bluuebunny/crossref_metadata_2025 huggingface dataset:
Auditory receptor of the red‐eared turtle: II. Afferent and efferent synapses and innervation patterns
Authors: Sneary Michael G.
Published: January 2005

Innervation patterns in the auditory receptor of the red‐eared turtle were reconstructed from serial ultrathin sections. Four locations were studied, including three on the basilar membrane and one on the basal limbus. In that area of the papilla located above the apical end of the basilar membrane most cells were innervated by single afferent fibers which, in turn, supplied as many as three cells. Although afferents in the midmembrane area of the papilla supplied fewer cells, the innervation pattern was similar in other respects to that in the apical area including an abundance of efferent synapses on afferents. In contrast, hair cells in the basal membrane area were contacted by two afferent fibers and had five times as many afferent synapses as observed previously. Here, each afferent made twice as many synapses as fibers in the previous two areas and supplied one or two hair cells but received no efferent synapses. In the basal limbus area, each hair cell was contacted by as many as eight afferents and each afferent supplied as many as seven hair cells. The significance of these innervation patterns is discussed in the light of structural information obtained from other vertebrate auditory receptors and in the light of available functional information derived from the turtle papilla.
Postnatal development of cat hind limb motoneurons. III: Changes in size of motoneurons supplying the triceps surae muscle
Authors: Ulfhake Brun , Cullheim Staffan
Published: January 2005

The postnatal changes of neuronal dimensions were studied in cat triceps surae motoneurons intracellularly labeled with horseradish peroxidase.

Systematic correlations were observed in the analysis of single dendrites at each studied stage, from birth to 44–46 days post natum (d.p.n.) age, between size parameters intrinsic to the dendrites as the diameter of a 1st‐order dendrite, the combined dendritic length, the dendritic membrane area, and the degree of branching. Some variability among samples was evident in each studied age group. The correlations were, however, sufficiently close to permit indirect estimations of both combined dendritic length and dendritic membrane area for larger samples of neurons from data on dendritic stem caliber.

The total postnatal increase in dendritic membrane area was, on the average, 400%, i.e., from close to 100 × 103 μm2 to about 500 × 103 μm2. The corresponding increase in soma area amounted to 100%. Analysis revealed that there was a time lag between the increase in somatic and dendritic size. Thus, adult somatic dimensions were attained at age 44–46 d.p.n.; however, at this stage, the mean total dendritic membrane area was only about half of the adult value. The postnatal increase in size appeared to vary among neurons, yielding a wider neuronal size spectrum in the adult cat than that observed in kittens.

The measured increase in size corresponded to a calculated average addition of dendritic membrane area of 3700 μm2/day from birth to 22–24 d.p.n. and from that stage to 44–46 d.p.n. of 2700 μm2 per day. Likewise, the increase in combined dendritic length could initially be as large as 1 mm/day down to 0.4 mm/day between 22–24 and 44–46 d.p.n., with a mean growth during the first 44–46 d.p.n. of 0.5 to 0.6 mm/day.

The ratios of daughters to parent branch diameters (∑dd1.5: dp1.5) and the dendritic trunk parameter (∑d1.5) recorded along the proximodistal dendritic path distance revealed transient changes that might impact on the electronic properties of the dendrites during postnatal development. Computations from the measured changes in dendritic branch lengths and calibers indicated that if membrane and internal resistivity remain unaltered during postnatal development. the dendritic domain is electrotonically more compact inthe newborn kitten than in the adult cat.

Based on the data we obtained on total neuronal membrane area available for synaptic junctions and previously published data on bouton packing density, it seems that any net change in the total number of synaptic boutons occurring postnatally should be small, and the mean number of boutons impinging on a triceps surae α‐motoneuron should be in the range of (50–60) × 103.
Topographic analysis of the retinal ganglion cell layer and optic nerve in the sandlance Limnichthyes fasciatus (Creeiidae, Perciformes)
Authors: Collin Shaun P. , Collin H. Barry
Published: January 2005

The sandlance or tommy fish Limnichthyes fasciatus (Creeiidae, Perciformes) is a tiny species that lives beneath the sand with only its eyes protruding and is found throughout the Indopacific region.

The retina of the sandlance possesses a deep convexiclivate fovea in the central fundus of its minute eye (1.04 mm in diameter). A Nissl‐stained retinal whole mount in which the pigment epithelium had been removed by osmotic shock was used to examine the retinal topography of the ganglion cell layer. There was a foveal density of between 13.0 × 104 cells per mm2 (S.D. ± 1.8 × 104 cells per mm2), counted in the retinal whole mount, and 15.0 × 104 cells per mm2, counted in transverse sections, which diminished to a peripheral density of 4.5 × 104 cells per mm2 (S. D. ± 0.8 × 104 cells per mm2). The total population of axons within the optic nerve was assessed by electron microscopy. Optic axon densities ranged from 2 × 106 axons per mm2 in the caudal apex to over 16 × 106 axons per mm2 within a specialized region of unmyelinated axons in the rostral apex. The topography of the proportion of unmyelinated axon population (26%) follows closely that of the total population of optic nerve axons. There was a total of 104,452 axons within the optic nerve compared with 102,918 cells within the retinal ganglion cell layer. A close relationship is revealed between ganglion cell soma areas and axon areas where the organization in the optic nerve and retina may reflect some functional retinotopicity.
Transient projections from the lateral geniculate to the posteromedial lateral suprasylvian visual cortex in kittens
Authors: Bruce Laura L. , Stein Barry E.
Published: January 2005

