bluuebunny/crossref_metadata_2025 huggingface dataset:
Telencephalic ascending acousticolateral system in a teleost (sebastiscus marmoratus), with special reference to the fiber connections of the nucleus preglomerulosus
Authors: Murakami Takeshi , Fukuoka Toshio , Ito Hironobu
Published: January 2005

Acousticolateral systems were examined by means of the horseradish peroxidase tracing method in a teleost (Sebastiscus marmoratus). The torus semicircularis projected bilaterally to the optic tectum, nucleus ventromedialis thalami of Schnitzlein ('62), and reticular formation; contralaterally to the torus semicircularis; and ipsilaterally to the nucleus preglomerulosus of Schnitzlein ('62) and the inferior olive. No topographic organization was detected between the torus semicircularis and the nucleus preglomerulosus. Ipsilateral inputs to the torus were from dorsal telencephalic areas (pars centralis, Dc; pars dorsalis, Dd; and the dorsal part of pars medialis, dDm) and the optic tectum. Contralateral inputs to the torus were from the torus semicircularis, a caudal part of the cerebellum; and a portion of the trigeminal complex. The torus also received bilateral input from the nucleus ventromedialis thalami, nucleus of lemniscus lateralis, nucleus medialis, anterior octaval nucleus, descending octaval nucleus, and the reticular formation. Retrogradely labeled cells in the octaval nuclei were seen predominantly subsequent to HRP injections in the medial torus, while cells in the nucleus medialis were retrogradely labeled following injections into the lateral torus. HRP injections into the nucleus preglomerulosus labeled cells in the superficial region of the torus, while injections into the nucleus ventromedialis thalami labeled cells in the deep region. The nucleus preglomerulosus received inputs bilaterally from the nucleus of the lemniscus lateralis and reticular formation and ipsilaterally from the dorsal telencephalic areas (Dc, Dd, and dDm) and the torus semicircularis. In turn the nucleus preglomeru'‐osus projected to Dd and Dm. Fibers arising in the nucleus ventromedialis thalami ended in Dc, Dd, Dm, and area ventralis pars supracommissuralis (Vs).

Homology between the nucleus preglomerulosus and the central thalamic nucleus in amphibians, the nucleus reuniens in reptiles, the nucleus ovoidalis in birds, and the medial geniculate body in mammals is discussed.
Neuropeptide‐Fmrfamide‐Like immunoreactivity in drosophila: Development and distribution
Authors: White Kalpana , Hurteau Teresa , Punsal Patricia
Published: January 2005

Neuropeptide‐FMRFamide‐like immunoreactivity was characterized in the fruit fly, Drosophila melanogaster. In the adult central nervous system, a stereotypic pattern of immunoreactive cell bodies and immunoreactive nerve processes and varicosities was observed, indicating a neurochemical role for FMRFamide‐like substance(s) in Drosophila. Localization of immunoreactivity in the central nervous system of early larval stage revealed that the majority of the prominent FMRFamide‐like immunoreactive neurons were already differentiated. The FMRFamide‐like immunoreactive neurons remain immunoreactive throughout postembryonic stage and persist in the adult central nervous system. In the larva, in addition to the central nervous system, FMRFamide‐like immunoreactivity was localized in the fibers innervating the ring gland, in the ganglion innervating the gut and in the gastric caeca.
Physiology and morphology of the lamina i spinomesencephalic projection
Authors: Hylden Janice L. K. , Hayashi D. R. Haruhide , Dubner Ronald , Bennett Gary J.
Published: January 2005

We have examined the physiological and morphological characteristics of spinal dorsal horn lamina I neurons with projections to the midbrain in the cat by combining physiological recording of neurons with the intracellular injection of HRP. Lamina I spinomesencephalic neurons were antidromically activated from the region that included the cuneiform nucleus and lateral periaqueductal gray at the intercollicular level. The majority of mesencephalic projection neurons (50 of 55) responded exclusively to noxious stimulation (nociceptive‐specific) of their peripheral receptive fields. Lamina I spinomesencephalic neurons were activated from both the ipsilateral and contralateral midbrain and had slow antidromic conduction velocities (1 to 18 m/second). We identified eight cells with projections to both the midbrain and the thalamus and eight cells that were antidromically activated only from the thalamus. Intracellular injection of HRP revealed that lamina I spinomesencephalic neurons were of diverse morphological types, but generally had extensive, rostrocaudally oriented, dendritic arbors confined to lamina I and the overlying white matter. Axons were observed on nine of the HRP‐filled spinomesencephalic neurons; five of the axons issued collateral branches. The morphological characteristics of these neurons did not appear to correlate with functional categories (i.e., wide‐dynamic‐range‐ or nociceptive‐specific‐type neurons). The large number of nociceptive‐specific neurons with projections to the midbrain and the interconnections of these midbrain sites with hypothalamic and limbic structures suggest that the lamina I spinomesencephalic pathway plays an important role in the autonomic and affective responses to pain.
Influence of reduced neuron pool on the magnitude of naturally occurring motor neuron death
Authors: Sohal G. S. , Stoney S. D. , Arumugam T. , Yamashita T. , Knox T. S.
Published: January 2005

