ABSTRACT
Visually responsive neurons were recorded in the superficial layers of rat superior colliculus from postnatal day 12 to 28. Receptive field properties such as size, type (ON, OFF, ON-OFF and motion sensitive) and direction selectivity were analyzed to disclose changes during maturation. Although some aspects of sensory properties are modified during development (latency, receptive field sizes, and proportions of receptive field types), a high level of sophistication is also present in young animals even before eyelid opening. For instance, direction selective and direction biased cells, which require complex synaptic relations, are already observed when the first light evoked responses emerge in the superior colliculus (P13), strongly suggesting that this property develops without visual experience. Furthermore, direction selectivity is present in the colliculus prior to the appearance of visually evoked activity in the cortex. This indicates that direction selectivity can not be attributable to incoming cortical afferents. This study provides the first direct evidence that, unlike the cat, the rat's cortico-tectal pathway is only weakly involved in the establishment of direction selectivity in collicular neurons.
Subject(s)
Aging/physiology , Animals, Newborn/physiology , Superior Colliculi/growth & development , Visual Pathways/growth & development , Animals , Animals, Newborn/growth & development , Brain Mapping , Electrophysiology , Photic Stimulation , Rats , Rats, Long-Evans , Reaction Time/physiology , Superior Colliculi/physiology , Visual Pathways/physiologyABSTRACT
The present investigation is aimed at characterizing the development of ON and OFF visually evoked responses in the rat superior colliculus from postnatal day 13 (P13) to postnatal day 25. Depth profiles of field potentials reveal that ON and OFF long latency biphasic field potentials are already present when collicular cells are first responsive to light (P13). There is an inversion in the polarity of these responses as the electrode penetrates the collicular layers, suggesting a synaptic organization similar to the one found in adult animals. At P15, OFF field potentials begin to exhibit oscillatory activity. Local cobalt injections within the superior colliculus abolishes these OFF oscillations, suggesting a postsynaptic origin. Fast Fourier transform (FFT) analysis of the OFF field potentials demonstrates that oscillatory activity increases in frequency during development. This increase is thought to reflect the myelination and stabilization of synaptic connections that occur during this period. To our knowledge, this is the first report of OFF oscillatory responses in the superior colliculus.
Subject(s)
Biological Clocks/physiology , Evoked Potentials, Visual/physiology , Rats/physiology , Superior Colliculi/growth & development , Animals , Fourier Analysis , Photic Stimulation , Superior Colliculi/physiologyABSTRACT
During the first 10 days after birth in the rat there are a succession of major developmental stages in the retinotectal pathway. During most of this time, the only recordable event in the superior colliculus is spontaneous activity. We studied and characterized this spontaneous activity, hypothesizing that it could play an important role in pathway development. The spontaneous discharges are detectable on postnatal day 5 (P5). After P5, the number of spontaneously active cells per penetration increases up to P10, after which they decrease to adult-like levels by P14-P15. Between P5 and P10, the spontaneous discharges exhibit several patterns of activity, from constant firing to intermittent bursts with periods of quiescence, without any bearing to age. We isolated the retina and superior colliculus by injecting xylocaine onto the optic nerve and found no change in collicular activity. While this suggests that the spontaneous activity in the colliculus is independent of the retina at the ages studied, the opposite experiment, i.e., electrically stimulating the optic nerve, resulted in increased firing by collicular neurons, perhaps via nonclassical synaptic transmission. Finally, we compared interval histograms for spontaneously active cells between P5 and P15. The histograms suggest that at certain ages, spontaneous firing is more regular; moreover, these ages precede major functional advances, e.g., onset of numerous spontaneously firing cells at P6, the first response to optic nerve stimulation at P10, and the first light-evoked response at P12-P13. Our results support the hypothesis that spontaneous activity in the neonatal superior colliculus has a role in development of the retinotectal pathway, but the data also indicate that classical synaptic transmission is not involved.
Subject(s)
Optic Nerve/physiology , Superior Colliculi/growth & development , Superior Colliculi/physiology , Visual Pathways/growth & development , Animals , Animals, Suckling , RatsABSTRACT
Electrophysiological activity in the neonatal rat superior colliculus was recorded to measure neuronal and synaptic activity, and, therefore, functional development. Neonatal rat pups were studied from five days to two weeks of age. The earliest activity in the superior colliculus were spontaneous discharges at a frequency of one unit per animal on postnatal day 6 (P6). Spontaneously discharging units were more numerous at P8, and the number peaked on P10. The first clear response to optic nerve stimulation was seen on P10, with relatively long and variable latencies. By P14, electrically evoked responses had much shorter latencies. The results are in line with the first response to light flash in the superior colliculus at P12/13. The evidence suggests that functional development of the rat retinotectal pathway begins at the end of the first week after birth, and that much of the functional maturation occurs mainly during the second week after birth.