The postnatal maturation of the projection from the lateral geniculate nucleus to the posteromedial lateral suprasylvian visual cortex (PMLS) was studied with injections of fluorescent dyes into the PMLS at various postnatal ages. Labeled neurons projecting to the PMLS were present in all laminae of the ipsilateral lateral geniculate on the day of birth. However, there was a conspicuous change in the distribution of labeled geniculo‐PMLS neurons by 11 days of age: now very few labeled neurons were present in lamina A, indicating a loss of geniculo‐PMLS connections. The loss of connections began at the peripheral margins of lamina A and proceeded through other laminae toward laminae C1‐3. By adulthood, labeled geniculo‐PMLS neurons were largely confined to laminae C1‐3; they were never observed in lamina A or A1 and were rarely observed in lamina C.

To determine whether the lateral geniculate neurons survived after their projections to PMLS were lost, injections of fast blue were made at 1 or 2 days postnatally and the animals were allowed long postinjection survival times. Labeled neurons were found in all lateral geniculate laminae, thereby indicating that for many neurons the loss of connections could be attributed to a loss of their axon collaterals rather than to the death of the neurons themselves.

After injections of fast blue into the PMLS and diamidino yellow dihydrochloride into area 17 shortly after birth, many double‐labeled neurons were present in all laminae, indicating that they have collaterals to both targets. Thus, the survival of many of the geniculo‐PMLS neurons contributing to the transient geniculo‐PMLS projection seems to be due to sustaining collateral projections to area 17 or other cortical targets.
Ultrastructure of ChAT‐immunoreactive synaptic terminals in the thalamic reticular nucleus of the rat
Authors: Hallanger Anne E. , Wainer Bruce H.
Published: January 2005

The thalamic reticular nucleus has been shown to receive cholinergic innervation from both the nucleus basalis of Meynert in the forebrain and the pedunculopontine and laterodorsal tegmental nuclei in the brainstem (Steriade et al.: Brain Res. 408:372–376, '87; Levey et al.: Neurosci. Lett. 74:7–13, '87). Relatively dense populations of choline acetyltransferase‐ (ChAT) immunoreactive axons and terminallike varicosities have been shown to be distributed throughout this nucleus (Levey et al.: J. Comp. Neurol. 257:317–332, '87). In this study, the ultrastructure of ChAT‐immunoreactive axons and of their synaptic terminals in the reticular nucleus was examined in the electron microscope. All ChAT‐immunoreactive axonal profiles in the reticular nucleus were presynaptic; the postsyaptic elements were exclusively dendritic profiles; and no axo‐axonic or axosomatic contacts from labelled axons were observed. Most ChAT‐immunoreactive synaptic contacts were made by profiles less than 0.25 μm in minor diameter. Single ChAT‐immunoreactive axons made synaptic contact with several dendritic profiles as the axons were followed through serial sections. These results suggest that the cholinergic innervation of the reticular nucleus will modulate the function of reticular neurons by synapsing onto the dendrites of its neurons without direct effect on the corticothalamic and thalamocortical terminals which also innervate the reticular nucleus.
Differential projections of B and C sympathetic axons in peripheral nerves of the bullfrog
Authors: Horn John P. , Fatherazi Sahba , Stofer William D.
Published: January 2005

Accumulating evidence indicates that electrophysiologically distinct subsets of sympathetic neurons selectively innervate different classes of targets. The organization of this system may therefore be reflected in the sympathetic fiber contents of peripheral nerves. To test this possibility, we have mapped the pathways followed by three groups of postganglionic sympathetic axons in the bullfrog by recording compound action potentials and by retrograde tracing with horseradish peroxidase (HRP). The axons that were studied arise from fast B, slow B, and C‐type neurons in ganglia 9 and 10 at the lumbar end of the paravertebral sympathetic chain. They project to peripheral targets primarily by way of the sciatic nerve and can be distinguished by the velocities with which they conduct action potentials.

Action potentials were recorded with suction electrodes from isolated preparations composed of paravertebral chain ganglia 7–10, the sciatic nerve, and branches of the sciatic nerve that supply striated muscles, skin, and the bladder. Preganglionic B fibers were selectively activated by stimulating the paravertebral chain rostral to ganglion 7, and preganglionic C fibers were selectively activated by stimulating spinal nerves 7 and 8 at points central to their rami communicantes. Compound action potentials recorded from the sciatic, peroneal, tibial, and sural nerves and from the primary trunk of the pelvic nerve were each found to contain three components produced, respectively, by fast B, slow B, and C‐type sympathetic axons. Similarly, action potentials recorded from cutaneous branches of the sciatic tree were found to contain three sympathetic components. By contrast, when compound action potentials were recorded from branches of the sciatic tree that directly enter and innervate striated muscles and also the bladder, the sympathetic responses were found to arise solely from C‐type axons.

HRP was used to label the sympathetic neurons that project to the sartorius muscle and into the cutaneous lateral crural nerve. Retrograde transport of HRP from the sartorius muscle labeled 17 ± 4 (mean ± s.d.) sympathetic neurons and 27 ± 3 spinal motoneurons while transport from the lateral crural nerve labeled 68 ± 47 sympathetic neurons but no spinal neurons. The average somatic diameter of ganglion cells projecting to the sartorius muscle was significantly smaller than that of cells projecting to the lateral crural nerve.

