bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of visual callosal connections in neonatally enucleated rats
Authors: Olavarria Jaime , Malach Rafael , Van sluyters Richard C. 
Published: January 2005

AbstractThe present report extends previous descriptions of the mature distributions of callosal cells and axonal terminations in rats monocularly or binocularly enucleated at birth. It also describes the time course of callosal development in these animals, and establishes the age at which eye removal ceases to alter the normal course of callosal development.Although our results indicate that the callosal pattern is anomalous in adult, neonatally enucleated rats, the major features of the normal callosal pattern are nonetheless clearly recognizable in both monocularly and binocularly enucleated rats. Thus, as in normally reared rats, there are dense accumulations of callosal cells and terminations at the 17/18a border region, at the lateral border of area 18a, and within area 18b in enucleated rats. In addition, several narrow bands of callosal connections bridge the width of area 18a at several rostrocaudal levels, and a ring‐like callosal configuration is located anterolateral to area 17.In monocularly enucleated rats, the most prominent anomaly develops in the hemisphere ipsilateral to the remaining eye, where a dense band of callosal connections runs rostrocaudally through the center of area 17. Periodic fluctuations in the density of labeling along the length of this extra band give it a beaded appearance. The callosal pattern in the hemisphere contralateral to the remaining eye in these rats appears normal. Binocular enucleation causes the appearance of discrete regions of reduced labeling within the 17/18a callosal band and several densely labeled tongue‐like regions that extend medially from this band well into area 17. The laminar distribution of callosal cells and terminations is not significantly altered by loss of one or both eyes at birth.Our data indicate that enucleation does not affect the time course of callosal development. Thus, in enucleated pups, all features of the mature callosal pattern can be recognized by 6–7 days of age, and by 12 days of age the patterns appear virtually mature. Finally, our data reveal that monocular or binocular enucleations performed at 6 days of age or later allow the callosal pattern to develop normally, whereas enucleations performed between birth and 5 days of age produce anomalies similar to those observed in rats enucleated at birth. Thus, at about 6 days of age—just as the earliest features of the mature callosal pattern become discernible, and long before rats first open their eyes—the developing callosal pathway is no longer susceptible to disruptions of visual input.
The spinothalamic tract: An examination of the cells of origin of the dorsolateral and ventral spinothalamic pathways in cats
Authors: Jones M. W. , Apkarian A. V. , Stevens R. T. , Hodge C. J. 
Published: January 2005

AbstractThe locations of Spinothalamic neurons and the funicular trajectories of their axons were studied in cats by retrograde transport of horseradish peroxidase (HRP). Five animals were used as controls to determine the cervical and lumbar laminar distributions of neurons contributing to the Spinothalamic tract. An additional eight animals were used to determine the funicular trajectories of the Spinothalamic axons of lumbar neurons by utilizing a series of thoracic spinal cord lesions in conjunction with retrograde transport of HRP from the sensory thalamus. Three of these animals underwent midthoracic ventral quadrant lesions, four animals underwent midthoracic dorsolateral funiculus lesions, and one animal underwent total spinal cord transection sparing the dorsal columns. The locations of the cells containing the HRP reaction product were then determined after a 3– to 5– day survival time, and the patterns of labeled cell locations of the lesion groups were compared to the control group patterns. In the lesioned animals, the cervical Spinothalamic cell locations were used as a control to confirm the uniformity of the injection sites, transport and tissue processing.The major finding of this study is that there exist two distinct components of the spinothalamic tract. The dorsolateral Spinothalamic tract (DSTT) is made up of axons originating in contralateral spinal cord lamina I and has negligible contribution from the deeper spinal cord laminae. The axons of lamina I cells cross segmentally and ascend exclusively in the dorsolateral funiculus (DLF). The DSTT comprises approximately 25% of the total spinothalamic input from the lumbar enlargement. The ventral Spinothalamic tract (VSTT) is made up of axons originating in spinal cord laminae IV–V and VII–X. Very few lamina I cells contribute axons to the VSTT. This crossed pathway ascends in the ventrolateral and ventromedial portions of the spinal cord. No cells contributing to the Spinothalamic tract were identified in spinal cord segments caudal to a dorsal column sparing lesion, indicating that there are no Spinothalamic tract axons traveling in the dorsal columns.These results expand the classical concept of information processing by the Spinothalamic tract. The DSTT is made up of lamina I cell axons. All lamina I Spinothalamic cells respond exclusively to noxious peripheral stimuli. Hence the DSTT is a major nociceptive‐specific ascending spinal pathway, yet lies outside the confines normally assigned to the spinothalamic tract. In contrast, the spinothalamic tract axons ascending in the traditional ventral location originate predominantly from neurons of wide dynamic range as well as from low‐threshold neurons. These findings have novel implications concerning the relative importance, for nociception, of lamina I and deeper laminar input to the thalamus.
The neuronal composition of area 17 of rat visual cortex. IV. The organization of pyramidal cells
Authors: Peters Alan , Kara Daniel A. 
Published: January 2005

