bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual mode of corticothalamic synaptic termination in the mediodorsal nucleus of the rhesus monkey
Authors: Schwartz Michael L , Dekker Jan J. , Goldman‐Rakic P. S.
Published: January 2005

Electron microscopic autoradiography (EM‐ARG) was used to assess the synaptic organization of corticothalamic terminals in the parvicellular division of the mediodorsal thalamic nucleus. Examination of the synaptic organization in unreacted tissue revealed several distinct synaptic types distributed among glomerular and nonglomerular regions of the neuropil. Within glomeruli, three presynaptic terminal classes were found. The majority of profiles (as many as eight to ten per glomerulus) were presynaptic dendrites (PSDs) forming symmetric synaptic contacts with a central dendrite, and occasionally with other PSDs. One or two largo terminals densely packed with round vesicles (LR terminals) were also present in each glomerulus. This terminal class made multiple asymmetric contacts with the central dendrite, as well as with many PSDs within the glomerulus. Finally, small terminals with round vesicles (SR terminals) formed asymmetric synaptic junctions with PSDs in some glomeruli. PSDs and SR terminals were also found in the extraglomerular neuropil, although in different proportions than in the glomeruli. In the extraglomerular neuropil SR terminals were the most abundant terminal class and these terminals made synaptic contacts with dendrites of all sizes. PSDs were seen in considerably smaller numbers than in the glomeruli. Finally, the extraglomerular neuropil contained a moderate number of small to medium terminals that formed, symmetric synaptic junctions (SF terminals) with cell bodies and dendrites of all sizes.

Synaptic profiles related to corticothalamic inputs were identified by injecting the prefrontal cortex of two rhesus monkeys with 3H‐leucine and ‐proline and analyzing the distribution and morphology of radiolabeled terminals. Quantitative analysis of the density of silver grains over different tissue compartments revealed a positive labeling index for two terminal classes: SR and LR terminals. Labeled SR terminals were concentrated in the extraglomerular neuropil and labeled LR terminals were found within glomeruli where they formed synaptic contact with the central dendrite, as well as with presynaptic dendrites of the glomerulus. In contrast to many other thalamic nuclei, cortical input to the mediodorsal nucleus arrives via two distinctive synaptic pathways, one terminating extraglomerularly and the other terminating within the synaptic glomeruli. The dual mode of corticothalamic terminations in the mediodorsal nucleus suggests a more potent and possibly different role for cortical input in the regulation of neuronal activity in this association nucleus than in sensory nuclei of the thalamus.
Common projection areas of antennal and visual pathways in the honeybee brain, apis mellifera
Authors: Maronde Ulrike
Published: January 2005

The convergence of primary sensory neurons of the antennae, higher order visual interneurons, and antennal motoneurons was analysed with neuroanatomical techniques in the honeybee, Apis mellifera. The different modalities evoke specific antennal responses in this insect. Three different fluorescent dyes were applied successively in the same preparation in order to visualise the various fiber projections from the antennae and the lobula in the brain of the honeybee. Three neuropile areas where sensory fibers of the antennae overlap with visual projection neurons from the lobula were found. Within the posterior‐median protocerebrum the antennal tract T6‐1 comes in close vicinity to the lobula tract Lo T‐9 and to some other lobula fibers that cannot be assigned to a special tract. Antennal T6‐3 fibers overlap with lobula LoT‐7 neurons within the posterior protocerebrum more laterally. Antennal T5 fibers arborise in the dorsal lobe and show common projection sites with lobula LoT‐3 neurons. The multimodal convergence in the three common neuropiles demonstrates that these areas are important centers for multimodal information processing between sensory, motor, and descending neurons in insects.
Dendritic architecture of nucleus ambiguus motoneurons projecting to the upper alimentary tract in the rat
Authors: Altschuler Steven M. , Bao Xinman , Miselis Richard R.
Published: January 2005

The motor innervation for palatal, pharyngeal, laryngeal, and esophageal muscles originates within the nucleus ambiguus. Although the viscerotopic organization of the upper alimentary tract in the nucleus ambiguus has been extensively studied, little information concerning the dendritic arborization of nucleus ambiguus motoneurons is available. The neural tracer cholera toxin‐horseradish peroxidase, which is particularly effective at revealing dendrites of retrogradely labeled neurons, was used to determine the dendritic architecture and organization of nucleus ambiguus motoneurons.

In 72 rats, cholera toxin‐horseradish peroxidase in volumes of 1.0–18 m̈l was directly applied under pressure to the musculature of various sites along the upper alimentary tract. Motoneurons innervating the soft palate, pharynx, cricothyroid muscle, and cervical esophagus were all found to have extensive dendrites that extended into the adjacent reticular formation with a distinct pattern for each muscle group. In contrast, the dendrites of motoneurons innervating the thoracic and sub diaphragmatic esophagus were confined to the compact formation of the nucleus ambiguus. Dendritic bundling within the confines of the nucleus ambiguus was prominent following injection of tracer into the soft palate, pharynx, and esophagus. The bundles were primarily oriented in a rostrocaudal direction.