The present investigation was undertaken to examine the role of peripheral competition in survival of motor neurons during development. A loss of approximately half of the trochlear motor neurons in duck and quail occurs during the course of normal embryogenesis. The number of motor neurons in the nucleus of quail prior to the onset of cell death is identical to the final number of survivors in the nucleus of duck embryos (about 1,300 neurons). In the present study competition at the peripheral target was decreased by reducing the number of trochlear motor neurons initially projecting to their target muscle. This was accomplished by substituting the midbrain of duck embryos with the same neural tissue from quail embryos. Midbrain transplantation was performed before motor axon outgrowth and normal cell death begin. The development of the motor neurons and their sole target of innervation, the superior oblique muscle, was examined by using a variety of techniques. The source of the grafted motor neurons and of a reduction in the size of the motor neuron pool was confirmed from histological sections and cell counts. The grafted motor neurons projected their axons into the appropriate peripheral target, which was determined by the use of HRP tracing techrique. Counts of muscle fibers, motor endplates, and acetylcholine receptors and measurement of total muscle protein indicated that the size of the superior oblique muscle in the chimera embryos was similar to that of the normal duck but significantly larger than the muscle in quail embryos. Electrophysiological observations indicated that the grafted trochlear motor neurons made functional connections with the superior oblique muscle. Counts of the trochlear motor neurons after the period of cell death indicated an average of 1,310 neurons in the nucleus of duck, 772 in quail, and 690 in the chimera embryos. The number of motor neurons in the chimera embryos is not significantly different from that in the normal quail. In other words, in spite of reduced peripheral competition trochlear motor neuron death of normal magnitude occurred. Lack of increased cell survival in our study suggests that trochlear motor neurons do not compete for survival at the peripheral target.
Projections to the superior temporal sulcus from the central and peripheral field representations of V1 and V2
Authors: Ungerleider Leslie G. , Desimone Robert
Published: January 2005

In a series of three studies, we have begun to explore the sequence of visual information processing along the pathway from striate cortex (V1), through MT, into the parietal lobe. In this first study, we sought to establish the relationships among MT, the heavily myelinated zone of the superiortemporal sulcus (STS), and the V1 and V2 projection fields in the STS.

Autoradiographic material from seven hemispheres of six macaques injected with tritiated amino acids into either V1 or V2 was analyzed in detail, and the results were plotted onto two‐dimensional reconstructions of the STS. Autoradiographic material from eight additional macaques with V2 injections was also examined.

The results indicate that the central visual field representations of both V1 and V2 project into the heavily myelinated zone in the lower bank and floor of the STS, confirming prior studies, whereas the far peripheral representations of both V1 and V2 project into the cortex medial to this zone on the upper bank of the sulcus. There is no evidence that this medial cortex is a separate area that receives projections from V1 and V2 in parallel with the projections these areas send to the heavily myelinated zone. Rather, there seems to be a single projection field of V1 and V2 whose central representation lies within the heavily myelinated zone and whose most peripheral representation lies medial to it.

Because of the difference in myelination between the central and peripheral field representations as well as visuotopic anomalies between them, we retain the term “MT” for the heavily myelinated zone and apply the term “MTp” to the far peripheral projection zone. Both MT and MTp are required to process the complete outputs of V1 and V2 within the STS and thus should probably be regarded as two distinctive parts of a single visual area. The difference in myelination between MT and MTp suggests that there is a difference in visual processing between the central and peripheral visual fields. The average size of MT is estimated to be 62 mm2, and the average size of MT and MTp combined to be 76 mm2, which is consistent with estimates derived from several other studies.
Development of cell and fiber lamination in the mouse superior colliculus
Authors: Edwards M. A. , Caviness V. S. , Schneider G. E.
Published: January 2005

