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Gunther K H Zupanc - One of the best experts on this subject based on the ideXlab platform.

  • corticotropin releasing factor in the brain of the gymnotiform fish apteronotus leptorhynchus immunohistochemical studies combined with neuronal Tract Tracing
    General and Comparative Endocrinology, 1999
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke, David A Lovejoy
    Abstract:

    AbsTract The expression of corticotropin-releasing factor (CRF) has been studied by immunohistochemistry in the brain of the gymnotiform fish, Apteronotus leptorhynchus. Labeled somata were found exclusively in the posterior subdivision of the nucleus preopticus periventricularis and in the hypothalamus anterioris, where these cells form a continuous cluster of neurons. Combination of anti-peptide immunohistochemistry with an in vitro Tract-Tracing technique confirmed that at least some of these neurons project to the pituitary. Additional terminal fields were present in the following areas of the telencephalon and the diencephalon: ventral subdivision of the ventral telencephalon, supracommissural subdivision of the ventral telencephalon, anterior subdivision of the nucleus preopticus periventricularis, inferior subdivision of the nucleus recessus lateralis, central posterior/prepacemaker nucleus, hypothalamus dorsalis and lateralis, medial subdivision 2 of the nucleus recessus lateralis, and in the region between the dorsal edge of the nucleus tuberis anterior on the one side and both the glomerular nucleus and the central nucleus of the inferior lobe on the other side. It is likely that the projection of CRF-expressing neurons of the posterior subdivision of the nucleus preopticus periventricularis/hypothalamus anterioris to the pituitary provides, similarly as in other fishes, the neural substrate for the activation of the hypothalamo-pituitary adrenal axis through CRF. In addition to this function, CRF may be involved in the regulation of several other processes, including neural control of communicatory behavior exerted by neurons of the central posterior/prepacemaker nucleus.

  • Expression of somatostatin in neurons of the central posterior/prepacemaker nucleus projecting to the preglomerular nucleus: immunohistochemical evidence for a non-synaptic function
    Neuroscience Letters, 1997
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke, Thomas Stroh
    Abstract:

    In the diencephalon of the weakly electric gymnotiform fish Apteronotus leptorhynchus, part of the central posterior/prepacemaker nucleus innervates the preglomerular nucleus. A minor population of these neurons expresses immunoreactivity against somatostatin, as has been shown by combining peptide immunohistochemistry with an in vitro Tract-Tracing technique. In contrast to the expectation, however, this neuropeptide does not appear to be transported along the axons to the projection site, as somatostatin-like immunoreactivity could not be detected in the preglomerular nucleus. It is, therefore, likely that somatostatin expressed in these neurons exerts a non-synaptic function in the region of the central posterior/prepacemaker nucleus itself.

  • tectal input to the central posterior prepacemaker nucleus of weakly electric fish apteronotus leptorhynchus an in vitro Tract Tracing study
    Brain Research, 1996
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke
    Abstract:

    AbsTract The weakly electric fish Apteronotus leptorhynchus produces electric organ discharges which are highly stable in waveform and frequency. Short-term modulations of these discharges, typically displayed during social interactions, are controlled by the prepacemaker nucleus (PPn). Neurons of this thalamic cell group intermingle with cells of the central posterior nucleus (CP) to form a complex called ‘CP/PPn’. By employing in vitro Tract-Tracing techniques, we have, in the present investigation, demonstrated that this complex receives input from the tectum opticum. The tectal input is mediated by varicose fibers forming an elongated stripe at the ventral rim of the CP/PPn. As suggested by retrograde Tracing from the CP/PPn, this projection is likely to arise from ‘multipolar cells with an ascending axon’ previously characterized in a Golgi study [14] . As this tectal cell type has been shown to be predominantly driven by electrosensory stimuli [6] , information arising from these cells may be used in controlling modulations of the electric organ discharges.