These data suggest that the extensive extranuclear dendritic arborization of motoneurons innervating the soft palate, pharynx, larynx, and cervical esophagus provide a wide ranging target for multiple central afferents that may be involved in the differential control of muscles that participate in multiple complex motor functions. The lack of extensive extranuclear dendrites of motoneurons innervating the distal esophagus suggest that they receive focused central afferents. The prominent bundling of dendrites within the nucleus ambiguus may provide for synchronization of motoneurons innervating a specific muscle and perhaps for synchronization of motoneurons innervating different muscles acting in sequence.
Immunohistochemical localization of serotoninergic, enkephalinergic, and catecholaminergic cells in the brainstem and diencephalon of a cartilaginous fish, hydrolagus colliei
Authors: Stuesse Sherry L. , Cruce William L. R.
Published: January 2005

We localized serotonin (5‐HT), leu‐enkephalin (LENK), and tyrosine hydroxylase (TH) immunoreactive cells in the brain of a holocephalian, Hydrolagus colliei, by use of antibodies made in rabbit and the peroxidase‐antiperoxidase technique. Only three locations contained TH+ cells, the caudal myelencephalon, the locus coeruleus, and the diencephalon. Of these locations, the diencephalon contained the most cells and the locus coeruleus the least cells. The caudal TH+ myelencephalic cells formed a single large group that spanned both the dorsal and ventral portions of the brain (A1A2). The diencephalic TH+ cells were located in the posterior tuberculum, in the ventromedial and ventrolateral thalamic nuclei, and in the inferior lobe of the hypothalamus. Hydrolagus differed from mammals and the elasmobranchs, their sister group, in that no substantia nigra (A9), ventral tegmental area (A10), or A5 cell group was found.

Distribution of LENK+ and 5‐HT+ cells were similar to each other; the raphe nuclei contained most of the 5‐HT+ and LENK+ cells. These 5‐HT+ and LENK+ cells were found at all rostrocaudal levels of the myelencephalon. The nucleus reticularis magnocellularis, reticularis magnocellularis lateralis, the ventral met‐ and mesencephalon (B7 and B9 cell groups), the hypothalamus, and the pretectal area contained additional 5‐HT+ and LENK+ cells. The solitary complex contained LENK+ cells but not but 5‐HT+ cells. A dorsal raphe nucleus, which is the largest 5‐HT+ cell group in mammals, was absent m Hydrolagus. A dorsal raphe nucleus is present in one galeomorph shark radiation but is absent in three radiations of batoids (rays, skates, and guitarfish). Thus even within cartilaginous fish, there are differences in the distribution of neurochemicals and possibly nuclei within their brains.
Expression of nerve growth factor (NGF) receptors in the brain and retina of chick embryos: Comparison with cholinergic development
Authors: von Bartheld Christopher S. , Heuer Josef G. , Bothwell Mark
Published: January 2005

The expression of nerve growth factor receptor (NGFR) transcripts was investigated with in situ hybridization techniques in the CNS of chick embryos from 3 days of incubation (E3) to 14 days posthatch (P14). The time course and distribution of NGFR expression was compared with the development of the cholinergic phenotype. Cholinergic properties were assessed by immunolabeling for choline acetyltransferase (ChAT) and histochemistry for acetylcholinesterase (AchE) activit.

NGFR transcripts are expressed transiently in the inner plexiform layer and ganglion cell layer of the retina (E4–P1), neostriatum and hippocampus (E18), infundibular hypothalamus (E7–18), spiriform complex (E9–15), layers 2,3 (E9–18), and 10 (E11–18) of the optic tectum, nucleus mesencephalicus profundus, pars ventralis (E9–18), parvicellular isthmic nucleus (E7–P1), magnocellular isthmic nucleus (E9‐E18), nucleus semilunaris (E7–18), isthmo‐optic nucleus (E7–P14), rostral motor nuclei (E5–18), developing cerebellum (E7–15), internal granule cell layer (E11–18) and Purkinje cell layer (E15–P14) of the cerebellar cortex, and the inferior olivary nucleus (E9–15). A small number of neuronal populations with embryonic expression of NGFR remain strongly NGFR‐positive in the posthatch animal: habenular nuclei (labeled after E5), nucleus subrotundus (after E9), mesencephalic trigeminal nucleus (after E5), caudal parts of locus ceruleus and nucleus subceruleus (after E7), medullar reticular nuclei (after E11), and motor nuclei IX, X, and XII (after E9).

The majority of neuronal populations with NGPR expression show cholinergic properties in development, and NGFR expression always precedes the onset of ChAT immunoreactivity. Postnatal expression of growth factor receptors is largely confined to neurons of the reticular type. NGFR expression in avian CNS nuclei differs from that in mammals. Early loss of NGFR expression in the cholinergic basal forebrain (which remains strongly NGFR positive in mammals) and persistent NGFR expression in parts of the avian locus ceruleus indicate changes of growth factor receptor expression and growth factor requirements in phylogeny. Knowledge of the time and distribution of NGFR expression in the chick embryo will facilitate the assessment of specific functions of NGF and NGF‐like molecules in an embryonic model with easy access for experimental manipulation.
Postembedding immunocytochemistry for GABA and glycine reveals the synaptic relationships of the dopaminergic amacrine cell of the cat retina
Authors: Kolb Helga , Cuenca Nicolas , Dekorver Laura
Published: January 2005