The emergence of laminar organization in the superior colliculus was investigated in the mouse with several anatomical methods, including tritiated‐thymidine autoradiography, Golgi impregnation, and general stains for cell bodies and for fibers. The sequence of neurogenesis, cell migration, and early morphological differentiation of neurons was shown to exhibit a discontinuity between the lower and upper divisions (i.e., between the deep and intermediate “gray” and “white” layers and the superficial “gray” and “white” layers). These events proceed in an inside‐out order within the lower division, but tho same events within the upper division commence in advance of the completion of this progression. Thus, peak generation times for layers of the lower division proceed from (embryonic day) E11 to E13 and for the upper division from E12 to E13. Cell migration, as monitored with tritiated‐thymidine labelling, reflects closely the pattern of cytogenesis. This is most clearly evident on E15 when a population of E11‐labelled cells is divided into superficial and deep layers (the strata superficiale and profundum–SS and SP) by the interposition of E13‐labelled cells at an intermediate level (stratum inter medium–SI). A contingent of the latter cells continue their migration and join their predecessors within the SS on E17, a time point when cell migrations are largely complete. Paralleling this sequence of arrival of neurons and the formation of three primary layers, both the time course of accumulation of fiber fascicles and the early morphological differentiation of neurons in the interval from E13 to E17 tends to proceed from SP to SS and from SS to SI. Thus, the transverse fiber system and large multipolar neurons of SP develop in advance of the longitudinal fiber system and vertically oriented neurons of SS, which in turn develop precociously with respect to the longitudinal fibers and medium‐sized multipolar neurons of SI. In contrast, later events of differentiation that underly a major radial growth and an architectonic sublamination of the primary strata proceed in a simpler inside‐out sequence from E17 to (postnatal day) P6. The major morphogenetic events underlying the establishment of statification in the colliculus appear to involve the operation of relatively independent programs of assembly for the two basic subdivisions. It is probable that selective cell‐cell interactions contribute to the delivery of concurrently generated neurons to different laminae as well as to the deployment of axons in a manner that respects laminar boundaries.
Distribution of galaninlike immunoreactivity in the rat central nervous system
Authors: Melander Tor , Hökfelt Tomas , Rökaeus Ake
Published: January 2005

The localization of galanin (GAL) immunoreactive (IR) neuronal structures in the rat central nervous system has been investigated by using the indirect immunofluorescence technique. GAL‐IR structures were seen in high concentrations in the hypothalamus, medulla oblongata, and spinal cord. Less extensive systems were detected in the telencephalon, thalamus, mesencephalon, and pons, while virtually no GAL‐positive structures were seen in the olfactory bulb and cerebellum.

Major populations of cell bodies staining for GAL‐like material were seen in many areas. In the telencephalon somata were revealed in the bed nucleus of stria terminalis, in the nucleus of the diagonal band, medial septum, and in the medial aspects of the central amygdaloid nucleus, and in small numbers in cortical areas. The anterodorsal and periventricular nuclei of the thalamus contained positive cell bodies. In the hypothalamus GAL‐IR somata were seen in the medial and lateral preoptic nuclei, arcuate nucleus, periventricular nucleus, in the dorsomedial nucleus, in the medial forebrain bundle area, in the tubular, caudal, accessory, supraoptic, and paraventricular magnocellular nuclei and lateral to the mammillary recess. The dorsal raphe nucleus hosted a large number of GAL‐positive somata. Locus coeruleus of the pons contained a large number of GAL‐IR perikarya. In the medulla oblongata positive somata were found in the caudal spinal trigeminal nucleus, the nucleus of the solitary tract, and in the ventral lateral area just rostral to area postrema. Small cell bodies were detected in the superficial layers of the dorsal horn of the spinal cord at all levels and in lamina X at lumbar levels.

Analysis of GAL‐positive fibers in the telencephalon revealed highly or medium‐dense networks in the lateral septal nucleus, in the bed nucleus of stria terminalis, and in the central and medial amygdaloid nuclei. Positive fibers were found in the thalamus in and around the periventricular nucleus as well as to the lateral habenular nucleus and extending in a lateral, caudal direction from the third ventricle and fasciculus retroflexus to the lateral tip of the medial lemniscus. In the hypothalamus the external layer of the median eminence contained a very dense fiber network. Dense or medium‐dense GAL‐IR networks were detected in the periventricular nucleus, throughout the medial and lateral preoptic areas, in the medial forebrain bundle area, in the dorsomedial nucleus, and lateral to the mammillary recess. In the pons GAL‐IR fibers were seen in the parabrachial nuclei, dorsal to the superior olive, and in the periaqueductal central gray. The external layers of the caudal spinal trigeminal nucleus, the nucleus of the solitary tract, and the ventral portions of the medulla oblongata contained extensive positive fiber networks. In the spinal cord GAL‐IR fibers were noted in high numbers in the superficial layers (lamina I and II) of the dorsal horn and at lumbar and sacral levels in lamina X.
The accessory optic system in a prosimian primate (Microcebus murinus): Evidence for a direct retinal projection to the medial terminal nucleus
Authors: Cooper H. M.
Published: January 2005

The accessory optic system (AOS) was studied in the prosimian primate, Microcebus murinus, by using intraocular injections of the anterograde tracers 3H‐proline and horseradish peroxidase (HRP). Retinal fibers were found to terminate bilaterally in all three mesencephalic AOS nuclei as defined by Hayhow ('66, J. Comp. Neurol 126:653‐672). In contrast to previous reports in primates, we find that both the ventral and dorsal divisions of the medial terminal nucleus (MTN) receive projections from the retina. The ventral MTN is composed of a compact triangular group of cells, situated at the medial base of the cerebral peduncle, rostral to the rootlets of the third cranial nerve. The dorsal MTN extends dorsomedial to the substantia nigra and is composed of characteristic fusiform cells embedded in a fibrous neuropil. Although the cells of the dorsal MTN intermingle somewhat with the nigral cells, the nucleus is clearly distinguished by cytoand myeloarchitectural features. The large lateral terminal nucleus (LTN) receives a dense projection from the retina and forms a prominent bulge on the lateral surface of the cerebral peduncle. The dorsal terminal nucleus (DTN) is located between the brachia of the superior and inferior colliculi, near the origin of the superior fasciculus of the accessory optic tract (AOT). This fasciculus is composed of anterior, middle, and posterior branches. In addition, a ventral group of fibers, corresponding to the inferior fasciculus of the AOT previously described in nonprimates, was identified in all planes of section. The results confirm the existence of a common plan of AOS organization in mammals.
Lectins demarcate the barrel subfield in the somatosensory cortex of the early postnatal mouse
Authors: Cooper Nigel G. F. , Steindler Dennis A.
Published: January 2005