Subject(s)
Animals, Newborn/growth & development , Retina/growth & development , Superior Colliculi/growth & development , Visual Pathways/growth & development , Animals , Animals, Newborn/physiology , Electric Stimulation , Evoked Potentials , Photic Stimulation , Rats , Retina/physiology , Superior Colliculi/physiology , Visual Pathways/physiologyABSTRACT
Wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) is a neuroanatomical tracer which is transported transneuronally. In order to investigate whether transport of WGA-HRP is across synapses, labeling was studied in the developing retinotectal pathway where it is known that enucleation results in increased ipsilateral synaptic connections from the remaining eye. While little or no transneuronal labeling was evident in controls, after enucleation transneuronal labeling was consistently observed. Furthermore, the critical period for enucleation-induced transneuronal labeling coincides with the known critical period for enucleation-induced neuronal survival and synaptic formation. The results suggest that transneuronal exchange of WGA-HRP depends on the presence of synapses, and is therefore transsynaptic.
Subject(s)
Axonal Transport , Horseradish Peroxidase/pharmacokinetics , Peroxidases/pharmacokinetics , Retina/metabolism , Retinal Ganglion Cells/metabolism , Superior Colliculi/metabolism , Synapses/metabolism , Wheat Germ Agglutinins/pharmacokinetics , Animals , Rats , Rats, Inbred Strains , Retinal Ganglion Cells/cytology , Superior Colliculi/cytology , Superior Colliculi/growth & development , Synapses/ultrastructure , Wheat Germ Agglutinin-Horseradish Peroxidase ConjugateABSTRACT
Wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to study transneuronal transport in the developing rat visual pathways. Intraocular injections of WGA-HRP were made in neonatal albino rat pups at different ages from the day of birth, postnatal day 0 (P0), to one month of age. Transneuronal labeling in geniculostriate fibers and in tectoparabigeminal terminals was observed as early as P1 and showed little change with eye-opening. However, at early ages, consistent transneuronal labeling was found to require injection of up to 4 times the amount of tracer (0.18 mg WGA-HRP) as adults (0.04 mg WGA-HRP), delivered in two injections. Control injections of HRP alone produced heavy anterograde labeling at all ages, without requiring increased injections. The results suggest that transneuronal transport precedes synaptic transmission, and may illustrate a mechanism for exchanging molecules between neurons. One explanation for the requirement of increased tracer is that axonal and/or transneuronal transport of WGA-HRP may be selectively limited to certain cells in the postnatal retina.
Subject(s)
Aging/metabolism , Axonal Transport , Horseradish Peroxidase/metabolism , Neurons/metabolism , Peroxidases/metabolism , Visual Pathways/metabolism , Wheat Germ Agglutinins/metabolism , Animals , Animals, Newborn , Eye , Geniculate Bodies/cytology , Geniculate Bodies/growth & development , Geniculate Bodies/metabolism , Horseradish Peroxidase/administration & dosage , Injections , Neurons/physiology , Rats , Rats, Inbred Strains , Superior Colliculi/cytology , Superior Colliculi/growth & development , Superior Colliculi/metabolism , Visual Pathways/growth & development , Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate , Wheat Germ Agglutinins/administration & dosageABSTRACT
The transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was studied in rat olfactory pathways. After applications of tracer to the vomeronasal organ, the olfactory epithelium or injections into the olfactory bulb, WGA-HRP reaction product was observed in second-order neuron terminal areas of each pathway, e.g. within posteromedial cortical amygdaloid nucleus, primary olfactory cortex and contralateral primary olfactory cortex, respectively. The results indicate that anterograde transsynaptic transport of WGA-HRP occurs in olfactory pathways, as has been shown in visual, somatosensory and limbic systems, and thus, anterograde transsynaptic transport may be a mechanism for neurons to exchange materials and/or messages.
Subject(s)
Central Nervous System/metabolism , Olfactory Pathways/metabolism , Animals , Biological Transport , Cell Communication , Horseradish Peroxidase , Limbic System/metabolism , Olfactory Bulb/metabolism , Rats , Rats, Inbred Strains , Staining and Labeling , Synapses/metabolism , Wheat Germ AgglutininsABSTRACT
The lectin tracer, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP), was injected into the entorhinal cortex in rat and monkey brains. Tracer labeling was followed in the entorhinal projection to dentate gyrus and hippocampus, i.e. along the perforant pathway. Besides labeling perforant pathway terminals in the outer two-thirds of stratum moleculare in the dentate gyrus, reaction product was also observed within stratum granulosum. We conclude that labeling of dentate granule cells was the result of anterograde transsynaptic transport of WGA-HRP. The evidence thus provides an example of anterograde transsynaptic transport: in the limbic system; and at an excitatory synapse.
Subject(s)
Limbic System/metabolism , Animals , Biological Transport , Hippocampus/metabolism , Horseradish Peroxidase , Macaca fascicularis , Neural Pathways/metabolism , Rats , Synapses/metabolism , Wheat Germ AgglutininsABSTRACT
Tritiated proline, horseradish peroxidase (HRP), and wheat germ agglutinin conjugated to HRP (WGA-HRP) were used as anterograde tracers in the monkey to reveal visual pathways. After intravitreal injections, three separate, direct routes of labeled retinal axons were followed to the thalamus. These routes eventually converged to innervate the lateral dorsal and anterodorsal thalamic nuclei. Thus, retinal input may reach the posterior cingulate cortex after a single synapse in lateral and anterior thalamic nuclei.
