bluuebunny/crossref_metadata_2025 huggingface dataset:
The origin of the spinomesencephalic tract in the rat: An anatomical study using the retrograde transport of horseradish peroxidase
Authors: Menétrey Daniel , Chaouch Athmane , Binder Denise , Besson Jean Marie
Published: January 2005

An anatomical technique based on the retrograde transport of horseradish peroxidase (HRP) was used to investigate the projections of spinal cord neurons to the mesencephalic tegmentum in the rat. Restricted unilateral injections were confined to central grey, cuneiformis area, and superior colliculus. Injections into all these loci produced labeling in similar spinal areas. Only quantitative differences were noted.

In the spinal grey matter, numerous labeled cells were regularly encountered in the marginal zone, the lateral part of the neck of the dorsal horn, and the dorsal grey commissure. Projections from the marginal zone and neck of the dorsal horn were predominantly contralateral. In the white matter, a pronounced bilateral labeling was observed in the nucleus of the dorsolateral funiculus, thus confirming our previous electrophysiological findings (Menétrey et al., '80). This distribution of labeled cells was commonly observed throughout the whole length of the cord. Additional sites of projecting cells have also been identified at the most rostral levels (obex, C1, C2). They mostly derived from spinal extensions of the dorsal column nuclei and lateral cervical nucleus contralaterally; from the lateral ventral horns bilaterally and from the nucleus commissuralis ipsilaterally.

This study is thus a clear confirmation that the mesencephalic tegmentum constitutes a target for various somatosensory inputs originating from spinal cord, dorsal column nuclei, and lateral cervical nucleus. Moreover, from these results together with those obtained for the spinothalamic tract in the rat, it appears that marginal and dorsolateral funiculus neurons preferentially project to the mesencephalic tegmentum. The importance of marginal zone projections underlines the involvement of the spinomesencephalic tract in pain mechanisms.
A quantitative analysis of the ipsilateral retinocollicular projection in the cat: An EM degeneration and EM autoradiographic study
Authors: Behan Mary
Published: January 2005

The ipsilateral projection to the binocular segment of the superior colliculus in the cat was quantified by means of electron microscopic (EM) degeneration and electron microscopic autoradiography. Because of the patchy distribution of ipsilateral terminals, contiguous samples were taken across the mediolateral extent of the colliculus. The results from both EM degeneration and EM autoradiography are in substantial agreement: In the binocular segment, the ipsilateral projection represents 5.3% and 5.6%, respectively, of the total retinal input to the superior colliculus. As the contralateral projection extends over the whole colliculus but is greatest in the caudal region, while the ipsilateral projection is restricted to the middle one‐third of the colliculus, it follows that the total ipsilateral retinocollicular projection is less than earlier estimates (5–10%, Kanaseki and Sprague, '74) and probably closer to 1%, as suggested by Sterling ('73) on the basis of an electron microscopic degeneration study. A significant finding is that there are many more terminals per axon in the contralateral than in the ipsilateral superficial gray. The ratio of degenerated terminals in SGS1 and SGS2 to degenerated axons in SGS3 is 3.1 contralaterally, while in the ipsilateral colliculus the figure is 1.2. This may reflect a difference in the arborization pattern of Y‐type and W‐type retinal ganglion cells in the colliculus.
Electron microscopic immunocytochemical localization of tyrosine hydroxylase in the area postrema of rat
Authors: Armstrong D. M. , Pickel V. M. , Joh T. H. , Reis D. J.
Published: January 2005

The ultrastructural morphology and specialized neuronal, vascular, and ventricular associations of tyrosine hydroxylase‐labeled neurons are examined within the area postrema of rat brain. Specific antiserum to the purified enzyme is localized throughout the rostrocaudal and dorsoventral extent of the area postrema by means of the peroxidase‐antiperoxidase technique. In all regions, peroxidase immunoreactivity for tyrosine hydroxylase is distributed throughout the cytoplasm of selectively labeled neuronal perikarya and processes. The perikarya contain a large nucleus, infolded nuclear membrane, numerous cytoplasmic organelles, and form axosomatic synapses with unlabeled terminals. The majority of the labeled processes are dendrites, which contain ribosomes, microtubules, mitochondria, and scattered vesicles. These dendrites are postsynaptic to unlabeled axon terminals and show membrane specializations with other labeled dendrites and perikarya. In contrast to dendrites, peroxidase‐labeled profiles clearly distinguished as axons or axon terminals are sparse and never show membrane specializations with other neuronal or nonneuronal structures within the area postrema. Numerous large processes which could be either axons or dendrites are associated with blood vessels and the ventricular surface of the area postrema. With respect to blood vessels, processes are located either in direct apposition to the external glial membrane, or less frequently, within the perivascular space. The ventricular processes are either associated with blood vessels in the subpial space or distributed among the cilia and villi at the anterior margins of the area postrema. The neuronal and nonneuronal associations of the tyrosine hydroxylase‐labeled processes are consistent with a receptor or chemosensor function for catecholamines in this circumventricular organ.
Electrophysiological response properties of spinoreticular neurons in the monkey
Authors: Haber L. H. , Moore B. D. , Willis W. D.
Published: January 2005

