bluuebunny/crossref_metadata_2025 huggingface dataset:
An intracellular HRP study of the rat globus pallidus. II. Fine structural characteristics and synaptic connections of medially located large GP neurons
Authors: Falls W. M. , Park M. R. , Kitai S. T.
Published: May 2005

In order to classify the presynaptic elements contacting the principle class of globus pallidus neurons, electron microscopic examination of serial sections made from a medially located large globus pallidus neuron, labeled with intracellular horseradish peroxidase, was undertaken. In addition, the use of labeled and light microscopically reconstructed material allowed us to quantitatively determine the distribution of each bouton type along the soma and dendrites. Six types of presynaptic terminals contacting the labeled cell have been recognized. Type 1 endings, the most numerous (84%), make symmetrical contacts on all portions of the cell, except spines, contain large pleomorphic, and a few large dense‐core vesicles. Type 2 endings are filled with small spherical‐to‐ellipsoidal synaptic vesicles. They make asymmetrical contacts only with higher‐order dendrites and account for 12% of synaptic contacts onto the labeled neuron. Type 3 endings are large, contain sparsely distributed large pleomorphic vesicles, and make two symmetrical synapses per bouton, one onto a spine head and the other onto the underlying dendritic shaft. They are infrequent (0.2%), being found only in association with dendritic spines. Type 4 endings contain large pleomorphic synaptic vesicles and no dense‐core vesicles. They make symmetrical contacts with the short primary dendrites. Type 5 endings contain a mixture of small clear pleomorphic vesicles and numerous large dense‐core vesicles. They contact only the cell body and the short primary dendrites, making up 20% of somatic synaptic contacts but less than 1% of contacts onto dendrites. Type 6 boutons contain oval and flattened synaptic vesicles and establish symmetrical contacts with higher‐order dendritic branches and the cell body.
Morphology of physiologically identified X‐, Y‐, and W‐type retinal ganglion cells of the cat
Authors: Saito Hide‐Aki
Published: May 2005

Retinal ganglion cells of the cat have been classified physiologically into X‐, Y,‐ and W‐cells, on the basis of the receptive field properties, and morphologically into α‐, β‐, and γ‐cells.

In order to study directly the correspondence between these classifications, intracellular recordings from the ganglion cells in supervised eye‐cup preparations were made with the aid of microelectrodes filled with Lucifer yellow CH. The cells were stained after their photic responses were studied under mesopic adaptation.

X‐cells, showing sustained depolarization (on‐center cells) or hyperpolarization (off‐center cells) in response to a spot of light had medium‐sized round somata and spread bushy dendrites within a narrow retinal area. On the other hand, on‐center and off‐center Y‐cells, showing transient responses to the spot stimulus, had large somata and widely expanded thick dendrites which were sparsely branched. W‐cells which showed weak sustained responses had widely extended thin and winding dendrites, despite a small somal size. These morphological features of Y‐, X‐, and sustained W‐cells correspond well to those of α‐, b̃‐, and δ‐cells (a subtype of γ‐cells), respectively. The hypothesis of “morphology reflecting function” is strongly supported.
Distribution in area 17 of neurons projecting to the pontine nuclei: A quantitative study in the cat with retrograde transport of HRP‐WGA
Authors: Bjaalie Jan G. , Brodal Per
Published: May 2005

The number and distribution of corticopontine neurons within area 17 of the cat were studied quantitatively with the use of retrograde transport of horseradish peroxidase‐wheat germ agglutinin. Eight cats received stereotactic injections in the pontine nuclei; in three of these complete staining of the parts of the pontine nuclei receiving fibers from the visual cortex was achieved. Labeled cells were counted in frontal sections through the hemisphere, spaced at 0.5 mm.

The borders of area 17 were determined cyto‐ and myeloarchitectonically and a flat map was produced for each animal. A map of the representation of the visual field in 10° × 10° blocks in the first visual area (Tusa et al., '78, '81) was transferred to our maps of area 17. The density and number of labeled corticopontine cells could then be determined within blocks of the cortex representing 10° × 10° of the visual field.

The cell density (number of labeled cells per mm2 cortex) was found in general to be highest in parts of the cortex representing peripheral parts of the visual field. The cell density is low in cortex representing the central visual field, but the lowest density was found in the representation of a paracentral region in the upper visual field. Furthermore, cortical regions representing the lower part of the visual field have a higher cell density than those representing the upper part; in four cases, 68–86% of all labeled cells were found in parts of area 17 representing the visual field below the horizontal meridian.

Since there is an enlarged cortical representation of central vision, the much lower cell densities in ‘central’ parts of area 17 than in “peripheral” parts may mean that all parts of the visual field are represented with equal numbers of corticopontine neurons (“linear” representation). This is not the case, however, since the number of labeled cells per 10° × 10° is considerably higher in the cortex representing the central 10° and medial parts of the lower visual field than in the rest of area 17. Assuming that the corticopontine cells in the visual cortex transmit spatially relevant information, we conclude that there is an overrepresentation of central vision and the medial parts of the lower visual field in the corticopontine projection from area 17.
Assessment of possible transneuronal changes in the retina of rats with inherited retinal dystrophy: Cell size, number, synapses, and axonal transport by retinal ganglion cells
Authors: Eisenfeld Amy Jill , Lavail Matthew M. , Lavail Jennifer H.
Published: May 2005

In pigmented RCS rats with inherited retinal dystrophy, most photoreceptor cells disappear between postnatal days 20 and 100. We have examined the time course of the degeneration of photoreceptor nuclei and synapses and determined whether transneuronal changes occur in the inner nuclear layer (INL), inner plexiform layer (IPL), und retinal ganglion cells following loss of photoreceptor cells in these animals.

