bluuebunny/crossref_metadata_2025 huggingface dataset:
Retinotopic and chronotopic organization of goldfish retinal ganglion cell axons throughout the optic nerve
Authors: Springer Alan D. , Mednick Adam S.
Published: January 2005

The organization of the retinal ganglion cell (RGC) axons within the goldfish optic nerve head and optic nerve was established by labeling select groups of axons either autoradiographically or with cobaltous lysine. In the optic nerve head, the axons are organized eccentrically with respect to their time of development. Axons of older RGCs are located dorsally and those of younger RGCs are located ventrally. The retinal sectors map across the rostrocaudal axis of the optic nerve head, resulting in four dorsoventrally oriented columns that contain, from rostral to caudal, the axons of ventronasal, dorsonasal, dorsotemporal, and ventrotemporal RGCs. Thus, the optic nerve head is organized into orthogonally oriented laminae. One dimension maps the age of the axons and the other maps the retinal sector of the axons' origin.

The optic nerve is organized virtually in the same fashion as the optic nerve head. However, glial septa that invade the optic nerve severely distort, but do not eliminate, the columnar organization of the retinal sectors. These septa deflect many RGC axons and disrupt nearest‐neighbor relationships. The distortions produced by the glial septa include folding of the columns and distortion of the chronological lamination. However, the glial septa do not extend into the optic foramen. Therefore, a virtually undistorted columnar organization reappears in the optic foramen. Several roles for the glial septa are discussed.
Multiple visual areas in the caudal superior temporal sulcus of the macaque
Authors: Desimone Robert , Ungerleider Leslie G.
Published: January 2005

Anatomical and physiological evidence indicates that, in addition to area MT, much of the cortex in the caudal superior temporal sulcus (STS) of the macaque has visual functions. Yet the organization of areas outside of MT remains unclear, and there are even conflicting data on the boundaries of MT itself. To examine these issues, we recorded from neurons throughout this region in three monkeys. Anterograde or retrograde tracers were injected into MT at the conclusion of recording to identify its projection fields. Based on differences in their visuotopic organization, neuronal properties, receptive field size, myeloarchitecture, and pattern of connections with MT, several visual areas were distinguished within the caudal STS.

Area MT, defined as the heavily myelinated portion of the striate (VI) projection zone in STS, contained a systematic representation of only about the central 30°–40° of the contralateral field. The far peripheral field was represented medial to MT in MTp, which we had previously found receives projections from far peripheral V1 and V2 (Ungerleider and Desimone: J. Comp. Neurol 248:147–163, 1986). Like MT, MTp contained a high proportion of directionally selective cells, and receptive field size in MTp was the size expected of MT fields if the latter were to extend into the periphery.

Areas MST (medial superior temporal) and PP (posterior parietal) were found medial to MT and MTp. Both MST and PP had a high proportion of directionally selective cells, but only MST received a direct projection from MT. Cells in MST had larger receptive fields than those in either MT or MTp butnonetheless displayed a crude visuotopic organization. Receptive fields of cells in PP were even larger, some including the entire contralateral visual field. Furthermore, unlike cells in MST, some in PP responded to auditoryor somesthetic stimuli in addition to visual stimuli.

Area FST, which has a distinctive myeloarchitecture, was found anterior to MT in the fundus of the STS, for which it is named. FST received a direct projection from MT, but only about a third of its cells were directionally selective. Receptive fields of cells in FST were large, often included the center of gaze, and often crossed into the ipsilateral visual field.

Area V4t (transitional V4) and a portion of V4 were found lateral to MT within the STS, and both received direct projections from MT. V4t has a distinctive, light myelination. Both areas had a low incidence of directionally selective cells, and both contained coarse representations of the lower visual field.

The neuronal properties of areas in the caudal STS suggest that MT, MTp, MST, and PP, together with the superior temporal polysensory area, constitute a cortical system for motion analysis. At successive stages in this system, neurons appear to integrate motion information over an increasingly large portion of the retina, respond selectively to more complex types of motion, and respond to inputs from additional sensory modalities.
Immunohistochemical study on the distribution of neuron‐specific enolase‐ and peptide‐containing nerves in the reticulorumen and the reticular groove of cattle
Authors: Kitamura N. , Yamada J. , Yamashita T.
Published: January 2005

The distribution of nerves containing immunoreactivity for substance P (SP), vasoactive intestinal polypeptide (VIP), leucine‐enkephalin (LENK), gastrin‐releasing polypeptide (GRP), and somatostatin (SOM) was studied in the reticulorumen and the reticular groove of the calf and cow, use immunohistochemistry. Neuron‐specific enolase (NSE) antiserum was used to determine the general distribution of nerves, which was then compared to distribution of immunoreactive (IR) nerves stained for five kinds of peptides.

