The cytoarchitecture of the torus semicircularis in the golden skink Mabuya multifasciata

The skink, Mabuya multifasciata, torus semicircularis was subdivided into the central (CN), the laminar (LN), and the superficial (SN) nuclei using Golgi and Nissl methods. The central nucleus consisted of small ovoid neurons surrounding a core of fewer large ovoid-triangular and fusiform neurons. The ovoid cells had scant cytoplasm and two to five dendritic trunks. Most of these processes were directed around the periphery of the central nucleus. The large neurons had clumped, darkly staining Nissl substance and a central nucleus. The sparse dendritic spine population on these cells increased distally on the three to five radiate dendrites. The laminar nucleus was present caudal and ventral to the central nucleus. At more rostral levels it was medial and dorsomedial to the central nucleus. The NL had three to five layers of ovoid and fusiform neurons. Scattered within these layers were a few ovoid-triangular neurons. Ovoid neurons had eccentric or central nuclei. The arborization of their dendrites was generally medial and lateral but was frequently oriented caudomedial and rostrolateral. Fusiform neurons had pale Nissl substance, central nuclei, and one to two dendritic processes. The ovoid-triangular neurons had dense, clumped Nissl substance and at least two dendritic trunks with few spines. The superficial nucleus was dorsal, lateral, and caudal to the central nucleus. Extending ventrolaterally around the central nucleus, the superficial nucleus became confluent with the laminar nucleus, ensheathing the central nucleus ventrally, laterally, and dorsally. Rostrally the central nucleus was covered by the layers of the laminar nucleus. Within the superficial nucleus were ovoid, fusiform and sparse ovoid-triangular neurons. The study indicated that the morphology of the torus semicircularis in the golden skink was similar to that in other lizards. This similarity correlates with the degree of development as it relates to the auditory function, but was independent of the type of inner ear restraint mechanism.     

The torus semicircularis in a gekkonid lizard

The cytoarchitecture and neuromorphology of the torus semicircularis in the tokay gecko, Gekko gecko, were examined in Nissl-stained, fiber-stained, and Golgi-impregnated tissues. From a superficial position, the torus semicircularis extends rostrally under the caudal half of the optic tectum. Caudally, the two tori abut upon one another; rostrally, they diverge. The torus semicircularis consists of central, laminar, and superficial nuclei. The central nucleus consists of fusiform, spherical and triangular neurons. Their dendrites are highly branched, with numerous dendritic spines, and are oriented mediolaterally, dorsoventrally, and rostrocaudally. Fusiform and spherical neurons display two dendritic patterns: “single axis,” ramifying in one axis, and “dual axis,” exhibiting higher-order branches perpendicular to the primary dendrites. Triangular neurons exhibit a “radiate” dendritic pattern. In the rostral half of the torus semicircularis, the laminar nucleus caps the central nucleus. The laminar nucleus encircles the central nucleus in the caudal torus semicircularis. The neurons of the laminar nucleus have dendritic arrays oriented parallel to the border of the central nucleus. These dendrites exhibit a paucity of dendritic spines and higher-order branches. Fusiform and spherical neurons exhibit “single axis” and “dual axis” dendritic patterns. Triangular neurons display “radiate” patterns. The caudal superficial nucleus lies dorsal and dorsolateral to the central nucleus. The superficial nucleus is sparsely populated by small fusiform and spherical neurons with moderately branched dendrites and moderate numbers of dendritic spines. These neurons display “single axis” (fusiform neurons) as well as “dual axis” and “radiate” (spherical neurons) dendritic patterns. They are oriented either parallel to or perpendicular to the boundary of the laminar nucleus.     

Morphology of neurons in the torus semicircularis of the northern leopard frog,Rana pipiens pipiens