Electron microscopic photomontages of the entire thickness of the IPL of dystrophic (RCS‐p+) and control (RCS‐rdy+ p+) rats 334 to 515 days old were prepared, and synapses were counted and identified as either conventional (amacrine) or ribbon (bipolar) types. Neither the incidence of synapses in the IPL nor the ratio of conventional to ribbon synapses differed in the dystrophic and control retinas.

Ganglion cell diameter, perimeter, area, and density were measured from drawings of wholemount preparations of dystrophic and control rats 105 days and older. Diameter, perimeter, area and number of ganglion cells were not significantly different in the two genotypes. Anterograde axonal transport was measured by studying the displacement of labeled material as it traveled along ganglion cell axons and accumulated in the superior colliculus. The normal and dystrophic rats showed no significant difference in (1) the rates of rapidly moving components (approximately 110–180 mm/day) and slowly moving components (1.7–2.5 mm/day) or (2) the amount of radioactive material transported to the superior colliculus.

The absence of transneuronal changes in retinal ganglion cells of RCS rats contrasts with results obtained earlier in rd mice (Graftstein et al., '72). Unlike the RCS rat, retinal degeneration in rd mice occurs before the maturation of the retina. We hypothesize that the ganglion cells may be more affected by loss of input early in development, and, therefore, ganglion cells of retinal dystrophic rats are less affected despite little or no synaptic input for several months. Furthermore, any reduction in the electrical activity of retinal ganglion cells that might follow loss of photoreceptor cells does not result in a significantly decreased rate of axonal transport.
Studies on the factors that govern directionality of axonal growth in the embryonic optic nerve and at the chiasm of mice
Authors: Silver Jerry
Published: May 2005

What are the forces residing at the presumptive chiasm of embryonic mice that control the directionality (i.e., side specificity) of the optic axons? In an attempt to answer this question, the overall trajectories of individual fascicles of early growing axons and the various environments that they encounter along their pathway have been charted from the eye through the nerve and into the base of the diencephalon. Serial sections and reconstructive computer graphic techniques were used for the analysis.

The early optic axons (embryonic (E) day 13.5) arrive at the chiasm in a stereotyped topographic arrangement. However, the fiber array at the primitive chiasm is not retinotopically organized nor is it maintained with the same level of spatial precision as it is at the disc. Thus, the annular, inverted retinotopic contingent of “pioneering” axons that exists in the primitive nerve becomes reorganized at the chiasm into a crescent‐shaped configuration, with fascicles from ventrotemporal and ventronasal retina at either side of the crescent and with fascicles from dorsal retina interposed. Because of their gross locations in the crescent, particular clusters of fibers, each largely originating from different retinal sectors, but “contaminated” with fibers from other regions, come in contact with different types of nonneuronal structures at the chiasm. One, a dense, knotlike glial formation that lies along the margin of the diencephalic‐telencephalic junction, directs all adjacent (ventronasal) fibers contralaterally. The other, a discrete pathway of lengthy marginal glial processes, separated by an anastomotic system of large extracellular spaces, guides all nearby fibers from ventrotemporal retina ipsilaterally. The results suggest that fiber topography as well as local environmental factors may play important roles in guiding axons at the chiasm.
Synaptic contacts of somatostatin immunoreactive amacrine cells in goldfish retina
Authors: Marshak David W. , Yamada Tadataka , Stell William K.
Published: May 2005

Retinal amacrine cells containing somatostatinlike immunoreactivity (SLI) were labeled by the peroxidase‐antiperoxidase technique and their connections were analyzed by light and electron microscopy. The labeled processes were found in two distinct plexuses—one near the most proximal border of the inner plexiform layer and the other near the most distal border. They received most (89%) of their input from amacrine cells and the remainder from bipolar cells. A majority (56%) of their output synapses go to processes of amacrine cells, a substantial proportion (38%) go to ganglion cell dendrites, and the remainder go to bipolar cell axon terminals. The relative frequencies of each of the types of contacts were nearly identical in the distal and proximal plexuses. The cells containing SLI are different in their morphology and synaptic connections from any goldfish amacrine cells containing conventional neurotransmitters, but one type of amacrine cell containing SLI resembles certain other peptidergic amacrine cells in the goldfish retina.
The somatotopic organization of primary afferent terminals in the superficial laminae of the dorsal horn of the rat spinal cord
Authors: Swett John E. , Woolf Clifford J.
Published: May 2005

Transganglionic transport of wheatgerm agglutinin conjugated horseradish peroxidase (WGA‐HRP) was used to reveal the central distribution of terminals of primary afferent fibers from peripheral nerves innervating the hind leg of the rat. In separate experiments the sizes and locations of cutaneous peripheral receptive fields were determined by electrophysiological recording techniques for each of the nerves that had been labeled with WGA‐HRP. By using digital image analysis, the sizes and positions of the peripheral receptive fields were correlated with the areas of superficial dorsal horn occupied by terminals of primary afferents from each of these receptive fields.

