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Harukazu Nakamura - One of the best experts on this subject based on the ideXlab platform.
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role of pax3 7 in the Tectum regionalization
2001Co-Authors: Isato Araki, Harukazu Nakamura, Eiji MatsunagaAbstract:Pax3/7 is expressed in the alar plate of the mesencephalon. The optic Tectum differentiates from the alar plate of the mesencephalon, and expression of Pax3/7 is well correlated to the Tectum development. To explore the function of Pax3 and Pax7 in the Tectum development, we misexpressed Pax3 and Pax7 in the diencephalon and ventral mesencephalon. Morphological and molecular marker gene analysis indicated that Pax3 and Pax7 misexpression caused fate change of the alar plate of the presumptive diencephalon to that of the mesencephalon, that is, a Tectum and a torus semicircularis were formed ectopically. Ectopic Tectum in the diencephalon appeared to be generated through sequential induction of Fgf8, En2 and Pax3/7. In ventral mesencephalon, which expresses En but does not differentiate to the Tectum in normal development, Pax3 and Pax7 misexpression induced ectopic Tectum. In normal development, Pax3 and Pax7 expression in the mesencephalon commences after Otx2, En and Pax2/5 expression. In addition, expression domain of Pax3 and Pax7 is well consistent with presumptive Tectum region in a dorsoventral axis. Taken together with normal expression pattern of Pax3 and Pax7, results of misexpression experiments suggest that Pax3 and Pax7 define the Tectum region subsequent to the function of Otx2 and En.
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Control of chick Tectum territory along dorsoventral axis by Sonic hedgehog.
2000Co-Authors: Yuji Watanabe, Harukazu NakamuraAbstract:Chick midbrain comprises two major components along the dorsoventral axis, the Tectum and the tegmentum. The alar plate differentiates into the optic Tectum, while the basal plate gives rise to the tegmentum. It is largely unknown how the differences between these two structures are molecularly controlled during the midbrain development. The secreted protein Sonic hedgehog (Shh) produced in the notochord and floor plate induces differentiation of ventral cell types of the central nervous system. To evaluate the role of Shh in the establishment of dorsoventral polarity in the developing midbrain, we have ectopically expressed Shh unilaterally in the brain vesicles including whole midbrain of E1.5 chick embryos in ovo. Ectopic Shh repressed normal growth of the Tectum, producing dorsally enlarged tegmentum region. In addition, the expression of several genes crucial for Tectum formation was strongly suppressed in the midbrain and isthmus. Markers for midbrain roof plate were inhibited, indicating that the roof plate was not fully generated. After E5, the Tectum territory of Shh-transfected side was significantly reduced and was fused with that of untransfected side. Moreover, ectopic Shh induced a considerable number of SC1-positive motor neurons, overlapping markers such as HNF-3(beta) (floor plate), Isl-1 (postmitotic motor neuron) and Lim1/2. Dopaminergic and serotonergic neurons were also generated in the dorsally extended region. These changes indicate that ectopic Shh changed the fate of the mesencephalic alar plate to that of the basal plate, suppressing the massive cell proliferation that normally occurs in the developing Tectum. Taken together our results suggest that Shh signaling restricts the Tectum territory by controlling the molecular cascade for Tectum formation along dorsoventral axis and by regulating neuronal cell diversity in the ventral midbrain.
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a role for gradient en expression in positional specification on the optic Tectum
1996Co-Authors: Nobue Itasaki, Harukazu NakamuraAbstract:Abstract The optic Tectum, the primary visual center in nonmammalian vertebrates, receives retinal fibers in a topographically ordered manner. en ( en-1 and en-2 , homologs of the Drosophila segment polarity gene engrailed ) is expressed in the tectal primordium in a rostrocaudal gradient, around the stage when the polarity of the retinotectal projection map is being determined. Here we report that scattered en expression, caused by retroviral gene transfer, perturbed the retinotopic order. Nasal retinal fibers, which normally recognize the caudal side of the Tectum (strong en expression side) as a target, arborized at ectopic sites, as if they found their targets, or degenerated. Temporal retinal fibers, which normally recognize the rostral side of the Tectum (weak en expression side) as a target, were also affected in some cases by degeneration or prevention of innervation in the Tectum. These results suggest that gradient en expression defines the positional identity of the Tectum along the rostrocaudal axis.