Plant lectins were used to examine the disposition of glycosylated molecules in vibratome sections through the barrel subfield of mouse somatosensory cortex at selected times during postnatal development. The peroxidase conjugates of peanut agglutinin (PNA, specific for N‐acetygalactosamine), concanavalin A (specific for mannose), and wheat germ agglutinin (specific for N‐acetylglucosamine and N‐acetylneuraminic acid) were used to study lectin binding in aldehyde‐fixed tissue sections of cortex. Following peroxidase cytochemistry and light microscopy, it was found that all three lectins bound in the region of the barrel subfield as early as postnatal day 3 (day of birth = postnatal day 1). The lectins bound to the prospective sides and/or septae of individual barrels in preference to the prospective hollows. This lectin demarcation of the barrel field occurred prior to the detection of this region with cresyl violet staining and was still demonstrable on postnatal day 6, when the individual barrels became discernible with cresyl violet. This suggests that the lectin binding material is present before tie barrel field becomes a fully formed and organized region. A decrease in lectin affinity for binding sites in these tissue sections occurs during postnatal development (Cooper and Steindler: Soc. Neurosci. (Abstr.) 10: 43a, '84) and this study demonstrates that lectins do not delineate the barrel field of more mature animals (2‐3 months old), whereas barrels can be detected with cresyl violet at this time. A preliminary electron microscope analysis of the postnatal day 6 somatosensory cortex demonstrates that the lectin PNA binds to elements of the forming neuropil and also to Golgi apparatus intermediate saccules in neuronal cells. The prospective barrel field can be detected with lectins during a critical period in development in which alterations can occur in the barrel field in response to peripheral deprivation (Jeanmonod et al: Neuroscience 6:1503‐35, '81) and therefore we suggest that the glycans visualized with lectin‐peroxidase conjugates denote possible candidates for molecules involved in shaping barrel structure.
Metamorphosis of the cerebral neuroendocrine system in the moth Manduca sexta
Authors: Copenhaver Philip F. , Truman James W.
Published: January 2005

We have examined the morphology and neuronal elements of the cerebral neuroendocrine system in the larval, pupal, and adult stages of the moth Manduca sexta with a variety of neuroanatomical techniques. The larval brain contains several discrete groups of neurosecretory and non‐neurosecretory cells that project to the associated neurohemal organs (the corpora cardiaca‐allata complex, or CC‐CA) and to a variety of more peripheral structures. A previously undescribed set of cells in the subesophageal ganglion have also been found that project out the neurosecretory nerves.

During metamorphosis, the cerebral neuroendocrine system undergoes a dramatic structural reorganization, including the reduction or loss of many larval nerves and a repositioning of the cell groups and their dendritic fields. Despite these changes, most of its central elements are retained. In addition, by the completion of adult development a new cluster of cells can be found on either side of the dorsal midline of the brain. We have also determined the relative contributions of the different cell groups to the moth neuroendocrine system by intracellular iontophoresis of dye into individual cells. Within the dorsal protocerebrum, five separate morphological types of cells can be recognized, each with a distinctive pattern of dendritic arborization in the brain and terminal neurohemal processes that project to the CC, the CA, the aorta, or to a combination of these regions. The large intrinsic cells of the CC have also been filled, revealing an unusual set of morphological features in these peripheral neurosecretory cells.
Degeneration and regeneration of peripheral nerve in the rat trigeminal system. II. Response to nerve lesions
Authors: Renehan William E. , Munger Bryce L.
Published: January 2005