Data were obtained from the posterior cutaneous nerve of the thigh, lateral sural, sural, saphenous, superficial peroneal, and tibial nerves. The subdivisions of the sciatic nerve, the sural, lateral sural, superficial peroneal, and tibial nerves each projected to a separate and distinct region of the superficial dorsal horn and collectively formed a “U”‐shaped zone of terminal labeling extending from lumbar spinal segments L2 to the caudal portions of L5. The gap in the “U” extended from L2 to the L3‐4 boundary and was occupied by terminals from the saphenous nerve. Collectively, all primary afferents supplying the hindlimb occupied the medial 3/4 of the superficial dorsal horn with terminals from the tibial nerve lying most medially and occupying the largest of all the terminal fields. Afferents from the superficial peroneal lay in a zone between the medially situated tibial zone and the more laterally placed sural zone. Afferents from the posterior cutaneous nerve were located most caudally and laterally. Terminal fields from the posterior cutaneous and saphenous nerves differed from the others in having split representations caused presumably by their proximity to the mid‐axial line of the limb. Comparisons between the peripheral and the central representations of each nerve revealed that 1 mm2 of surface area of the superficial dorsal horn serves approximately 600–900 mm2 of hairy skin and roughly 300 mm2 of glabrous skin. The vast majority of terminal labeling observed in the dorsal horn was found in the marginal layer and substantia gelatinosa, suggesting that small diameter afferents have an orderly somatotopic arrangement in which each portion of the skin surface is innervated by afferent fibers that terminate in preferred localities within the dorsal horn.
Immunocytochemical localization of choline acetyltransferase within the rat neostriatum: A correlated light and electron microscopic study of cholinergic neurons and synapses
Authors: Phelps Patricia E. , Houser Carolyn R. , Vaughn James E.
Published: May 2005

Monoclonal antibodies to choline acetyltransferase (ChAT) were used in an immunocytochemical study to characterize putative cholinergic neurons and synaptic junctions in rat caudate‐putamen. Light microscopy (LM) revealed that ChAT‐positive neurons are distributed throughout the striatum. These cells have large oval or multipolar somata, and exhibit three to four primary dendrites that branch and extend long distances. Quantitative analysis of counterstained preparations indicated that ChAT‐positive neurons constitute 1.7% of the total neuronal population. Electron microscopy (EM) of immunoreactive neurons initially studied by LM revealed somata characterized by deeply invaginated nuclei and by abundant amounts of organelle‐rich cytoplasm. Surfaces of ChAT‐positive neurons are frequently smooth, but occasional somatic protrusions and dendritic spines occur. Although infrequently observed, axons of ChAT‐positive neurons branch, receive synapses, and become myelinated. Unlabeled boutons make both symmetrical and asymmetrical synapses with ChAT‐positive somata and proximal dendrites, but are more numerous on distal dendrites. In addition, some unlabeled terminals form asymmetrical synapses with ChAT‐positive somata and dendrites that are distinguished by prominent subsynaptic dense bodies. Light microscopy demonstrated a dense distribution of ChAT‐positive fibers and punctate structures in the striatum, and these structures appear to correlate, respectively, with labeled preterminal axons and presynaptic boutons identified by EM. ChAT‐positive boutons contain pleomorphic vesicles, and make symmetrical synapses primarily with unlabeled dendritic shafts. Furthermore, they establish synaptic contacts with somata, dendrites and axon initial segments of unlabeled neurons that ultrastructurally resemble medium spiny neurons. These observations, together with the results of other investigations, suggest that medium spiny GABAergic projection neurons receive a cholinergic innervation that is probably derived from ChAT‐positive striatal cells. The results of this study also indicate that cholinergic neurons within caudate‐putamen belong to a single population of cells that have large somata and extensive sparsely spined dendrites. Such neurons, in combination with dense concentrations of ChAT‐positive fibers and terminals, are the likely basis for the large amounts of ChAT and acetylcholine detected biochemically within the neostriatum.
The very distal part of the basilar papilla in the chicken: A morphological approach
Authors: Lavigne‐Rebillard Mireille , Cousillas Hugo , Pujol Reḿy
Published: May 2005

The very distal part of the chicken basilar papilla was investigated by light and electron (scanning and transmission) microscopy. The rostral tip of the basilar papilla has a lenticular area with atypical sensory hair cells which are more similar to vestibular than to auditory cells. The structure of the lenticular area appears to be suitable for vestibular function or, more likely, for auditory perception at very low frequencies. Several hypotheses can be proposed to explain this very peculiar portion of the avian cochlea. It is difficult to consider it a continuously growing area since it remains stable in adulthood. A better explanation would be that there is an incomplete ontogenetic or phylogenetic process.
Afferent influences on brain stem auditory nuclei of the chicken: Effects of conductive and sensorineural hearing loss on N. Magnocellularis
Authors: Tucci Debara L. , Rubel Edwin W
Published: May 2005

Nucleus magnocellularis is the avian homologue of the spherical cell region of the mammalian anteroventral cochlear nucleus. Its primary excitatory synaptic input is from large end bulbs of Held from the eighth nerve ganglion cells. We have examined the effects of three peripheral manipulations–middle ear ossicle (columella) removal (monaural and binaural), columella removal and oval window puncture (monaural), and monaural earplug–on cross‐sectional cell area (“cell size”) of second‐order auditory neurons in n. magnocellularis of the chicken. Manipulations were performed between embryonic day 19 and posthatch day 4. Survival time was varied from 2 to 60 days. Air conduction and bone conduction thresholds were determined to assess for conductive and sensorineural hearing loss associated with each of these manipulations. Hair cell counts were made from basilar papillae of each experimental group.