  • Tectal input to the central posterior/prepacemaker nucleus of weakly electric fish, Apteronotus leptorhynchus: an in vitro Tract-Tracing study.
    Brain research, 1996
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke
    Abstract:

    The weakly electric fish Apteronotus leptorhynchus produces electric organ discharges which are highly stable in waveform and frequency. Short-term modulations of these discharges, typically displayed during social interactions, are controlled by the prepacemaker nucleus (PPn). Neurons of this thalamic cell group intermingle with cells of the central posterior nucleus (CP) to form a complex called 'CP/PPn'. By employing in vitro Tract-Tracing techniques, we have, in the present investigation, demonstrated that this complex receives input from the tectum opticum. The tectal input is mediated by varicose fibers forming an elongated stripe at the ventral rim of the CP/PPn. As suggested by retrograde Tracing from the CP/PPn, this projection is likely to arise from 'multipolar cells with an ascending axon' previously characterized in a Golgi study [14]. As this tectal cell type has been shown to be predominantly driven by electrosensory stimuli [6], information arising from these cells may be used in controlling modulations of the electric organ discharges.

Ingrid Horschke - One of the best experts on this subject based on the ideXlab platform.

  • corticotropin releasing factor in the brain of the gymnotiform fish apteronotus leptorhynchus immunohistochemical studies combined with neuronal Tract Tracing
    General and Comparative Endocrinology, 1999
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke, David A Lovejoy
    Abstract:

    AbsTract The expression of corticotropin-releasing factor (CRF) has been studied by immunohistochemistry in the brain of the gymnotiform fish, Apteronotus leptorhynchus. Labeled somata were found exclusively in the posterior subdivision of the nucleus preopticus periventricularis and in the hypothalamus anterioris, where these cells form a continuous cluster of neurons. Combination of anti-peptide immunohistochemistry with an in vitro Tract-Tracing technique confirmed that at least some of these neurons project to the pituitary. Additional terminal fields were present in the following areas of the telencephalon and the diencephalon: ventral subdivision of the ventral telencephalon, supracommissural subdivision of the ventral telencephalon, anterior subdivision of the nucleus preopticus periventricularis, inferior subdivision of the nucleus recessus lateralis, central posterior/prepacemaker nucleus, hypothalamus dorsalis and lateralis, medial subdivision 2 of the nucleus recessus lateralis, and in the region between the dorsal edge of the nucleus tuberis anterior on the one side and both the glomerular nucleus and the central nucleus of the inferior lobe on the other side. It is likely that the projection of CRF-expressing neurons of the posterior subdivision of the nucleus preopticus periventricularis/hypothalamus anterioris to the pituitary provides, similarly as in other fishes, the neural substrate for the activation of the hypothalamo-pituitary adrenal axis through CRF. In addition to this function, CRF may be involved in the regulation of several other processes, including neural control of communicatory behavior exerted by neurons of the central posterior/prepacemaker nucleus.

  • Expression of somatostatin in neurons of the central posterior/prepacemaker nucleus projecting to the preglomerular nucleus: immunohistochemical evidence for a non-synaptic function
    Neuroscience Letters, 1997
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke, Thomas Stroh
    Abstract:

    In the diencephalon of the weakly electric gymnotiform fish Apteronotus leptorhynchus, part of the central posterior/prepacemaker nucleus innervates the preglomerular nucleus. A minor population of these neurons expresses immunoreactivity against somatostatin, as has been shown by combining peptide immunohistochemistry with an in vitro Tract-Tracing technique. In contrast to the expectation, however, this neuropeptide does not appear to be transported along the axons to the projection site, as somatostatin-like immunoreactivity could not be detected in the preglomerular nucleus. It is, therefore, likely that somatostatin expressed in these neurons exerts a non-synaptic function in the region of the central posterior/prepacemaker nucleus itself.

  • tectal input to the central posterior prepacemaker nucleus of weakly electric fish apteronotus leptorhynchus an in vitro Tract Tracing study
    Brain Research, 1996
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke
    Abstract:

    AbsTract The weakly electric fish Apteronotus leptorhynchus produces electric organ discharges which are highly stable in waveform and frequency. Short-term modulations of these discharges, typically displayed during social interactions, are controlled by the prepacemaker nucleus (PPn). Neurons of this thalamic cell group intermingle with cells of the central posterior nucleus (CP) to form a complex called ‘CP/PPn’. By employing in vitro Tract-Tracing techniques, we have, in the present investigation, demonstrated that this complex receives input from the tectum opticum. The tectal input is mediated by varicose fibers forming an elongated stripe at the ventral rim of the CP/PPn. As suggested by retrograde Tracing from the CP/PPn, this projection is likely to arise from ‘multipolar cells with an ascending axon’ previously characterized in a Golgi study [14] . As this tectal cell type has been shown to be predominantly driven by electrosensory stimuli [6] , information arising from these cells may be used in controlling modulations of the electric organ discharges.