The neuronal morphology of the torus semicircularis of the northern leopard frog, Rana pipiens pipiens, was examined in Golgi-impregnated material. Neurons in each of the five subdivisions of the torus semicircularis (Potter, '65a) have distinct morphologies which are characteristic of the subdivision. Laminar nucleus neurons are mostly multipolar with spherical or ovoidal somata and smooth dendrites oriented primarily parallel and perpendicular to the cell laminae. Principal nucleus neurons have variable soma shapes with short dendrites ( < 100 μm) radiating in all directions. In the magnocellular nucleus, there are three major cell types: neurons characterized by small, spherical-shaped somata, with short, thin, radiating dendrites and many varicosities; bi- or tripolar neurons with ovoidal somata, and long (100–200 μm) and smooth dendrites orienting primarily dorsoventrally and mediolaterally; and multipolar neurons with triangular-shaped somata and very long (200–350 μm) dendrites, which are either smooth or highly spiny. Neurons in the commissural nucleus are mostly multipolar cells with ovoidal somata and beaded dendrites projecting mostly dorsally and ventrally. The subependymal midline nucleus contains mostly uni- or bipolar neurons with small ovoidal somata and straight, spiny dendrites. In addition to revealing the morphological features of neurons in the torus, the counterstained material shows further cytoarchitectural organization of the principal nucleus, i.e., the presence of a circular lamellar organization. The functional significance of these anatomical features is discussed.     

FMRFamide-like immunoreactivity in the brain and pituitary of the teleost. Eigenmannia lineata (Gymnotiformes)

The distribution of cells immunoreactive for the molluscan tetrapeptide FMRFamide in the brain and the pituitary of Eigenmannia was investigated immunohistochemically by the use of the peroxidase-antiperoxidase (PAP) technique and unlabelled antibodies. FMRFi neurons were located in the ganglion of the nervus terminalis at the rostroventral side of the bulbus olfactorius. FMRFi perikarya were also found in a dorsomedial diencephalic nucleus, in the nucleus ventromedialis, in some liquor-contacting neurons of the nucleus lateralis tuberis and of the nucleus recessus lateralis and posterior. The perikarya of the midbrain pre-pacemaker nucleus were only weakly immunoreactive for FMRFamide while large FMRFi neurons (T-cells) occurred in lamina VI of the torus semicircularis, in the brain stem, in dorsal and medial layers of the lobus lineae lateralis posterior (LLLp) and in the medullary electric organ pacemaker nucleus (pm). FMRFi fibers and nerve endings were found in the bulbus olfactorius, in medial areas of the telencephalon, and rather densely in the rostral diencephalon. Ventrocaudally to most of the hypothalamic nuclei the occurrence of immunoreactive fibres increased; many coursed to the pituitary through the pituitary stalk. FMRFi fibres also appeared in the deep layers of the tectum opticum, in the torus semicircularis, in the medial and lateral medulla and below the pacemaker nucleus. Wherever FMRFamide-immunoreactivity occurred fibres and nerve endings could be found in close contact with blood vessels.     

Directional selectivity and frequency tuning of midbrain cells in the oyster toadfish, Opsanus tau

Single-unit recordings were made from areas in the midbrain (torus semicircularis) of the oyster toadfish. We evaluated frequency tuning and directional responses using whole-body oscillation to simulate auditory stimulation by particle motion along axes in the horizontal and mid-sagittal planes. We also tested for bimodality in responses to auditory and hydrodynamic stimuli. One recording location in each animal was marked by a neurobiotin injection to confirm the recording site. Recordings were made in nucleus centralis, nucleus ventrolateralis, and the deep cell layer. Most units were frequency-selective with best frequencies between 50 and 141 Hz. Suppression of activity was apparent in 10% of the cells. Bimodality was common, including inhibition and suppression of background activity by auditory or hydrodynamic stimulation. The majority of the cells were directionally selective with directional response patterns that were sharpened compared with those of primary saccular afferents. The best directional axes were arrayed widely in spherical space, covering most azimuths and elevations. This representation is adequate for the computation of the motional axis of an auditory stimulus for sound source localization.Abbreviations BF best frequency - DCL deep cell layer - DON descending octaval nucleus - DRP directional response pattern - FFT fast Fourier transform - LL lateral lemniscus - NC nucleus centralis - NVL nucleus ventrolateralis - PVC periventricular cells - R coefficient of synchronization - TS torus semicircularis - Z Rayleigh statistic     

Fine structure of the torus semicircularis of some teleosts

Fine structure of the torus semicircularis of the loach, carp, common eel and rainbow trout was studied by light and elecron microscopy. The torus semicircularis of each species is divided into four layers. The subependymal first layer comprises numerous unmyelinated fibers and their terminals which contain cored vesicles. The second and the third layers are composed of small cell bodies and their dendrites respectively. These layers develop equally in the four species and contain the usual axodendritic synapses. On the other hand, the fourth layer varies in different species. The mediumsized cells in this layer, which are inferred to be of the same origin as the small cells from their configuration and size, show differences in lamination in each species. Compared with the usual axodendritic synapse of the small cells, the medium-sized cells have quite different synaptic patterns, which include inhibitory and electrical as well as the usual excitatory chemical synapses. From these findings, the medium-sized cells are surmized to receive sound of different degrees of intensity from that received by the small cells, which may have an effect on feeding behaviors of the species. In the deepest portion of the torus semicircularis of all species, there are large multipolar cells on which numerous axon terminals synapse in much the same way as they do on the medium-sized cells. These findings suggest that the synaptic patterns in the torus semicircularis may depend not on the receptive cells in each layer but on the various characteristics of the afferent fibers.     