We found that a columella removal alone, which produced a 50–55‐dB purely conductive hearing loss, was not associated with changes in cell size of n. magnocellularis neurons. Similarly, chronic monaural earplugging did not affect the cross‐sectional area of these second‐order auditory neurons. Conversely, a combined columella removal and oval window puncture, which produced a mixed hearing loss with a 15–40‐dB sensorineural component was associated with an 18–20% reduction in n. magnocellularis cell area. Hair cell counts for experimental ears were not significantly different from control ears. These results, in conjunction with measurements of multiunit activity recorded in n. magnocellularis, suggest that manipulations which markedly attentuate extrinsic auditory stimulation, but do not result in chronic change in the average activity levels, also do not influence the size of n. magnocellularis cell bodies. On the other hand, a manipulation which influences overall activity levels, but does not result in degeneration of receptor cells, resulted in marked changes in n. magnocellularis cell size.
Peptidergic and aminergic innervation of the facial nucleus of the rat with special reference to ontogenetic development
Authors: Senba Emiko , Tohyama Masaya , Shiotani Yahe , Kawasaki Yoshiyuki , Kubo Takeshi , Matsunaga Toru , Emson Piers C. , Steinbusch Harry W. M.
Published: May 2005

The distribution and ontogenetic development of several neuropeptides such as enkephalin, substance P, somatostatin, neuropeptide Y, and of monoamines such as serotonin and catecholamines in the facial nucleus of the rat were investigated with immunocytochemistry. The neuropeptides were concentrated in certain subnuclei. Enkephalin‐immunoreactive fibers were distributed in the medial and dorsal subnuclei, substance P in the intermediate and dorsal subnuclei, somatostatin in the intermediate subnucleus, and neuropeptide Y in the dorsal subnucleus. The amines were distributed evenly throughout the nucleus. These distribution patterns suggest that peptidergic fibers are closely related to the functions of different subnuclei, while fibers containing monoamines are more basic–not specific to individual muscles. Few of these fibers were observed in the prenatal stage of the rat, but they increased markedly in number during the first postnatal week, and had established their innervation pattern by the tenth postnatal day, which coincides with the establishment of nerve‐muscle innervation.

The present study further showed that fibers containing serotonin are supplied mainly from the raphe nucleus, that catecholamine fibers are from neurons containing catecholamine surrounding the facial nucleus, and that fibers containing neuropeptide Y are from the lateral part of the caudal medullary reticular formation. These findings suggest that catecholamine and neuropeptide Y are not both present in the single neurons projecting to the facial nucleus.
Morphology of sympathetic preganglionic neurons in the thoracic spinal cord of the cat: An intracellular horseradish peroxidase study
Authors: Dembowsky K. , Czachurski J. , Seller H.
Published: May 2005

Horseradish peroxidase was intracellularly injected into sympathetic preganglionic neurons (SPN) of the third thoracic segment in cats. Seven neurons were reconstructed from serial horizontal or parasagittal sections of the spinal cord.

The cell bodies of all neurons were located in the n. intermediolateralis pars principalis (ILp). They were spindle‐shaped with the long axis in craniocaudal direction or large and multipolar or small and oval in shape. Preferentially on the cranial and caudal pole of the cell body, five to eight primary dendrites arose from the cell body. Dendritic branches were traced to their terminations at distances up to 1,330 μm from the cell body. The dendritic fields of all SPNs were strictly oriented in the longitudinal direction with a total length of 1,500–2,540 μm. The cranial and caudal dendritic fields were about equal in length but, with one exception, the degree of branching was always greater in the cranial than in the caudal dendritic field. The dendritic fields of all SPNs were primarily restricted to the ILp. In the mediolateral direction it extended from 130 to 360 μm and in the dorsoventral direction from 50 to 180 μm. Only rarely, a higher‐order dendrite left the boundaries of the ILp and projected dorsolaterally or laterally into the white matter or ventromedially or medially into the adjacent n. intercalatus. All dendrites showed various forms of spines. At a distance of 132–437 μm from the cell body the axon arose as a direct extension of a process which closely resembled a primary or second‐order dendrite. The axons projected ventrally and mostly caudally along the lateral border of the gray matter until they turned laterally at the end of the ventral horn. No axon collaterals were observed.
NADPH diaphorase cells in the mammalian inner retina
Authors: Sandell J. H.
Published: May 2005

The distribution of the enzyme NADPH diaphorase was examined histochemically in the retina of the rat, rabbit, cat, owl monkey, squirrel monkey, rhesus macaque, and human being. In all species tested the enzyme was concentrated in cells 10–12 μm in diameter at the vitread margin of the inner nuclear layer. The population was sparse (< 2,000 cells/rat retina). In several species additional minor populations were observed. While a clear function for NADPH diaphorase has yet to be described, an abundance of the enzyme characterizes a similar subpopulation of retinal cells in a wide variety of mammals.
The central organization of the vagus nerve innervating the stomach of the rat
Authors: Shapiro Robert E. , Miselis Richard R.
Published: May 2005