Nerve fibers and cell bodies were observed in all segments examined; however, both elements showed considerable variation in different segments and age groups. The densities of nerve fibers and ganglia were most concentrated in the reticular groove and least numerous in the ruminal wall. VIP‐, SP‐, and LENK‐IR nerves were detected in all segments, whereas GRP‐ and SOM‐IR nerves were detected only in the reticular groove. NSE‐IR nerves were moderately abundant in the reticulorumen, but peptide‐IR nerves composed onlya minor population of nerves with VIP‐IR nerves being most abundant. SP‐IR nerves were less abundant and LENK‐IR nerves were rarely observed. Abundantnerves were detected in the lips of the reticular groove and of these, SP‐IR nerves were most abundant, and in order of decreasing abundance, VIP‐, LENK‐, SOM‐, and GRP‐IR nerves were observed also. Immunoreactive nerves were more abundant in the calf than in the cow. The reduced abundance of immunoreactive nerves in the cow as compared to calf was striking, particularly with‐regard to the SP‐IR nerves located in the lips of the reticular groove.
Ultrastructural analysis of synaptic relationships of intracellularly stained pyramidal cell axons in piriform cortex
Authors: Haberly Lewis B. , Presto Susan
Published: January 2005

Axons of pyramidal cells in piriform cortex stained by intracellular injection of horseradish peroxidase (HRP) have been analyzed by light and electron microscopy. Myelinated primary axons give rise to extensive, very fine caliber (0.2 μm) unmyelinated collaterals with stereotyped radiating branching patterns. Serial section electron microscopic analysis of the stained portions of the collateral systems (initial 1–2 mm) revealed that they give rise to synaptic contacts on dendritic spines and shafts. These synapses typically contain compact clusters of large, predominantly spherical synaptic vesicles subjacent to asymmetrical contacts with heavy postsynaptic densities. On the basis of comparisons with Golgi material and intracellularly stained dendrites, it was concluded that dendritic spines receiving synapses from the proximal portions of pyramidal cell axon collaterals originate primarily from pyramidal cell basal dendrites. Postsynaptic dendritic shafts contacted closely resemble dendrites of probable GABAergic neurons identified in antibody and [3H]‐GABA uptake studies.

Electron microscopic examination of pyramidal cell axon initial segments revealed a high density of symmetrical synaptic contacts on their surfaces. Synaptic vesicles in the presynaptic boutons were small and flattened.

It is concluded that pyramidal cells synaptically interact over short distances with other pyramidal cells via basal dendrites and with deep nonpyramidal cells that probably include GABAergic cells mediating a feedback inhibition. This contrasts with long associational projections of pyramidal cells that terminate predominantly on apical dendrites of other pyramidal cells (Haberly and Behan: J. Comp. Neurol. 219:448–460, '83).
Three morphologically distinct types of interface develop between adult host and fetal brain transplants: Implications for scar formation in the adult central nervous system
Authors: Krüger Stefan , Sievers Jobst , Hansen Christian , Sadler Martin , Berry Martin
Published: January 2005

The development of the host/graft interface of cerebellar and cerebral transplants was studied 1‐60 days after operation. Grafts from fetal Wistar rats were transplanted to a cavity over the superior colliculus of adult rats by removing parts of the overlying cortex and hippocampus according to the Björklund/Stenevi technique. In sham‐operated control rats, in which a cavity was made in the brain but no graft was implanted, the parenchyma bordering the entire cavity developed a complete glial‐meningeal scar within 2 weeks after operation consisting of multilayered glial processes, a basal lamina, and fibroblasts (meningeal cells).

A similar interface also developed between graft and host in the most superficial parts of the transplantation cavity. In the basal parts of the transplantation cavity, the host/graft interface consisted either of an incomplete sheet of astrocyte processes aligned in parallel to each other but without a covering basal lamina or of completely fused neuropil without any morphological signs of separation between host and transplant.

It is concluded that these three zones of host/graft interface are established by differential interaction between the growing transplant and the host cicatrix. At the basal host/graft parenchymatous interface the fetal transplant interferes with the normal adult cicatrization process of the host, possibly by either releasing inhibitory factors or by preventing contact between the astroglia of the host and fibroblasts (meningeal cells). In white matter regions of the transplantation cavity, voluminous cysts developed, both in sham‐operated controls and in graft recipients, which were invaded by transplanted neurons.
Galanin immunoreactivity in hypothalamic histamine neurons: Further evidence for multiple chemical messengers in the tuberomammillary nucleus
Authors: Köhler C. , Ericson H. , Watanabe T. , Polak J. , Palay S. L. , Palay V. , Chan‐Palay V.
Published: January 2005

By using a specific antibody against the 29 amino‐acid peptide galanin (Gal) with light and electron microscopic immunocytochemistry, we have studied the distribution of Gal immunoreactivity in the posterior hypothalamic magnocellular neurons of the rat. In colchicine‐treated rats, a large number of Gal‐immunoreactive cells were identified within all subdivisions of the tuberomammillary nucleus. The majority of these cells are large multipolar or fusiform neurons, with long, sparsely branching dendrites. A small number project to the ventral hippocampus, as shown by experiments with the retrograde tracing of Fast Blue. Ultrastructural examination of the Gal‐immunoreactive cells confirms their indentity as magnocellular neurons, with dense deposits of immunoreaction product, particularly in small ribosomal arrays and in large, dense‐cored vesicles. Axosomatic synapses occur on these neurons. The axonal boutons synapse with asymmetric and symmetric junctions and contain small synaptic vesicles as well as numerous large, dense‐cored vesicles, which display Gal immunoreactivity. Sequential staining of thin, alternate sections with antibodies against Gal and Lhistidine decarboxylase (HDCase; EC 4.1.1.22) showed colocalization of Galand HDCase‐immunoreactivities in a majority of tuberomammillary neurons. The finding of Gal immunoreactivity within histamine‐producing neurons of the tuberomammillary nucleus adds to the multiplicity of potential neuronal messengers utilized by these cells.
Mapping of an olfactory receptor population that projects to a specific region in the rat olfactory bulb
Authors: Pedersen Patricia E. , Jastreboff Pawel J. , Stewart William B. , Shepherd Gordon M.
Published: January 2005