The course of vibrissa sensory receptor denervation and subsequent reinnervation was studied following transection or crush of the rat infraorbital nerve. Eighteen hours after nerve lesion, the large‐diameter myelinated nerves supplying the lanceolate receptors of the intermediary zone and the Merkel cells of the stratum basale contained areas of focal axoplasmic abnormalities, and some of the nerve terminals exhibited vacuolization, mitochondrial swelling, and disruption of the neurofilament pattern. The Merkel cells and lanceolate receptors of the intermediary zone were completely deafferented by 24 hours after the nerve injuries. The Ruffini complex, free nerve endings and lanceolate receptors of the inner conical body, as well as the free nerve endings and lanceolate receptors of the connective tissue below the Ringwulst, were completely normal 24 hours after crush or transection of the nerve. These receptors underwent progressive degeneration from days 2 through 6 and the vibrissa was totally denervated by day 7. Regenerating axons were first seen entering the vibrissae 2 weeks after the crush lesion and 1 month following nerve transection. Except for a slight decrease in the percentage of Merkel cells innervated, vibrissae from postcrush animals were virtually indistinguishable from normal by 3 months. In contrast, vibrissae from rats subjected to the transection lesion exhibited evidence of misdirected axons and abnormally reinnervated receptors throughout the course of regeneration. Axons entering the hairs with the main vibrissal nerve were observed contributing to the innervation of the inner conical body, an area normally supplied exclusively by the conus nerve. Many of the lanceolate receptors contained multiple unmyelinated axons, and the usually highly ordered circular innervation of the inner conical body was markedly abnormal. It is suggested that these results may help explain the faulty sensory localization and abnormal sensations reported by patients suffering a peripheral nerve injury.
The distribution of choline acetyltransferase in the rat amygdaloid complex and adjacent cortical areas, as determined by quantitative micro‐assay and immunohistochemistry
Authors: Hellendall R. P. , Godfrey D. A. , Ross C. D. , Armstrong D. M. , Price J. L.
Published: January 2005

The distribution of choline acetyltransferase (ChAT) within the amygdaloid complex has been studied to evaluate what should primarily represent the terminal field of the cholinergic projection from the basal forebrain. Two currently available methods have been combined for the comparison: immunohistochemistry with a monoclonal antibody against ChAT, by a double peroxidase‐antiperoxidase procedure, and quantitative histochemistry involving micro‐assay of the ChAT activity of contiguous microdissected samples. Both methods indicate prominent ChAT activity in the basolateral amygdaloid nucleus (especially rostrally), the nucleus of the lateral olfactory tract (especially layer II), and the amygdalohippocampal area. Regions of lower ChAT activity were not accurately represented, by the immunohistochemistry, but could be discriminated by the quantitative assays. Lowest activity was found in the medial nucleus of the amygdala. Most other regions had activities at least as high as average brain or neocortex. Gradients of enzyme activity were found within several regions, including the basolateral and lateral amygdaloid nuclei and the nearby posterior piriform cortex. In the piriform cortex, a region of particularly high ChAT activity was found at its medial edge near the nucleus of the lateral olfactory tract. The immunohistochemical method shows a few intensely reactive somata in layer III within this zone. Comparison of the results seen with immunohistochemistry and quantitative histochemistry suggests an advantage in using them together, since their respective strengths and weaknesses tend to complement each other.
The organization of the motoneurons innervating the axial musculature of vertebrates: II. Florida water snakes (Nerodia fasciata pictiventris)
Authors: Fetcho Joseph R.
Published: January 2005

The motor pools of axial muscles in Florida water snakes (Nerodia fasciata pictiventris) were studied by applying horseradish peroxidase (HRP) to branches of spinal nerves innervating individual muscles or groups of muscles. Motor pools of different muscles or muscle groups were located in characteristic positions in both the transverse and the longitudinal extent of the motor column. Epaxial pools were located ventromedially in the column, segregated from most hypaxial ones, which were dorsolateral. The only exception to this general rule was the motoneurons innervating the levator costae muscle. Some of the motoneurons innervating this hypaxial muscle were located in the ventral part of the motor column, like epaxial motoneurons, but they were segregated longitudinally from epaxial ones.

The arrangement of the motor pools was strikingly similar to the motor pools of presumptive homologous muscles in rats Smith and Hollyday: J. Comp. Neurol. 220:29–43, '83), even though the locomotor mechanics in the two animals are very different. The similarities may reflect a comparable relationship between the location of motoneurons in. The motor column and the location, in embryonic life, of the muscles they innervate. They also suggest that differences in the locomotor mechanics in the two species are accomplished without any dramatic reorganization of the medial motor column, in marked contrast to the substantial reorganization necessary to account for differences in the motor columns of amniotes and anamniotes.
The topography of expanded uncrossed retinal projections following neonatal enucleation of one eye: Differing effects in dorsal lateral geniculate nucleus and superior colliculus
Authors: Reese B. E.
Published: January 2005

The topographic organization of the uncrossed retinal projections to the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) was studied in normal adult hooded rats and in rats subjected to unilateral ocular enucleation on the day of birth. Sections were stained for anterograde degeneration products following discrete retinal lesions at various locations. The projection from the temporal crescent to the dLGN in neonatally enucleated rats had an expanded but topographically normal organization, with the nasotemporal and dorsoventral retinal axes displaying polarities identical to those in normal adults. Neonatal enucleation permits the remaining uncrossed retinogeniculate projection to extend primarily along the “lines of projection” into neuropil normally recipient of binocularly conjugate crossed projections. In the SC, the dorsoventral axis of the temporal crescent showed a normal polarity, but the nasotemporal axis failed to display any topographic organization. Retinal loci in the temporal crescent projected throughout the rostrocaudal extent of the ipsilateral SC. Retinal lesions placed outside the temporal crescent failed to produce any substantial degeneration in ipsilateral dLGN or SC.