Extracellular recordings were made from 29 spinoreticular cells in the spinal cords of anesthetized monkeys. The cells were in either the cervicalor the lumbar enlargement, and they were identified by antidromic activation from the medial part of the pontomedullary reticular formation. More spinoreticular neurons were sampled in the cervical than in the lumbar cord. Most of the cells were contralateral to the side from which antidromic activation was observed, but a higher proportion of the spinoreticular neurons inthe cervical enlargement than in the lumbar enlargement was ipsilateral to the antidromic stimulus. Three cells in the lumbar cord were antidromicallyactivated not only from the reticular formation but also from the contralateral thalamus, confirming that some spinoreticular projections are formed by collaterals from spinothalamic cells. Most of the spinoreticular neurons were in the ventral horn in laminae VII and VIII, although a few were in laminae IV‐VI. Nearly half of the spinoreticular cells in the sample could not be activated by any form of peripheral stimulation tested. The other cells could be activated by stimulation of receptive fields that varied from small to large, that were sometimes bilateral regions of the skin or of deep tissues. Although some spinoreticular cells could be classified as low threshold or wide dynamic range, the largest proportion were high threshold, requiring noxious stimulation for their activation. Descending volleys resulting from stimulation in the reticular formation could often be shown to inhibit or to excite spinoreticular neurons. It can be concluded that at leastsome spinoreticular neurons may play a role in nociception.
The contribution of late‐generated neurons to the callosal projection in the rat: A study with prenatal x‐irradiation
Authors: Jensen Karl F. , Altman Joseph
Published: January 2005

Studies utilizing horseradish peroxidase tracing methods have suggested that there are species differences in the relative contribution of the different neocortical layers to the callosal projection. The present investigation utilized x‐irradiation at different gestational ages to eliminate the late‐generated neurons of the rat neocortex. The caudorostral gradient of reduction in the neuronal population of the supragranular layers is closely correlated with the gradient of reduction in the size of the corpus callosum. Furthermore, the callosal projection is absent in anteroposterior cortical segments in which the development of the supragranular layers was prevented without a reduction of the number of neurons in the infragranular layers of the neocortex. These results indicate that late‐generated neurons residing primarily in the supragranular layers are essential for the formation of the corpus callosum.
The postnatal development of the substantia nigra: A light and electron microscopy study
Authors: Phelps Patricia E. , Adinolfi Anthony M.
Published: January 2005

The early postnatal development of neurons, dendrites, and synaptic connectivity in kitten substantia nigra (SN) was studied by light and electron microscopy. The compact and reticular divisions of the SN are present at birth but boundaries are indistinct. Most nigral neurons stain deeply in routine histological sections and their diameters increase slightly with age. Ultrastructurally, cell bodies are characterized by eccentrically located and often invaginated nuclei surrounded by cytoplasm rich in well‐formed or‐ganelles. Axosomatic synapses are infrequent and cell surfaces are enveloped by glial processes. Immature dendritic features, including growth cones and filiform processes, are commonly observed during the first 10 days. Gradually the dendritic profiles elongate and thicken and contours become smoother, retaining only scattered spinelike appendages.

Clear examples of the three synaptic types described in cat are found in newborn kittens, but immature terminals contain fewer synaptic vesicles and mitochondria. Approximately 90% of synapses present at birth in both nigra subdivisions are Type I, which contain large pleomorphic vesicles and contact dendrites symmetrically. Asymmetrical contacts characterize most of the remaining definable synapses. The postnatal increase in synaptic connectivity, which was estimated from random photographs of pars reticulata neuropil, is twofold during the first 50 days of life. Initially young dendrites are enveloped by glia and then gradually become ensheathed by axon terminals. Synaptogenesis in pars reticulata reflects the postnatal increase of neostriatal inputs to this subdivision and can be correlated with functional changes in strionigral connectivity.
The locations of stapedius and tensor tympani motoneurons in the cat
Authors: Shaw Marjorie D. , Baker Robert
Published: January 2005

The numbers and locations of motoneurons to the Stapedius and tensor tympani muscles were determined by retrograde transport of horseradish peroxidase. Stapedius motoneurons lay outside the traditionally recognized facial nucleus, in several distinct locations: (1) in the interface between the facial nucleus and the superior olive; (2) in a thin, scattered lamina of somewhat smaller cells spread dorsal to the facial nucleus; and (3) in a cluster located ventromedial to the rostral third of the facial nucleus. Some cells also lay dorsal to the superior olive or scattered in the reticular formation, just medial to the descending loop of the facial nerve. Tensor tympani motoneurons also lay outside the traditionally recognized trigeminal motor nucleus, in an areajust ventral to it. Both motoneuron pools were large, producing in‐nervation ratios that establish Stapedius and tensor tympani among the most finely innervated muscles yet studied. The degree of intermingling of large and small cells in these pools may explain, in part, why it has been easier to identify slow muscle fibers physiologically in tensor tympani than in Stapedius.
NADPH‐diaphorase: A selective histochemical marker for striatal neurons containing both somatostatin‐ and avian pancreatic polypeptide (APP)‐like immunoreactivities
Authors: Vincent S.R. , Johansson O. , Hökfelt T. , Skirboll L. , Elde R. P. , Terenius L. , Kimmel J. , Goldstein M.
Published: January 2005