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establishment of rostrocaudal polarity in tectal primordium engrailed expression and subsequent tectal polarity
1991Co-Authors: Nobue Itasaki, Hiroyuki Ichijo, C Hama, Toru Matsuno, Harukazu NakamuraAbstract:In the E4 (embryonic day 4) chick tectal primordium, engrailed expression is strong at the caudal end and gradually weakens toward the rostral end. We used quail-chick chimeric tecta to investigate how the caudorostral gradient of engrailed expression is established and whether it is correlated with the subsequent rostrocaudal polarity of tectal development. To examine the positional value of the tectal primordium, we produced ectopic tecta in the diencephalon by transplanting a part of the mesencephalic alar plate heterotopically. In the ectopic Tectum, the gradient of the engrailed expression reversed and the strength of the expression was dependent on the distance from the mes-diencephalon junction; the nearer the ectopic Tectum was to the junction, the weaker the expression was. Consequently, the pattern of the engrailed expression in the host and ectopic tecta was nearly a mirror image, suggesting the existence of a repressive influence around the mes-diencephalon junction on the engrailed expression. We examined cytoarchitectonic development in the ectopic tecta, which normally proceeds in a gradient along the rostrocaudal axis; the rostral shows more advanced lamination than the caudal. In contrast, the caudal part of the ectopic tecta (near to the mes-diencephalon junction) showed more advanced lamination than the rostral. In both the host and ectopic tecta, advanced lamination was observed where the engrailed expression was repressed, and vice versa. Next we studied the correlation between engrailed expression and retinotectal projection from a view of plasticity and rigidity of rostrocaudal polarity in the Tectum. We produced ectopic tecta by anisochronal transplantations between E3 host and E2 donor, and showed that there is little repressive influence at E3 around the mes-diencephalon junction. We then made chimeric double-rostral Tectum (caudal half of it was replaced by rostral half of the donor Tectum) or double-caudal Tectum at E3. The transplants kept their original staining pattern in hosts. Consequently, the chimeric tecta showed wholly negative or positive staining of engrailed protein on the grafted side. In such tecta retinotectal projection pattern was disturbed as if the transplants retained their original position-specific characters. We propose from these heterotopic and anisochronal experiments that the engrailed expression can be a marker for subsequent rostrocaudal polarity in the Tectum, both as regards cytoarchitectonic development and retinotectal projection.
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projection of the retinal ganglion cells to the Tectum differentiated from the prosencephalon
1991Co-Authors: Harukazu Nakamura, Shin Takagi, Kohji A. Matsui, Hajime FujisawaAbstract:Abstract The alar plate of the prosencephalon differentiates into a Tectum-like structure when transplanted into the mesencephalon around the 10-somite stage. Here, we report on the projection pattern of the retinal ganglion cells to the transplants. Optic nerve fibers were labeled with horseradish peroxidase (HRP) and 3 H-proline, and the innervation of the optic nerve fibers to the chimeric Tectum was analyzed by HRP histochemistry on whole-mounted specimens, by autoradiography and by electron microscopy on embryonic day 16. In the chimeric Tectum, the transplant was distinguished from the host by difference in nuclear structure between the quail and the chick cells. It was shown that the transplant had the laminar pattern of the optic Tectum when the transplant was integrated into the host mesencephalon. The whole-mount HRP histochemistry showed that the optic nerve fibers extend to the transplants. Autoradiography showed that the distribution pattern of silver grains was similar in both the host and the transplant. These results may indicate that the optic nerve fibers turn to the transplant and terminate on the transplant. Electron microscopy further confirmed that optic nerve fibers ended by making synaptic contacts with the dendrites in the transplant region of the Tectum. These results indicate that the transplant with the laminar pattern of the optic Tectum is a true Tectum receiving input from the eye.
Carlos D. Aizenman - One of the best experts on this subject based on the ideXlab platform.
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in vivo spike timing dependent plasticity in the optic Tectum of xenopus laevis
2010Co-Authors: Blake A Richards, Carlos D. Aizenman, Colin J AkermanAbstract:Spike-timing-dependent plasticity (STDP) is found in vivo in a variety of systems and species, but the first demonstrations of in vivo STDP were carried out in the optic Tectum of Xenopus laevis embryos. Since then, the optic Tectum has served as an excellent experimental model for studying STDP in sensory systems, allowing researchers to probe the developmental consequences of this form of synaptic plasticity during early development. In this review, we will describe what is known about the role of STDP in shaping feed-forward and recurrent circuits in the optic Tectum with a focus on the functional implications for vision. We will discuss both the similarities and differences between the optic Tectum and mammalian sensory systems that are relevant to STDP. Finally, we will highlight the unique properties of the embryonic Tectum that make it an important system for researchers who are interested in how STDP contributes to activity dependent development of sensory computations.