The electrophysiological results indicate that fast B and slow B sympathetic axons in the sciatic trunk and its primary branches project selectively into cutaneous nerves while sympathetic C axons project into all peripheral nerves. The HRP data support these findings given that C cells are, on average, smaller than B cells. Together the results provide an anatomical basis for the hypothesis that B and C neurons serve different physiological functions.
GABA‐like immunoreactivity in the cat retina: Light microscopy
Authors: Wässle H. , Chun M. H.
Published: January 2005

Semithin sections of the cat retina were stained with antibodies against GABA conjugated to bovine serum albumin with glutaraldehyde. Labelled cells were visualized by means of the peroxidase‐antiperoxidase method. In the outer plexiform layer both A‐ and B‐type horizontal cells and the B‐type axon terminal system expressed GABA‐like immunoreactivity. Approximately 25–30% of all amacrine cells and the whole inner plexiform layer were heavily labelled. Two types of putative GABA‐ergic interplexiform cells could be distinguished. One of them also expressed tyrosine‐hydroxylase‐like immunoreactivity. A few bipolar cells were also GABA‐immunolabelled. GABA‐like immunoreactivity and 3H‐muscimol uptake were colocalized in 90% of the amacrine cells labelled. However, horizontal cells did not accumulate 3H‐muscimol.
Distribution of substance P‐like immunoreactivity in the goldfish brain
Authors: Sharma S. C. , Berthoud V. M. , Breckwoldt R.
Published: January 2005

Immunohistochemical methods were used to study the distribution of SP‐like immunoreactivity (SPLI) in the brain of the common goldfish (Carassius auratus). SPLI cell bodies and fibers were seen in distant areas and nuclei throughout the brain. In the telencephalon, SPL1 was found in the area dorsalis telencephali pars centralis and pars lateralis, areas that have been compared to the basal ganglia of land vertebrates. In the diencephalon, SPLI somata were seen in the hypothalamus. Four primary visual centers contained SPLI fibers: the nucleus of the posterior commissure, the area pretectalis, the nucleus dorsolateralis thalami and the optic tectum; the origin of these fibers could not be determined. SPLI cell bodies were seen in the oculomotor nucelus; the possibility that this may be the Edinger‐Westphal nucleus is discussed. A high density of immunoreactive fibers was seen in the tractus retroflexus and the interpeduncular nucleus, though the habenula showed a few SP‐like immunopositive fibers. In the hindbrain, SPLI cell bodies and fibers were seen in the nuclei ambiguus and commissuralis of Cajal and in the dorsal motornucleus of the vagus nuclei; even though these nuclei are known to belong to the visceral and sensory motor columns, the exact role SP plays in processing this information is at present unknown.
Comparison of trigeminal receptor location and structure in the periodontal ligament of different types of teeth from the rat, cat, and monkey
Authors: Byers Margaret R. , Dong Willie K.
Published: January 2005

The periodontal ligament is richly innervated by mechanoreceptors whose cell bodies are located either in the trigeminal ganglion (TG) or the mesencephalic (MS) trigeminal nucleus. Both are sensitive to stretch of the ligament induced by tooth movement, but their thresholds, central connections, and functional significance differ. This study compared the location of TG and MS receptors in the periodontal ligament of cat teeth after labeling each by anterograde axonal transport. We also compared the location and ultrastructure of the feline TG receptors with labeled TG receptors in the periodontal ligament of monkey teeth and rat incisors in order to determine their location and ultrastructural properties.

We found that the MS and TG receptors had a different distribution in the periodontal ligament of cat teeth; the MS terminals were concentrated below and next to the base of the roots, whereas the TG receptors were most numerous around the middle of the roots. The TG receptors of monkey teeth had a similar location to the feline TG receptors, but those of rat incisors were very different. Rat incisors are curved, continuously erupting teeth, and their TG receptors were located primarily on the lingual side in the alveolar (nonerupting) portion of the ligament. Ultrastructural comparisons found that most mechanoreceptors in the periodontal ligament of all the teeth had an unencapsulated branched Ruffini‐like structure. The TG receptors in the rat incisor ligament were the largest; those of monkey had the most varied form. Some coiled or encapsulated receptors were found in the monkey and cat ligament, but not in the rat incisor ligament. The TG receptors appear to be located at sites that would be most easily stretched during tooth contact. The different sites and intensity of the stretch forces occurring during the use of different types of teeth may determine the variations in the size and location of the TG mechanoreceptors and of their associated support cells. The different distribution of MS receptors may contribute to their response thresholds and static properties, which differ from those of TG receptors.
Telencephalic cholinergic system of the new world monkey (Cebus apella): Morphological and cytoarchitectonic assessment and analysis of the projection to the amygdala
Authors: Kordower Jeffrey H. , Bartus Raymond T. , Marciano Frederick F. , Gash Don Marshall
Published: January 2005