Certain neurons in the brain are specifically and intensely stained by a histochemical method which demonstrates nicotinamide adenine dinucleo‐tide phosphate NADPH‐diaphorase activity. The cell types containing this enzyme in certain areas of the rat forebrain were examined by combining NADPH‐diaphorase histochemistry with the indirect immunofluorescence technique. Neurons containing somatostatin‐ or avian pancreatic polypep‐tide (APP)‐like immunoreactivities were found throughout the forebrain including the striatum and neocortex. These two neuropeptides were also found to coexist in many telencephalic neurons. After photography, the sections processed for immunohistochemistry were stained for NADPH‐diaphorase activity by a histochemical method. It was found that within the striatum all of the neurons that were selectively stained by this technique also contained both somatostatin‐ and APP‐like immunoreactivities. Also in the neocortex NADPH‐diaphorase was found only in those neurons displaying somatostatin‐ or APP‐like immunoreactivity. In other brain regions such as the nucleus laterodorsalis tegmenti, NADPH‐diaphorase‐containing cells did not contain these neuropeptides.

The results indicate that NADPH‐diaphorase histochemistry provides a simple, reliable, histochemical method to demonstrate those striatal neurons in which somatostatin‐ and APP‐like immunoreactivities coexist. The selective occurrence of this enzyme within these neurons may provide a useful target for pharmacological studies of these neuropeptide‐containing cells.
The distribution of neocortical projection neurons in the locus coeruleus
Authors: Waterhouse Barry D. , Lin Chia Sheng , Burne Richard A. , Woodward Donald J.
Published: January 2005

The present study was conducted to examine the spatial organization of locus coeruleus (LC) neurons that project to rat cerebral cortex. Long‐Evans hooded rats received unilateral pressure injections of horseradish peroxi‐dase (HRP) in either frontal (n = 6) or sensorimotor (n = 11) or occipital (n = 7) cortex to determine the intranuclear location of LC neurons which project to specific neocortical regions. Coronal and sagittal sections (40–100 μm) through the LC were examined by light microscopy after carrying out the tetramethyl benzidine reaction and staining with neutral red. The locations of retrogradely labeled cells were recorded on a three‐dimensional biological coordinate system maintained by a computer linked to the light microscope. LC neurons labeled from cerebrocortical injections of HRP were primarily located in the ipsilateral and to a lesser extent (fewer than 5% of total labeled cells) in the contralateral nucleus. Coeruleocortical projection neurons were concentrated in the caudal three‐fifths of the dorsal division of the ipsilateral LC. Within this portion of the nucleus, HRP‐filled neurons were distributed so that individual groups of cells projecting to occipital or sensorimotor or frontal cortex were coarsely aligned in a dorsal to ventral array, respectively. Moreover, in the sagittal plane of the nucleus the pattern of labeling was spatially graded so that the subset of neurons projecting to the occipital cortex was displaced more caudally in the LC than the groups of cells sending axons to sensorimotor or frontal cortex. Only the frontal area of the cortex received a projection from both dorsal and ventral divisions of the ipsilateral LC. Computer‐assisted analysis of the data further suggested that neocortical projection neurons in the dorsal LC are loosely organized into two groups which run rostrocaudally through the core of the caudal nucleus. The zone of labeling resulting from injections confined to the neocortical gray matter overlapped with but was not coextensive with that observed following injections into the caudate, hippocampus, and cerebellum. These results suggest that partially overlapping subsets of LC cells might independently influence separate populations of neurons within noradrenergic terminal fields of the neocortex.
Four types of neuron in layer IVab of cat cortical area 17 accumulate 3H‐GABA
Authors: Hamos James E. , Davis Thomas L. , Sterling Peter
Published: January 2005

Roughly 10% of the neurons in layer, IVah.of cat area 17 accumulate exogenous 3H‐gamma‐aminobutyric acid (GABA) but how many types of neuron comprise this population was unknown. We characterized these neurons by partial reconstruction of their somas from serial electron microscope autoradiograms and distinguished four types. GABA 1 was large (> 16.5 μm) and dark with a dense distribution of synaptic terminals, substantial geniculate input to the soma, and a moderate accumulation of GABA. GABA 2 was small (< 13 μm) and pale, also with a dense distribution of terminals but without evidence of somatic geniculate input, and a moderate accumulation of GABA. GABA 3 was radially fusiform (20μm × 8 μm) with varicose dendrites, a sparse distribution of synaptic terminals, and a heavy accumulation of GAB A. GAB A 4 was medium in size (15 μm) with a moderate distribution of synaptic terminals and a heavy accumulation of GABA. Reasons are presented for believing that each of these four categories of GABA‐accumulating neuron represents a fundamental cell type.
The effect of forebrain lesions in the neonatal rat: Survival of midbrain dopaminergic neurons and the crossed nigrostriatal projection
Authors: Jaeger C. B. , Joh T. H. , Reis D. J.
Published: January 2005