Efferent vestibular neurons in the guinea pig by horseradish peroxidase and fluorochrome labeling techniques

Neurons with projections into the vestibular receptor apparatus (efferent vestibular neurons) were identified in different medullary regions by retrograde labeling with horseradish peroxidase and transport-specific fluorochromes in the guinea pig. Two groups of efferent vestibular neurons could be distinguished, located dorsally and ventrally to the facial nerve fiber pathway. The dorsal group of efferent vestbular neurons consisted of small cells located close to the genu and the root of the facial nerve and the subependymal granular layer of the 4th ventricle floor. The ventral group was primarily composed of medium-sized cells, usually with only slight tracer accumulation; these were scattered over an extensive area of the lateral tegmental field within nucleus reticularis lateralis parvocellularis. The question of whether the test cells belong to the system of true vestibular efferents and satellite cells is discussed in the light of findings on cell location, morphology, and pattern of tracer accumulation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 738–747, November–December, 1986.     

Distribution of parvalbumin-immunoreactivity in the rat thalamus using a monoclonal antibody

1. The distribution of parvalbumin cell bodies and fibers in the thalamus of the rat was studied using a monoclonal antibody and the avidin-biotin-peroxidase method. The densest clusters of immunoreactive perikarya were observed in the nuclei ventralis posterior, reticularis, ventralis anterior and zona incerta, whereas the nuclei habenularis lateralis, lateralis posterior, lateralis, centralis lateralis and ventralis lateralis had the lowest density. In the nucleus geniculatum laterale ventralis, the density of parvalbumin cell bodies was intermediate. In all these thalamic nuclei, small, round or fusiform immunoreactive cells with short immunolabeled dendritic processes were observed. 2. The densest network of immunoreactive fibers was observed in the nuclei geniculatum laterale ventralis, reticularis and zona incerta. The nuclei geniculatum laterale dorsalis, ventralis posterior, medialis ventralis, ventralis anterior, anterior ventralis, anterior dorsalis and rhomboidens contained a moderate number of parvalbumin fibers, whereas the nuclei lateralis posterior, habenularis lateralis, parataenialis, centrum medianum, lateralis, centralis lateralis, ventralis lateralis, medialis dorsalis, anterior medialis, ventralis medialis and lateralis anterior had the lowest density of immunoreactive fibers. In addition, a large number of immunoreactive fibers was found in the lemniscus medialis and a scarce number in the stria medullaris. 3. No immunoreactive structure was observed in the nuclei habenularis medialis, paraventricularis, reuniens and geniculatum mediale. 4. Thus, perikarya and fibers containing parvalbumin are widely distributed throughout the thalamus of the rat, suggesting that parvalbumin might play a role, directly or indirectly, in limbic, visual and somatosensory mechanisms.     

Horseradish peroxidase-positive neurons of nonspecific thalamic nuclei projecting to the primary somatosensory cortex in cats

The morphology and topography of neurons whose axons form the nonspecific thalamic input in the primary somatosensory area were studied in the cat forebrain by the retrograde axonal horseradish peroxidase transport method. Stained cells were found in the dorsolateral part of the nucleus ventralis anterior, and were diffusely distributed in the nucleus centralis, lateralis, the lateral part of the nucleus dorsalis medialis, and the dorsal part of the centrum medianum. In the nucleus paracentralis only solitary, palely stained neurons were detected. Cells stained with horse-radish peroxidase were multipolar, triangular, or fusiform. The results are evidence that besides the ventrobasal complex, the nonspecific nuclei of the diencephalon also project into the somatosensory cortex. This indicates the existence of multiple afferent thalamic inputs into the somatic cortex.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 435–440, September–October, 1979.     

