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doi: 10.1002/cne.902150102pmid: 6853762
Twenty‐seven medial lemniscal axons were traced to their terminations in the thalamic ventrobasal complex of monkeys, following injection of horseradish peroxidase into the lemniscus at midbrain levels.
Newman, Donald B.; Cruce, William L. R.; Bruce, Laura L.
doi: 10.1002/cne.902150103pmid: 6853763
Horseradish peroxidase was injected into various levels of the spinal cord of turtles (Pseudemys and Chrysemys), lizards (Tupinambis, Iquana, Gekko, Sauromelus, and Gerrhonotus), and a crocodilian (Caiman). The results suggest that brainstem reticulospinal projections in limbed reptiles rival mammalian reticulospinal systems in complexity. The reptilian mye‐lencephalic reticular formation can be divided into four distinct reticulospinal nuclei. Reticularis inferior pars dorsalis (RID) contains multipolar neurons which project bilaterally to the spinal cord. Reticularis inferior pars ventralis (RIV), which is only found in lizards and crocodilians, contains fusiform neurons with horizontally running dendrites and it projects ipsi‐laterally to the spinal cord. Reticularis ventrolateralis (RVL), which is found only in teiid lizards, contains triangular neurons whose dendrites parallel the ventrolateral edge of the brainstem and it projects ipsilaterally to the spinal cord. The myelencephalic raphe (Ral) varies considerably. Ral of turtles contains large reticulospinal neurons which form a continuous population with more laterally situated RID cells. Ral of lizards contains a few small reticulospinal neurons. Ral of the crocodilian Caiman contains giant reticulospinal neurons with laterally directed dendrites.
Robertson, R. M.; Pearson, K. G.
doi: 10.1002/cne.902150104pmid: 6853764
The organization and functional properties of interneurons in the flight system of the locust, Locusta migratoria, were investigated by using intra‐cellular recording and staining techniques. Interneurons were found to be distributed within the three thoracic and the first three abdominal ganglia, and they could be subdivided into three organizational categories: (1) members of one of two serially homologous groups controlling either the forewing or the hindwing, (2) unique individuals with no known homologues in other ganglia, and (3) members of a set of serial homologues in the metathoracic and first three abdominal ganglia. Interneurons in the last two categories influenced both forewing and hindwing motoneurons in a similar manner. Thus interneuronal organization is not characterized by two distinct homologous groups of interneurons for the separate control of forewing and hindwing motor activity.
Szamier, R. Bruce; Ripps, Harris
doi: 10.1002/cne.902150105pmid: 6853765
Earlier studies have shown that visual function in skate is subserved solely by the rod mechanism and that the retina of this elasmobranch contains only rod photoreceptors. Nevertheless, the skate retina is capable of responding to levels of illumination that extend well into the photopic range, and we have detected in histological sections (usually from younger animals) small, proximally displaced, conelike photoreceptors which possibly represent another class of visual cell. However, ultrastructural and histochem‐ical studies showed that the membranous discs of the outer segments of these cells were isolated from the plasma membrane, and that their synaptic terminals appeared immature and unlike those usually associated with cone receptors. In addition, the pattern of incorporation of 3H‐fucose, as revealed by radioautography, was similar for both the rods and the smaller visual cells; i.e., the label was concentrated along the basal discs of the outer segment. When we examined the disc‐shedding behavior of the visual cells in skates entrained for 2 weeks or longer to a 12‐hour light: 12‐hour dark cycle, enhanced phagocytic activity was seen only following light onset; there was no significant increase following light offset. On the available evidence, it seems reasonable to conclude that the small visual cells are rods that have recently differentiated, and are growing and being incorporated into the photoreceptor layer of the retina.
Price, Joseph L.; Slotnick, Burton M.
doi: 10.1002/cne.902150106pmid: 6853766
A combination of electrophysiological and anatomical techniques was used to determine the sites of termination of olfactory projections to the thalamus and the distribution of the cells of origin of these projections within the olfactory cortex. Following electrical stimulation of the olfactory bulb, short‐latency unit responses were recorded not only in the central segment of the mediodorsal thalamic nucleus but also in the ventral and anterior parts of the submedial thalamic nucleus. Responses were not obtained in the ventral or lateral parts of the mediodorsal nucleus, in the dorsal part of the submedial nucleus, or in the intralaminar nuclei between the mediodorsal and submedial nuclei.
Mitsacos, Ada; Reisine, Harvey; Highstein, Stephen M.
doi: 10.1002/cne.902150107pmid: 6853767
Superior vestibular neurons were penetrated with horseradish perox‐idase (HRP)‐loaded glass microelectrodes in anesthetized cats. Responses to electrical stimulation of the oculomotor complex and the vestibular nerves were characterized and selected neurons were injected with HRP. Neurons antidromically activated by oculomotor complex stimulation were generally monosynaptically excited by the ipsilateral vestibular nerve. Notable was the absence of strong commissural inhibition by stimulation of the contra‐lateral vestibular nerve. Light microscopy of antidromically identified injected cells demonstrated that these cells are predominantly located at the central levels of the superior vestibular nucleus along the incoming vestibular nerve fibers but a few are found at more caudal levels. Cell bodies, elongated or pyramidal, are mainly medium‐sized to large (30–50 μm). Dendritic trees extend in a plane at an acute angle to the collaterals of the vestibular nerve fibers. Dendrites remain within the nuclear territory and generally display an isodendritic branching pattern. Dendritic spines and appendages are mainly distributed on secondary and distal dendrites. A few terminal enlargements similar to growth cones are observed in these neurons.
Mitsacos, Ada; Reisine, Harvey; Highstein, Stephen M.
doi: 10.1002/cne.902150108pmid: 6304153
Superior vestibular neurons were penetrated with horseradish perox‐idase (HRP)‐loaded glass microelectrodes in anesthetized cats and identified electrophysiologically following electrical stimulation of the vestibular nerves and oculomotor complex. Neurons that were not antidromically activated from the oculomotor complex were stained by intracellular injection of horseradish peroxidase.
Lázár, Gy.; Tóth, P.; Csank, Gy.; Kicliter, E.
doi: 10.1002/cne.902150109pmid: 6602154
Tectal projection neurons were labeled by retrograde transport of horseradish peroxidase (HRP) or cobaltic‐lysine. The tracer substances were delivered iontophoretically or by pressure injection or diffusion into various regions of the brain or spinal cord. Histochemical procedures allowed identification of labeled cells projecting to the injected regions. Many neurons were filled with cobaltic‐lysine, resulting in a Golgi‐like staining.
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