We employed the neural tracers cholera toxin‐norseradish peroxidase and wheat germ agglutinin‐horseradisn peroxidase to examine the organization of the afferent and efferent connections of the stomach within the medulla oblongata of the rat. The major finding of this study is that gastric motoneurons of the dorsal motor nucleus (DMN) possess numerous dendrites penetrating discrete regions of the overlying nucleus of the solitary tract (NTS). In particular, dendritic labelling was present in areas of NTS which also received terminals of gastric vagal afferent fibers such as the subnucleus gelatinosus, nucleus commissuralis, and medial nucleus of NTS. This codistribution of afferent and efferent elements of the gastric vagus may provide loci for monosynaptic vagovagal interactions. A small number of dendrites of DMN neurons penetrated the ependyma of the fourth ventricle and a few others entered the ventral aspect of the area postrema, thus making possible the direct contact of preganglionic neurons with humoral input from the cerebrospinal fluid and/or the peripheral plasma. Nucleus ambiguus neurons projecting to the stomach predominantly innervate the forestomach. The dendrites of these cells, when labelled, were generally short, and extended beyond the compact cluster of ambiguus neurons in a ventrolateral direction, parallel to the fascicles of vagal efferent fibers traversing the medulla.
The fine structural organization of tyrosine hydroxylase immunoreactive neurons in rat arcuate nucleus
Authors: Piotte M. , Beaudet A. , Joh T. H. , Brawer J. R.
Published: May 2005

The fine structure of the tyrosine hydroxylase (TH) immunoreactive neurons of the hypothalamic arcuate nucleus was examined by means of immunocytochemistry [peroxidase‐antiperoxidase (PAP) method], utilizing an antibody against TH. Immunolabeled axon terminals were observed infrequently and were located predominantly in the lateral region, whereas numerous labeled perikarya and dendrites were found throughout the nucleus. The labeled terminals, containing primarily clear and occasionally dense core vesicles, were never observed in synaptic contact. On the other hand, unlabeled axon terminals were frequently seen synapsing on labeled dendrites. In addition, the labeled dendrites were often seen in direct apposition to other neuronal elements such as both labeled and unlabeled perikarya. In contrast, unlabeled dendrites were never seen apposed to labeled perikarya. Labeled dendrites also occurred in direct contact with one another and with unlabeled dendrites. Moreover, numerous labeled dendrites were encountered along tanycytic processes. Dendrites engaged in tanycytic appositions were occasionally partially encompassed by thin sheaths emanating from the tanycytic process. The extensive contact made by the labeled dendritic profiles on both labeled perikarya and dendrites suggests that tubero‐infundibular dopaminergic (TIDA) cells may communicate with each other by means of dendritic release of dopamine. The presence of appositions between labeled dendrites and both unlabeled perikarya and dendrites suggests that the TIDA system also influences other neuronal populations through its dendrites. Finally, the dendrotanycytic relationship suggests that the TIDA system may play some role in the regulation of tanycytic function.
Population dynamics of adult‐formed granule neurons of the rat olfactory bulb
Authors: Kaplan Michael S. , McNelly Nancy A. , Hinds James W.
Published: May 2005

The population dynamics of internal granule cells in the rat olfactory bulb during adult life were analyzed in histological sections and in autoradiograms with (1) counts of granule cells, (2) counts of labeled granule cells 1 month after injection of 3H‐thymidine at various ages, and (3) counts of labeled granule cells at varying survival times (up to 18 months) after injection at 3 months and 24 months. The total number of granule cells increases linearly throughout life, approximately doubling between 3 and 31 months. Autoradiographic studies show that the rate of production of new granule cells decreases from 3 to 12 months and then is approximately constant during the rest of the life span. The number of labeled cells found 6 months after injection at 3 and 24 months is about one‐fourth and one‐half, respectively, that of the number at a 1‐month survival, suggesting that many of the cells produced to do not survive. However, at least some granule cells labeled at 3 months survive for 18 months. A model is suggested in which granule cells are produced continuously throughout life and control of the total number of granule cells is effected chiefly through the rate of cell death.
Nigral inhibitory termination on efferent neurons of the superior colliculus: An intracellular horseradish peroxidase study in the cat
Authors: Karabelas A. B. , Moschovakis A. K.
Published: May 2005