Postembedding electron microscope immunocytochemistry of glycine and GABA conjugated to colloidal gold has been applied to pre‐embedded cat retina stained with the antibody against tyrosine hydroxylase (Toh+). Toh+ stained cells are the equivalent of A18 amacrine cells of Golgi descriptions (Kolb et al., 1981). The dendrites of Toh+ cells synapse upon several different types of glycine‐positive amacrine cell bodies. We suggest that these are the A8, A3/A4, and AII amacrine cell varieties by analogous immunocytochemical staining intensity, to glycine autoradiographic labeling intensity (Pourcho and Goebel, 1985). The greatest number of synapses from Toh+ dendrites are directed at the least glycine‐positive amacrine, which is the AII cell by all morphological criteria. A few glycine‐positive profiles are also presynaptic to the Toh+ stained cell body itself.

Toh+ profiles are also presynaptic to GABA‐positive amacrine cell bodies. The commonest amacrine synapsed upon is very heavily labeled with GABA immunocytochemistry. We consider it to be the A17 amacrine cell, which is known to label strongly by [3H] muscimol autoradiography (Pourcho and Goebel, 1983). The cell body of the Toh+ amacrine cell also receives many synapses, which appear to be GABA‐positive, and Toh+ profiles running in stratum 1 of the inner plexiform layer (IPL) are both pre‐ and postsynaptic to GABA‐positive amacrine cell profiles. In addition, the cell body and primary dendrites of the Toh+ cell receive input from a bipolar type and GABA‐ or glycine‐negative profiles. GABA‐positive profiles, belonging to the interplexiform cell (IPC), are synapsed upon by Toh+ profiles that run in the outer plexiform layer (OPL). Horizontal cells identified on morphological criteria as the B‐type may also receive Toh+ synaptic input.
Development of the rabbit retina: II. Müller cells
Authors: Reichenbach A. , Schnitzer J. , Friedrich A. , Knothe A.‐K. , Henke A.
Published: January 2005

Müller (glial) cells of the rabbit retina were stained with antibodies against the intermediate filament protein vimentin in retinal wholemounts from various developmental stages. Both the density of stained profiles and the mean diameter of these profiles were measured, with the microscope focus in the inner plexiform layer of the retinae. Within this retinal layer, every Müller cell possesses one stout vitread process; thus counts of the stained profiles allow an estimation of their number.

After postnatal day (P) 9, the total number of stained cells was slightly above 4 million per retina; for the adult rabbit retina, this agrees well with earlier data obtained by our group based on another method, as well as with published data from other groups. We suggest that after P 9, only Müller cells are stained, and this population is numerically stable. In contrast, neonatal retinae contained significantly more stained profiles. This indicates that either the total number of Muller cells is reduced by “physiological cell death” or that additional cells are stained neonatally. We discuss why we favour the second possibility.

After P 9, two peculiarities occur in the Müller cell population: (1) their density decreases gradually, to a greater extent in the retinal periphery than in the center (i.e., in the “visual streak”), and (2) Müller cell diameters increase, again more in the periphery than in the center. We argue that differential retinal expansion leads to dispersion of the pre‐existing cell population and allows for widening of the Müller cell processes. We conclude that Müller cells can be used postnatally in the rabbit retina as “landmarks” of expansion.
Sexually dimorphic distribution of neurotensin/neuromedin N mRNA in the rat preoptic area
Authors: Alexander Mark J. , Kiraly Zsolt J. , Leeman Susan E.
Published: January 2005

Neurotensin release from estrogen‐responsive neurons in the rostral preoptic area of the female rat may play an important role in triggering preovulatory secretion of gonadotropin‐releasing hormone on proestrus. We investigated the possibility of sexually differentiated biosynthesis of neurotensin in the rostral preoptic area, using in situ hybridization histochemistry to detect neurotensin/neuromedin N (NT/N) mRNA in adult male rats and adult female rats at proestrus and the first day of diestrus. In sections through the anteroventral periventricular nucleus (AVPv), the number of labeled cells in proestrous females was four times that in males. Diestrous females exhibited half the number of labeled cells present at proestrus, and there was evidence for a significant correlation between circulating estradiol level and number of labeled cells in the AVPv. In the rostral portion of the medial preoptic nucleus (MPN), two contiguous groups of labeled cells were especially prominent. One group, in the medial half of the MPN, was located closer to the midline in females than in males and displayed greater labeling in males than in females. Furthermore, labeling in the rostral MPN was greater at proestrus than at diestrus. These results indicate that biosynthesis of neurotensin and neuromedin N in the rostral preoptic area may be sexually differentiated and, in the female, may vary across the estrous cycle in parallel with circulating estradiol levels, consistent with the view that neurotensin neurons in this area are involved in the regulation of preovulatory secretion of gonadotropin‐releasing hormone. The sex‐ and region‐specific expression of NT/N mRNA in the rostral preoptic area suggests functional heterogeneity of neurotensin neuronal populations in this area and implies complex regulation of NT/N gene expression in the rat brain.
Compartmental organization of the thalamostriatal connection in the cat
Authors: Ragsdale Clifton W. , Graybiel Ann M.
Published: January 2005