  • Tectal input to the central posterior/prepacemaker nucleus of weakly electric fish, Apteronotus leptorhynchus: an in vitro Tract-Tracing study.
    Brain research, 1996
    Co-Authors: Gunther K H Zupanc, Ingrid Horschke
    Abstract:

    The weakly electric fish Apteronotus leptorhynchus produces electric organ discharges which are highly stable in waveform and frequency. Short-term modulations of these discharges, typically displayed during social interactions, are controlled by the prepacemaker nucleus (PPn). Neurons of this thalamic cell group intermingle with cells of the central posterior nucleus (CP) to form a complex called 'CP/PPn'. By employing in vitro Tract-Tracing techniques, we have, in the present investigation, demonstrated that this complex receives input from the tectum opticum. The tectal input is mediated by varicose fibers forming an elongated stripe at the ventral rim of the CP/PPn. As suggested by retrograde Tracing from the CP/PPn, this projection is likely to arise from 'multipolar cells with an ascending axon' previously characterized in a Golgi study [14]. As this tectal cell type has been shown to be predominantly driven by electrosensory stimuli [6], information arising from these cells may be used in controlling modulations of the electric organ discharges.

R. S. G. Jones - One of the best experts on this subject based on the ideXlab platform.

  • Direct projections from the ventrolateral medulla oblongata to the limbic forebrain: Anterograde and retrograde Tract‐Tracing studies in the rat
    The Journal of Comparative Neurology, 1994
    Co-Authors: A. Zagon, S. Totterdell, R. S. G. Jones
    Abstract:

    Neurons in the ventrolateral medulla oblongata, a brain region implicated in central vasomotor regulation, have previously been reported to project to some forebrain limbic structures. The aim of the present study was (1) to describe the termination pattern of ventral medullary afferents in forebrain limbic areas using anterograde Tract Tracing, and (2) to determine the location and some morphological characteristics of the projection neurons using retrograde Tract Tracing from selected forebrain sites. Following ionophoretic microinjections of the anterograde Tract tracer Phaseolus vulgaris leucoagglutinin into the rostral ventrolateral medulla, labelled afferents were observed in the hippocampus, entorhinal and retrosplenial cortices, dorsal septum, nucleus accumbens, and the medial prefrontal cortex. Anterogradely labelled axons, ascending from the caudal ventrolateral medulla, could be traced only to the rostral aspects of the investigated forebrain limbic structures. Here, the main target of the ascending projection was in the ventral septum. However, labelled terminals were also present in the nucleus accumbens, the dorsolateral septum, and in the infralimbic cortex. The density of the ventrolateral medullary projections into all examined forebrain areas was low. The location of the cells in the ventral medulla oblongata which give rise to direct forebrain projections was examined using retrograde Tract Tracing with wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Following WGA-HRP injections into the septo-accumbens region, retrogradely labelled cells were present in both the rostral and caudal ventrolateral medulla. When the Tract tracer injection was restricted to the ventral region of the septal complex, the labelled cells were concentrated in the caudal aspects of the ventrolateral medulla (and the nucleus of the solitary Tract). Following tracer injections into the anterior cingulate cortex or the hippocampus or the entorhinal cortex, retrogradely labelled cells in the medulla oblongata were predominantly in the rostral ventrolateral medulla. As a first attempt to reveal the chemical nature of the projection cells, the contribution of tyrosine hydroxylase-immunoreactive cells to the innervation of the septo-accumbens area was also investigated: tyrosine hydroxylase-immunoreactive cells of both the caudal ventrolateral medulla and the nucleus of the solitary Tract were found to contribute to the innervation of the septo-accumbens area. The distribution of retrogradely labelled cells as well as the termination pattern of the anterogradely labelled terminals indicated that the innervation of the various forebrain limbic areas arises from cells, diffusely distributed in the rostral and/or the caudal ventrolateral medulla oblongata. Considering the important role of the ventrolateral medulla oblongata in autonomic coordination, it is proposed that direct projections from the ventral medulla oblongata to limbic forebrain structures might contribute to the coordination of behavioural states and cardiovascular performance. © Wiley-Liss, Inc.