An anatomically distinct group of glomeruli, termed the modified glomerular complex (MGC), is present in the posterior dorsomedial portion of the main olfactory bulb. This region has been strongly implicated as part of the pathway that processes odor cues for suckling in neonatal rat pups. We studied the distribution pattern of olfactory receptor neurons that project to the MGC region after ionophoretic injections of WGA‐HRP into the olfactory bulbs of 12‐day‐old rat pups. HRP label was confined to an identifiable localized region in the MGC of the main olfactory bulb. Label extended over 2–7% of the glomerular sheet of the main olfactory bulb, including the MGC. Olfactory receptor neurons within the olfactory epithelium of the nasal cavity were labeled with HRP ipsilateral to the injected side. Maps constructed of the olfactory epithelium revealed that the labeled neurons occurred within topographically defined regions. Anteriorly, labeled olfactory neurons were confined to a narrow strip medial to the dorsal recess, and, more posteriorly, this strip widened medially along the septal wall and laterally onto a limited area on the nasal turbinates. Only a portion of the receptor population within a region was labeled. The boundaries between labeled and unlabeled regions were sharp. These findings support the concept that the olfactory epithelium is an anatomical mosaic in which receptors with different glomerular projections sites are intermingled. In conjunction with previous evidence on the functional specificity of the MGC, and staining of receptor neuron subgroups with monoclonal antibodies, these findings further suggest that olfactory receptor neurons form a functional mosaic within the olfactory epithelium.
Mesencephalic trigeminal sensory neurons of cat: Axon pathways and structure of mechanoreceptive endings in periodontal ligament
Authors: Byers Margaret R. , O'Connor Theresa A. , Martin Richard F. , Dong Willie K.
Published: January 2005

We injected 3H‐proline into cat brainstem in order to label the entire mesencephalic trigeminal nucleus (Mes‐V) for autoradiographic analysis of the size and pathways of Mes‐V sensory axons and for microscopic study of. Mes‐V receptor structure in dental tissue. Labeled sensory axons were found in the trigeminal motor and sensory tracts and roots; approximately equal numbers of axons were found in both roots. The sensory root and all three divisions of the trigeminal nerve contained larger Mes‐V axons than the motor root. Labeled Mes‐V axons were found at the ganglion in the dorsomedial (infratrochlear) branch of the ophthalmic nerve but not in the ventrolateral branch. The mean diameter of Mes‐V axons in periodontal ligament was 4.0 ± 1.9 μm compared to 7.3 ± 2.1 μm in maxillary and mandibular nerve, suggesting axonal arborization prior to innervation of ligament.

Mes‐V receptors in dental tissue were confined to ipsilateral periodontal ligament close to the root apex, with greater innervation on the posterior side. Receptor incidence was moderate for most teeth; however, maxillary first and second incisors and maxillary and mandibular canines had focal areas with remarkably dense innervation. No labeled axons were found in pulp of any ipsilateral teeth, and none was found in any contralateral dental tissue.

EM‐autoradiography demonstrated that Mes‐V axons form unencapsulated Ruffini‐like mechanoreceptors in periodontal ligament. The preterminal axons were small and myelinated. Neighboring bundles of unmyelinated axons and rare encapsulated endings were not labeled. The labeled mechanoreceptors branched to varying degrees among the ligament fibers; they contained numerous mitochondria and glycogen particles, as well as some vesicles and rare multivesicular bodies. They were surrounded by special Schwann cells that formed one or several layers around the ending. The endings were exposed to the basal lamina at numerous sites and occasionally extended fingers beyond the lamellar Schwann cells to contact ligament collagen.
Thalamic fiber connections in a teleost (Sebastiscus marmoratus): Visual somatosensory, octavolateral, and cerebellar relay region to the telencephalon
Authors: Ito Hironobu , Murakami Takeshi , Fukuoka Toshio , Kishida Reiji
Published: January 2005

Fiber connections of the nucleus ventromedialis thalami (VM) of Schnitzlein (J. Comp. Neurol. 118:225–267, '62) in a teleost (Sebastiscus marmoratus) were examined by means of the horseradish peroxidase (HRP) tracing method. This nucleus receives fibers from the ipsilateral telencephalon (area dorsalis pars centralis), contralateral retina, contralateral VM, ipsilateral optic tectum, ipsilateral torus semicircularis, contralateral corpus cerebelli, contralateral sensory nucleus of the trigeminal nerve, bilateral bulbospinal reticular formation, contralateral obex region, and contralateral dorsal portion of upper spinal segments. In turn, axons arising from VM terminate in the dorsal telencephalic areas (pars centralis, pars dorsalis, and pars medialis) ipsilaterally, ventral telencephalic area (pars supracommissuralis) bilaterally, nucleus prethalamicus of Meader (J. Comp. Neurol. 60:361–407, '34) bilaterally, nucleus dorsomedialis thaiami bilaterally, VM contralaterally, optic tectum bilaterally, torus semicircularis bilaterally, and nucleus lateralis valvulae ipsilaterally. Based on the cytoarchitecture and fiber connections, VM is subdivided into rostral and caudal components. The caudal part of VM in Sebastiscus is considered to be a multimodal thalamic complex that contains some cells that constitute the dorsal thalamus in other vertebrate groups.
Thickness of the basal lamina at the frog neuromuscular junction
Authors: Kuffler D. P.
Published: January 2005