The compartmental organization of the thalamostriatal connection in the cat was studied by labelling thalamic fibers in anterograde axonal transport experiments and comparing their striatal distributions with the arrangement of striosomes and matrix tissue identified by histochemical staining methods. When analyzed according to their principal compartmental targets in dorsal striatum, the thalamic deposits indicated the existence of medial and lateral divisions within the thalamostriatal projection. Nuclei of the medial division, which includes parts of the thalamic midline, projected primarily to striosomes. The lateral division, which embraces the anterior and posterior intralaminar groups, the rostral ventral tier nuclei, and parts of the posterior lateral nuclear complex, predominantly innervated matrix tissue. In the dorsal division of the nucleus accumbens, the medial system preferentially terminated in zones that stain heavily in butyrylcholinesterase and substance P preparations, but fibers from both the medial and the lateral systems largely avoided the histochemically marked compartments such as the border islands of the nucleus accumbens that are seen elsewhere in the ventral striatum.

Medial division: Thalamic deposits involving the paraventricular and rhomboid nuclei of the thalamic midline elicited labelling of striosomes and, invariably, ventral extrastriosomal matrix, the nucleus accumbens, and the amygdala. This projection was topographically organized: rostral thalamic deposits elicited labelling in the medial caudate nucleus and the medial nucleus accumbens. More caudal injections produced more lateral labelling.

Lateral division: The lateral division is composed of at least three projection systems distinguished by their patterns of matrix innervation. Deposits involving the anterior intralaminar nuclei and the striatally projecting cells located lateral to the stria medullaris (anterior intralaminar complex) produced an even, diffuse labelling of the matrix tissue and weak labelling of the striosomes. Injections placed in the ventroanterior, ventrolateral, and ventromedial nuclei (rostral ventral complex) elicited fibrous labelling of matrix tissue that often showed nonstriosomal inhomogeneities. Deposits involving the centromedian and parafascicular nuclei (posterior intralaminar complex) produced a highly variable pattern of matrix labelling that included both homogeneous and decidedly patchy innervations of the extrastriosomal matrix. Each of these lateral thalamostriatal systems showed a similar spatial organization, whereby dorsoventral and mediolateral thalamic axes were roughly preserved in the projection to striatum.
Serotoninergic varicosities make synaptic contacts with pleural sensory neurons of Aplysia
Authors: Zhang Z. S. , Fang B. , Marshak D. W. , Byrne J. H. , Cleary L. J.
Published: January 2005

Serotonin is a modulatory neurotransmitter that produces many of the cellular changes associated with sensitization of reflexes in Aplysia. These changes have been carefully documented in sensory neurons located in the abdominal ganglion that mediate the gill‐siphon withdrawal reflex and in sensory neurons located in the pleural ganglion that mediate the tail‐siphon withdrawal reflex. Although serotonin appears to be necessary for sensitization, there is no direct evidence that serotoninergic neurons make synaptic contacts with sensory neurons. In this study, the immunoperoxidase technique was used to label serotonin‐immunoreactive neurites surrounding the cell bodies of sensory neurons in the pleural ganglion. Serotonin‐immunoreactive neurites had varicosities whose mean short axis diameter was 1.1 ± 0.6 μm (mean ± S.D.). The shape of the size distribution was skewed toward larger sizes, however, suggesting that there were multiple subpopulations of varicosities. One subpopulation was that of varicosities located at branch points whose average short axis diameter was larger than normal (1.7 ± 0.5 μm). Serotonin‐immunoreactive varicosities were directly apposed to the sensory neurons without intervening glial cells. In most contacts, serotonin‐immunoreactive neurites invaginated into the plasma membranes of the sensory neurons. There were also a few contacts onto spinelike processes, but these were flat rather than invaginated. Serotoninergic neurons whose activity produces changes in the electrophysiological properties of sensory neurons have been identified, but this study provides the first direct evidence for synaptic connections between serotoninergic neurons and sensory neurons in Aplysia.
Differential complementary localization of metabolic enzymes for quinolinic acid in olfactory bulb astrocytes
Authors: Poston Michael R. , Bailey Mary S. , Schwarcz Robert , Shipley Michael T.
Published: January 2005

The cellular localizations of the synthetic [3‐hydroxyanthranilic acid oxygenase (3HAO)] and degradative [quinolinic acid phosphoribosyltransferase (QPRT)] enzymes of the endogenous excitotoxin quinolinic acid were studied in the adult rat main olfactory bulb by immunohistochemical techniques. 3HAO and QPRT were expressed only in astrocytes. The two enzymes were differentially expressed by astrocytes in a complementary pattern: 3HAO staining was strongest at the glomerular–external plexiform layer junction; QPRT staining was strongest at the glomerular–olfactory nerve layer junction. The complementary distributions of these metabolic enzymes suggests that there could be a gradient of quinolinic acid across the glomerular layer of the main olfactory bulb. Such a gradient could function to restrict the ingrowth of new olfactory axons to the glomeruli and/or to stabilize the formation of new synapses.
Acoustic chiasm IV: Eight midbrain decussations of the auditory system in the cat
Authors: Hutson K. A. , Glendenning K. K. , Masterton R. B.
Published: January 2005

Conventional retrograde and orthograde axonal transport tract‐tracing techniques were used in cats to explore the auditory decussations and commissures in the upper pons and midbrain. In all, 8 decussations differing either in origin or in contralateral termination were found. Three of the 8 decussations (from the dorsal nucleus of the lateral lemniscus to the contralateral dorsal nucleus of the lateral lemniscus, from the dorsal nucleus of the lateral lemniscus to the contralateral inferior colliculus, from the sagulum to the contralateral sagulum) reach their targets via the commissure of Probst. The remaining 5 decussations (from the inferior colliculus to the contralateral inferior colliculus or medial geniculate, from the intermediate nucleus of the lateral lemniscus to the contralateral medial geniculate, from the sagulum to the contralateral inferior colliculus or medial geniculate) reach their targets via the commissure of the inferior colliculus.