These topographically distinct effects in dLGN and SC following unilateral eye removal on the day of birth are discussed in the context of differing constraints upon axonal ingrowth and connectivity during early development, which may normally bring about the characteristically distinct features of retinogeniculate and retinocollicular organization.
A light and electron microscopic analysis of the sacral parasympathetic nucleus after labelling primary afferent and efferent elements with HRP
Authors: Mawe Gary M. , Bresnahan Jacqueline C. , Beattie Michael S.
Published: January 2005

Primary afferent input to the cat sacral parasympathetic nucleus (SPN) has been examined by injury filling sacral dorsal roots, ventral roots, or both with horseradish peroxidase (HRP). Appropriate spinal segments were processed for the demonstration of HRP with diaminobenzidine and prepared for sequential light (LM) and electron (EM) microscopy.

At the LM level, a large fascicle of primary afferent fibers was observed passing ventrally along the lateral edge of the dorsal horn into the region of the SPN. Varicosities were seen throughout the course of the axons but were particularly abundant within the SPN. Injury filling of the ventral roots with HRP resulted in a Golgi‐like labelling of preganglionic neurons and their dendritic arbors, as well as ventral root afferent fibers. Swellings on both dorsal and ventral root afferent axons were observed in close apposition to labelled preganglionic neurons and their dendrites.

At the ultrastructural level, labelled afferent terminals were found to contain clear spherical vesicles; 66% of these terminals also contained at least one dense‐cored vesicle. Of particular interest was the presence of labelled dorsal and ventral root afferent terminals synapsing on labelled preganglionic neurons. Preganglionic neurons were also pestsynaptic to unlabelled terminals containing clear spherical (79.7%) or pleomorphic vesicles (20.3%). These data indicate that preganglionic neurons receive direct input from several sources, and provide the first demonstration of direct input to these cells from sensory fibers in the dorsal and ventral roots. The connections described in the present study provide interesting and, as yet, unexplored possibilities for sensory and autonomic reflex integration.
Axonal regeneration in spinal cord injury: A perspective and new technique
Authors: Borgens Richard B. , Blight Andrew R. , Murphy D. J.
Published: January 2005

A set of techniques is described for determining the response of mammalian spinal axons to transection. The logical‐selection and the advantages of these techniques are discussed. The dorsal column of guinea pig thoracic spinal cord was transected with a tungsten needle and the position of the lesion was marked by a staple‐shaped wire device (Foerster: J. Comp. Neurol 210:335–356, '82). The morphology of dorsal column axons projecting rostrally toward the lesion was examined between 1 and 50 days postlesion by anterograde staining with horseradish peroxidase, applied to a second lesion of the dorsal column two to three vertebral segments caudal to the first. Axons damaged by the original lesion were found to die back 1–2 mm from the plane of transection and at 18–20 hours were characterized by terminal club‐shaped swellings attached to the proximal axon by a thin connection. At 50 days postlesion there was some evidence of limited regenerative responses in terms of growth‐cone‐like axon terminals, and the presence of aberrant axonal branching, but no evidence of regenerating axons approaching close to the plane of transection. These findings are in agreement with previous studies indicating little or no effective regrowth of myelinated axons in the mammalian spinal cord. These same techniques were used in a succeeding study to examine the effects of applied electric fields on the axonal response to transection.
Transected dorsal column axons within the guinea pig spinal cord regenerate in the presence of an applied electric field
Authors: Borgens Richard B. , Blight Andrew R. , Murphy D. J. , Stewart Lygia
Published: January 2005

Using an implanted battery and electrodes, we have imposed a weak, steady electrical field across partially severed guinea pig spinal cords. We have analyzed regeneration of dorsal column axons in experimental animals and sham‐treated controls at 50‐60 days postirjury by anterograde filling of these axons with the intracellular marker horseradish peroxidase and by employing a marking device to identify precisely the original plane of transection (J. Comp. Neurol. 250: 157‐167, '86). In response to electric field applications, axons grew into the glial scar, as far as the plane of transection in most experimental animals. In a few animals axons could be traced around the margins of the lesion (but never through it). Moreover, these fibers returned to their approximate positions within the rostral spinal cord before turning toward the brain.

In sham‐treatede controls, ascending axons were found to terminate caudal to the glial scar, and rarely were any fibers found within the scar itself. Axons were never observed to cross into the rostral cord segment. These findings suggest that an imposed electrical field promotes growth of axons within the partially severed mammalian spinal cord, that a steady voltage gradient may e an environmental component necessary for axonal development and regeneration, and that some component(s) of the scar impede or deflect axonal growth and projection.
Alterations of the blood‐brain barrier after transplantation of autonomic ganglia into the mammalian central nervous system
Authors: Rosenstein Jeffrey M. , Brightman Milton W.
Published: January 2005

Autonomic (superior cervical) ganglia, the vessels of which are freely permeable to macromolecules, from mature rat donors (allografts or autografts) were transplanted to different sites in the central nervous system (CNS). Minimal trauma was caused by grafts into the IVth ventricle while grafts to intraparenchymal locations such as cerebral cortex and spinal cord were necessarily traumatic and produced glial scarring. Postoperative periods were between 4 weeks and 30 months. A potentially significant aspect of neural transplantation is the functional vascular connections between host and graft. It is highly likely that grafting procedures alter the bloodbrain barrier (BBB) in the recipient brain. In order to determine permanent BBB changes, the glycoprotein horseradish peroxidase (HRP) (M.W. 40,000) was injected intravascularly for circulation periods ranging between 50 seconds and 90 minutes. Protein exudatation was monitored by using the chromagens DAB and the highly sensitive TMB.