Lesions were placed in the striaturn and the olfactory tubercle of 1‐day‐old rat pups. Control and experimental animals were raised to adulthood. Efferent projections of mesencephalic neurons were examined by injecting the retrograde tracers horseradish peroxidase or Fast Blue into the undamaged striata of some experimental animals. The survival of the mesencephalic dopaminergic neurons was monitored by using immunocytochemical localization of tyrosine hydroxylase. Small lesions in the caudate‐putamen had no appreciable effect on the survival of tyrosine hydroxylase‐containing neurons in the mesencephnlon, but the density of dopaminergic terminals adjacent to the lesion increased in the remaining caudate‐putamen. Striatal lesions that involved an estimated area of more than one‐third resulted in loss of dopamine neurons of the substantia nigra compacta. Rostral lesions in the striatum affected mostly rostrally positioned neurons in the substantia nigra. Dorsal lesions of the caudate‐putamen resulted in disappearance of dorsal A9 neurons. Reduction of the A10 and A8 dopamine neuron groups occurred if the neonatal lesions involved the olfactory tubercle and nucleus accumbens. Some tyrosine hydroxylase‐containing neurons persisted even after the largest lesions. These dopaminergic neurons formed a crossed ni‐grostriatal pathway which was confirmed by retrogradely transported tracers. The density of this crossed projection in the adult appeared unaffected by the neonatal lesion.

We concluded that dopaminergic neurons form topographically ordered projections with their targets in the newborn rat. Rearrangement of these fibers appeared limited, but compensatory increase of axon terminal density was evident in partially lesioned target areas.
Anatomy of layer IV in cat primary auditory cortex (AI)
Authors: Winer Jeffery A.
Published: January 2005

The structure of neurons and axons in layer IV was studied as part of a larger inquiry into the organization of primary auditory cortex (AI) in the cat. Tissue from the convexity of the middle ectosylvian gyrus between the anterior and posterior ectosylvian sulci was studied in Golgi, Nissl, Bodian, plastic‐embedded, and other preparations from adult animals. Layer IV is defined as a strip about 200–250 μm thick consisting predominantly of small non‐pyramidal neurons intercalated between the pyramidal somata of layers III and V, and in which few commissurally projecting cells occur. Lying some 800–900 μm beneath the pia, layer IV has six types of neurons, as seen in Golgi‐stained material from anatomically and physiologically defined AI. These include three varieties (small, medium‐sized, and large) of tufted neurons with intracortically branching axons and vertically polarized, cylindrical dendritic fields. Besides the tufted cells, which are the most numerous neurons in layer IV, large multipolar, double bouquet, and spiny stellate cells are scattered through layer IV. Each has a characteristic neuronal architecture and intracortical axonal branches. Smaller tufted cell somata dominate the upper half of layer IV (IVa), larger tufted cells are more common deep in layer IV (IVb). The average somatic area in midnuclear, plastic‐embedded sections is 158 μm2. Layer IV (and layer IIIb) receive thick, probably ascending fibers, forming narrow, vertical terminal fields. These axons may be of thalamic origin and overlap with alternating, 50–75‐μm‐wide columns of somata and neuropil in layer IV. Layer III pyramidal cell axons often project to layer IV and ramify vertically and horizontally. The average height‐width ratio of the dendritic domains of layer IV cells is about 3.6:1. The vertically disposed dendrites of layer IV cells, the columnar arrangement of their local axonal branches, and the polarized form of intrinsic and extrinsic axons collectively reinforces the columnar pattern in layer IV. Many layer IV cells structurally resemble neurons in layer IV in the primary visual and somatic sensory cortex. However, most AI cells have a pronounced columnar arrangement of their somata and an elongated, narrow form. The axons of many layer IV cells preserve this vertical arrangement and often branch in layer III and, to a lesser degree, in layer V. Layer IV cells contribute little if at all to the commissural system in the primary auditory cortices, nor do they project extensively to the second auditory field adjoining AI. They might have a role in the function of local circuits within AI. Certain types of neurons appear to be common constituents in layer IV in other primary sensory cortical regions. These may represent fundamental elements of neocortical circuitry.
Distribution and morphology of nociceptive cells in the CNS of three species of leeches
Authors: Johansen Jørgen , Hockfield Susan , McKay Ronald D. G.
Published: January 2005

The present study describes the segmental variation in the distribution and morphology of nociceptive neurons (N cells) in the central nervous system of the leech.

N cells of midbody ganglia can be segregated into lateral and medial types. We show that monoclonal antibodies specific for N cells can distinguish between the two populations. The monoclonal antibodies were used to map the complete distribution of the cells along the nervous cord. There are two pairs of medial and lateral nociceptive neurons in the midbody ganglia, one pair of the medial type in the sex ganglia (5 and 6), and a pair of the lateral type in ganglia 20 and 21. The caudal brain is without nociceptive neurons. This distribution was confirmed by electrophysiological means.

The morphology of N cells in different parts of the nervous system was investigated by intracellular horseradish peroxidase (HRP) injections. In the terminal segmental ganglia the N cells showed extensive arborizations in the head and tail brains and, contrary to N cells in the midbody ganglia, their arborizations spanned more than three segments. N cells are absent in the tail brain, but the N cells of ganglia 20 and 21 were shown to innervate the entire caudal region. The basic morphology of all N‐cell homologues was found to be very similar for three leech species.

In the sex ganglia the pair of N‐cell homologues were examined in Haemopis, Hirudo, and Macrobdella. The results showed a progressive modification in the three species of the cell's morphology, peripheral projections, and physiological responses, possibly correlated with the evolution and complexity of the sexual organs.