The results also suggest that the commissure of Probst is not a general avenue for decussating auditory fibers of the lateral lemniscus but is instead a specific avenue only for fibers from the dorsal nucleus of the lateral lemniscus and sagulum. The results also show that, in the cat at least, the dorsal nucleus of the lateral lemniscus does not project beyond the inferior colliculus to either the superior colliculus or medial geniculate‐the cells previously reported as doing so are probably those of the immediate neighbors of the dorsal nucleus, the intermediate nucleus of the lateral lemniscus and sagulum.
Medial terminal nucleus terminals in the nucleus of the optic tract contain GABA: An electron microscopical study with immunocytochemical double labeling of GABA and PHA‐L
Authors: Van Der Togt Chris , Cardozo Bob Nunes , Van Der Want Johannes
Published: January 2005

In this study the medial terminal nucleus (MTN) projection to the nucleus of the optic tract (NOT) was investigated in pigmented rats at the light and electron microscopical levels with a new combination of techniques. MTN terminals were anterogradely labeled with Phaseolus vulgaris‐leucoagglutinin (PHA‐L). Preembedding immunocytochemistry, followed by gold intensification, was used to visualize PHA‐L. Postembedding immunocytochemistry with 15 nm immunogold particles was carried out to demonstrate the inhibitory neurotransmitter gamma‐aminobutyric acid (GABA). Both PHA‐L and GABA labeling can be easily discriminated at the electron microsopical level even when present in the same neuronal profiles.

Light microscopically MTN‐NOT fibers proved to have several branches with many varicosities. MTN terminals were found concentrated in terminal fields. Electron microscopically, it was shown that MTN boutons display characteristics resembling F‐type terminals, i.e., terminals with dark mitochondria, pleomorphic vesicles, and symmetrical synapses. All NOT afferents originating from the MTN contained GABA and made multiple contacts exclusively with GABA negative NOT somata and dendrites. These results indicate the existence of a strong and direct inhibitory input onto GABA negative projection neurons in the NOT. This substantiates earlier physiological and morphological reports. It was further demonstrated that the location and organization of MTN terminals in the neuropil differ from that of the retinal input: MTN terminals are largely separated from retinal terminals. MTN terminal fields contain large amounts of GABA positive F terminals in contrast to retinal terminal areas. MTN terminals take part in irregularly shaped agglomerations of terminals, which contain many F terminals and dendritic processes and are surrounded by a glial sheet. Retinal terminals are found grouped together in small circular arrangements contacting a central dendrite.
Substance P immunoreactivity identifies a projection from the cat's superior colliculus to the principal tectorecipient zone of the lateral posterior nucleus
Authors: Hutsler Jeffrey J. , Chalupa Leo M.
Published: January 2005

Cells in the superficial layers of the superior colliculus innervate multiple visual regions within the pulvinar‐lateral posterior complex of the cat. To characterize these neurons we have examined their immunocytochemical properties in conjunction with their projection patterns. In the present study, we show that a monoclonal antibody for substance P recognizes a morphologically diverse population of neurons, which can be classified as granular, stellate, angular, and horizontal or nonhorizontal fusiform cell types. These neurons are distributed throughout the superficial layers of the colliculus, with a peak density corresponding to sublayer 2 of the stratum griseum superficial. Injections of rhodamine latex microspheres into the pulvinar‐lateral posterior complex demonstrate that a substantial proportion of these collicular cells (at least 35%) project to this region of the posterior thalamus. The overall population of substance P‐containing cells, as well as the immunoreactive projection neurons, is composed of the same proportions of cell classes, with the exception that granular cells were not found to be projection neurons.

A distinct wedge of substance P immunoreactivity, consisting of fiber and diffuse extracellular labeling, was discovered in the pulvinar‐lateral posterior complex. This staining was demonstrated to be confined entirely within the medial division of the lateral posterior nucleus, which is considered to be the principal tectorecipient zone of the extrageniculate visual thalamus. Lesions of the superior colliculus largely abolished the substance P immunoreactivity in the ipsilateral tectorecipient zone. These results are consistent with the view that substance P plays a role in the functional organization of the principal tectothalamic pathway of the cat's extrageniculate visual system.
PNS‐CNS transitional zone of the first cranial nerve
Authors: Doucette R.
Published: January 2005