The Schwann cell basal lamina at the frog neuromuscular junction is much thicker than previously supposed. Its thickness has been demonstrated by modifying the fixation: the nerve muscle preparation is fixed in situ without prior exposure to Ringer solution and the osmolarity of the glutaraldehyde fixative is increased to 285 mOsm. With this procedure the basal lamina is seen to be up to 1 μm thick around the Schwann cells of the nerve terminal and the preterminal axon. The thickness of the basal lamina surrounding the Schwann cells of the myelinated portion of the axons within the perineural sheath (20 nm) is not changed by this modification of fixation. The present results indicate that in addition to the ability to form myelin, other properties of the Schwann cells differ inside and outside the perineurial sheath.
Descending projections and excitation during fictive swimming in Xenopus embryos: Neuroanatomy and lesion experiments
Authors: Roberts Alan , Alford Simon T.
Published: January 2005

We describe the distribution of “descending” interneurons in late Xenopus laevis embryos after retrograde filling with horseradish peroxidaze via their ipsilateral, descending axons in the spinal cord. These multipolar neurons, with dendrites spread throughout the marginal zone, form a longitudinal column extending from midtrunk spinal cord into the brainstem to the level of the vagus. In the hindbrain these neurons are part of the uncrossed reticulospinal projection. They are most numerous in the caudal brainstem, their density falling by half at the eighth postotic segment.

To examine their possible role in swimming we reduced the population of descending interneurons by making progressive transections of the brainstem or spinal cord at the first to fifth postotic segments: These led to progressive reduction in the initial frequency of fictive swimming in immobilized embryos, even when the brainstem was divided sagittally. Transecting the spinal cord at the fourth postotic segment did not reduce initial frequency rostral to the lesion. The effects of these lesions on the duration of fictive swimming episodes were similar.

The results suggest (1) that descending interneurons could provide excitatory drive during swimming and (2) that some reticulospinal and spinal interneurons may form single homogenecus populations.
GABAergic input to cholinergic forebrain neurons: An ultrastructural study using retrograde tracing of HRP and double immunolabeling
Authors: Źborszky L. , Heimer L. , Eckenstein F. , Leranth C.
Published: January 2005

Amygdalopetal cholinergic neurons in the ventral pallidum were identified by combining choline acetyltransferase (ChAT) immunohistochemistry with retrograde tracing of horseradish peroxidase (HRP) following injections of the tracer in the basolateral amygdaloid nucleus. Although ChAT‐positive terminals were identified in the ventral pallidum, they were never seen in contact with either immunonegative or ChAT‐positive amygdalopetal neurons; In material, in which immunostaining against glutamic acid decarboxylase (GAD), the synthesizing enzyme for GABA was combined with retrograde tracing of HRP from the basolateral amygdaloid nucleus, GAD‐positive terminals were seen to contact immunonegative amygdalopetal neurons. In addition, when sections of the rostral forebrain were processed, first to preserve and identify the transported HRP, and then were sequentially tested for both ChAT and GAD immunohistochemistry with the immunoperoxidase reaction for both tissue antigens, GAD‐immunopositive terminals were seen to make synaptic contacts with cholinergic amygdalopetal neurons. These results suggest that amygdalopetal, presumably cholinergic, neurons receive GAD‐positive terminals. In separate experiments using immunoperoxidase for ChAT and ferritin‐avidin for GAD labeling, we confirmed the presence of GAD‐containing terminals on cholinergic neurons. In addition, cholinergic terminals were seen in synaptic contact with GAD‐positive cell bodies. These morphological studies suggest that direct GABAergic‐cholinergic and cholinergic‐GABAergic interactions take place in the rostral forebrain.
The dopaminergic innervation of the ventral striatum in the rat: A light‐ and electron‐microscopical study with antibodies against dopamine
Authors: Voorn P. , Jorritsma‐Byham B. , Van Dijk C. , Buijs R. M.
Published: January 2005

Dopamine (DA) in the dorsal and ventral striatum is associated with different aspects of locomotor activity control. The ventral striatum may form an interface between the limbic system and the extrapyramidal motor system. The distribution of dopaminergic fibers in this interface position was studied in detail with a method applying antibodies against DA. Furthermore, the ultrastructural morpholohy of the DA fibers was examined by means of immuno‐electron microscopy. The results show that DA immunoreactivity is distributed over the ventral striatum in a highly compartmentalized fashion. In jthe dorsal striatum few compartments were found. The DA fibers in the ventral striatum establish mainly symmetric synaptic contacts, preferably with dendritic shafts and spines. The results are discussed in relation to previous data concerning the light and electron‐microscopic identification of catecholaminergic fibers in the ventral and sorsal striatum.
Topographic representation of lower and upper teeth within the trigeminal sensory nuclei of adult cat as demonstrated by the transganglionic transport of horseradish peroxidase
Authors: Shigenaga Y. , Suemune S. , Nishimura M. , Nishimori T. , Sato H. , Ishidori H. , Yoshida A. , Tsuru K. , Tsuiki Y. , Dateoka Y. , Nasution I. D. , Hosoi M.
Published: January 2005