A Golgi study of the isthmic nuclei in the pigeon (Columba Iivia)

Summary The isthmic nuclei of the pigeon were studied with the use of three different Golgi techniques. The nucleus isthmo-opticus (IO) consists of a single cell type in which all dendrites of one neuron take the same direction and ramify at identical distances from the perikaryon to form dense dendritic arborizations. The cell bodies of the IO neurons form two parallel layers. The dendrites of these neurons always extend to the area between the two layers so that the dendritic arborizations of opposite neurons overlap. A model of the cellular organization of the IO was constructed based upon these morphological characteristics. The neurons of the n. isthmi/pars parvocellularis (Ipc) have oval perikarya and long, smooth, infrequently branching dendrites. All neurons except those at the borders of the nucleus show the same dorsoventral orientation in their dendritic arborizations and together with their afferents seem to have a columnar organization. The dendrites of the neurons located at the margin of the nucleus ramify within the Ipc along its border. The n. semilunaris (Slu) consists of neurons with round somata that have on an average three dendrites with small spines. The axons leave the nucleus from the medial side and join the lemniscus lateralis. The neurons of the n. isthmi/pars magnocellularis (Imc) comprise a generalized isodendritic type resembling the cells of the reticular formation. Axons from the tectum penetrate the nucleus, making numerous en-passant contacts with several neurons.     

Distribution of neuropeptide Y-like immunoreactivity in the brain and hypophysis of the cloudy dogfish,Scyliorhinus torazame

Summary Using a specific antiserum raised against synthetic neuropeptide Y, we examined the localization of immunoreactivity in the brain and hypophysis of the cloudy dogfish, Scyliorhinus torazame, by the peroxidase-antiperoxidase method. Immunoreactive perikarya were demonstrated in the ganglion of the nervus terminalis, the dorsocaudal portions of the pallium dorsale, the basal telencephalon, and the nucleus lateralis tuberis and the nucleus lobi lateralis in the hypothalamus. Labeled perikarya were also found in the tegmentum mesencephali, the corpus cerebelli, and the medulla oblongata. Some of the immunoreactive neurons in the hypothalamus were of the CSF-contacting type. The bulk of the labeled fibers in the nervus terminalis ran toward the basal telencephalon, showing radial projections and ramifications. Large numbers of these fibers coursed into the nucleus septi caudoventralis and the nucleus interstitialis commissurae anterioris, where they became varicose and occasionally formed fine networks or invested immunonegative perikarya. In the diencephalon, immunoreactive fibers were observed throughout the hypothalamus, e.g., in the pars neurointermedia of the hypophysis, the subependymal layer of the lobus inferior hypothalami, and in the neuropil of the posterior (mammillary) recess organ. Labeled fibers were scattered throughout the rest of the brain stem and were also seen in the granular layer of the cerebellum. These results suggest that, in the dogfish brain, neuropeptide Y or a related substance is involved in a variety of physiological processes in the brain, including the neuroendocrine control of the hypophysis.     

A horseradish peroxidase study on the mammillothalamic tract in the rat

The mammillary projections to the anterior thalamic nuclei were investigated in the rat, using the horseradish peroxidase (HRP) method. Pars centralis of the medial mammillary nucleus projects to the medial portion of the ateromedial nucleus (AM). Pars medialis (Mm) of the medial mammillary nucleus sends fibers to the ipsilateral AM and sparsely to the medial portion of the contralateral side. The ventral and dorsal portions of Mm project to the anterior and posterior portions of AM, respectively. The pars latralis (Ml) and pars posterior (Mp) of the medial mammillary nucleus send fibers predominantly to the ipsilateral anteroventral nucleus and sparsely to the contralateral side. A slight difference between Ml and Mp projections was observed. The lateral mammillary nucleus projects bilaterally to the anterodorsal nucleus.     

Branching-pattern analysis of the dendritic arborization in the thalamic nuclei of the rat brain