Intracellularly recorded responses of deeper tectal neurons to stimulation of the substantia nigra and the cerebral peduncle were obtained to demonstrate the monosynaptic inhibitory nature of the nigrotectal pathway in the cat. We also employed antidromic stimulation (contralateral predorsal bundle and superior colliculus) and intracellular labeling with HRP to demonstrate which types of tectal efferent neurons are nigrorecipient. The response to nigral stimulation in 61% of the cells studied was a monosynaptic IPSP of short duration. Recovered HRP‐labeled nigrorecipient neurons include X1 (large multipolar radiating), X2 (tufted), X4 (mediumsize vertical), X5 (mediumsize horizontal), T1 (mediumsize trapezoid radiating), T2 (small ovoid vertical), I (small sparsely ramified), and A (small horizontal) neurons. Nigrorecipient cells participate in all four of the major efferent axonal systems of the deeper tectal layers: crossed descending (X and T neurons), ipsilateral descending (I and T neurons), ascending (A, X, and T neurons), and commissural (T neurons). EPSPs accompanied by long‐lasting hyperpolarizing potentials were recorded from the remaining tectal neurons in response to stimulation of the substantia nigra, cerebral peduncle, and pericruciate cortex. Collision experiments indicate that at least part of the excitatory responses of tectal neurons to nigral and penduncular stimulation are mediated by corticotectal fibers traversing the cerebral peduncle and the substantia nigra. Excitatory effects of nigral, peduncular, and cortical stimulation were disclosed in X neurons including the non‐nigrorecipient large vertical neurons of the X3 subgroup. Cortical excitatory and nigral inhibitory inputs converge only on X neurons (X1, X2, X4, X5). In this case, nigrally evoked IPSPs were preceded by a brief EPSP. Collectively, these results demonstrate the inhibitory termination of tne nigrotectal pathway on a wide variety of deeper tectal efferent neurons. Such findings imply the versatility of the nigral involvement in tectal mechanisms of gaze control. We suggest that the substantia nigra pars reticulata contacts tectal neurons differing as to their response properties and shapes the signal carried by all the major tectofugal bundles.
Ascending projections of the mammillary region in the pigeon: Emphasis on telencephalic connections
Authors: Berk Mitchell L. , Hawkin Randall K.
Published: May 2005

The ascending projections of the mammillary region of the hypothalamus and adjacent posterolateral hypothalamus were investigated by autoradiographic and horseradish peroxidase histochemical techniques. Analysis of the anterograde data revealed that the main contingent of mammillary fibers ascends in the medial forebrain bundle (MFB) in the lateral hypothalamic area. These fibers distribute to a number of telencephalic regions via three pathways. (1) Fibers course dorsomedially into the medial and lateral parts of the septum and continue into the hippocampus with a dense terminal field in the parahippocampal area. (2) Laterally coursing fibers project to area corticoidea dorsolateralis, area temporo%parieto%occipitalis, cortex piriformis, and the posterior part of archistriatum. (3) The fibers remaining in the MFB ascend into the “ventral paleostriatum,” olfactory tubercle, and into the lateral and ventral borders of the rostral portion of lobus parolfactorius (LPO). Numerous fibers leave the LPO region and course dorsally into the deep layer of the Wulst, hyperstriatum dorsale (HD). Many fibers continue dorsolaterally through the HD and enter an unnamed region of the dorsolateral telencephalon (lateral to the vallecula) at the level of the olfactory bulb. Retrograde transport experiments revealed that the perikarya of origin‐of‐fiber projections to the parahippocampal area and to the rostral, dorsolateral telencephalon reside not only in nucleus mammillaris lateralis but also in posterolateral hypothalamic cells rostral and dorsal to this nucleus. The projection of these hypothalamic cells to the hippocampal formation and many other telencephalic regions in birds suggests that these cells are similar to the mammalian supramammillary nucleus and posterolateral hypothalamus rather than the mammillary nuclei.
GABAergic neurons containing CCK‐8‐like and/or VIP‐like immunoreactivities in the rat hippocampus and dentate gyrus
Authors: Kosaka Toshio , Kosaka Katsuko , Tateishi Kayoko , Hamaoka Yoshiyuki , Yanaihara Noboru , Wu Jan‐Yen , Hama Kiyoshi
Published: May 2005

The coexistence of cholecystokinin‐octapeptide‐like (CCK‐L) and/or vasoactive‐intestinal‐polypeptide‐like immunoreactive (VIP‐LI) materials and glutamate decarboxylase (GAD) was studied in the rat hippocampus and dentate gyrus by means of immunohistochemistry. Consecutive 40‐μm‐thick sections were incubated in different antisera and those cells which were bisected by the plane of sectioning so as to be included at the paired surfaces of two adjacent sections were identified. The coexistence of the immunoreactivities for these peptides and GAD in the same cell could thus be determined by observing the immunoreactivity of the two halves of the cell, incubated in two different antisera.

Almost all of the CCK‐LI neurons were also GAD immunoreactive, whereas only about 10% of the GAD‐immunoreactive neurons were CCK‐LI. The percentages of GAD‐immunoreactive neurons which were also immunoreactive for CCK were dependent on the laminar area in which they were found: i.e., 15–20% in the stratum radiatum of the hippocampus, about 10% in the stratum pyramidale, and about 6% in the stratum oriens.