Transganglionic transport of horseradish peroxidase‐wheat germ agglutinin conjugate (HRP‐WGA) entrapped in hypoallergenic polyacrylamide gel was used to study the patterns of termination of primary afferents that innervate the lower and upper tooth pulps within the trigeminal sensory nuclear complex (TSNC). HRP injections were made into the inferior and superior alveolar nerves in order to compare the central projections of the whole nerve with those from tooth pulps. In addition, the relationship between the distribution of the trigeminothalamic tract cells and the projection sites of the tooth pulp afferents was investigated by injecting HRP into the posterior ventral thalamus. HRP‐labeled tooth pulp afferent fibers innervating the lower and upper teeth projected to the subnucleus dorsalis (Vpd) of pars principalis, the rostrodorsomedial part (Vo.r) and nucleus dorsomedialis (Vo.dm) of pars oralis, the medial regions of pars interpolaris, and laminae I, II, and V of pars caudalis. Terminal fields of the lower tooth pulp afferents formed a rostrocaudally running, uninterrupted column from the midlevel of Vpd to the caudal tip of caudalis. In contrast, the column of termination of upper tooth pulp afferents was discontinuous at the Vpd/Vo.r transition, and ended at the more rostral level of the caudalis than that of the lower tooth pulp afferents. The representation of the lower and upper teeth in the TSNC was organized in a somatotopic fashion which varied from one subdivision to the next, although terminal zones of the inferior and superior alveolar nerves overlapped within the Vo.r, Vo.dm, and dorsomedial part of rostral pars interpolaris. The lower and upper teeth were represented in the Vpd, Vo.r, Vo.dm, medial region of pars interpolaris, and laminae I, II, and V, in a ventrodorsal or caudorostral, dorsoventral, lateromedial, dorsoventral, and mediolateral or dorsomedial‐ventrolateral sequence, respectively. The smaller, more focal terminal areas of the teeth contrasted sharply with more extensive terminal fields of the alveolar nerves. The HRP injections within the thalamus indicated that neurons in Vpd, the caudal pars inter polaris, and laminae I/V of caudalis, which are subdivisions of TSNC that receive pulpal projections, sent their axons to the ipsilateral and contralateral posterior ventral thalamus. The present data reconfirmed our previous suggestion (Shigenaga et al.: J. Comp. Neurol. 243:388–408, '86a, J. Comp Neurol. 244:1–18, '86b) of a functional segregation among the cytoarchitectonically different zones of the TSNC, and further suggested that the sub nucleus dorsalis of the principal nucleus in addition to the caudal parts of interpolaris and laminae W of the caudalis plays an important role in the relay of pain from the oral regions.
Neuropeptide Y localization in the rat amygdaloid complex
Authors: Gustafson Eric L. , Card J. Patrick , Moore Robert Y.
Published: January 2005

Neuropeptide Y (NPY)‐, avian pancreatic polypetide (APP)‐, and molluscan cardioexcitatory peptide (FMRF)‐like immunoreactivity in the amygdaloid complex of the rat was investigated immunohistochemically. The distribution of each of these peptides within the amygdala is identical and cross‐blocking studies indicate that all three antisera recognize the NPY antigen. Morphologically distinct populations of NPY immunoreactive neurons are differentially distributed in the medial amygdaloid nucleus and at the base of the stria terminalis. Dense plexuses of immunoreactive axons are present in the medial third of the central nucleus and in the dorsal half of the medial nucleus, with light to moderate fiber plexuses present in the lateral and basolateral nuclei and scattered axons present throughout the remainder of the amygdala. The distribution and appearance of NPY immunoreactive plexuses in the amygdala is similar to that described previously for noradrenergic axons arising from brainstem cell groups (Fallon, Koziell, and moore: J. Comp. Neurol. 180:509–532, '78). However, injections of the noradrenergic neurotoxin 6‐hydroxydopamine into the amygdala result in a complete loss of dopamine‐beta‐hydroxylase (DBH) immunoreactivity in the amygdala and surrounding cortex but leave much of the NPY immunoreactive plexus intact. Similarly, lesions of the locus coeruleus deplete DBH immunoreactivity, leaving NPY‐like immunoreactivity in the amygdala unaffected. These results indicate that much of the NPY immunoreactive plexus observed in the amygdala does not arise from brainstem sources in which NPY and noradrenaline are colocalized. Lesions of the stria terminalis of medial nucleus have no observable effect on the density or distributiion of NPY immunoreactive terminal fields in the basal forebrain and hypothalamus, suggesting that immunoreactive neurons in the amygdaloid complex do not contribute significantly to this innervation.
3H‐nicotine‐ and 125I‐alpha‐bungarotoxin‐labeled nicotinic receptors in the interpeduncular nucleus of rats. II. Effects of habenular deafferentation
Authors: Clarke Paul B. S. , Hamill Geoffrey S. , Nadi N. Suzan , Jacobowitz David M. , Pert Agu
Published: January 2005

The cholinergic innervation of the interpeduncular nucleus (IPN) is wholly extrinsic and is greatly attenuated by bilateral habenular destruction. We describe changes in the labeling of putative nicotinic receptors within this nucleus at 3, 5, or 11 days after bilateral habenular lesions. Adjacent tissue sections of the rat IPN were utilized for 3H‐nicotine and 125I‐α‐bungarotoxin (125I‐BTX) receptor autoradiography.