We investigated the dendritic patterns of rapid Golgi-impregnated, highly similar multipolar neurons from two functionally different thalamic regions of the rat brain: two dorsal nuclei (the nucleus laterodorsalis thalami, pars dorsomedialis and the nucleus laterodorsalis thalami, pars ventrolateralis), and two ventral nuclei (the nucleus ventrolateralis thalami and the nucleus ventromedialis thalami). The analysis involved conventional morphometric parameters (height and size) and a new parameter derived from graph theory, the relative imbalance (RI), derived from the branching patterns of the dendrites, which permits quantitative characterization of the dendritic arborization of a neuron. On this basis, neurons can be grouped into three fundamentally different types: type A, or highly-polarized (imbalanced) neurons (RI values close to 1); type B, or medium-polarized neurons (RI values around 0.5); and type C, or balanced neurons with low polarization (RI values close to 0). The orientations of the dendritic arbor, and thus the receptive fields, of the dorsal and ventral thalamic neurons, were mutually perpendicular. The H and S values indicated that the neurons in the dorsal and ventral thalamic nuclei differed significantly. However, their RI values demonstrated that they were similar neurons of type B. Our data reveal that 1 ) the dendritic arbor cannot be reliably characterized purely on the basis of height and size, and 2) RI is a valuable morphometric parameter that identifies the true nature of the dendritic arborization.     

Structure and function of neurons in the complex of the nucleus electrosensorius of the gymnotiform fish Eigenmannia: Detection and processing of electric signals in social communication

Summary The complex of the diencephalic nucleus electrosensorius (nE) provides an interface between the electrosensory processing performed by the torus semicircularis and the control of specific behavioral responses. The rostral portion of the nE comprises two subdivisions that differ in the response properties and projection patterns of their neurons. First, the nEb (Fig. 1 B), which contains neurons that are driven almost exclusively by beat patterns generated by the interference of electric organ discharges (EODs) of similar frequencies. Second, the area medial to the nEb, comprising the lateral pretectum (PT) and the nE-acusticolateralis region (nEar, Fig. 1 B-D), which contains neurons excited predominantly by EOD interruptions, signals associated with aggression and courtship. Neurons in the second area commonly receive convergent inputs originating from ampullary and tuberous electroreceptors, which respond to the low-frequency and high-frequency components of EOD interruptions, respectively. Projections of these neurons to hypothalamic areas linked to the pituitary may mediate modulations of a fish's endocrine state that are caused by exposure to EOD interruptions of its mate.Abbreviations a axon - ATh anterior thalamic nucleus - CCb corpus cerebelli - CE central nucleus of the inferior lobe - CP central posterior thalamic nucleus - Df frequency difference between neighbor's EOD and fish's own - DFl nucleus diffusus lateralis of the inferior lobe - DFm nucleus diffusus medialis of the inferior lobe - DTn dorsal tegmental nucleus - EOD electric organ discharge - G glomerular nucleus - Hc caudal hypothalamus - Hd dorsal hypothalamus - Hl lateral hypothalamus - Hv ventral hypothalamus - JAR jamming avoidance response - LL lateral lemniscus - MGT magnocellular tegmental nucleus - MLF medial longitudinal fasciculus - nB nucleus at the base of the optic tract - nE nucleus electrosensorius - nEar nucleus electrosensorius-acusticolateral region - nEb nucleus electrosensorius-beat related area - nE nucleus electrosensorius, area causing rise of EOD frequency - nE nucleus electrosensorius, area causing fall of EOD frequency - nLT nucleus tuberis lateralis - nLV nucleus lateralis valvulae - PC posterior commissure - Pd nucleus praeeminentialis, pars dorsalis - PeG periglomerular complex - PG preglomerular nucleus - PLm medial division of the perilemniscal nucleus - Pn pacemaker nucleus - PPn prepacemaker nucleus - PT pretectal nucleus - PTh prethalamic nucleus - R red nucleus - Sc suprachiasmatic nucleus - SE nucleus subelectrosensorius - TAd nucleus tuberis anterior-dorsal subdivision - TAv nucleus tuberis anterior-ventral subdivision - TeO optic tectum - TL torus longitudinalis - TSd dorsal (electrosensory) torus semicircularis - TSv ventral (mechanosensory and auditory) torus semicircularis - tTB tecto-bulbar tract - VCb cerebellar valvula - VP valvular peduncle - VPn nucleus of the valvular peduncle     

Distribution of NT-IR perikarya in the brain of the guinea pig with special reference to cardiovascular centers in the medulla oblongata