  • direct projections from the ventrolateral medulla oblongata to the limbic forebrain anterograde and retrograde Tract Tracing studies in the rat
    The Journal of Comparative Neurology, 1994
    Co-Authors: A. Zagon, S. Totterdell, R. S. G. Jones
    Abstract:

    Neurons in the ventrolateral medulla oblongata, a brain region implicated in central vasomotor regulation, have previously been reported to project to some forebrain limbic structures. The aim of the present study was (1) to describe the termination pattern of ventral medullary afferents in forebrain limbic areas using anterograde Tract Tracing, and (2) to determine the location and some morphological characteristics of the projection neurons using retrograde Tract Tracing from selected forebrain sites. Following ionophoretic microinjections of the anterograde Tract tracer Phaseolus vulgaris leucoagglutinin into the rostral ventrolateral medulla, labelled afferents were observed in the hippocampus, entorhinal and retrosplenial cortices, dorsal septum, nucleus accumbens, and the medial prefrontal cortex. Anterogradely labelled axons, ascending from the caudal ventrolateral medulla, could be traced only to the rostral aspects of the investigated forebrain limbic structures. Here, the main target of the ascending projection was in the ventral septum. However, labelled terminals were also present in the nucleus accumbens, the dorsolateral septum, and in the infralimbic cortex. The density of the ventrolateral medullary projections into all examined forebrain areas was low. The location of the cells in the ventral medulla oblongata which give rise to direct forebrain projections was examined using retrograde Tract Tracing with wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Following WGA-HRP injections into the septo-accumbens region, retrogradely labelled cells were present in both the rostral and caudal ventrolateral medulla. When the Tract tracer injection was restricted to the ventral region of the septal complex, the labelled cells were concentrated in the caudal aspects of the ventrolateral medulla (and the nucleus of the solitary Tract). Following tracer injections into the anterior cingulate cortex or the hippocampus or the entorhinal cortex, retrogradely labelled cells in the medulla oblongata were predominantly in the rostral ventrolateral medulla. As a first attempt to reveal the chemical nature of the projection cells, the contribution of tyrosine hydroxylase-immunoreactive cells to the innervation of the septo-accumbens area was also investigated: tyrosine hydroxylase-immunoreactive cells of both the caudal ventrolateral medulla and the nucleus of the solitary Tract were found to contribute to the innervation of the septo-accumbens area. The distribution of retrogradely labelled cells as well as the termination pattern of the anterogradely labelled terminals indicated that the innervation of the various forebrain limbic areas arises from cells, diffusely distributed in the rostral and/or the caudal ventrolateral medulla oblongata. Considering the important role of the ventrolateral medulla oblongata in autonomic coordination, it is proposed that direct projections from the ventral medulla oblongata to limbic forebrain structures might contribute to the coordination of behavioural states and cardiovascular performance. © Wiley-Liss, Inc.

A. Zagon - One of the best experts on this subject based on the ideXlab platform.

  • Direct projections from the ventrolateral medulla oblongata to the limbic forebrain: Anterograde and retrograde Tract‐Tracing studies in the rat
    The Journal of Comparative Neurology, 1994
    Co-Authors: A. Zagon, S. Totterdell, R. S. G. Jones
    Abstract:

    Neurons in the ventrolateral medulla oblongata, a brain region implicated in central vasomotor regulation, have previously been reported to project to some forebrain limbic structures. The aim of the present study was (1) to describe the termination pattern of ventral medullary afferents in forebrain limbic areas using anterograde Tract Tracing, and (2) to determine the location and some morphological characteristics of the projection neurons using retrograde Tract Tracing from selected forebrain sites. Following ionophoretic microinjections of the anterograde Tract tracer Phaseolus vulgaris leucoagglutinin into the rostral ventrolateral medulla, labelled afferents were observed in the hippocampus, entorhinal and retrosplenial cortices, dorsal septum, nucleus accumbens, and the medial prefrontal cortex. Anterogradely labelled axons, ascending from the caudal ventrolateral medulla, could be traced only to the rostral aspects of the investigated forebrain limbic structures. Here, the main target of the ascending projection was in the ventral septum. However, labelled terminals were also present in the nucleus accumbens, the dorsolateral septum, and in the infralimbic cortex. The density of the ventrolateral medullary projections into all examined forebrain areas was low. The location of the cells in the ventral medulla oblongata which give rise to direct forebrain projections was examined using retrograde Tract Tracing with wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Following WGA-HRP injections into the septo-accumbens region, retrogradely labelled cells were present in both the rostral and caudal ventrolateral medulla. When the Tract tracer injection was restricted to the ventral region of the septal complex, the labelled cells were concentrated in the caudal aspects of the ventrolateral medulla (and the nucleus of the solitary Tract). Following tracer injections into the anterior cingulate cortex or the hippocampus or the entorhinal cortex, retrogradely labelled cells in the medulla oblongata were predominantly in the rostral ventrolateral medulla. As a first attempt to reveal the chemical nature of the projection cells, the contribution of tyrosine hydroxylase-immunoreactive cells to the innervation of the septo-accumbens area was also investigated: tyrosine hydroxylase-immunoreactive cells of both the caudal ventrolateral medulla and the nucleus of the solitary Tract were found to contribute to the innervation of the septo-accumbens area. The distribution of retrogradely labelled cells as well as the termination pattern of the anterogradely labelled terminals indicated that the innervation of the various forebrain limbic areas arises from cells, diffusely distributed in the rostral and/or the caudal ventrolateral medulla oblongata. Considering the important role of the ventrolateral medulla oblongata in autonomic coordination, it is proposed that direct projections from the ventral medulla oblongata to limbic forebrain structures might contribute to the coordination of behavioural states and cardiovascular performance. © Wiley-Liss, Inc.

  • direct projections from the ventrolateral medulla oblongata to the limbic forebrain anterograde and retrograde Tract Tracing studies in the rat
    The Journal of Comparative Neurology, 1994
    Co-Authors: A. Zagon, S. Totterdell, R. S. G. Jones
    Abstract:

    Neurons in the ventrolateral medulla oblongata, a brain region implicated in central vasomotor regulation, have previously been reported to project to some forebrain limbic structures. The aim of the present study was (1) to describe the termination pattern of ventral medullary afferents in forebrain limbic areas using anterograde Tract Tracing, and (2) to determine the location and some morphological characteristics of the projection neurons using retrograde Tract Tracing from selected forebrain sites. Following ionophoretic microinjections of the anterograde Tract tracer Phaseolus vulgaris leucoagglutinin into the rostral ventrolateral medulla, labelled afferents were observed in the hippocampus, entorhinal and retrosplenial cortices, dorsal septum, nucleus accumbens, and the medial prefrontal cortex. Anterogradely labelled axons, ascending from the caudal ventrolateral medulla, could be traced only to the rostral aspects of the investigated forebrain limbic structures. Here, the main target of the ascending projection was in the ventral septum. However, labelled terminals were also present in the nucleus accumbens, the dorsolateral septum, and in the infralimbic cortex. The density of the ventrolateral medullary projections into all examined forebrain areas was low. The location of the cells in the ventral medulla oblongata which give rise to direct forebrain projections was examined using retrograde Tract Tracing with wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Following WGA-HRP injections into the septo-accumbens region, retrogradely labelled cells were present in both the rostral and caudal ventrolateral medulla. When the Tract tracer injection was restricted to the ventral region of the septal complex, the labelled cells were concentrated in the caudal aspects of the ventrolateral medulla (and the nucleus of the solitary Tract). Following tracer injections into the anterior cingulate cortex or the hippocampus or the entorhinal cortex, retrogradely labelled cells in the medulla oblongata were predominantly in the rostral ventrolateral medulla. As a first attempt to reveal the chemical nature of the projection cells, the contribution of tyrosine hydroxylase-immunoreactive cells to the innervation of the septo-accumbens area was also investigated: tyrosine hydroxylase-immunoreactive cells of both the caudal ventrolateral medulla and the nucleus of the solitary Tract were found to contribute to the innervation of the septo-accumbens area. The distribution of retrogradely labelled cells as well as the termination pattern of the anterogradely labelled terminals indicated that the innervation of the various forebrain limbic areas arises from cells, diffusely distributed in the rostral and/or the caudal ventrolateral medulla oblongata. Considering the important role of the ventrolateral medulla oblongata in autonomic coordination, it is proposed that direct projections from the ventral medulla oblongata to limbic forebrain structures might contribute to the coordination of behavioural states and cardiovascular performance. © Wiley-Liss, Inc.