Compared to sham‐operated controls, habenular destruction significantly reduced autoradiographic 3H‐nicotine labeling in rostral (−25%), intermediate (−13%), and lateral subnuclei (−36%). Labeling in the central subnucleus was unchanged. Loss of labeling was maximal at the shortest survival time (3 days) and did not change thereafter. In order to establish whether this loss was due to a reduction in the number or the affinity of 3H‐nicotine‐binding sites, a membrane assay was performed on microdissected IPN tissue from rats that had received surgery 3 days previously. Bilateral habenular lesions produced a 35% reduction of high‐affinity 3H‐nicotine‐binding sites, with no change in binding affinity.

Bilateral habenular lesions reduced 125I‐BTX labeling in the intermediate subnuclei, and a slight increase occurred in the rostral subnucleus. In the lateral subnuclei, 125I‐BTX labeling was significantly reduced (27%) at 3 days but not at later survival times.

In view of the known synaptic morphology of the habenulointerpeduncular tract, it is conculded that a subpopulation of 3H‐nicotine binding sites within the IPN is located on afferent axons and/or terminals. This subpopulation, located within rostral, intermediate, and lateral subnuclei, may correspond to presynaptic nicotinic cholinergic receptors. Sites that bind 125I‐BTX may include a presynaptic subpopulation located in the lateral and possibly the intermediate subnuclei.
Development of projections from somatic motor‐sensory areas of neocortex to the diencephalon and brainstem in the North American opossum
Authors: Cabana T. , Martin G. F.
Published: January 2005

The development of projections from somatic motor‐sensory areas of neocortex to the diencephalon and brainstem was studied by using the orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) in a series of pouch‐young opossums. The opossum was chosen for study because it is born in a very immature state, 12 days after conception, and has a protracted postnatal development. Cortical axons form a cerebral peduncle by at least postnatal day (PD) 10, a medullary pyramid by estimated PD (EPD) 17, a pyramidal decussation by EPD 26, and reach the first cervical segment of the spinal cord by EPD 29. Cortical axons innervate diencephalic nuclei and perhaps the substantia nigra by EPD 17, but do not grow into more caudal brainstem nuclei until EPD 26. The first brainstem areas innervated by cortical axons are the mesencephalic and rostral pontine tegmentum and parts of the pontine gray adjacent to the pyramidal tract (EPD 29). By EPD 31, cortical axons project to additional areas of the pontine gray, the gigantocellular reticular formation, the medial accessory olive, and the cuneate nucleus. Cortical innervation of the red nucleus and superior colliculus begins at EPD 31 but is not well developed until EPD 35. Cortical axons do not innervate the parvicellular reticular formation or the sensory trigeminal nuclei until EPD 35. Evidence for transient cerebrocerebellar axons was also found.
A comparative light microscopic analysis of the sensory innervation of the mystacial pad. II. The common fur between the vibrissae
Authors: Rice Frank L. , Munger Bryce L.
Published: January 2005

The innervation to the common fur between the vibrissae was examined in the hamster, mouse, rat, gerbil, rabbit, guinea pig, and cat. Samples were taken from central locations among the more caudal vibrissae in the mystacial pad and processed with Richardson's variant of the Bielschowsky silver techique or with Winkelmann's silver technique to selectively stain peripheral axons and terminals. Additional samples were taken among the rostral vibrissae in the rat. We found major unpredictable species‐related variations in the distribution of receptor types, innervation density, and the quantity of innervation in the skin between neighboring vibrissae. The common fur is composed of numerous larger guard hairs and even more numerous smaller vellus hairs. The guard hairs usually are richly innervated with fully developed piloneural complexes composed primarily of a pallisade of Ianceolate endings and a circumferential array of Ruffini and free nerve endings. The vellus hairs are usually innervated by individual or shared free nerve endings. The piloneural complexes in the cat, rat, and mouse are usually complete, whereas those in the other species were usually incomplete and lacked Ruffini endings. There is considerable interspecies variation in the relative quantity of innervation between homologous neighboring vibrissae. The quantity of innervation is related to a combination of receptor completeness, innervation density, and distance between vibrissae. The quantity of intervibrissal fur innervation is by far highest in the cat, relatively high in the rabbit, relatively low in the hamster and caudal mystacial pad of the rat, and lowest in the mouse, gerbil, guinea pig, and rostral mystacial pad of the rat. The differences in the innervation between the cat and the rabbit correlate well with published physiologic data on types of receptor units. Also, barrels are most prominent in species having relatively low quantities of intervibrissal innervation and are less prominent or absent in species having high quantities of intervibrissal innervation.
Reactive synaptogenesis in hippocampal area CA1 of aged and young adult rats
Authors: Anderson Kevin J. , Scheff Stephen W. , DeKosky Steven T.
Published: January 2005

Selective lesions that result in a partial loss of neuronal input appear to signal residual, undamaged inputs to sprout and replace synaptic connections that have been lost. Previous investigations have compared this process of reactive synaptogenesis in young and old animals in the hippocampal dentate gyrus and have demonstrated that the aged brain has a diminished capacity for reinnervation following massive denervation of a target area. This investigation has focused on the lesion‐induced plasticity of an adjacent area of the hippocampal formation, area CA1 of regio superior, in young adult and aged rats.