Summary The occurrence and distribution of neurotensin-immunoreactive (NT-IR) perikarya was studied in the central nervous system of the guinea pig using a newly raised antibody (KN 1). Numerous NT-IR perikarya were found in the nuclei amygdaloidei, nuclei septi interventriculare, hypothalamus, nucleus parafascicularis thalami, substantia grisea centralis mesencephali, ventral medulla oblongata, nucleus solitarius and spinal cord. The distribution of NT-IR perikarya was similar to that previously described in the rat and monkey. In the gyrus cinguli, hippocampus and nucleus olfactorius, though, no NT-IR neurons were detected in this investigation. Additional immunoreactive perikarya, however, were observed in areas of the ventral medulla oblongata, namely in the nucleus paragigantocellularis, nucleus retrofacialis and nucleus raphe obscurus.The relevance of the NT-IR perikarya within the ventral medulla oblongata is discussed with respect to other neuropeptides, which are found in this area, and to cardiovascular regulation.Abbreviations abl nucleus amygdaloideus basalis lateralis - abm nucleus amygdaloideus basalis medialis - acc nucleus amygdaloideus centralis - aco nucleus amygdaloideus corticalis - ahp area posterior hypothalami - ala nucleus amygdaloideus lateralis anterior - alp nucleus amygdaloideus lateralis posterior - ame nucleus amygdaloideus medialis - atv area tegmentalis ventralis - bst nucleus proprius striae terminalis - CA commissura anterior - CC corpus callosum - cgld corpus geniculatum laterale dorsale - cglv corpus geniculatum laterale ventrale - cgm corpus geniculatum mediale - CHO chiasma opticum - CI capsula interna - co nucleus commissuralis - cod nucleus cochlearis dorsalis - cp nucleus caudatus/Putamen - cs colliculus superior - cu nucleus cuneatus - dmh nucleus dorsomedialis hypothalami - DP decussatio pyramidum - em eminentia mediana - ent cortex entorhinalis - epi epiphysis - FLM fasciculus longitudinalis medialis - fm nucleus paraventricularis hypothalami pars filiformis - FX fornix - gd gyrus dentatus - gp globus pallidus - gr nucleus gracilis - hl nucleus habenulae lateralis - hm nucleus habenulae medialis - hpe hippocampus - ift nucleus infratrigeminalis - io oliva inferior - ip nucleus interpeduncularis - LM lemniscus medialis - MT tractus mamillo-thalamicus - na nucleus arcuatus - nls nucleus lateralis septi - nms nucleus medialis septi - npca nucleus proprius commissurae anterioris - ns nucleus solitarius - n III nucleus nervi oculomotorii - nt V nucleus tractus spinalis nervi trigemini - ntm nucleus mesencephalicus nervi trigemini - osc organum subcommissurale - P tractus cortico-spinalis - PC pedunculus cerebri - PCI pedunculus cerebellaris inferior - pir cortex piriformis - pol area praeoptica lateralis - pom area praeoptica medialis - prt area praetectalis - pt nucleus parataenialis - pvh nucleus paraventricularis hypothalami - pvt nucleus paraventricularis thalami - r nucleus ruber - re nucleus reuniens - rgi nucleus reticularis gigantocellularis - rl nucleus reticularis lateralis - rm nucleus raphe magnus - ro nucleus raphe obscurus - rp nucleus raphe pallidus - rpc nucleus reticularis parvocellularis - rpgc nucleus reticularis paragigantocellularis - sch nucleus suprachiasmaticus - SM stria medullaris thalami - snc substantia nigra compacta - snl substantia nigra lateralis - snr substantia nigra reticularis - ST stria terminalis - tad nucleus anterior dorsalis thalami - tam nucleus anterior medialis thalami - tav nucleus anterior ventralis thalami - tbl nucleus tuberolateralis - tc nucleus centralis thalami - tl nucleus lateralis thalami - tmd nucleus medialis dorsalis thalami - TO tractus opticus - TOL tractus olfactorium lateralis - tpo nucleus posterior thalami - tr nucleus reticularis thalami - trs nucleus triangularis septi - TS tractus solitarius - TS V tractus spinalis nervi trigemini - tvl nucleus ventrolateralis thalami - vmh nucleus ventromedialis hypothalami - vh ventral horn, Columna anterior - zi zona incerta Supported by the Deutsche Forschungsgesellschaft (DFG) SFB 90, Carvas     

The Monoaminergic Paraventricular Organ in the Teleost Ictalurus nebulosus LeSueur,with Special Reference to Its Vascularization

Specific, fluorescent, subependymal perikarya were found in the pars anterior of the paraventricular organ (PVOpa), in the nucleus recessus lateralis (NRL) and in the nucleus recessus posterioris (NRP). No fluorescent perikarya were present in the nucleus lateralis tuberis (NLT). Fluorescent nerve tracts connect the PVOpa and the NRL with the NRP, and interconnect the paired NRP. The nucleus preopticus (NPO) and the NLT receive a large input of aminergic nerve fibers. The monoaminergic nuclei are well vascularized, and their vascular plexes seem to be connected. A capillary plexus is situated dorsal to the NRP and exhibits no contact with the pituitary. It is surrounded by the prominent fluorescent tracts connecting the aminergic nuclei.     