All autonomic ganglia transplants, regardless of postoperative or HRP circulation times, were permeable to the injected protein; no qualitative differences were found between allografts and autografts. The blood‐borne protein traversed the autonomic graft and infiltrated into the host brain for distances between 200 μm in intraparenchymal grafts to over 1 mm in intraventricular grafts; a smaller exudate was found in the intraparenchymal model than in the intraventricular site probably due to glial scarring, that impeded the protein movement in the interstitial spaces. Significantly, TMB demonstrated that the systemic protein entered the cerebrospinal fluid. HRP was detected on the ventricular floor and in the perivascular spaces of the microvasculature.

Transplantation of an autonomic ganglion into the brain provides a biological portal that bypasses normal barriers to macromolecules. The vascular and extracellular confluences between host and graft could provide direct access for systemically administered substances to enter brain regions where they, normally, would be excluded.
Neck muscle afferent projections to the brainstem of the monkey: Implications for the neural control of gaze
Authors: Edney Daniel P. , Porter John D.
Published: January 2005

Brainstem projections of first‐order afferent neurons that innervate the suboccipital muscles of the monkey have been determined by using the technique of transganglionic transport of wheat‐germ‐agglutinin‐conjugated horseradish peroxidase (WGA/HRP) and HRP. Neck muscle afferents distribute to several distinct regions located within the caudal brainstem and rostral spinal cord. Terminal labeling was heaviest within the ventral portion of the ipsilateral lateral cuneate nucleus. Muscle afferent terminals also distributed to ventrolateral portions of the pars triangularis division of the cuneate nucleus. Projections were consistent with the known somatotopic (i.e., both place and modality) organization of the cuneate nucleus. Moreover, neck muscle projections to the cuneate nucleus were, in part, coincident with those previously demonstrated for the extraocular muscles (Porter: J. Comp. Neurol. 247:133–143, '86). Sparse terminal projections were noted in the central cervical nucleus. In addition, light terminal labeling was present in group x of the vestibular complex and in an ill‐defined region along the lateral margin of the brainstem.

Present observations, which provide the first complete description of the central distribution of neck muscle afferent neurons in the primate, may contribute to the known substrate for eye/head coordination.
Differential origin of brainstem serotoninergic projections to the midbrain periaqueductal gray and superior colliculus of the rat
Authors: Beitz A. J. , Clements J. R. , Mullett M. A. , Ecklund L. J.
Published: January 2005

Previous studies have shown that both the midbrain periaqueductal gray (PAG) and the superior colliculus receive a significant serotoninergic (5‐HT) innervation. In the present study the origins of these 5‐HT projections to the rodent PAG and superior colliculus were analyzed by using a combined immunohistochemical‐retrograde transport technique. Thirteen brainstem regions were found to contain double‐labelled 5‐HT‐like immunoreactive neurons following HRP injections into the PAG while only four brainstem nuclei contained double‐labelled neurons following superior collicular injections. After HRP deposits into the ventral PAG, the largest percentage of double‐labelled neurons was identified in nucleus raphe magnus, pars alpha of the nucleus gigantocellularis, and the paragigantocellular nucleus. The dorsal PAG, on the other hand, received the largest percentage of its 5‐HT projections from nuclei raphe dorsalis, raphe obscurus, raphe pontis, and raphe medianis. The 5‐HT input to the superior colliculus was found to arise exclusively from nuclei raphe dorsalis, raphe medianis, and raphe pontis and from the contralateral periaqueductal gray. Raphe nuclei were found to contribute serotoninergic projections to both the PAG and the superior colliculus while reticular nuclei contributed 5‐HT projections only to the PAG. Injections of the fluorescent retrograde tracers true blue and nuclear yellow were then made into the PAG and superior colliculus to ascertain if neurons located in raphe nuclei that projected to both structures provided axon collaterals to both areas. Generally, less than 10% of raphe neurons projecting to the superior collicuius were identified as providing axon collaterals to the PAG.