HRP injections and monoclonal antibody staining revealed that a common feature of N‐cell homologues is the presence of processes that tightly surround the cell soma of other cells. This suggests that N cells may have other functional properties in addition to being primary sensory neurons.
Thalamic connections of the insula in the rhesus monkey and comments on the paralimbic connectivity of the medial pulvinar nucleus
Authors: Mufson Elliott J. , Mesulam M. Marsel
Published: January 2005

Thalamic connections of the insula in the rhesus monkey were studied with axonal transport methods. Tritiated amino acid injections limited to the insula revealed autoradiographic label in the principal and parvicellular components of the ventroposterior medial nucleus, the ventroposterior inferior nucleus, the oral and medial pulvinar nuclei, the nucleus reuniens, the parvicellular and magnocellular components of the medial dorsal nucleus, the centromedian‐parafasicularis nuclei, and the reticular nucleus.

In additional animals, tritiated amino acids and horseradish perioxidase injections were made within different regions of the insula. Although the injection sites in these additional cases may have included minor extensions into claustrum and adjacent structures, several tentative conclusions emerged with respect to the antero‐posterior gradient in insulothalamic connectivity.

The anterior insula appears to have a more extensive relationship with the ventroposterior medial complex, the medial dorsal nucleus, the centromedian‐parafasicularis nuclei and with some midline nuclei. In contrast, the posterior insula is more extensively connected with the ventroposterior inferior nucleus, the oral and medial pulvinar nuclei, and the suprageniculate nucleus.

The patterns of insulothalamic connections support conclusions derived from observations on the cortical connectivity of the primate insular cortex indicating that the anterior insula is related to olfactory, gustatory, and viscero‐autonomic behavior, whereas the posterior insula is related to auditory‐somesthetic‐skeletomotor function (Mesulam and Mufson, '82b).

The medial pulvinar nucleus has extensive connections with many paralimbic cortical regions including the insula as well as with high order polymodal association cortex. These findings suggest that the medial pulvinar may provide a region for the convergence of multisensory association input with limbic information.
Postnatal maturation of nonpyramidal neurons in the visual cortex of the cat
Authors: Meyer Gundela , Ferres‐Torres Romualdo
Published: January 2005

A Golgi study of nonpyramidal neurons in the visual cortex of kittens aged from 1 to 80 days revealed that different neuronal types undergo a differential sequence of maturation. The earliest nonpyramidal cells to differentiate are large multipolar cells of layers 3–5, which appear around birth and whose axons gradually establish long lateral, intracortical connections. They are followed by spiny stellate cells of layer 4, which appear in the first postnatal, week, and by neuroglioform cells in layers 4 and 5, a cell type which at 10 days displays a highly differentiated axonal plexus. In general, most classes of local axon cells can be identified by the end of the second week, though still possessing a very immature morphology, the axonal‐tuft cells of layer 2 maturing later, in the third week. With some exceptions, most neurons exhibit an adultlike axonal arborization by the end of the first month; however, immature chandelier terminals are observed until the 40th day, and in kittens aged from 30 to 80 days, the vertical terminal segments of chandelier cells are larger than in the adult. Some neuronal types seem to present an exuberant growth of axonal fibers in the late postnatal period and a subsequent reduction up to the adult stage.
Cellular and connective organization of slice cultures of the rat hippocampus and fascia dentata
Authors: Zimmer J. , Gähwiler B. H.
Published: January 2005

This study examined the cellular and connective organization of hippocampal tissue taken from 6–8‐day‐old rats and cultured by the roller tube technique for 3–6 weeks. In the cultures containing the fascia dentata and the hippocampus proper (CA1, CA3, CA4) the main cell and neuropil layers were organotypically organized when observed in ordinary cell stains. The normal distribution of smaller cell populations of AChE‐positive neurons and somatostatin‐reactive neurons was demonstrated by histochemical and immunohistochemical methods. Both cell types were mainly confined to str. oriens of CA3 and CA1 and the dentate hilus (CA4). Individual dentate granule fells and hippocampal pyramidal cells were injected with lucifer yellow and HRP, revealing great stability of the dendritic patterns of these cells in the culture condition. The same was found for the axonal branching and termination of HRP‐filled mossy fibers arising from an HRP‐injected granule cell. The preservation of organotypic afferent patterns in the cultures was also shown by Timm staining of the terminal distribution of the mossy fiber system. Mossy fiber terminals, with characteristic ultrastructural features verified in the electron microscope, were thus found in the hilus (CA4) and along the CAS pyramidal cell layer onto the CA3‐CA1 transition. Depending on the amount of dentate tissue relative to CA3 the terminals could stop before reaching CA1 (small fascia dentata) or take up additional intra and infrapyramidal locations along CA3 (small CA3). In cultures with a gap in the CA3 pyramidal cell layer some mossy fiber terminals were found in contact with the CA3 pyramidal cells beyond the gap. In all cultures there was an aberrant projection of supragranular mossy fibers. This projection is analogous to the one known from lesion and transplant studies to form in the absence of the entorhinal perforant path input to the dentate molecular layer. Also, in accordance with these studies the Timm staining pattern of the outer parts of the dentate molecular layer and the entire molecular layer of the hippocampus was altered corresponding to the spread of afferents normally confined to the inner zone of the dentate and str. radiatum of CA3 and CA1. Possibly as a consequence of the lack of normal targets for projections from CA1, this subfield contained an unusually dense Timm staining suggestive of autoinnervation.