The coding of signals in the electric communication of the gymnotiform fish Eigenmannia: From electroreceptors to neurons in the torus semicircularis of the midbrain

Summary In the context of aggression and courtship, Eigenmannia repeatedly interrupts its electric organ discharges (EODs) These interruptions (Fig. 1) contain low-frequency components as well as high-frequency transients and, therefore, stimulate ampullary and tuberous electroreceptors, respectively (Figs. 2, 3). Information provided by these two classes of receptors is relayed along separate pathways, via the electrosensory lateral line lobe (ELL) of the hindbrain, to the dorsal torus semicircularis (TSd) of the midbrain. Some neurons of the torus receive inputs from both types of receptors (Figs. 14, 15), and some respond predominantly to EOD interruptions while being rather insensitive to other forms of signal modulations (Figs. 12, 13). This high selectivity appears to result from convergence and gating of inputs from individually less selective neurons.Abbreviations CP central posterior thalamic nucleus - Df frequency difference between neighbor's EOD and fish's own - DPn dorsal posterior nucleus (thalamus) - EOD electric organ discharge - ELL electrosensory lateral line lobe - JAR jamming avoidance response - LMR lateral mesencephalic reticular formation - nE nucleus electrosensorius - nEb nucleus electrosensorius, beat-related area - nE nucleus electrosensorius, area causing rise of EOD frequency - nE nucleus electrosensorius, area causing fall of EOD frequency - nEar nucleus electrosensorius-acusticolateralis area - NPd nucleus praeeminentialis, pars dorsalis - PPn prepacemaker nucleus - PT pretectal nucleus - SE nucleus subelectrosensorius - TeO optic tectum - TSd dorsal (electrosensory) torus semicircularis - TSv ventral (mechano-sensory and auditory) torus semicircularis     

Histochemical studies on the morphology of the golgi apparatus and on the enzymes of carbohydrate metabolism in various nuclei of the rat mesencephalon

Summary Detailed histochemical studies have been conducted on the distribution of various enzymes such as thiamine pyrophosphatase, α-glucan phosphorylase, hexokinase, glucose-6-phosphate dehydrogenase, aldolase, lactate dehydrogenase and succinate dehydrogenase in various components of the nucleusEdinger-Westphali, nucleus n. oculomotorii, nucleus ruber and nucleus niger of healthy adult male Wistar strain rats. The thiamine pyrophosphatase reaction showed the morphological patterns of the Golgi apparatus characteristic for each nucleus. The Golgi apparatus was well developed in the nucleusEdinger-Westphali, composing a network of highly fenestrated plates in the nucleus n. oculomotorii and nucleus ruber, and a simple network in the nucleus niger. These results indicate that the former three nuclei need a rich energy supply and argue against the possibility that the four nuclei have a secretory role. The neurons of the nucleusEdinger-Westphali may derive their energy mainly from glucose of the circulating blood, but glial cells may serve as energy donators to the neurons in the pars compacta of the nucleus niger, and the neurons of the other nuclei may derive energy from both sources. These conclusions are consistent with the morphological patterns of the Golgi apparatus. It is suggested that the neurons of the nucleusEdinger-Westphali, nucleus n. oculomotorii, nucleus ruber and of the pars lateralis of the nucleus niger may be equipped almost equally with the Embden-Meyerhof pathway and with the hexose monophosphate shunt. But, the hexose monophosphate shunt is dominant in the pars compacta of the nucleus niger. It is also suggested that the pattern of distribution of succinate dehydrogenase may parallel that of lactate dehydrogenase. The nucleus n. oculomotorii, and nucleus ruber have a higher level of oxidative metabolism than the nucleusEdinger-Westphali and the nucleus niger. The nucleusEdinger-Westphali may be representative of autonomic nuclei with low oxidative metabolism whereas the nucleus n. oculomotorii may represent motor nuclei with high oxidative metabolism. Predominance of hexose monophosphate shunt, intense hexokinase reaction around the neurons, and weak activity of succinate dehydrogenase indicate that the pars compacta of the nucleus niger belongs to the category of “exceptional nuclei”.