In contrast to the CCK‐LI neurons, only about 40% of the VIP‐LI neurons were identified to be also GAD immunoreactive, which might correspond to only part of the GAD‐immunoreactive neurons. Furthermore the coexistence of VIP‐LI and CCK‐LI materials was recognized in about 10% of the CCK‐LI neurons or about 35% of the VIP‐LI neurons, indicating that some GABAergic neurons (presumably about 1%) in the rat hippocampus and dentate gyrus may contain both CCK‐LI and VIP‐LI materials.
Morphology of terminations of small and large myelinated trigeminal primary afferent fibers in the cat
Authors: Hayashi Haruhide
Published: May 2005

Horseradish peroxidase was injected intra‐axonally into functionally identified cutaneous primary afferent fibers in the cat's spinal trigeminal nucleus in order to study the morphology of their central terminations. They were determined physiologically to be large, myelinated primary afferents including vibrissa, G1‐hair, and slowly adapting type I afferents, as well as small, myelinated primary afferents including D‐hair and A‐delta high‐threshold mechanoreceptive (HTM) afferents. The axons were stained for distances of 4–12 mm at the levels of the subnuclei interpolaris (Vi) and caudalis (Vc) of the spinal trigeminal nucleus. The collaterals of large, myelinated primary afferents formed terminal arbors in the outer part of the spinal trigeminal nucleus when they were rostral to or near the obex (rostral‐type collaterals), in lamina V when in the rostral part of Vc (caudalis‐type collaterals), and in lamina III/IV when in the caudal part of Vc (spinal dorsal horn‐type collaterals). There were no transitional forms between the rostral and caudalis types, but there was a transitional type which terminated in laminae III/IV and V between the caudalis and spinal dorsal horn types. Major morphological differences were not observed among the three functional types of large, myelinated primary afferents. The collaterals of D‐hair afferents showed the same types of collaterals as were seen in the large, myelinated primary afferents, except that terminal arbors of the spinal dorsal horn‐type collaterals were distributed in lamina IIb in addition to lamina III/IV. Collaterals of A‐delta HTM afferents formed extensive terminal arbors in the superficial part of Vi. In Vc they were distributed mainly in lamina I and few terminals existed in lamina IIa. The frequency of collaterals of A‐delta HTM afferents was less than that of the other types of afferents. The collaterals of A‐delta HTM afferents in Vi were distributed less frequently than those in Vc. The terminal arbors of A‐delta HTM afferents were less extensive than those of the other types of afferents. The average size of varicosities of A‐delta HTM afferents was smaller and that of vibrissa afferents was larger than that of the other types of afferents. This study demonstrated that there are large differences in the terminations of nociceptive and non‐nociceptive primary afferents and that Vi receives direct nociceptive input from facial skin. However, the sparse distribution of collaterals of HTM afferents in Vi suggests that the rostral trigeminal nucleus contributes partially to sensory processing of facial pain.
Segmental distribution of peptide‐like immunoreactivity in cell bodies of the thoracolumbar sympathetic nuclei of the cat
Authors: Krukoff Teresa L. , Ciriello John , Calaresu Franco R.
Published: May 2005

The distribution of leucine‐enkephalin, methionine‐enkephalin, neurotensin, somatostatin, substance P. oxytocin, vasopressin, and neurophysin II in cell bodies of sympathetic autonomic nuclei of the thoracolumbar (T‐L) spinal cord was studied immunohistochemically in cats after intrathecal administration of colchicine. Neurons containing only enkephalin‐, neurotensin‐, somatostatin‐, and substance P‐like immunoreactivity (ENK, NT, SS, SP, respectively) were found in the intermediolateral nucleus pars principalis (IMLp) and pars funicularis (IMLf), the nucleus intercalatus (IC), and the central autonomic area (CA). The size, shape, location, and numbers of the peptide‐positive neurons in the IMLp, IMLf, and IC suggested that they were sympathetic preganglionic neurons (SPN). This was confirmed by a combined retrograde tracing/immunohistochemical study showing that most of these neurons at the levels of the T‐L cord known to provide preganglionic fibers to the stellate ganglion were SPN. On the other hand, the functional identification of the neurons in the CA is uncertain as neurons were not observed which were both retrogradely labelled and contained ENK, NT, SS, or SP. Immunoreactive neurons in each area were counted in ten sections from each segment from C8 to L4. In the IMLp, the SPN with ENK were greatest in number (up to 25) in segments T4–T7 and L2–L3. The maximum number of SPN containing NT was found in segments T4–T7 (45 neurons). Of the four peptides, neurons containing SS were found in the greatest number (up to 48 in segments T2–T6); neurons containing SP were found in the smallest number (15 or fewer per segment). Few SPN containing each of the four peptides were found in the IC; CA neurons with ENK and NT were also few in number. A comparison of the numbers of immunoreactive neurons in the IML with earlier estimates for the total numbers of SPN in the IML at each level showed that the proportions of IML neurons containing each of the four peptides were fairly consistent throughout the T‐L cord, with some exceptions. These results suggest that the innervation of visceral organs is not obviously peptide‐specific, although some organs may be innervated by a greater proportion of SPN containing one of these peptides. Finally, the presence of ENK, NT, SS, and SP in SPN suggests that these four peptides act as neurotransmitters in preganglionic pathways to sympathetic ganglia.
Projections from the cochlear nucleus to the inferior colliculus in normal and neonatally cochlea‐ablated gerbils
Authors: Moore David R. , Kitzes Leonard M.
Published: May 2005