In the analysis of the cellular and connective organization of hippocampal slice cultures both normal and additional traits were found. The normal traits demonstrated the stability of the intrinsic structure once it survives in vitro. The additional traits had formed according to the principles for reorganization of nerve connections known from lesion and transplant studies of hippocampal and dentate tissue.
Quantitative studies of auditory hair cells and nerves in lizards
Authors: Miller Malcolm R.
Published: January 2005

Because the lizard cochlear duct is anatomically accessible as well as relatively simple in structure it is an excellent model in which to study auditory hair cells, nerve fibers, and innervational patterns. The objectives of this study were to determine the intra‐ and interspecific variations of auditory hair cell and nerve fiber numbers, nerve fiber/hair cell ratios, and nerve fiber sizes in a variety of lizard species and to relate these to auditory function and phylogeny.

Hair cell numbers were determined by SEM and serial frontal sections of the papilla basilaris and nerve fiber numbers and diameters by use of a Zeiss TGZ3 particle counter. The coefficient of variation of hair cell numbers varied from 3.2 to 16.6 (171 specimens, 15 species) and of nerve fiber numbers from 1.2 to 14.4 (381 specimens, 35 species). There was no correlation between hair cell or nerve fiber number and age or sex.

The nerve fiber number/hair cell number ratio was 3.5–11.1/1 in small papillae basilares of the iguanid‐agamid‐anguid type, 2.4–3.2/1 in the teiid type, and 0.6–1.5/1 in the larger specialized papillae of the scincid and gekkonid types.

Nerve fibers varied in diameter from 0.8 to 6.0 μm (largest percentage were 2–4 μm) and were unimodally distributed. Larger nerve fibers usually supplied the unidirectionally oriented hair cells of the papilla basilaris.

Variations in hair cell and nerve fiber numbers in other vertebrate classes and the functional and phylogenetic aspects of lizard papilla basilaris structure and innervation are discussed.
T reticular interneurons: A class of serially repeating cells in the zebrafish hindbrain
Authors: Kimmel Charles B. , Metcalfe Walter K. , Schabtach Eric
Published: January 2005

We describe a class of reticular neurons, named T interneurons after the branching pattern of their axons, in young larvae of the zebrafish Brachydanio rerio. The cells were identified by filling them with HRP from application sites within the CNS. A serially repeating set of about ten such neurons is present in a longitudinal column on each side of the caudal hindbrain. The T axons project across the midline, and branches course both rostrally and caudally within the medial longitudinal fascicle (mlf). The cells receive synaptic input from the Mauthner neurons, from unidentified axons in the mlf, and perhaps from trigeminal sensory fibers. They project to cranial and pectoral motor nuclei.

T interneurons appear to be homologous to giant fiber neurons in the hatchetfish and to some of the cranial relay neurons in the goldfish. We discuss a possible functional role and comparative implications of their distribution in the hindbrain.
Organization of the rostral thalamus in the rat: Evidence for connections to layer I of visual cortex
Authors: Rieck Richard W. , Carey Russell G.
Published: January 2005

The present study demonstrates the organization of a thalamocortical projecting system which terminates within layer I of the visual cortex in the hooded rat. Horseradish peroxidase (HRP) injections restricted to layer I resulted in retrograde labeling of large and medium‐sized multipolar and fusiform neurons that are located within the ventromedial (VM) nucleus and a dorsomedial subunit of the ventral anterolateral nucleus (VAL). Retrograde cellular labeling also occurs within the anteromedial nucleus (AM) following these injections. After restriction of HRP injections to layer I, peroxidase labeling was not found within neurons of the classically defined intralaminar system, i.e., central medial, paracentral, and central lateral nuclei, or within the rostral continuations of the intralaminar system. Since the VM, dorsomedial VAL, and AM nuclei are directly adjacent to portions of the internal medullary lamina, we refer to this amalgam of rostral thalamic nuclei that project to layer I as the “paralaminar” system. We also provide cytoarchitectonic criteria that can be used to distinguish three separate subdivisions within the VAL complex, including that portion of the VAL which is part of the “paralaminar” system. In contrast, when control injections of WGA‐HRP are placed within either the cellular supragranular or infragranular layers of the visual cortex, no appreciable number of neurons are labeled within the VM, VAL, or AM.
Afferent connections of gudden's tegmental nuclei in the rabbit
Authors: Hayakawa Tetsu , Zyo Katuya
Published: January 2005

The regions projecting to Gudden's tegmental nuclei were examined by retrograde transport of horseradish peroxidase or wheat‐germ‐agglutinin‐conjugated horseradish peroxidase. Gudden's tegmental nuclei in the rabbit can be divided into a pars principalis of the ventral tegmental nucleus (TVP), a pars ventralis of the dorsal tegmental nucleus (TDV), and a pars dorsalis of the dorsal tegmental nucleus (TDD).