AbstractIn area 17 of the rat visual cortex, most of the apical dendrites of the large layer V pyramidal cells aggregate into oriented clusters, each containing three or more such dendrites. These clusters are not randomly distributed, but have a basic hexagonal packing distribution in which the mean center‐to‐center spacing is 55–60 microns. The majority of medium‐size pyramidal cells of layer V also add their apical dendrites to the clusters. As these clusters pass through layer IV they remain intact, and successively layer III and finally layer II pyramids add their apical dendrites to them. Perhaps because the pyramidal cells in layer II/III are so numerous, some of their apical dendrites form independent groups.Apical dendrites of the small pyramidal neurons in layers VIa and IV seem not to specifically add to the clusters. Instead, apical dendrites of layer VIa pyramids form into contiguous fascicles and sheets, which pass around the groups of layer V pyramidal cell bodies to ascend to layer IV, where most of them form their apical tufts. Layer IV pyramidal cell apical dendrites behave somewhat similarly. These apical dendrites have to pass between the cell bodies of the lower layer III pyramidal cells. To do this, some join the clusters, but others form independent bundles.It is suggested that the pyramidal cells whose apical dendrites are clustered represent vertically oriented neuronal modules whose activity is synchronized, and that different combinations of these modules are excited by afferents to the cortex to provide the bases for the various kinds of functional columns.
Distribution of acetylcholine and catecholamine neurons in the cat brainstem: A choline acetyltransferase and tyrosine hydroxylase immunohistochemical study
Authors: Jones Barbara E. , Beaudet Alain 
Published: January 2005

AbstractThe distribution of acetylcholine neurons in the brainstem of the cat was studied by choline acetyltransferase (ChAT) immunohistochemistry and compared to that of catecholamine neurons examined in the same or adjacent sections by tyrosine hydroxylase (TH) immunohistochemistry. The largest group of ChAT‐positive (+) neurons was located in the lateral pontomesencephalic tegmentum within the pedunculopontine tegmental nucleus and the laterodorsal tegmental nucleus rostrally and within the parabrachial nuclei and locus coeruleus nucleus more caudally. TH+ neurons were found to be coextensive and intermingled with ChAT‐h neurons in the dorsolateral pontomesencephalic tegmentum, where the number of ChAT+ cells (approximately 18,500) exceeded that of the TH+ cells (approximately 12,000). In the caudal pons, scattered ChAT+ neurons were situated in the ventrolateral tegmentum together with TH+ neurons. In the medulla, numerous ChAT+ cells were located in the lateral tegmental field, where they extended in a radial column from the dorsal motor nucleus of the vagus to the ventrolateral tegmentum around the facial and ambiguus nuclei, occupying the position of preganglionic parasympathetic neurons of the 7th, 9th, and 10th cranial nerves. TH+ cells were also present in this field. Neurons within the general visceral, special visceral, and somatic motor cranial nerve nuclei were all imrnunoreactive to ChAT. Scattered ChAT+ neurons were also present within the medullary gigantocellular and magnocellular tegmental fields together with a small number of TH+ neurons. Other groups of ChAT+ cells were identified within the periolivary nuclei, parabigeminal nucleus, prepositus hypoglossi nucleus, and the medial and inferior vestibular nuclei. Acetylcholine neurons thus constitute a heterogeneous population of cells in the brainstem, which in addition to including the somatic and visceral efferent systems, comprises many other discrete systems and represents an important component of the brainstem reticular formation. The proximity to and interdigitation with catecholamine neurons within these systems may be of important functional significance.
Prenatal growth of fine‐diameter primary afferents into the rat spinal cord: A transganglionic tracer study
Authors: Fitzgerald Maria 
Published: January 2005

AbstractThe aim of this study was to examine the growth of fine‐diameter, Aδ and C, primary afferents into the dorsal horn of the spinal cord. To do this, Aδ and C primary afferents were transganglionically labeled with wheat germ agglutinin‐horseradish peroxidase (WGA–HRP) in fetal rats at various ages and their growth was traced into the lumbar spinal cord. Sciatic or common peroneal nerves were injected with WGA–HRP at E18–E21.5 (just before birth) and the fetuses were returned to the uterus for 24 h before histochemical analysis. The results show fine‐diameter afferent fibers growing into the L4/L5 spinal cord at E19 when they reach the white matter overlying the dorsal horn and begin to penetrate lamina I. Twelve hours later at E19.5 terminals can be seen in lamina IIo and by E20 they are increasing in density and have reached Hi. By birth they have achieved the density in laminae I and II that is found in the neonate and young rat. Labeling of only the peroneal branch of the sciatic nerve, leaving the tibial unlabeled, demonstrated that the somatotopic specificity of central terminal fields is apparent from the time fine afferent fibers first grow into the spinal cord.
Central terminations of cutaneous mechanoreceptive afferents in the rat lumbar spinal cord
Authors: Woolf Clifford J. 
Published: January 2005