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development of multisensory convergence in the xenopus optic Tectum
2009Co-Authors: Katherine E Deeg, Irina B Sears, Carlos D. AizenmanAbstract:The adult Xenopus optic Tectum receives and integrates visual and nonvisual sensory information. Nonvisual inputs include mechanosensory inputs from the lateral line, auditory, somatosensory, and vestibular systems. While much is known about the development of visual inputs in this species, almost nothing is known about the development of mechanosensory inputs to the Tectum. In this study, we investigated mechanosensory inputs to the Tectum during critical developmental stages (stages 42–49) in which the retinotectal map is being established. Tract-tracing studies using lipophilic dyes revealed a large projection between the hindbrain and the Tectum as early as stage 42; this projection carries information from the Vth, VIIth, and VIIIth nerves. By directly stimulating hindbrain and visual inputs using an isolated whole-brain preparation, we found that all tectal cells studied received both visual and hindbrain input during these early developmental stages. Pharmacological data indicated that the hindbrain-tectal projection is glutamatergic and that there are no direct inhibitory hindbrain-tectal ascending projections. We found that unlike visual inputs, hindbrain inputs do not show a decrease in paired-pulse facilitation over this developmental period. Interestingly, over this developmental period, hindbrain inputs show a transient increase followed by a significant decrease in the α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA)/N-methyl-d-aspartate (NMDA) ratio and show no change in quantal size, both in contrast to visual inputs. Our data support a model by which fibers are added to the hindbrain-tectal projection across development. Nascent fibers form new synapses with tectal neurons and primarily activate NMDA receptors. At a time when retinal ganglion cells and their tectal synapses mature, hindbrain-tectal synapses are still undergoing a period of rapid synaptogenesis. This study supports the idea that immature tectal cells receive converging visual and mechanosensory information and indicates that the Xenopus Tectum might be an ideal preparation to study the early development of potential multisensory interactions at the cellular level.
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Development and spike timing-dependent plasticity of recurrent excitation in the Xenopus optic Tectum.
2008Co-Authors: Kara G. Pratt, Wei Dong, Carlos D. AizenmanAbstract:Development and spike timing–dependent plasticity of recurrent excitation in the Xenopus optic Tectum
Sten Grillner - One of the best experts on this subject based on the ideXlab platform.
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the Tectum superior colliculus as the vertebrate solution for spatial sensory integration and action
2021Co-Authors: Tadashi Isa, Sten Grillner, Emmanuel Marquezlegorreta, Ethan K ScottAbstract:The superior colliculus, or Tectum in the case of non-mammalian vertebrates, is a part of the brain that registers events in the surrounding space, often through vision and hearing, but also through electrosensation, infrared detection, and other sensory modalities in diverse vertebrate lineages. This information is used to form maps of the surrounding space and the positions of different salient stimuli in relation to the individual. The sensory maps are arranged in layers with visual input in the uppermost layer, other senses in deeper positions, and a spatially aligned motor map in the deepest layer. Here, we will review the organization and intrinsic function of the Tectum/superior colliculus and the information that is processed within tectal circuits. We will also discuss tectal/superior colliculus outputs that are conveyed directly to downstream motor circuits or via the thalamus to cortical areas to control various aspects of behavior. The Tectum/superior colliculus is evolutionarily conserved among all vertebrates, but tailored to the sensory specialties of each lineage, and its roles have shifted with the emergence of the cerebral cortex in mammals. We will illustrate both the conserved and divergent properties of the Tectum/superior colliculus through vertebrate evolution by comparing tectal processing in lampreys belonging to the oldest group of extant vertebrates, larval zebrafish, rodents, and other vertebrates including primates.