While the cholinergic projection from the nucleus basalis to the cortical mantle has received considerable attention, a similar projection to the magnocellular basal nucleus of the amygdala has not been studied in such detail. The present study analyzed the cholinergic basal forebrain projection to the amygdala in the Cebus apella monkey by using combined tract‐tracing and immunocytochemical techniques. As a foundation for this assessment, the morphological and cytoarchitectonic organization of the cholinergic telencephalic system of the New World C. apella monkey was examined by using choline acetyltransferase (ChAT) immunocytochemistry. Although there were minor differences, the telencephalic cholinergic system of Cebus monkeys is similar to that seen in Old World nonhuman primates. ChAT‐immunoreactive neurons were observed throughout the Ch1‐4 regions of the basal forebrain, with subdivisions of the Ch4 region similar to those previously described (Mesulam et al., '83a). Most cholinergic neurons were hyperchromic and magnocellular; however, some neurons were parvicellular. Like most species, cholinergic neurons were also observed throughout the striatum. However, unlike in rodents, cholinergic perikarya were not observed within the cortex or hippocampus. To analyze the cholinergic fiber projections from the basal forebrain to the amygdala, monkeys received an intra‐amygdaloid injection of the retrograde tracer horseradish peroxidase conjugated to wheat germ agglutinin. Retrogradely labeled neurons that colocalized ChAT or acetylcholinesterase (AChE) were found predominantly in the anterolateral portion of the CH4 region. Fewer double‐labeled neurons were found in the anteromedial and intermediate portion of CH4 and in the CH3 region. Neurons that exhibited retrograde labeling were only occasionally discerned in the posterior portions of the CH4 region, in the medullary laminae of the globus pallidus, or lodged within the internal capsule. These data are discussed in terms of the putative role this cholinergic input might play in cognitive processing in primates.
Purkinje cell reduction in the reeler mutant mouse: A quantitative immunohistochemical study
Authors: Heckroth John A. , Goldowitz Dan , Eisenman Leonard M.
Published: January 2005

We have used the immunohistochemical detection of the Purkinje cell marker cGMP‐dependent protein kinase to identify Purkinje neurons in the cerebellum of the reeler mutant mouse. Our quantitative analysis of Purkinje cell number based on this marker indicates that reeler mice possess approximately 82,000 Purkinje cells, slightly less than half the number found in normal mice. Our analysis also shows that 5% of the Purkinje cells in reeler are located in a normal position (between molecular and granular layers), 10% are found in the granular layer, and the remainder form the deep cellular masses characteristic of the reeler cerebellum. The finding of a major Purkinje cell deficit in reeler was surprising in that most investigators consider this mutation to effect cell migration as opposed to cell number. Although we cannot determine whether the Purkinje cell loss in reeler is a primary or secondary gene effect, the possibility that the reeler gene has its effect on migration through a primary effect on neurogenesis or cell survival should be considered.
Development of the peripheral trigeminal system in the chick revealed by an isotype‐specific anti‐beta‐tubulin monoclonal antibody
Authors: Moody Sally A. , Quigg Mark S. , Frankfurter Anthony
Published: January 2005

Using a monoclonal antibody directed against a class III β‐tubulin isotype, cβ4, we studied the time course of the expression of this protein, the morphological differentiation of the immunoreactive cells, and the time course of peripheral axon outgrowth in the chick trigeminal (V) system. The neural crest precursors of the V ganglion neurons do not express the antigen until they begin to differentiate as neurons. The placodal precursors of the V ganglion neurons express the antigen while they still are cuboidal epithelial cells. They continue to be immunoreactive as they migrate from the placode and settle in the ganglion, prior to sprouting axons. The V motoneurons express the antigen near the time of their terminal mitotic division. Using this antibody to visualize axons, we demonstrate that both ganglionic and motoneuron axons grow out as individual fibers, much like pioneer axons. Both halt their extension for several hours once they attain the vicinity of their targets. During this pause many other axons join the nerve bundles. Finally, single pioneer axons split from the main trunk to begin local target innervation.
Ultrastructural localization of immunoreactive calbindin‐D28k in the rat and monkey basal ganglia, including subcellular distribution with colloidal gold labeling
Authors: DiFiglia Marian , Christakos Sylvia , Aronin Neil
Published: January 2005

Normal cellular function depends on the controlled flux of Ca++ within intracellular compartments and across the plasma membrane. Proteins that bind Ca++ are thought to contribute to the regulation of intracellular Ca++ and, perhaps more importantly, signal functional changes in cell activity. In the brain, calbindin‐D28k is among a class of calcium‐binding proteins that are widely and heterogeneously distributed in select populations of neurons, among them neostriatal cells, but whose function is largely unknown. In this study of the monkey and rat neostriatum and globus pallidus, calbindin‐D28k was localized with immunoperoxidase and immunogold methods in order to identify striatal cell populations that contain this protein and the subcellular compartments in which it is likely to function.

Light and electron microscopy showed intense and extensive labeling of immunoreactive calbindin‐D28k in the cell bodies, dendrites, and spines of medium‐sized neostriatal spiny neurons and in their axon terminals which end in the globus pallidus. More discrete labeling with a gold‐conjugated second antibody showed that the predominant site of calbindin‐D28k was the matrix of the cytoplasm. Gold label was also associated with the karyoplasm of spiny cells and with the neurofilaments and axoplasmic matrix of striatopallidal axons and terminals, respectively. Membranes were either sparsely labeled (endoplasmic reticulum, mitochondria) or devoid of gold particles (nuclear envelope and plasmalemma). Radioimmunoassays of striatal subcellular fractions supported the anatomical findings by indicating that the soluble fractions of neostriatal tissue homogenates contained most of the calbindin‐D28k immunoreactivity and that washes from forebrain synaptosomes treated with Triton X‐100 yielded high levels of immunoreactive calbindin‐D28k.