Young adult aged Fischer 344 rats were subjected to a unilateral, intraventricular injection of kainic acid that selectively destroyed the CA3‐CA4 hippocampal pyramidal neurons. Following a 2‐day interoperative interval, the rats sustained an ipsilateral transection of the fimbria‐fornix. Animals were killed at 4, 10, 30, and 60 days following the second transection and processed for electron microscopic analysis. Photographic montages were constructed of area CA1 extending from the alveus to the hippocampal fissure. The density of synapses, both intact and degenerating, was determined and analyzed as a function of age, days postlesion, and zone of analysis.

Synaptic density decreased 30–40% contralaterally and 60–70% ipsilaterally in both aged and young adult rats. While both age groups restored synaptic density to preoperative levels, aged subjects required significantly more time. Aged rats appeared to be retarded in the initial phases of synaptic replacement. The delay in the aged animals' reactive response was not due to any differences in degeneration clearance between the age groups.
Genesis of interneurons in the dorsal lateral geniculate nucleus of the cat
Authors: Weber A. J. , Kalil R. E. , Hickey T. L.
Published: January 2005

Most neurons in the A‐laminae of the cat's dorsal lateral geniculate nucleus (LGN) are born between embryonic days 22 and 32. Whereas approximately 78% of these cells are destined to become geniculocortical relay cells, the remaining 22% of LGN neurons do not appear to establish connections with visual cortex, and therefore can be considered interneurons. In the present study we have combined the 3H‐thymidine method for labeling dividing neurons with the retrograde horseradish peroxidase (HRP) method for identifying LGN relay cells in order to study specifically the genesis of interneurons in the cat's LGN.

Developing LGN interneurons in 12 kittens were labeled with 3H‐thymidine by injecting the radioactive label into the allantoic cavity of their pregnant mothers on different embryonic days. Approximately 8–22 weeks after birth LGN relay cells in the A‐laminae were labeled retrogradely by injecting large volumes of HRP into visual cortex areas 17 and 18. LGN cells that could not be labeled retrogradely with HRP were considered to be interneurons.

Our results show that interneurons are born on each of the embryonic days studied, E24–E30. This period represents approximately the middle two‐thirds of the entire period of LGN neurogenesis. Although the birth rate for interneurons is not uniform, there is no indication from our data that interneurons and relay cells in the cat's LGN are born at different times during LGN neurogenesis.
Thalamic afferents to cytoarchitectonic subdivisions of area 6 on the anterior sigmoid gyrus of the dog: A retrograde and anterograde tracing study
Authors: Stanton Gregory B. , Tanaka Duke , Sakai Sharleen T. , Weeks Ophelia I.
Published: January 2005

The cytoarchitecture and thalamic afferents of cortical area 6 located on the anterior sigmoid gyrus were mapped and analyzed in the dog by means of cytoarchitectonic, horseradish peroxidase (HRP), and autoradiographic methods.

Cytoarchitectonically, area 6 consists of medial and lateral subdivisions that correspond, respectively, to areas 6aα and 6aβ in the cat. In the dog, area 6aα is characterized by a wide layer III, the merging of borders between layers III and V, the presence of small‐to‐medium‐size pyramidal cells in layer V, and a pallisade arrangement of cells in layer VI. Area 6aβ appears more stratified, with a relatively acellular layer present between layers V and VI and the presence of large pyramidal cells in layer V. Neither area 6aα nor 6aβ contains a layer IV.

Data obtained from injections of HRP into areas 6aα or 6aβ revealed that labeled thalamic neurons were distributed in a longitudinal band extending from the rostral part of the ventral anterior nucelus (VA) through the caudal part of the mediodorsal nucleus (MD). Labeled cells were observed in the ventral and ventral medial thalamic nuclei as well as in several of the intralaminar nuclei including the central lateral, central medial, parafascicular, and centrum medianum nuclei. A few labeled cells were also located in the suprageniculate nucleus. The densest thalamic labeling was present in VA and MD following injections into area 6aα. Equivalent or even larger injections into area 6aβ resulted in much less thalamic labeling. The band of labeled cells also extended into the hypothalamus, zona incerta, amygdala, claustrum, periaqueductal gray of the midbrain, and the nucleus of Darkschewitsch.

Results from autoradiographic experiments showed that area 6 subdivisions receive a loosely organized topographic input from VA. Injections of tritiated amino acids were made into selected regions of VA and into the caudal part of MD, areas in which the largest numbers of HRP‐labeled cells were located. Area 6aα receives afferents primarily from the rostromedial part of VA and the caudal part of MD while area 6aβ receives its principal input from the caudal and lateral parts of VA with minimal input from MD. Axons originating from VA terminate in both layers I and III of area 6 while those originating from the caudal part of MD terminate only in layer III.

