalic command‐associated nuclei. The latter two nuclei project to separate regions which in turn project to the electroreceptive lateral line lobe. There are thus at least two different paths by which the presumed EOD command nucleus, nucleus C, can affect the electroreceptive lateral line lobe.
Opiate receptor localization in rat cerebral cortex
Authors: Lewis Michael E. , Pert Agu , Pert Candace B. , Herkenham Miles
Published: January 2005

The differential distributions of [3H]naloxone‐labeled and [3H]D‐Ala‐D‐Leu‐enkephalin‐labeled opiate receptors in rat cerebral cortex were localized autoradiographically and quantified by grain counting and computerized densitometry. In addition, receptor distributions were compared to terminal patterns of thalamocortical projections labeled by axoplasmion transport of [3H]amino acids. Opiate receptors labeled with [3H]naloxone ligand selectivity pattern show striking laminar heterogeneity and are densest in limbic cortical areas, intermediate in the motor cortex, and fewest in the primary sensory areas. By contrast, opiate receptors labeled with [3H]D‐Ala2‐D‐Leu5‐enkephalin in a delta ligand selectivity pattern are much more homogeneously distributed across both regions and laminae within regions.

Mu receptors in most cortical areas have density peaks in layers I and VI and each peak shows a density gradient that is sloped within the layer so that the highest densities are at the most superficial and the deepest portions of cortex. In addition, there is an intermediate peak whose laminar position varies depending on the area in which it is found. In rostral agranular cortex, including limbic and motor areas, the [3H]naloxone binding peaks are in layers I, III, and VI. In primary somatosensory cortex, the intermediate peak is in layer Va and in most of remaining homotypical cortex it is in layer IV. Some areas have only bilaminar labeling, in superficial and deep layers; these include portions of the sulcal and retrosplenial cortices. Piriform and entorhinal cortices have dense [3 H]naloxone binding only in the deepest layer and show a descending gradient of density toward the superficial layer.

The positions of the mu receptor peaks were compared with termination patterns of projections originating in the thalamus. Close correspondence was found between receptor binding in the prelimbic, primary somatosensory, and entorhinal areas and projection terminations arising from the thalamic mediodorsal, posterior, and central medial nuclei, respectively.

Although regional variations in [3H]D‐Ala2‐D‐Leu5‐enkephalin‐labeled receptor density are uncommon, a gradual decrease in the number of sites along the dorsomedial wall of the cortex from anterior cingulate to caudal retrosplenial limbic cortex can be observed. Laminar variations in binding density are small as well; higher concentrations of the peptide binding sites are usually found in the deep cortical layers. These findings emphasize aspects of opiate receptor architecture which may be relevant to identifying cortical “opiatergic” neurocircuitry and raise the possibility of opiate modulation of thalamocortical transmission.
Programmed cell death in the nervous system of an adult insect
Authors: Truman James W.
Published: January 2005

The tobacco hornworm moth, Munducasexta, shows extensive degeneration of abdominal neurons after the adult moth emerges (ecloses) from the old pupal skin. Death of interneurons begins about 2 hours before eclosion and continues through the next 30 hours. Motorneuron degeneration starts slightly later, commencing at about 8 hours after eclosion. Analysis of the death of identified motorneurons showed that there was a precise spatial and temporal program of neuronal death. Particular cells invariably either continued to live or died and, among the latter, the time of death varied from cell to cell but for a given cell was constant. This program of cell death was somewhat flexible in that the fates of certain cells could be adaptively modified by behaviors that might naturally occur in the life of the insect.