AbstractThe morphology in the dorsal horn of the lumbar spinal cord of the collateral branches and terminal arborizations of three different types of low‐threshold mechanoreceptor innervating the skin of the rat hindlimb has been studied by the intracellular injection of horseradish peroxidase into physiologically characterized afferent fibres. The central terminals of five rapidly adapting glabrous skin mechanoreceptors (RA), six hair follicle afferents (HFA), and four slowly adapting type I afferent fibres (SA I; two from glabrous and two from hairy skin) were recovered for detailed analysis. The number of collaterals per axon varied from eight to 12, and the length of axon stained from 3.5 to 4.7 mm. In each afferent, while the majority (52–67%) of the terminal arborizations displayed extensive branching with large numbers of en passant and terminal synaptic boutons, the arborizations at the caudal and rostral extremes of the terminal field tended to be much simpler and less profuse, with few and in some cases no boutons. This did not appear to be the consequence of inadequate filling.The general pattern of the terminal arborizations was one of mediolaterally compressed, rostrocaudally oriented sheets. In the case of the RA afferents there was no overlap between the adjacent terminal arborizations; a few of the arborizations of the SA I afferents overlapped; most, but not all, of the HFA terminal arborizations overlapped. The terminal arborizations of the HFAs had a distinctive morphology identical to the flame‐shaped arbors described in earlier Golgi studies and included synaptic boutons extending from inner lamina II to lamina IV. The morphologies of the RA and SA terminal arborizations were similar to each other, but the former tended to be concentrated in lamina IV with branches in III and V, whereas the latter tended to V with few branches more superficial than lamina IV. There were also differences in the intercollateral spacing between these two types of afferent fibre.While there are similarities between the morphology of the central terminals of cutaneous low‐threshold mechanoreceptors in the rat and those previously described in the cat (for example, the longitudinally continuous arrangement of the mediolaterally restricted flame‐shaped HFA arborizations and the discontinuous RA arborizations arising from a dorsally located axon), there are also some major differences: the large number of HFA arbors extending to lamina Hi and to lamina IV rather than being restricted to lamina III, the deeper location of the RA arbors (in laminae IV and V rather than lamina III), and the absence of a regular lateral convexity in the collateral axon of the SA type I afferents.
Anatomy and electrophysiology of neurons terminating in the corpora allata of the cockroach Diploptera punctata
Authors: Thompson C. S. , Lococo D. J. , Tobe S. S. 
Published: January 2005

AbstractIntracellular recording and dye injection were used to study the structure and electrophysiological properties of individual neurons that project to the corpora allata of the cockroach, Diploptera punctata. Neurons in the pars intercerebralis generate long‐duration, tetrodotoxin‐sensitive action potentials. Dye injection revealed two cell types. One type extends axons to the contralateral nervi corporis cardiaci I, some of which innervate the corpora allata, and another type extends a major axon down each of the circum‐oesophageal connectives. Neurons in the pars lateralis also generate long‐duration action potentials. These neurons extend axons to the ipsilateral nervi corporis cardiaci II, which continue on to terminate in the corpora cardiaca and the corpora allata. Small groups of all the above neuronal types are dye and electrically coupled. Penetration and dye injection into nerve terminals in the corpora allata and corpora cardiaca confirmed the innervation of the corpora allata by neurons located in the pars intercerebralis and pars laterally and revealed a third class of neurons that have terminals in the corpora allata: intrinsic neurons of the corpora cardiaca.
Axonal arborization in the developing chick retinotectal system
Authors: Thanos Solon , Bonhoeffer Friedrich 
Published: January 2005