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direct dopaminergic projections from the snc modulate visuomotor transformation in the lamprey Tectum
2017Co-Authors: Juan Perezfernandez, Brita Robertson, Andreas A Kardamakis, Daichi G Suzuki, Sten GrillnerAbstract:Summary Dopamine neurons in the SNc play a pivotal role in modulating motor behavior via striatum. Here, we show that the same dopamine neuron that targets striatum also sends a direct branch to the optic Tectum (superior colliculus). Whenever SNc neurons are activated, both targets will therefore be affected. Visual stimuli (looming or bars) activate the dopamine neurons coding saliency and also elicit distinct motor responses mediated via Tectum (eye, orienting or evasive), which are modulated by the dopamine input. Whole-cell recordings from tectal projection neurons and interneurons show that dopamine, released by SNc stimulation, increases or decreases the excitability depending on whether they express the dopamine D1 or the D2 receptor. SNc thus exerts its effects on the visuomotor system through a combined effect directly on Tectum and also via striatum. This direct SNc modulation will occur regardless of striatum and represents a novel mode of motor control.
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spatiotemporal interplay between multisensory excitation and recruited inhibition in the lamprey optic Tectum
2016Co-Authors: Andreas A Kardamakis, Juan Perezfernandez, Sten GrillnerAbstract:Many events occur around us simultaneously, which we detect through our senses. A critical task is to decide which of these events is the most important to look at in a given moment of time. This problem is solved by an ancient area of the brain called the optic Tectum (known as the superior colliculus in mammals). The different senses are represented as superimposed maps in the optic Tectum. Events that occur in different locations activate different areas of the map. Neurons in the optic Tectum combine the responses from different senses to direct the animal’s attention and increase how reliably important events are detected. If an event is simultaneously registered by two senses, then certain neurons in the optic Tectum will enhance their activity. By contrast, if two senses provide conflicting information about how different events progress, then these same neurons will be silenced. While this phenomenon of ‘multisensory integration’ is well described, little is known about how the optic Tectum performs this integration. Kardamakis, Perez-Fernandez and Grillner have now studied multisensory integration in fish called lampreys, which belong to the oldest group of backboned animals. These fish can navigate using electroreception – the ability to detect electrical signals from the environment. Experiments that examined the connections between neurons in the optic Tectum and monitored their activity revealed a neural circuit that consists of two types of neurons: inhibitory interneurons, and projecting neurons that connect the optic Tectum to different motor centers in the brainstem. The circuit contains neurons that can receive inputs from both vision and electroreception when these senses are both activated from the same point in space. Incoming signals from the two senses activate the areas on the sensory maps that correspond to the location where the event occurred. This triggers the activity of the interneurons, which immediately send ‘stop’ signals. Thus, while an area of the sensory map and its output neurons are activated, the surrounding areas of the Tectum are inhibited. Overall, the findings presented by Kardamakis, Perez-Fernandez and Grillner suggest that the optic Tectum can direct attention to a particular event without requiring input from other brain areas. This ability has most likely been preserved throughout evolution. Future studies will aim to determine how the commands generated by the optic Tectum circuit are translated into movements.
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afferents of the lamprey optic Tectum with special reference to the gaba input combined tracing and immunohistochemical study
2006Co-Authors: Brita Robertson, Kazuya Saitoh, Ariane Menard, Sten GrillnerAbstract:The optic Tectum in the lamprey midbrain, homologue of the superior colliculus in mammals, is important for eye movement control and orienting responses. There is, however, only limited information regarding the afferent input to the optic Tectum except for that from the eyes. The objective of this study was to define specifically the γ-aminobutyric acid (GABA)-ergic projections to the optic Tectum in the river lamprey (Lampetra fluviatilis) and also to describe the tectal afferent input in general. The origin of afferents to the optic Tectum was studied by using the neuronal tracer neurobiotin. Injection of neurobiotin into the optic Tectum resulted in retrograde labelling of cell groups in all major subdivisions of the brain. The main areas shown to project to the optic Tectum were the following: the caudoventral part of the medial pallium, the area of the ventral thalamus and dorsal thalamus, the nucleus of the posterior commissure, the torus semicircularis, the mesencephalic M5 nucleus of Schober, the mesencephalic reticular area, the ishtmic area, and the octavolateral nuclei. GABAergic projections to the optic Tectum were identified by combining neurobiotin tracing and GABA immunohistochemistry. On the basis of these double-labelling experiments, it was shown that the optic Tectum receives a GABAergic input from the caudoventral part of the medial pallium, the dorsal and ventral thalamus, the nucleus of M5, and the torus semicircularis. The afferent input to the optic Tectum in the lamprey brain is similar to that described for other vertebrate species, which is of particular interest considering its position in phylogeny. J. Comp. Neurol. 499:106–119, 2006. © 2006 Wiley-Liss, Inc.