This study examined the ultrastructure of the region of transition where fascicles of olfactory axons leave the peripheral nervous system (PNS) to enter the central nervous system (CNS), the so‐called PNS‐CNS transitional zone. Adult rats were transcardially perfused with a solution of 1% glutaraldehyde and 1% paraformaldehyde, decapitated, and the heads decalcified over a period of several weeks in a solution of 1% glutaraldehyde in 0.1 M tetrasodium ethylenediamine tetraacetic acid; the latter solution was changed daily. It was found that astrocytes did not form the glia limitans at the nerve entry zone, unlike the situation that exists in other cranial and spinal nerves. Rather, the glia limitans in this region of the olfactory bulb was formed by a special type of glial cell, referred to as an ensheathing cell. Ensheathing cells are found only in the nerve fiber layer of the olfactory bulb. They possess a mixture of Schwann cell and astrocytic features and are more likely to be of placodal than of CNS origin. The meningeal coverings of the olfactory nerve rootlets and of the olfactory bulb are also described and the functional implications of the findings discussed.
Nerve growth factor differentially modulates the expression of its receptor within the CNS
Authors: Fusco M. , Polato P. , Vantini G. , Cavicchioli L. , Bentivoglio M. , Leon A.
Published: January 2005

The effect of nerve growth factor on the expression of nerve growth factor receptor in the central nervous system of newborn and adult rats was studied by means of immunohistochemistry with the monoclonal antibody 192‐IgG. Both during development and in adulthood, the intracerebroventricular administration of nerve growth factor elicited a pronounced increase of nerve growth factor receptor‐like immunoreactivity in the cell bodies and neural processes of the basal forebrain cholinergic nuclei, as compared to cytochrome c‐treated rats (controls). A pronounced nerve growth factor‐induced increase of nerve growth factor receptor‐like immunoreactivity was also observed in central regions innervated by trigeminal and spinal ganglia. A moderate to a marked increase of nerve growth factor receptor‐like immunoreactivity was evident in some mesencephalic visual system‐related structures and thalamic nuclei expressing nerve growth factor receptor. In contrast, NGF treatment did not induce appreciable modification of nerve growth factor receptor‐like immunoreactivity in cerebellar, brainstem, and spinal motor structures of newborn rats. In adult nerve growth factor‐treated rats, a decrease of nerve growth factor receptor‐like immunoreactivity was detected in the cerebellum, whereas no re‐expression of nerve growth factor receptor‐like immunoreactivity occurred in the motor structures that had expressed it in the first postnatal week. Finally, nerve growth factor was also found to enhance, in both adult and newborn rats, nerve growth factor receptor‐like immunoreactivity associated with ependymal and subependymal cellular elements of the lateral and third ventricles, as well as with the leptomeninges overlying the superior colliculus and supraoptic area. The present results indicate that endogenous nerve growth factor or nerve growth factor‐like molecules may play a dynamic role in a variety of cell populations of both the developing and mature mammalian central nervous system. We thus propose the nerve growth factor ability to modulate its receptor in vivo as a novel criterion to define nerve growth factor or nerve growth factor‐like molecules, sensitive neuronal, and non‐neuronal cells. Whereas this criterion does not intrinsically possess absolute physiological validity, its pharmacological concomitants might be relevant in view of the proposed therapeutical use of this trophic factor.
Immunocytochemical localization of argininosuccinate synthetase in the rat brain
Authors: Nakamura Hiroyuki , Saheki Takeyori , Ichiki Hitoshi , Nakata Kimihiko , Nakagawa Shiro
Published: January 2005

The neuronal distribution of argininosuccinate synthetase (ASS) was mapped in the rat brain. Argininosuccinate synthetase is one of the enzymes of the arginine metabolic pathway and catabolizes the synthesis of argininosuccinate from aspartate and citrulline. Since arginine is the precursor of nitric oxide, argininosuccinate synthetase may act as part of the nitric oxide producing pathway. Argininosuccinate is also suggested to have a messenger function in the nervous system. Therefore, the localization of ASS is of great interest.

Polyclonal antisera against purified rat liver argininosuccinate synthetase revealed a characteristic distribution pattern of argininosuccinate synthetase‐like immunoreactivity: (1) many neurons with strong argininosuccinate synthetase‐like immunoreactivity were observed in the septal area, basal forebrain, anterior medial and premammillary nuclei of the hypothalamus, anterior and midline thalamic nuclei, dorsal endopiriform nucleus of the amygdala, basal nucleus of Meynert, subthalamic nucleus, laterodorsal tegmental nucleus, raphe nuclei, nucleus ambiguus, and the area postrema, (2) neuropile staining was dense in the septal areas, hypothalamus, area postrema, nucleus of the solitary tract, and the laminae I and II of the caudal subnucleus of the spinal trigeminal nucleus and the spinal dorsal horn, (3) relay nuclei of the specific sensory systems such as the dorsal lateral geniculate nucleus and the ventral nuclei of the thalamus were devoid of argininosuccinate synthetase‐like immunoreactivity, (4) no staining was seen in the large white matter structures such as the internal capsule, corpus callosum, and the anterior commissure, and (5) most of the neurons stained were small or medium in size and appeared to be interneurons. The results suggest that argininosuccinate synthetase affects the widely distributed, neuromodulatory system in the brain.
Central projections of auditory‐nerve fibers of differing spontaneous rate. I. Anteroventral cochlear nucleus
Authors: Liberman M. Charles
Published: January 2005