AbstractThe growth and arborization of chicken retinal ganglion cell axons have been investigated by means of an intraaxonally transported fluorescent marker in the developing retinotectal system. The fluorescent dye D282 or diI from the carbocyanine group of dyes is taken up by ganglion cells and labels the axon as well as the axonal growth cones and the terminal arborizations on the tectum.Branching and arborization start in the chick retinotectal system on embryonic day 9 (E9). At this stage retinal axons leave the stratum opticum (SO) and invade the stratum griseum et fibrosum superficiale (SGFS), where arborization takes place. On day E12 several axons were found to arborize in the SGFS. At this stage arbors appear to have small branches with less than 4 branching points. The extension of terminal arbors in the anterior/posterior (A/P) and in the dorsal/ventral (D/V) direction was determined for 50 axonal trees at days E13–14 and for 24 arbors at days E15–16. Few axonal terminals were investigated at day E18. The mean A/P extent of axonal terminal trees increases from 0.23 ± 0.12 to 0.36 ± 0.22 mm from E13–14 to E15–16 and seems to stay at this order of magnitude on E18. The mean D/V extent increases from 0.23 ± 0.17 to 0.30 ± 0.18 mm in the same embryonic period of development. The number of branching points calculated from the same number of axonal trees increases from 7.50 ± 2.98 at E13–14 to 11.70 ± 4.10 at E15–16. This number seems to increase further after day E16 achieving values of about 20 to 25 at E18. This was, however, not quantifiable by the technique used here and represents an approximate value estimated from 6 completely labeled terminal fields at E18.The data presented here suggest that the modeling of the final branching pattern in the chick retinotectal system takes place within a relatively short period of embryonic development. Prior to the beginning of terminal arborization two important events contribute to the formation of a retinotopic projection. One event is the change of the D/V position by a minority of axons lying ectopic in terms of retinotopy. Some axons turn at right angles and change their D/V position. The other event is the appearance of side branches along the A/P axis.
GABA immunoreactive neurons in rat visual cortex
Authors: Meinecke Douglas L. , Peters Alan 
Published: January 2005

AbstractAn antiserum to γ‐aminobutyric acid (GABA) was used in a light and electron microscopic immunocytochemical study to determine the morphology and distribution of GABA‐containing neurons in the rat visual cortex and to ascertain whether all classes of nonpyramidal neurons in this cortex are GABAergic. The visual cortex used for light microscopy was prepared in such a way that the antibody penetrated completely through tissue sections, and in these sections large numbers of GABA immunoreactive neurons were apparent. The labeled neurons could be identified as being either multipolar, bitufted, bipolar, or horizontal neurons. In layers II through Via, GABA immunostained cells were distributed uniformly and accounted for approximately 15% of all neurons, but in layer I all neurons appeared to be immunostained.Electron microscopy of GABA immunostained visual cortex prepared to ensure good fine structural preservation confirmed the presence in layers II through Via of numerous immunoreactive bipolar neurons, both small and large varieties, as well as multipolar and bitufted neurons. Additionally, electron microscopy reveals that astrocytes are frequently GABA immunoreactive.From a correlated light and electron microscopic evaluation of neurons in GABA immunostained visual cortex, it was possible to confirm which kinds of neurons are GABAergic and what proportion of the neuronal population they represent. Thus, from an analysis of some 950 neurons, it was found that pyramidal neurons were never immunoreactive and that except for 20% of the bipolar cell population, all examples of other types of nonpyramidal neurons encountered in this material were GABA immunoreactive.
Regionally selective elimination of cutaneous thermal nociception in rats by neonatal capsaicin
Authors: Doucette R. , Theriault E. , Diamond J. 
Published: January 2005

AbstractWe have studied thermal and mechanical nociception in anesthetized adult rats that had received subcutaneous injections of capsaicin as neonates. This treatment appeared not to have impaired mechanonociception in any of the body regions that were examined. In contrast, thermal nociception was present in some locations and absent in others. Its total disappearance from back skin correlated with the loss of C fiber responsiveness in the dorsal cutaneous nerves (DCNs); electrical excitation of these nerves now failed to evoke the delayed component of the cutaneus trunci muscle reflex, although the early reflex response, elicited by excitation of the mechanosensitive Aδ axons, was unaffected. Heat nociception was similarly eliminated from the nonpad glabrous skin of the paws. When the stimulus was applied selectively to the pads, however, a normal foot‐withdrawal response was evoked. The probable basis of this differential heat responsiveness in the paws was revealed by the use of the Evans Blue technique in untreated animals; antidromic activation of the paw nerves to excite their C fiber population led to dye extravasation in the glabrous skin around the pads but to almost none in the pads themselves, indicating a relative absence in the pads of a nociceptive C fiber innervation. In capsaicin‐treated animals, the tail‐flick test revealed a significantly reduced responsiveness to noxious heat in the tail. These results may explain some of the anomalies among the reports of the effects of neonatal capsaicin. It appears that in strategically exposed locations exemplified by the paw pads and tail, capsaicin‐resistant axons that could be the relatively fast‐conducting Aδ ones are involved in the signalling of noxious heat. The heat‐nociceptive C fibers that seem to be solely responsible for such signalling from back skin and nonpad glabrous skin of the paws probably contribute to heat nociception in the tail but not to that in the paw pads.