The TVP receives many fibers from the medial division of the ipsilateral medial mammillary nucleus and bilaterally from the lateral habenular nucleus, and additionally some fibers from the posterior nucleus of the interpeduncular complex. The TDV receives many fibers from the ipsilateral lateral mammillary nucleus, from the ipsilateral prepositus hypoglossi nucleus, bilaterally from the lateral habenular nucleus, from the central and paramedian nuclei of the interpeduncular complex, from the bilateral gray matter along the floor of the fourth ventricle, and from the contralateral supragenual nucleus. The TDD receives a projection from the lateral habenular nucleus of both sides and from the central and paramedian nuclei of the interpeduncular complex, and a minor projection from the ipsilateral lateral mammillary nucleus, the posterior nucleus of the interpeduncular complex, the prepositus hypoglossi nucleus, and the contralateral supragenual nucleus.
Trigeminocerebellar, trigeminotectal, and trigeminothalamic projections: A double retrograde axonal tracing study in the mouse
Authors: Steindler Dennis A.
Published: January 2005

Double retrograde axonal tracing experiments were carried out in order to reveal potential patterns of divergence in axonal projections from the two major sensory nuclei of the mouse brainstem trigeminal complex: the principal sensory and spinal trigeminal nuclei (oralis, interpolaris, and caudalis divisions). The tracers wheat germ agglutinin, N‐[acetyl‐3H] and horseradish peroxidase were used in paired injection strategies within portions of the cerebellum, superior colliculus, and thalamic ventrobasal complex and/or posterior group of adult ICR white mice.

Trigeminal neurons with projections to tactile areas of the cerebellar cortex or underlying deep cerebellar nuclei were found scattered throughout the principal sensory nucleus and interpolaris division, and mainly in dorsal regions of the oralis division of the spinal trigeminal nucleus. Injections of either tracer which involved lateral portions of the rostral half of the superior colliculus labeled trigeminotectal neurons mainly in the contralateral interpolaris division, ventral half of the oralis division, and a ventral region of the principal sensory nucleus near the oralis border. Fewer trigeminotectal neurons were found scattered throughout the principal sensory nucleus and the magnocellular layer of the caudalis divisions, although an occasional labeled neuron was also found in the marginal layer. Contralaterally projecting trigeminothalamic neurons were observed throughout the principal sensory nucleus, interpolaris division, and within the marginal and magnocellular layers of caudalis.

Double‐labeled neurons were observed only after paired injections of the tracers in the thalamus and ipsilateral superior colliculus, and they were found within the caudoventral portion of the principal sensory nucleus near the oralis border, throughout the interpolaris division, within the magnocellular layer of caudalis, and only a few double‐labeled neurons were also found within the marginal layer. After such injections. 50% of the labeled tectum‐projecting neurons in the principal sensory nucleus, 64% in the interpolaris division, and 57% in the caudalis division are branched neurons which have collateralized projections to both the superior colliculus and thalamus. These projections, which have not been described before, appear to arise from more than one class of projection neuron which is differentially distributed within different regions of the trigeminus.
Corticothalamic connections of the posterior parietal cortex in the rhesus monkey
Authors: Yeterian Edward H. , Pandya Deepak N.
Published: January 2005

Corticothalamic connections of posterior parietal regions were studied in the rhesus monkey by using the autoradiographic technique. Our observations indicate that the rostral superior parietal lobule (SPL) is connected with the ventroposterolateral (VPL) thalamic nucleus. In addition, whereas the rostral SPL is connected with the ventrolateral (VL) and lateral posterior (LP) thalamic nuclei, the rostral IPL has connections with the ventroposteroinferior (VPI), ventroposteromedial parvicellular (VPMpc), and suprageniculate (SG) nuclei as well as the VL nucleus. The caudal SPL and the midportion of IPL show projections mainly to the lateral posterior (LP) and oral pulvinar (PO) nuclei, respectively. These areas also have minor projections to the medial pulvinar (PM) nucleus. Finally, the medial SPL and the caudal IPL project heavily to the PM nucleus, dorsally and ventrally, respectively. In addition, the medial SPL has some connections with the LP nucleus, whereas the caudal IPL has projections to the lateral dorsal (LD) nucleus. Furthermore, the caudal and medial SPL and the caudal IPL regions have additional projections to the reticular and intralaminar nuclei–the caudal SPL predominantly to the reticular, and the caudal IPL mainly to the intralaminar nuclei.

These results indicate that the rostral‐to‐caudal flow of cortical connectivity within the superior and inferior parietal lobules is paralleled by a rostral‐to‐caudal progression of thalamic connectivity. That is, rostral parietal association cortices project primarily to modality‐specific thalamic nuclei, whereas more caudal regions project most strongly to associative thalamic nuclei.
Large neurons in the primate neostriatum examined with the combined Golgi‐electron microscopic method
Authors: DiFiglia Marian , Carey Janice
Published: January 2005

Large neurons in the monkey neostriatum were examined in the electron microscope in tissue treated with the rapid‐Golgi impregnation method followed by the gold‐toning procedure. Two types of large neurons were investigated: an aspiny neuron (aspiny type II; N = 5) with numerous varicose dendrites and a spiny cell (spiny type II; N = 1) with few sparsely spined dendrites. The large aspiny neurons had variably shaped somata, an eccentric highly invaginated nucleus, and a cytoplasm rich in organelles. Mitochondria were distributed unevenly in dendrites and were localized primarily in varicosities. Some mitochondria exhibited dense hodies 80–300 nm in size. Most synapses (84%) onto large aspiny neurons occurred 20 μm or more from the cell body and contacted dendritic varicosities (63%). A smaller proportion of boutons (21%) contacted constricted portions of varicose segments. A low incidence of synaptic boutons was observed on smooth primary and secondary dendrites (11%), cell bodies (3%), and branch points (2%). Seven percent of the axons that synapsed with large aspiny neurons also contacted nearby dendrites or spines of medium‐sized spiny neurons. At least eight morphologically distinct types of axons making synapses with large aspiny neurons were identified and included both symmetric and asymmetric types.