Auditory nerve fibers have been subdivided into three functional groups (Liberman, M.C. [1978] J. Acoust. Soc. Am. 63:442–455) differing in acoustic sensitivity and spontaneous discharge rate (SR). Using intracellular injection of horseradish peroxidase, the present study analyzes the projections of these three neuronal subclasses to the various subdivisions of the anteroventral cochlear nucleus (AVON) and to the different cell types found therein. The average number of swellings and number of cells contacted decreased from low‐ to medium‐ to high‐SR groups. However, these differences in terminal elaboration were not evenly distributed throughout the AVCN. The small cell cap was almost exclusively innervated by low‐ and medium‐SR fibers, i.e., those with the highest acoustic thresholds. Within anterior AVCN, spherical‐cell innervation was seen from all SR groups, whereas almost all multipolar cell innervation was from low‐ and medium‐SR fibers. In the posterior AVCN, multipolar‐cell innervation was equally likely from all SR groups, whereas globular cells were preferentially contacted by high‐SR fibers. These SR‐based trends in cochlear nucleus innervation help explain some of the known physiological properties of cell‐types in each subdivision. They also suggest that additional physiological study of the small cell cap may be key in elucidating the functional significance of the low‐SR population.
Characterisation of two new monoclonal antibodies directed against rat microglia
Authors: Gehrmann Jochen , Kreutzberg Georg W.
Published: January 2005

With the aid of cultured rat microglial cells as immunogen, we raised two monoclonal antibodies, designated murine clone (MUC) 101 and 102, which recognised subsets of resident microglial cells in the normal central nervous system and cells of the mononuclear phagocyte system in peripheral organs. These antibodies were characterised by immunoperoxidase immunocytochemistry, immunoelectron microscopy, and immunoblotting.

The immunostained cells were identified as microglial cells by double‐immunofluorescence labelling with the B4‐isolectin from Griffonia simplicifolia, an established microglial cell marker. Under normal conditions, both antibodies labeled resident microglia but with different distribution patterns. Under pathological conditions, e.g., after facial nerve transection, they labeled activated, perineuronal microglia in the operated facial nucleus. Immunoelectron microscopy demonstrated a membrane localisation of the antigen recognised by MUC 102.

In peripheral organs, MUC 101 and 102 reacted with different cell populations of the mononuclear phagocyte system, particularly in thymus, spleen, and peripheral lymph node. Western blot experiments showed that MUC 101 recognised two proteins of 116 and 95 kD in fractions obtained from operated facial nucleus while MUC 102 reacted with two proteins of 62 and 70 kD molecular weight.

These immunocytochemical results (1) confirm the antigenic similarity between microglia and cells of the monocyte–macrophage cell lineage, and (2) indicate that considerable antigen heterogeneity might exist among resident microglia. MUC 101 and 102 could thus become useful for studying the function of microglial cells both under normal and pathological conditions.
Age‐related changes in galanin‐immunoreactive cells of the rat medial septal area
Authors: de Bilbao F. , Jazat F. , Lamour Y. , Senut M. C.
Published: January 2005

Age‐related changes in the cholinergic cells have been reported in the rat medial septal area. The neuropeptide galanin is colocalized with acetylcholine in the majority of the medial septal neurons. To assess possible age‐related changes in the galanin‐containing septal cells, we have examined, with immunohistochemical methods, the distribution pattern, density, and morphological features of galanin‐containing cells in the rat medial septal nucleus (MS) and the nucleus of the diagonal band of Broca (DBB) in 1, 3–6, 9–12, 16–18, 24–27, and 28–30 month‐old rats. A morphometric computerized analysis was also performed. In addition, the intensity of the immunolabelling was measured by densitometry. Galanin‐like immunoreactivity (galanin‐LI) was present in both the MS and the DBB. Our results clearly indicate a progressive age‐related decrease in the number of galanin‐positive cells throughout the MS‐DBB complex. Our quantitative study revealed a significant loss of galanin‐positive cells in the MS‐DBB complex of 16–18 (50.4%), 24–27 (52.3%), and 28–30 (52.4%) month‐old rats compared to 3–6 month‐old animals. A non‐significant reduction (28.6%) in galanin‐LI cell number was observed in 3–6 month‐old rats compared to 1 month‐old animals. The morphometric analysis demonstrated a significant reduction (18%) in the surface of galanin‐positive cells remaining in the 28–30 month‐old group. Furthermore, a significant decrease in the immunolabelling intensity was consistently observed in animals of 16 month‐old and older. To determine whether changes in galanin‐positive cells were associated with cholinergic changes, the number of cells stained for acetylcholinesterase.(AChE) was estimated in 3–6, 9–12, 16–18, and 24–27 month‐old rats. There was a 43% decrease in the number of AChE‐positive cells and a 71% loss of galanin‐positive cells in 24–27 month‐old rats compared to 3–6 month‐old. The galanin‐cell loss in, the medial septal area was therefore associated with a parallel, although smaller, cholinergic septal cell loss.
Different populations of parvalbumin‐ and calbindin‐D28k‐immunoreactive neurons contain GABA and accumulate 3H‐D‐aspartate in the dorsal horn of the rat spinal cord
Authors: Antal Miklos , Polgár E. , Chalmers J. , Minson J. B. , Llewellyn‐Smith I. , Heizmann C. W. , Somogyi P.
Published: January 2005