A B Butler - One of the best experts on this subject based on the ideXlab platform.
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retinofugal and retinopetal projections in the green sunfish lepomis cyanellus part 2 of 2
1991Co-Authors: Glenn R Northcutt, A B ButlerAbstract:The retinofugal and retinopetal connections in the green sunfish were studied by autoradiographic and horseradish peroxidase methods. All retinofugal fibers decussate in the optic chiasm. Some fibers project to contralateral preoptic and hypothalamic nuclei while others recross to project to the comparable ipsilateral nuclei. Contralaterally, the medial optic tract projects to the periventricular thalamic and pretectal nuclei and, sparsely, to the rostral optic Tectum. The dorsal optic tract projects to the parvocellular portion of the superficial pretectal nucleus, the central pretectal nucleus, nucleus corticalis, and the rostral portion of the optic Tectum. The ventral optic tract primarily projects to the caudal portion of the optic Tectum, giving off fibers in route to innervate various nuclei, including the parvocellular superficial pretectal nucleus and the dorsal and ventral accessory optic nuclei. The axial optic tract projects to the dorsal accessory optic nucleus, the central pretectal nucleus, and the caudal optic Tectum. Retinal fibers reach the ipsilateral thalamus, preTectum and other sites via a redecussation through the posterior commissure. From outgroup analysis it is concluded that such redecussating fibers are an independently derived character within actinopterygians and are homoplasous to nondecussating ipsilateral retinal projections in other vertebrates. Neurons retrogradely labeled with horseradish peroxidase were found to form a rostrocaudal column from the olfactory bulb and nerve through the ventral telencephalon to caudal diencephalic levels along the medial aspect of the optic tract. It is possible that all these neurons consist of one population of migrated ganglion cells of the nervus terminalis.
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retinofugal and retinopetal projections in the green sunfish lepomis cyanellus
1991Co-Authors: R G Northcutt, A B ButlerAbstract:The retinofugal and retinopetal connections in the green sunfish were studied by autoradiographic and horseradish peroxidase methods. All retinofugal fibers decussate in the optic chiasm. Some fibers project to contralateral preoptic and hypothalamic nuclei while others recross to project to the comparable ipsilateral nuclei. Contralaterally, the medial optic tract projects to the periventricular thalamic and pretectal nuclei and, sparsely, to the rostral optic Tectum. The dorsal optic tract projects to the parvocellular portion of the superficial pretectal nucleus, the central pretectal nucleus, nucleus corticalis, and the rostral portion of the optic Tectum. The ventral optic tract primarily projects to the caudal portion of the optic Tectum, giving off fibers in route to innervate various nuclei, including the parvocellular superficial pretectal nucleus and the dorsal and ventral accessory optic nuclei. The axial optic tract projects to the dorsal accessory optic nucleus, the central pretectal nucleus, and the caudal optic Tectum. Retinal fibers reach the ipsilateral thalamus, preTectum and other sites via a redecussation through the posterior commissure. From outgroup analysis it is concluded that such redecussating fibers are an independently derived character within actinopterygians and are homoplasous to nondecussating ipsilateral retinal projections in other vertebrates. Neurons retrogradely labeled with horseradish peroxidase were found to form a rostrocaudal column from the olfactory bulb and nerve through the ventral telencephalon to caudal diencephalic levels along the medial aspect of the optic tract. It is possible that all these neurons consist of one population of migrated ganglion cells of the nervus terminalis.
Ramon Anadon - One of the best experts on this subject based on the ideXlab platform.
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organization of the torus longitudinalis in the rainbow trout oncorhynchus mykiss an immunohistochemical study of the gabaergic system and a dii tract tracing study
2007Co-Authors: Monica Folgueira, Catalina Sueiro, Isabel Rodriguezmoldes, Julian Yanez, Ramon AnadonAbstract: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.
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organization of the torus longitudinalis in the rainbow trout oncorhynchus mykiss an immunohistochemical study of the gabaergic system and a dii tract tracing study
2007Co-Authors: Monica Folgueira, Catalina Sueiro, Isabel Rodriguezmoldes, Julian Yanez, Ramon AnadonAbstract: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