The large spiny neuron was different from the large aspiny neuron in its subcellular characteristics. Synapses were found on all portions of the cell, including the axon initial segment, but fewer types of axonal inputs were identified.

These findings confirm that the two types of large neurons identified in Golgi impregnations of the primate neostriatum are also different at the ultrastructural level, both in their cytological features and in their synaptic organization. The large aspiny neuron integrates synaptic inputs that innervate a relatively large area of caudate neuropil and appear to arise from a variety of extrinsic and intrinsic sources. The high density of synaptic inputs to dendritic varicosities suggests that they have an important functional role.
Telencephalic projections from midbrain and isthmal cell groups in the pigeon. II. The nigral complex
Authors: Kitt Cheryl A. , Brauth Steven E.
Published: January 2005

The trajectories and telencephalic terminal fields of neurons within the area ventralis of Tsai (AVT) and nucleus tegmenti pedunculopontinus pars compacta (TPc) were determined in the pigeon by using amino acid autoradiography and horseradish peroxidase histochemistry. Previous histochemical studies have considered these cell groups comparable to the A10 and A9 components of the mammalian nigral complex.

The results show the efferents derived from these cell groups ascend to the telencephalon via the medial and lateral forebrain bundles, ansa lenticularis, and quintofrontal and occipitomesencephalic tracts. All projections are bilateral and symmetrical, although projections to the contralateral hemisphere are extremely sparse.

Within the telencephalon many cell fields receive projections from the AVT and TPc nuclei; however, the most substantial projections reach structures within the basal telencephalon, especially the paleostriatal complex. Within the paleostriatal complex the paleostriatum augmentatum (PA) receives a very heavy projection from the TPc. AVT projections reach primarily rostromedial portions of PA as well as the lobus parolfactorius. The large‐celled portions of the paleostriatum including the paleostriatum primitivum and nucleus intrapeduncularis do not appear to receive projections from either AVT or TPc neurons.

Projections from AVT and TPc neurons terminate within other structures of the basal telencephalon including the lateral and medial septal nuclei, the olfactory tubercle, the ventral paleostriatum and the preoptic area. Pallial derivatives including the hyperstriatum dorsale, hyperstriatum ventrale, dorsal archistriatum, and hippocampus also receive projections from AVT and TPc neurons, although these projections are much sparser than those reaching subpallial structures. Large portions of the telencephalon including the hyperstriatum accessorium, most of the hyperstriatum ventrale, much of the archistriatum, and much of the neostriatum do not receive projections from AVT or TPc neurons. Furthermore, there is substantial overlap between the telencephalic projections of TPc and AVT neurons, as well as considerable overlap between the projections of both these nigral cell groups and the projections of the locus coeruleus complex in the pigeon. This high degree of overlap between locus coeruleus and nigral telencephalic terminal fields is quite different from the condition in mammals and suggests possible functional divergence for some of thesee pathways in contemporary amniote forms.
Co‐Localization of fixative‐modified glutamate and glutaminase in neurons of the spinal trigeminal nucleus of the rat: An immunohistochemical and immunoradiochemical analysis
Authors: Magnusson Kathy R. , Larson Alice A. , Madl James E. , Altschuler Richard A. , Beitz Alvin J.
Published: January 2005

The spinal trigeminal, nucleus (STN) is involved in processing orofacial sensory information, including tactile, thermal and nociceptive input, and relaying this information to higher brain centers, such as the thalamus. Very little information is available regarding the major excitatory neurotransmitters of this nucleus. The amino acid glutamate has been proposed as a major excitatory neurotransmitter in the central nervous system. In the present study, a novel monoclonal antibody, specific for fixative‐modified glutamate, was utilized in conjunction with polyclonal antisera against glutaminase and aspartate aminotransferase (AATase) in an attempt to identify and map the locations of possible glutamatergic neurons in the STN. Co‐localization experiments were performed by radiolabeling our monoclonal antibody and using this antibody in conjunction with the polyclonal antisera against glutaminase and AATase to evaluate the possible coexistence of glutamate with glutaminase or AATase in STN neurons.

In all three subnuclei of the STN, immunohistochemically labeled neuronal profiles were observed with both of the polyclonal antisera and with the monoclonal antibody. Subnucleus caudalis contained the greatest number of labeled profiles per coronal section followed by subnucleus interpolaris and subnucleus oralis. The number and the distribution of immunoreactive profiles observed after the use of the glutaminase antiserum was comparable to that obtained with the monoclonal antibody. Co‐localization experiments demonstrated that all glutaminase‐like immunoreactive neurons also contained fixative‐modified glutamate‐like immunoradioactivity. These results suggest that glutamatergic neurons are present in the spinal trigeminal nucleus. The AATase antiserum labeled more neuronal profiles in each of the three subnuclei than did the glutaminase antiserum or the monoclonal antibody. In addition, co‐localization experiments indicated that glutamate like immunoreactivity was present in only two‐thirds of AATase‐like immunoreactive neuronal profiles. These findings suggest that glutaminase may be a more reliable marker of glutamatergic function than AATase.