The results of this study show that area 6 in the dog may be divided cytoarchitectonically into two distinct regions, each of which receives a characteristic pattern of thalamic inputs. The organization of these inputs, as well as those from other, nonthalamic subcortical areas, lends anatomical support for the functional division of area 6 into an electrophysiologically defined medial eye movement field and a lateral supplementary motor area.
A developmental study of the quantitative distribution of LHRH neurons within the central nervous system of postnatal male and female rats
Authors: Wray Susan , Hoffman Gloria
Published: January 2005

The quantitative distribution of LHRH neurons within the central nervous system of male and female rats during postnatal development was investigated with light microscopic immunocytochemistry. Approximately 1,300 immunoreactive LHRH cells were found within the forebrain at all ages. The topographic distribution of LHRH neurons was adultlike in the earliest neonatal stage examined (2 days postnatal) and remained similar throughout development. Two LHRH cell subtypes, smooth LHRH cells and LHRH cells with spinelike processes (irregular LHRH cells), were found throughout the entire extent of the LHRH neuronal field in both sexes. A sex difference in the number of LHRH cells anterior to the organum vasculosum lamina terminalis/preoptic area (a 20% greater number in this region in females) was observed. This sex difference was present throughout development and was not limited to one specific LHRH cell subtype. These data are consistent with the hypothesis that the LHRH system is established early in postnatal development, and that the signal for reproductive maturation is related to the development of synaptic inputs to the LHRH cells.
Morphology of rabbit retinal ganglion cells projecting to the medial terminal nucleus of the accessory optic system
Authors: Buhl Eberhard H. , Peichl Leo
Published: January 2005

Rabbit retinal ganglion cells were retrogradely labeled following injection of rhodamine‐labeled microspheres into the medial terminal nucleus. The small fraction of rhodamine‐labeled neurons reached their peak concentration within the visual streak and then decreased with increasing eccentricity until none were encountered in the far periphery. The same rabbits also received injections of the fluorescent tracer Fast Blue into the superior colliculus. No double‐labeled neurons were observed, i.e., ganglion cells projecting to the medial terminal nucleus (MTN) had no axon collaterals to the superior colliculus. In fixed retinae rhodamine‐labeled ganglion cells were intracellularly injected with the fluorescent dye Lucifer Yellow to reveal their full dendritic arborization. MTN‐projecting cells had mediumsized to large somata with thin and frequently branched dendrites. The large dendritic trees had a distinct morphology and were predominatly unistratified in a narrow band that presumably corresponded to the electrophysiologically determined on‐sublamina of the inner plexiform layer. Dendritic field sizes were inversely related to ganglion cell density, thus providing an eccentricity‐independent, constant dendritic coverage factor. Approximately five to six dendritic fields from neighboring cells cover every point of the retina. Published reports claim that the physiological class of on‐direction‐selective ganglion cells provides the sole retinal input to the MTN in the rabbit. In this context morphological features of MTN‐projecting cells and their presumed functional correlation with on‐direction‐selective ganglion cells are discussed.
Structural and functional characteristics of commissural neurons in the superior colliculus of the hamster
Authors: Rhoades Robert W. , Mooney Richard D. , Szczepanik Ann Marie , Klein Bradley G.
Published: January 2005

Intracellular recording and horseradish peroxidase (HRP) injection techniques were employed to delineate the structural and functional properties of superior collicular (SC) neurons in the hamster that were antidromically activated by electrical stimulation of the contralateral tectum. A total of 39 such cells were completely characterized, injected, and recovered. In ten of these, the axonal filling allowed us to reconstruct at least a portion of the terminal arborization in the SC contralateral to the labelled cell. Two of the recovered neurons were located in the stratum griseum superficiale (SGS), three were in the stratum opticum (SO), ten were in the stratum griseum intermediale (SGI), 11 were in the stratum album intermedium (SAI), 11 were in the stratum griseum profundum (SGP) and two were located in the stratum album profundum (SAP). The recovered cells were highly varied in both their morphological and their physiological characteristics. Somal areas ranged between 74 μm2 and 364 μm2, and the sample of recovered neurons included horizontal cells, narrow field vertical cells, and a variety of other multipolar neurons. Over one‐third (38.5%) of the recovered cells were unresponsive, 2.6% were exlcusively visual, 33.3% responded only to innocuous cutaneous stimuli, 10.2% were bimodal, 7.7% were specifically nociceptive, and 7.7% had complex (Rhoades, Mooney, and Jacquin: J. Neurosci. 3:1342–1354, ′83) somatosensory receptive fields. We observed no clear‐cut correlations between the structural and functional characteristics of these neurons. The conduction latencies of the commissural SC neurons ranged between 0.8 and 14.0 ms. The most rapidly conducting cells were located in the SGP and SAP. Conduction latency had a significant negative correlation with soma area.

Labelled axons, in many cases, had at least one terminal arbor in a portion of the SC that was mirror symmetric with the location of the cell from which it originated. In several cases, however, commissural axons gave off a number of collaterals across the mediolateral extent of the tectum. Commissural axonal terminations were visible only in the laminae ventral to the SO. Several commissural SC neurons also had extensive ipsilateral axon collaterals. Both the ipsilateral and commissural axon branches of these cells gave off en passant and terminal swellings.