These findings show that immunoreactive calbindin‐D28k is localized to spiny neurons of the striatopallidal pathway and are consistent with previous observations on subcellular localization in nonneuronal tissues. If, as recently speculated, calbindin‐D28k regulates calcium concentrations in neostriatal spiny neurons, this feature may be particularly involved with the high density of glutamatergic inputs to these cells. More work is needed to determine whether calbindin‐D28k, when complexed to Ca++ in neostriatal spiny cells, signals the activation of protein kinases, phosphorylation, and/or neurotransmitter release, as has been shown for other Ca++‐binding proteins in mammalian tissues.
Anatomic connections of inferior parietal cortex (area 7) with subcortical structures related to vestibulo‐ocular function in a monkey (macaca fascicularis)
Authors: Faugier‐Grimaud S. , Ventre J.
Published: January 2005

Connections of the posterior parietal cortex (area 7) with subcortical structures related to the vestibulo‐ocular function were studied on four macaque monkeys by using anterograde and retrograde tracer. Wheat germ agglutinin (WGA)‐horseradish peroxidase (HRP) or tritiated amino acids were injected into the posterior part of area 7, including the caudal end of the superior bank of both the superior temporal sulcus and the lateral sulcus.

The posterior parietal cortex was found to be reciprocally connected with three different ipsilateral thalamic nuclei: the nucleus ventralis posterior inferior, the magnocellular part of the medial geniculate nucleus, and some intralaminar nuclei. Through these connections, area 7 might control the vestibulo‐ocular response (VOR) by modulating the ascending vestibular information. This cortical area 7 also projects to the ipsilateral intermediate and deep layers of the superior colliculus and to several ipsilateral pontine nuclei. The dorsolateral pontine nucleus is of particular interest because it is known to be related to smooth pursuit eye movements. Cortical area 7 also was seen to project to the accessory nucleus of Darkschewitsch, to all the vestibular nuclei, and to the nucleus propositus hypoglossi; the last two projections were found to be bilateral with a greater ipsilateral contribution. Efferents from posterior parietal cortex are directed to precise regions within the vestibular nuclei that are specifically involved in vestibulo‐ocular reflex, or that are in turn connected with brainstem structures implicated in smooth pursuit eye movements. These connections are consistent with the posterior parietal cortex exerting a multilevel influence on the different systems dealing with eye‐head movement coordination.
Quantitative autoradiographic mapping of serotonin 5‐HT1 and 5‐HT2 receptors and uptake sites in the neocortex of the rhesus monkey
Authors: Lidow Michael S. , Goldman‐Rakic Patricia S. , Gallager Dorothy W. , Rakic Pasko
Published: January 2005

The in vitro autoradiographic technique was used to characterize the distribution of serotonin 5‐HT1 and 5‐HT2 receptors and uptake sites in 11 cortical areas of frontal, parietal, and occipital lobes in the rhesus monkey; 5‐HT1 receptors were labeled with [3H]5‐HT; 5‐HT2 receptors were labeled with [3H]ketanserin; and 5‐HT uptake sites were labeled with [3H]citalopram. Five‐HT1 and 5‐HT2 receptors and 5‐HT uptake sites were found in every cortical area examined with the absolute concentration of 5‐HT1 receptors higher than that of 5‐HT2 receptors in all areas. In eight regions of prefrontal and parietal as well as in prestriate cortex, 5‐HT1 and 5‐HT2 receptors had complementary distribution profiles: 5‐HT1 receptors were concentrated in layers I and II and the upper strata of layer III, while 5‐HT2 receptors had their highest concentration throughout layers III and IV. Only the primary motor and visual cortex had receptor distributions different from that described above. Thus, in the primary visual cortex, both 5‐HT1 and 5‐HT2 receptors were found in high concentration in sublayer IVcß, though the density of 5‐HT1 receptor was also high in other subdivisions of layer IV and in layers III, V, and VI. In the primary motor cortex, both receptor subtypes were concentrated in layers I and II and the upper strata of layer III. The pattern of distribution of serotonin uptake sites did not match the patterns of distribution of either 5‐HT1 or 5‐HT2 receptors alone; rather it approximated the combined patterns of distribution of both receptor subtypes. The complementary patterns of distribution of 5‐HT1 and 5‐HT2 receptors in most areas of the monkey cerebral cortex suggest that these two receptor subtypes may make differential contributions to cortical functions.
Age changes in axon number along the cervical ventral spinal nerve roots in rats
Authors: Fraher J. P. , O'Sullivan V. R.
Published: January 2005

Axon counts were made at two standardised levels of C7 ventral spinal nerve roots from 46 female rats representing nine ages between birth and 500 days. The objective was to provide a definitive account of proximodistal changes in axon numbers and of age changes in axon numbers both during postnatal development and at several stages during maturity. At each age there is a proximodistal increase in the numbers of axons in all categories examined (myelinated, promyelin, transitional, and fetal) between levels midway along the subarachnoid course of the root and where it is apposed to but separate from the dorsal root ganglion.