The present results demonstrate major quantitative and qualitative differences in the origin of 5‐HT projections to the ventral PAG and superior colliculus. The origin of 5‐HT input to the dorsal PAG, on the other hand, showed many similarities to the origin of 5‐HT innervation of the superior colliculus. These data also indicate that approximately 35% of raphe neurons provide nonserotoninergic projections to the PAG and superior colliculus.
Times of generation of glutamic acid decarboxylase immunoreactive neurons in mouse somatosensory cortex
Authors: Fairén Alfonso , Cobas Alberto , Fonseca Montserrat
Published: January 2005

The birth dates of neurons showing glutamic acid decarboxylase (GAD) immunoreactivity have been determined in mouse somatosensory cortex. Pregnant C57B1 mice received pulse injections of (3H)thymidine from E10 through E17 (EO being the day of mating). The distributions of thymidinelabeled, GAD‐positive and nonimmunoreactive (non‐GAD) cells as a function of depth under the pial surface were recorded in adult animals. The maximum rate of generation of GAD‐positive neurons occurred at E14, whereas the generation of non‐GAD neurons reached its maximum rate at E13. Except for those in layer I, GAD‐positive neurons followed an inside‐out sequence of positioning. GAD‐positive neurons born at E12 and E13 were located in layers VI—IV. GAD‐positive neurons born at E14 were found throughout the cortical thickness, with a maximum in layer IV. The GAD‐positive neurons labeled after pulses at E15 or E16 or E17 were limited to the superficial strata, forming a band that became narrower as it moved toward the pial surface with increase in age of pulse labeling. GAD‐positive neurons in layer I were generated at a constant rate during the whole embryonic period analyzed. Non‐GAD neurons also followed an inside‐out spatiotemporal gradient. Two partially overlapping phases were distinguished in non‐GAD neurogenesis. During the first phase (from E12 to E14) neurons populating adult layers VI and V originated, while neurons located in layers IV through I were generated during the second phase (from E13 to E17). Since GAD‐immunoreactive neurons form a heterogeneous population, we envisage further studies in order to test whether differences exist in birth dates among the classes.
Organization of the reciprocal connections between the subiculum and the enthorhinal cortex in the cat: II. An electrophysiological study
Authors: Van Groen T. , Da Silva F. H. Lopes
Published: January 2005

The projection of the entorhinal cortex (EC) to the subiculum (SUB) and the projection in the opposite direction from the SUB to the EC have studied in the cat by using electrophysiological methods. Field potentials elicited by EC stimulation were recorded in the SUB. Different topographic distributions of the amplitude of the average evoked potentials (AEPs) were obtained dependig on the place of stimulation along a lateromedial axis in the EC. Stimulation of the lateral EC elicited the largest AEPs in the septal part of the SUB whereas stimulation of the medical EC evoked maximal responses in the temporal part of the SUB. Field potentials evoked by subicular stimulation were measured in the EC; the topographic distribution of the AEPs was dependent on the place of stimulation along the subicular septotemporal axis. Septal SUB stimulation elicited the largest field potentials in the laterocaudal part of the EC whereas temporal SUB stimulation evoked maximal responses in the mediocaudal part of the EC. These findings indicate that a topographical organization exists in the EC‐SUB connections and that these connections are reciprocal. Unit activity both orthodromicaally and antidromically elicited by SUB stimulation was recorded in the EC. Mean conduction velocities were estimated and found to vary around 1 m/second−1. The physiological evidence is discussed along with the anatomical data reported in the accompanying paper.
Role of competitive interactions in the postnatal development of X and Y retinogeniculate axons
Authors: Garraghty P. E. , Sur M. , Sherman S. M.
Published: January 2005

The cat's retinogeniculate pathway is largely composed of X and Y axons, which represent two distinct neuronal streams organized in parallel. Our earlier data, summarized in the previous paper, suggest that the postnatal development of retinogeniculate axon arbors is characterized by competitive interactions between the X and Y axons. Thus, during development, X arbors in lamina A or A1 are initially broad or exuberant before the Y arbors begin to develop adultlike arbors; the X arbors then shrink to their adult form as the Y arbors grow and establish their mature complement of connections; monocular lid suture prevents the rapid growth of Y arbors, which in turn prevents the pruning of X arbors; and monocular enucleation at birth allows X arbors from the remaining eye to retain their exuberance although completely confined to their appropriate lamina A or A1, whereas the Y arbors develop aberrant extensions into adjacent, previously denervated laminae. We now provide additional evidence for the role of competition between retinogeniculate X and Y axons during development. The addition of visual deprivation by lid suture of the remaining eye to monocular enucleation at birth causes no apparent change in the morphology of X arbors in laminae A and A1. In contrast, the Y arbors of such cats continue to form extensive translaminar sprouts in the previously denervated laminae despite severely reduced terminations in the lamina A or A1 normally innervated by the remaining eye. We interpret these new data, in conjunction with our earlier data, as follows. If retinogeniculate X and Y arbors compete for synaptic space during postnatal development, terminations of Y axon can be affected by lid suture only in geniculate laminae where terminations of X axons are also present. Thus, Y axon arbors are severely reduced in deprived lamina A or A1 following lid suture whether or not the other eye is removed. Where X arbors are not present, such as in lamina C or the laminae inappropriate for the remaining eye after removal of the other, the lid suture has no obvious effect on development of the Y arbors.