Ramon Anadon - One of the best experts on this subject based on the ideXlab platform.

  • organization of the torus longitudinalis in the rainbow trout oncorhynchus mykiss an immunohistochemical study of the gabaergic system and a dii Tract Tracing study
    The Journal of Comparative Neurology, 2007
    Co-Authors: Monica Folgueira, Catalina Sueiro, Isabel Rodriguezmoldes, Julian Yanez, Ramon Anadon
    Abstract:

    The torus longitudinalis (TL) is a tectum-associated structure of actinopterygian fishes. The organization of the TL of rainbow trout was studied with Nissl staining, Golgi methods, immunocytochemistry with antibodies to gamma-aminobutyric acid (GABA), glutamic acid decarboxylase (GAD), and the GABA(A) receptor subunits delta and beta2/beta 3, and with Tract Tracing methods. Two types of neuron were characterized: medium-sized GABAergic neurons and small GABA-negative granule cells. GABA(A) receptor subunit delta-like immunoreactivity delineated two different TL regions, ventrolateral and central. Small GABAergic cells were also observed in marginal and periventricular strata of the optic tectum. These results indicate the presence of local GABAergic inhibitory circuits in the TL system. For Tract-Tracing, a lipophilic dye (DiI) was applied to the TL and to presumed toropetal nuclei or toral targets. Toropetal neurons were observed in the optic tectum, in pretectal (central, intermediate, and paracommissural) nuclei, in the subvalvular nucleus, and associated with the pretectocerebellar Tract. Torofugal fibers were numerous in the stratum marginale of the optic tectum. Toropetal pretectal nuclei also project to the cerebellum, and a few TL cells project to the cerebellar corpus. The pyramidal cells of the trout tectum were also studied by Golgi methods and local DiI labeling. The connections of trout TL revealed here were more similar to those recently reported in carp and holocentrids (Ito et al. [2003] J. Comp. Neurol. 457:202-211; Xue et al. [2003] J. Comp. Neurol. 462:194-212), than to those reported in earlier studies. However, important differences in organization of toropetal nuclei were noted between salmonids and these other teleosts.

  • organization of the torus longitudinalis in the rainbow trout oncorhynchus mykiss an immunohistochemical study of the gabaergic system and a dii Tract Tracing study
    The Journal of Comparative Neurology, 2007
    Co-Authors: Monica Folgueira, Catalina Sueiro, Isabel Rodriguezmoldes, Julian Yanez, Ramon Anadon
    Abstract:

    The torus longitudinalis (TL) is a tectum-associated structure of actinopterygian fishes. The organization of the TL of rainbow trout was studied with Nissl staining, Golgi methods, immunocytochemistry with antibodies to -aminobutyric acid (GABA), glutamic acid decarboxylase (GAD), and the GABAA receptor subunits and 2/3, and with Tract Tracing methods. Two types of neuron were characterized: medium-sized GABAergic neurons and small GABA-negative granule cells. GABAA receptor subunit -like immunoreactivity delineated two different TL regions, ventrolateral and central. Small GABAergic cells were also observed in marginal and periventricular strata of the optic tectum. These results indicate the presence of local GABAergic inhibitory circuits in the TL system. For Tract-Tracing, a lipophilic dye (DiI) was applied to the TL and to presumed toropetal nuclei or toral targets. Toropetal neurons were observed in the optic tectum, in pretectal (central, intermediate, and paracommissural) nuclei, in the subvalvular nucleus, and associated with the pretectocerebellar Tract. Torofugal fibers were numerous in the stratum marginale of the optic tectum. Toropetal pretectal nuclei also project to the cerebellum, and a few TL cells project to the cerebellar corpus. The pyramidal cells of the trout tectum were also studied by Golgi methods and local DiI labeling. The connections of trout TL revealed here were more similar to those recently reported in carp and holocentrids (Ito et al. [2003] J. Comp. Neurol. 457:202–211; Xue et al. [2003] J. Comp. Neurol. 462:194 –212), than to those reported in earlier studies. However, important differences in organization of toropetal nuclei were noted between salmonids and these other teleosts. J. Comp. Neurol. 503:348 –370, 2007. © 2007 Wiley-Liss, Inc. Indexing terms: torus longitudinalis; GABA; GABAA receptors; pretectum; optic tectum; connections; teleosts