During maturation and throughout maturity axon totals change similarly at both levels: After a slight increase immediately postnatum, they decline sharply between 4 and 20 days due to a marked loss of unmyelinated axons. A gradual decline in myelinated axon numbers continues to 500 days. While these changes are occurring, axon numbers in all categories show a proximodistal increase throughout. The magnitude of this increase lessens with age for all but the transitional category due to a preferential decrease in numbers distally. Though these observations do not differentiate between axon branching and looping of sensory axons into the ventral root as a cause of the proximodistal increase in numbers, they tend to support the former.

At each age during maturation axon proportions at proximal and distal levels correspond well for each animal, indicating that axon segregation proceeds at related rates within each root. Age changes in axon proportions within the transitional and fetal categories indicate that the postnatal stage of axon segregation results from axon loss, rather than Schwann cell proliferation.
Synaptophysin expression during synaptogenesis in the rat cerebellar cortex
Authors: Leclerc Nicole , Beesley Philip W. , Brown Ian , Colonnier Marc , Gurd James W. , Paladino Toni , Hawkes Richard
Published: January 2005

In order to study the mechanisms of synaptogenesis in the rat cerebellar cortex, a library of monoclonal antibodies has been generated against proteins of the isolated synapse. One recognizes a glycosylated 38kDa protein that is concentrated in the synaptic vesicle fraction and resembles synaptophysin biochemically in its molecular weight, charge, and pattern of glycosylation. In the adult cerebellar cortex, the antisynaptophysin (mabQ155) immunoreactivity is codistributed with synapses. Immunoreactivity is strongest in the molecular layer where punctate deposits of reaction product outline the Purkinje cell dendrites. Discrete small profiles, consistent with the distribution of basket cell axon terminals, surround the Purkinje cells, and in the granular layer the synaptic glomeruli are intensely stained. There is no immunoreactivity in the white matter axon tracts. Electron microscope immunocytochemistry confirms the synaptic location of the antigen and suggests that the reaction product is associated with synaptic vesicles. Both round and flat vesicle populations are immunoreactive. Antisynaptophysin(mabQ155) has been used to follow synaptogenesis in the developing rat cerebellum. In the newborn rat (P0), despite the paucity of synapses, there is some specific immunoreactivity, especially in the subcortical white matter. Electron microscopy shows that the antigenicity is associated with vesicles within growth cones, filopodia, and immature axon profiles. During development, antisynaptophysin immunoreactivity increases progressively, along with the maturing cell populations, for both the granule cell‐Purkinje cell and the mossy fiber‐granule cell synapses. Quantitative biochemical analysis confirms the cytochemical results. These data suggest that neuronal growth cones express a synapse‐specific antigen before complete morphological synapses are present.
Central distribution of cervical primary afferents in the rat, with emphasis on proprioceptive projections to vestibular, perihypoglossal, and upper thoracic spinal nuclei
Authors: Neuhuber W. L. , Zenker W.
Published: January 2005

The projections of primary afferents from rostral cervical segments to the brainstem and the spinal cord of the rat were investigated by using anterograde and transganglionic transport techniques. Projections from whole spinal ganglia were compared with those from single nerves carrying only exteroceptive or proprioceptive fibers. Injections of horseradish peroxidase (HRP) or wheat germ agglutinin‐horseradish peroxidase conjugate (WGA‐HRP) were performed into dorsal root ganglia C2, C3, and C4. Free HRP was applied to the cut dorsal rami C2 and C3, greater occipital nerve, sternomastoid nerve, and to the C1/2 anastomosis, which contains afferents from suboccipital muscles and the atlanto‐occipital joint. WGA‐HRP injections into ganglia C7 and L5 were performed for comparative purposes.

Injections of WGA‐HRP or free HRP into rostral cervical dorsal root ganglia and HRP application to C2 and C3 dorsal rami produced labeling in dorsal and ventral horns at the level of entrance, the central cervical nucleus, and in external and main cuneate nuclei. From axons ascending to pontine and descending to upper thoracic spinal levels, medial collaterals were distributed to medial and descending vestibular, perihypoglossal and solitary nuclei, and the intermediate zone and Clarke's nucleus dorsalis in the spinal cord. Lateral collaterals projected mainly to the trigeminal subnucleus interpolaris and to lateral spinal laminae IV and V.

Results from HRP application to single peripheral nerves indicated that medial collaterals were almost exclusively proprioceptive, whereas lateral collaterals were largely exteroceptive with a contribution from suboccipital proprioceptive fibers. WGA‐HRP injections into dorsal root ganglia C7 and L5 failed to produce significant labeling within vestibular and periphypoglossal nuclei, although they demonstrated classical projection sites within the brainstem and spinal cord.

The consistent collateralisation pattern of rostral cervical afferents along their whole rostrocaudal course enables them to contact a variety of precerebellar, vestibulospinal, and preoculomotor neurons. These connections reflect the well‐known significance of proprioceptice neck afferents for the control of posture, head position, and eye movements.
Thalamic input to inferior area 6 and area 4 in the macaque monkey
Authors: Matelli Massimo , Luppino Giuseppe , Fogassi Leonardo , Rizzolatti Giacomo
Published: January 2005

Recent cytoarchitectonic, histochemical, and hodological studies in primates have shown that area 6 is formed by three main sectors: the supplementary motor area, superior area 6, which lies medial to the spur of the arcuate sulcus, and inferior area 6, which is located lateral to it. Inferior area 6 has been further subdivided into two histochemical areas: area F5, located along the inferior limb of the arcuate sulcus, and area F4, located between area F5 and area 4 (area F1).