The colocalization of parvalbumin (PV), calbindin‐D28k (CaBP), GABA immunoreactivities, and the ability to accumulate 3H‐D‐aspartate selectively were investigated in neurons of laminae I‐IV of the dorsal horn of the rat spinal cord. Following injection of 3H‐D‐aspartate into the basal dorsal horn (laminae IV‐VI), perikarya selectively accumulating 3H‐D‐aspartate were detected in araldite embedded semithin sections by autoradiography, and consecutive semithin sections were treated to reveal PV, CaBP and GABA by postembedding immunocytochemistry. Perikarya accumulating 3H‐D‐aspartate were found exclusively in laminae I–III, and no labelled somata were found in deeper layers or in the intermediolateral column although the labelled amino acid clearly spread to these regions. More than half of the labelled cells were localized in lamina II. In this layer, 16.4% of 3H‐D‐aspartate‐labelled perikarya were also stained for CaBP. In contrast to CaBP, PV or GABA was never detected in neurons accumulating 3H‐D‐aspartate. A high proportion of PV‐immunoreactive perikarya were also stained for GABA in laminae II and III (70.0% and 61.2% respectively). However, the majority of CaBP‐immunoreactive perikarya were GABA‐negative. GABA‐immunoreactivity was found in less than 2% of the total population of cells stained for CaBP in laminae I–IV. A significant proportion of the GABA‐negative but PV‐immunoreactive neurons also showed CaBP‐immunoreactivity in laminae IL and IV. These results show that out of the two calcium‐binding proteins, CaBP is a characteristic protein of a small subpopulation of neurons using excitatory amino acids and PV is a characteristic protein of a subpopulation of neurons utilizing GABA as a transmitter. However, both proteins are present in additional subgroups of neurons, and neuronal populations using inhibitory or excitatory amino acid transmitters are heterogeneous with regard to their content of calcium‐binding proteins in the dorsal horn of the rat spinal cord.
A serial section electron microscope study of an identified la afferent collateral in the cat spinal cord
Authors: Nicol Madeleine J. , Walmsley Bruce
Published: January 2005

Serial section electron microscopy has been used to examine a horseradish peroxidase (HRP)‐labelled group Ia afferent collateral from its entry point in the grey matter to its termination in Clarke's column of the cat spinal cord. A wide range of geometries and myelination patterns were identified along the collateral, including (1) nodes specialized to exhibit a single synaptic bouton, (2) nodes specialized to exhibit two or more synaptic boutons connected by fine, unmyelinated lengths of the collateral, (3) terminal heminodes, along which boutons were separated by unmyelinated branches, and (4) complex arrangements along which myelinated and unmyelinated branches gave rise to one or more boutons. Thirty‐six synaptic boutons of varied shape and size were exhibited by this collateral.

Previous studies have shown that the geometry, branching, and myelination pattern of an axon play an important role in determining the amplitude and duration of an action potential propagating along that axon. In turn, the amplitude and duration of a presynaptic action potential influence the efficacy of transmitter release. The varied axonal geometries and myelination patterns observed in the present study provide further evidence in support of our previous proposal that there may be considerable nonuniformity in the efficacy of synaptic transmission among release sites arising from the same primary afferent fiber.
Afferent and sympathetic neurons projecting into lumbar visceral nerves of the male rat
Authors: Baron Ralf , Jänig Wilfrid
Published: January 2005

The cell bodies of thoracolumbar sensory and sympathetic pre‐ and postganglionic neurons that project to the colon and pelvic organs of the male rat were labeled retrogradely with horseradish peroxidase (HRP) in order to study numbers, segmental distribution, and location of the somata of these neurons quantitatively. HRP was applied to one hypogastric nerve (HGN), to the lumbar colonic nerves (LCN) and to the intermesenteric nerve (IMN). In order to estimate the significance of the branching of one axon into both hypogastric nerves a double‐labeling technique with fluorogold and HRP was used.

About 2640 neurons project into the two HGN added together (800 afferent, 1320 pre‐, and 520 postganglionic), 4650 neurons into the LCN (360 afferent, 0 pre‐ and 4290 postganglionic), and 5990 into the IMN (1500 afferent, 1250 pre‐, and 3240 postganglionic). About 4190 sympathetic postganglionic prevertebral neurons innervate the colon and pelvic organs, 1900 are located in the inferior mesenteric ganglion and 2290 in ganglia of the IMN. Considering the efferent component, the HGN mainly are preganglionic and the LCN exclusively postganglionic nerves. Branching of one axon into both HGN is a rare event and quantitatively negligible (< 3%).

Afferent neurons of all three nerves were found in the dorsal root ganglia (DRG) T12‐L2 with the maximum in L1 and L2. The distribution of afferent neurons projecting into the LCN is shifted slightly more rostrally compared to neurons projecting into the HGN. The IMN distribution is located in a position in between. Preganglionic neurons projecting into the IMN are located in the spinal cord segments T12‐L3 with the maximum in LI and L2. Sympathetic postganglionic paravertebral neurons of all three types of nerves are more widely distributed (T12‐L5). Neurons projecting into the LCN are shifted more caudally than those projecting into the HGN.