The distribution of the projection from one cochlear nucleus (CN) within each inferior colliculus (IC) was studied in adult, normal gerbils and adult gerbils subjected to unilateral ablation of the contralateral cochlea at 2 days of age. The projection was studied by using the Fink‐Heimer technique for impregnating degenerating axons and their terminal processes with silver. Following an extensive, unilateral lesion of the CN, degeneration was seen in both ICs of all animals. In normal animals, degeneration was both more widespread and heavier in the contralateral than in the ipsilateral central nucleus of IC (ICC). Degeneration was most widespread in the rostral and lateral parts of both ICCs and in the ventral part of the contralateral ICC. Degeneration was observed in 26% of the area examined in ipsilateral ICC and in 73% of the area examined in contralateral ICC. In cochlea‐ablated animals there was a much greater similarity in the area of degeneration in the ICC ipsilateral (57%) and contralateral (67%) to the CN lesion. The same regional distributions of degeneration were observed as in the normal animals except that the distribution of degeneration in the ipsilateral ICC more closely resembled the normal contralateral than the normal ipsilateral profile. We conclude that the normal distribution of projections from the CN within the ipsilateral ICC is substantially modified by neonatal ablation of the contralateral chochlea.
A quantitative electron microscope study of the perikaryal projections of sensory ganglion neurons. II. Gecko and lizard
Authors: Pannese Ennio , Bianchi Rossella , Gioia Magda , Ventura Raoul
Published: May 2005

The perikaryal projections of the neurons in the thoracic spinal ganglia of gecko and lizard usually appear as finger‐shaped evaginations running roughly parallel to the surface of the nerve cell body; they show a nearly circular cross section with a rather uniform transverse diameter having an average value of about 0.2 μm. In both gecko and lizard a very high correlation was found between the surface area of perikaryal projections and both the volume and smoothed surface area of the corresponding nerve cell body.

The results of the present research agree with those obtained in a previous study on two mammal species (cat and rabbit) and lend further support to the hypothesis advanced in that study; i.e., that perikaryal projections in sensory ganglion neurons are normal formations which maintain the surface‐to‐volume ratio above the critical level for metabolic exchanges.

Perikaryal projections increase the surface area of the nerve cell body by 32.5% in gecko and 30% in lizard, while they increase it by 43% in cat and 39.5% in rabbit. This difference may be related to the lower metabolic rate of the neurons in poikilotherms than in mammals.
Somatostatin receptors: Distribution in rat central nervous system and human frontal cortex
Authors: Uhl George R. , Tran Vinh , Snyder Solomon H. , Martin Joseph B.
Published: May 2005

Somatostatins are a brain peptide family centered on a 14‐amino acid cyclic peptide (SS‐14) and a 28‐amino acid N‐terminally extended form (SS‐28). Using radioiodinated analogs of SS‐14 and SS‐28, we have identified specific binding sites in rat and human brain sections that display pharmacological properties anticipated for somatostatin receptors and discrete patterns of anatomical localization. High binding densities are found in many forebrain regions, with special densities in infragranular cerebral cortical laminae in rat and human brain. In the rat, other densities lie in olfactory zones, lateral and triangular septal nuclei, the CA‐1 hippocampal region, and claustrum with moderate densities in the striatum. Discrete hypothalamic areas, especially the median preoptic, paraventricular, and periventricular nuclei, display elevated binding levels, while the thalamus shows only scattered areas of modest binding. Midbrain receptor concentrations are found in portions of the periaqueductal gray, interpeduncular nucleus, and the substantia nigra. Notable pontine and medullary densities lie in the locus coeruleus, fourth ventricular floor, parabrachial, solitary, prepositus hypoglossal, dorsal column, and caudal trigeminal zones. Although the cerebellar cortex shows unimpressive densities, each of the deep cerebellar nuclei is heavily labeled. Modest spinal cord receptor densities are concentrated in the substantia gelatinosa and central cord regions.

These localizations show many parallels with the distributions of SS‐immunoreactive neurons, fibers, and terminals determined previously by immunohistochemistry. They provide plausible loci for several reported physiological or pharmacological activities of the SS‐peptides, and may improve understanding of the role of the SS alterations described in several human neurodegenerative disorders.
Topographic organization of the optic radiation of the cat
Authors: Nelson Sacha B. , Le Vay Simon
Published: May 2005

Pairs of injections of different neuroanatomical tracers–peroxidase‐conjugated wheat‐germ agglutinin (WGA) and [3H]proline–were made into the lateral geniculate nucleus (LGN) of the cat, and the course of the labeled fibers in the optic radiation was reconstructed. When the two injections were widely separated in the rostrocaudal dimension of the LGN (i.e., one in the representation of the lower quadrant of the visual field and one in the upper quadrant), the two sets of labeled fibers also remained separated in the long (roughly rostrocaudal) axis of the optic radiation. When the injections were widely separated in the mediolateral dimension of the LGN (i.e., one at the representation of the area centralis and one on the horizontal meridian in the far periphery of the field), the two sets of labeled fibers were separated in the short (mediolateral) dimension of the radiation. Shortly before reaching area 17, however, the medially and laterally placed fibers exchanged positions. This crossing is the basis of the topological inversion in the optic radiation deduced previously by Connolly and Van Essen (J. Comp. Neurol. 226:544–564, '84). The retinotopic organization of fibers in the radiation is less precise (in either dimension) than that of their terminal arborizations in visual cortex, but even injections as close as 1 mm to each other gave rise to spatially distinct fiber distributions. The WGA injections also labeled the corticogeniculate fibers by retrograde transport; these fibers traveled in a separate pathway medial to the optic radiation.