The present study traced the thalamocortical projections of inferior area 6 and the adjacent part of area 4 by injecting small amounts of WGA‐HRP in specific sectors of the agranular frontal cortex.

Our data showed that each histochemical area receives a large projection from one nucleus of the ventrolateral thalamus (motor thalamus) and additional projections from other nuclei of this thalamic sector. Area F5 receives a large projection from area X of Olszewski ('52) and additional projections from the caudal part of the nucleus ventralis posterior lateralis, pars oralis (VPLo), and the nucleus ventralis lateralis, pars caudalis (VLc) (VPLo‐VLc complex). Area F4 receives a large projection from the nucleus ventralis lateralis, pars oralis (VLo), and additional projections from area X and the VPLo‐VLc complex. The rostral part of area F1 is innervated chiefly by VLo, plus smaller contributions from rostral VPLo and the VPLo‐VLc complex. The caudal part of F1 receives its greatest input from VPLo, with a small contribution from VLo. In addition, each histochemical area receives projections originating from the intralaminar thalamic nuclei, the posterior thalamus, and–for area F4 and area F5–also from the nucleus medialis dorsalis (MD).

Analysis of the physiological properties of the various histochemical areas in relation to their main thalamic input showed that those cortical fields in which distal movements are predominant (area F5, caudal part of area F1) are innervated chiefly by area X and VPLo, wheras those cortical fields in which proximal movements are predominant receive their main input from VLo. Because VPLo and area X are targets of cerebellothalamic pathways, whereas VLo receives a pallidal input, we propose that the cortical fields in which distal movements are most heavily represented are mainly under the influence of the cerebellum, whereas the cortical fields in which proximal movements are most heavily represented are mainly under the influence of the basal ganglia.
Studies on the cellular architecture of the bed nuclei of the stria terminalis in the rat: I. cytoarchitecture
Authors: Ju G. , Swanson L. W.
Published: January 2005

The cytoarchitecture of the bed nuclei of the stria terminalis (BST) in the adult male rat was examined in the three standard planes of section, and the results were compared with the distribution of immunohistochemical staining for a variety of neuropeptides in a companion paper (Ju et al.: J. Comp. Neurol. 280:603–621, '89). It is clear that the BST is an extremely complex mass of gray matter that can be parcellated most clearly into anterior and posterior divisions, which are separated by a more‐or‐less vertical septum of fibers associated with the stria terminalis. The anterior division can be further parcellated into dorsal, lateral, and ventral areas, and each of these areas, along with the posterior division, can be thought of as containing more‐or‐less discrete nuclei embedded within a relatively undifferentiated region. Thus, we have recognized a central core in the anterodorsal area; oval, juxtacapsular, and rhomboid nuclei in the anterolateral area; and fusiform, dorsomedial, dorsolateral, magnocellular, and ventral nuclei in the anteroventral area. The most obvious cell groups in the posterior division include the principal, interfascicular, transverse, premedullary, and dorsal nuclei. Problems associated with defining the limits of the BST, and with comparing our results with the earlier literature, are discussed.
Hormonal control of neuron number in sexually dimorphic spinal nuclei of the rat: II. Development of the spinal nucleus of the bulbocavernosus in androgen‐insensitive (Tfm) rats
Authors: Sengelaub D. R. , Kurz E. M. , Jordan C. L. , Arnold A. P.
Published: January 2005

The spinal nucleus of the bulbocavernosus (SNB) is a sexually dimorphic motor nucleus whose development is under the control of steroid hormones. The SNB contains many more motoneurons in adult male rats than in females, and this sex difference is produced by a sexually dimorphic motoneuron death which is regulated by androgens. To study further the role of androgens in the development of sex differences in SNB motoneuron number, we examined SNB development in males with the testicular feminization mutation (Tfm) which renders them insensitive to androgens.

Counts of SNB motoneurons perinatally revealed that SNB development in normal male and female King‐Holtzman rats was similar to that reported previously for Sprague‐Dawley rats; SNB motoneuron number increased from initially low levels at embryonic day 18 through the day before birth, when motoneuron numbers in both sexes were substantially higher than adult levels. After this prenatal increase, motoneuron number declined in both sexes, until by postnatal day 10 motoneuron numbers were in their adult ranges and the sex difference was fully expressed. Females lost more motoneurons than did males during this period, and this loss was due to motoneuron death as revealed by counts of degenerating cells.

SNB development in King‐Holtzman Tfm males was similar to that of normal males through embryonic day 20, suggesting that androgens may not be necessary for the initial increase in motoneuron numbers in the SNB. Thereafter, SNB motoneuron numbers in Tfm males declined in a female‐typical fashion; Tfm males and normal females did not differ at any postnatal age. The incidence of degenerating cells in Tfm males over this period was like that of normal females and significantly higher than that of normal males. These results indicate that just as treatment of females with androgens during development attenuates cell death in the SNB to male‐typical levels, resulting in masculine motoneuron numbers, the Tfm male's insensitivity to androgens results in a female‐typical cell death resulting in feminine SNB motoneuron numbers.
Brainstem projections to the major respiratory neuron populations in the medulla of the cat
Authors: Smith Jeffrey C. , Morrison Debra E. , Ellenberger Howard H. , Otto Marianne R. , Feldman Jack L.
Published: January 2005

Efferent and afferent connections of the dorsal and ventral respiratory groups in the medulla of the cat were mapped by axonal transport of wheat germ agglutinin conjugated to horseradish peroxidase. Injections of wheat germ agglutinin‐horseradish peroxidase into the dorsal respiratory group and the three principal subdivisions of the ventral respiratory group (caudal, rostral, and Bötzinger Complex) revealed extensive interconnections between these regions and with a limited number of other brainstem neuron populations. Major neuron populations with efferent projections to the regions of the dorsal and ventral respiratory groups include the parabrachial nuclear complex (medial parabrachial, lateral parabrachial, and Kölliker‐Fuse nuclei), subregions of the lateral paragigantocellular reticular nucleus, subregions of the lateral and magnocellular tegmental fields, inferior central and postpyramidal nuclei of the raphe, and sensory trigeminal nuclei. A previously unidentified neuron population with extensive efferent projections to the dorsal and ventral respiratory groups was found near the ventral surface of the rostral medulla; we refer to this group as the retrotrapezoid nucleus. The results suggest that the dorsal and ventral respiratory groups form an extensively interconnected neuronal system receiving convergent inputs from the same brainstem nuclear groups, consistent with the hypothesis that the dorsal and ventral groups are primarily sites for integration of sensory and premotor respiratory drive inputs. Neuron populations in the rostral ventrolateral medulla with projections to both the dorsal and ventral respiratory groups, particularly the retrotrapezoid nucleus and neighboring subregions of the lateral paragigantocellular reticular nucleus, are candidate sites for participation in respiratory rhythmogenesis or other critical functions of the brainstem respiratory control system such as intracranial chemoreception.
Frontal lobe connections of the superior temporal sulcus in the rhesus monkey
Authors: Seltzer Benjamin , Pandya Deepak N.
Published: January 2005

The frontal lobe connections of different architectonic areas of the superior temporal sulcus (STS) in the rhesus monkey were investigated with the aid of both anterograde and retrograde tracing techniques. The proisocortical area in the rostralmost STS connects with proisocortical regions on the ventral and medial surfaces of the frontal lobe. The frontal lobe projections of polymodal cortex (area TPO) in the upper bank of the STS are organized according to the rostral‐to‐caudal topography of the sulcus. Rostral TPO interconnects with ventral (areas 13, 12, 11, and 14), medial (areas 24, 32, 14, and 9), and lateral (areas 10, 12, and 46) sectors of the frontal lobe. The midportion of polymodal cortex projects to, and receives fibers from, rostral subdivisions of lateral prefrontal cortex, viz. dorsal area 46, areas 9 and 10, whereas the caudal segment of TPO has reciprocal connections with caudal subdivisions (areas 46, 8, and 6) of the lateral frontal lobe.

Visual‐related zones (areas TEa and TEm) in the rostral lower bank of the STS have connectional relationships with orbitofrontal areas 11 and 12 and lateral frontal areas 46 and 8. A presumed somatic sensory‐related area in the rostral depth of the STS (area IPa) projects to orbital (areas 11 and 14) and lateral (areas 46, 10, and 12) sectors of the frontal lobe.
Brainstem afferents to the tuberomammillary nucleus in the rat brain with special reference to monoaminergic innervation
Authors: Ericson Hans , Blomqvist Anders , Köhler Christer
Published: January 2005

Monoaminergic innervation of a histamine‐producing cell group, the tuberomammillary nucleus in the posterior hypothalamus, was investigated in the rat by light and electron microscopic immunohistochemical techniques. Immunohistochemical staining of sections of the posterior hypothalamus was demonstrated afferent fibers immunoreactive to tyrosine hydroxylase in ventral and medial subgroups of the tuberomammillary nucleus afferent fibers immunoreactive to tyrosine hydroxylase (TH), dopamine‐ßhydroxylase (DBH), phenyletanolamineNmetyltransferase (PNMT), and serotonin (5‐HT). TH‐ and DBH‐immunoreactive fibers were similar and were evenly and densely distributed throughout the tuberomammillary nucleus. Fibers stained with 5‐HT antibodies were also present throughout the tuberomammillary nucleus but exhibited the densest labeling in the dendritic layer adjacent to the glia limitans in the ventral subgroup. Innervation by PNMT‐immunoreactive axons was sparse.

Electron microscopic analysis of TH−, DBH−, and 5‐HT‐immunoreactive fibers in the tuberomammillary nucleus revealed vesicle‐containing terminal boutons, which formed synapses with dendrites of varying size. Synaptic contacts with nerve cell bodies were not found.

Retrograde transport of the fluorescent dye Fast Blue injected into the tuberomammillary nucleus, combined with immunofluorescent staining with anti‐TH, anti‐DBH, anti‐PNMT, and anti‐5‐HT antibodies, showed that monoaminergic input to the tuberomammillary nucleus originated mainly from the adrenergic and noradrenergic cell groups C1C3 and A1‐A2, respectively, and from the serotoninergic cell groups B5‐B9 as designated by Dahlström and Fuxe ('65). Few double‐labeled neurons were found in the nucleus locus coeruleus and the dopaminergic cell groups of the rostral brain stem.

The present findings suggest that the activity of the histamine‐producing neurons of the tuberomammillary nucleus is influenced by monoaminergic neurons in the ventrolateral and dorsomedial medulla oblongata and the raphe nuclei of the rostral brainstem.