Subject(s)
Limbic System/physiology , Retina/physiology , Thalamus/physiology , Visual Pathways/physiology , Animals , Horseradish Peroxidase , Lectins , Macaca fascicularis , Macaca mulatta , Proline , Tritium , Wheat Germ AgglutininsABSTRACT
Intraocular injections of several different retrograde tracers were made in albino rats. Retrogradely filled neurons were observed in two locations: the medial pretectal area and the contralateral periaqueductal grey matter, indicating that the pretectum and the mesencephalon are sources of centrifugal innervation to the rat retina.
Subject(s)
Mesencephalon/anatomy & histology , Periaqueductal Gray/anatomy & histology , Retina/anatomy & histology , Animals , Efferent Pathways/anatomy & histology , Male , Rats , Rats, Inbred StrainsABSTRACT
The tracer, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP), was used as a transneuronal marker in the macaque monkey to study retino-geniculo-striate pathway terminals in area 17. Concomitantly, we stained matching sections for metabolic capacity using the cytochrome oxidase staining technique. Terminal labeling by WGA-HRP and cytochrome oxidase activity staining revealed duplicate patterns in layers II and III, IVA, IVC alpha, IVC beta, and VI. The absence of WGA-HRP-labeled neuronal cell bodies in area 17 supports the conclusion that WGA-HRP is a transsynaptic marker in the macaque visual pathways.
Subject(s)
Geniculate Bodies/anatomy & histology , Retina/anatomy & histology , Visual Cortex/anatomy & histology , Animals , Electron Transport Complex IV/metabolism , Histocytochemistry , Horseradish Peroxidase , Lectins , Macaca fascicularis , Staining and Labeling/methods , Visual Pathways/anatomy & histology , Wheat Germ AgglutininsABSTRACT
Horseradish peroxidase (HRP) and wheat germ agglutinin conjugated to HRP (WGA-HRP) were used as anterograde tracers to study the macaque monkey retinofugal pathways. Labeled axons were mapped beyond the lateral geniculate nucleus to the inferior (PI) and medial (PM) pulvinar nuclei, where they terminated. Retinofugal fibers project to the medial part of PI, adjacent to the brachium of the superior colliculus. A smaller projection to PM leaves the ventrolateral aspect of the lateral geniculate nucleus and travels parallel to the stria terminalis to reach the dorsal surface of the thalamus and PM. HRP reaction product was bilateral in PI and predominantly contralateral in P)M.
Subject(s)
Retina/anatomy & histology , Thalamic Nuclei/anatomy & histology , Animals , Brain Mapping , Geniculate Bodies/anatomy & histology , Macaca fascicularis/anatomy & histology , Macaca mulatta/anatomy & histology , Visual Pathways/anatomy & histologyABSTRACT
Horseradish peroxidase (HRP) and HRP conjugated to wheat germ agglutinin (WGA-HRP) were used as anterograde tracers in the monkey visual pathways. In addition to known optic pathways, we observed labeled fibers which left the lateral terminal nucleus of the accessory optic system, traveled around the cerebral peduncle, and could be followed as far as the medial terminal nucleus.
Subject(s)
Retina/anatomy & histology , Visual Pathways/anatomy & histology , Animals , Brain Mapping , Macaca fascicularis/anatomy & histology , Macaca mulatta/anatomy & histologyABSTRACT
Wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was injected intraocularly in monkeys and rats. All known primary visual pathways were labeled and, in addition, ocular dominance columns in visual cortex were labeled in monkey, and in rat, parabigeminal, oculomotor, thalamic reticular, and visual cortical areas were labeled as well as neuronal soma in superior colliculus. We conclude that WGA-HRP is a useful transneuronal marker for visual pathways.
Subject(s)
Axonal Transport , Brain Mapping/methods , Horseradish Peroxidase/metabolism , Lectins/metabolism , Peroxidases/metabolism , Visual Pathways/metabolism , Animals , Macaca fascicularis , Male , Rats , Rats, Inbred Strains , Retina/anatomy & histology , Retina/metabolism , Visual Pathways/anatomy & histology , Wheat Germ AgglutininsABSTRACT
Visual pathways were studied using horseradish peroxidase (HRP) as an anterograde tracer after intraocular injections in rats and monkeys. Retinal axons continue caudally from the stratum opticum of the contralateral superior colliculus at the medial and lateral sides of the superior colliculus. Fibers near the midline spread out as a flat sheet within the pericentral nucleus of the inferior colliculus. The optic axons travel through the dorsal pericentral nucleus and some reach the posterior pericentral nucleus, but their numbers diminish along the route, suggesting that the fibers terminate. The fact that a similar pathway was observed in rodent and primate suggests that the retino-pericentral nucleus pathway exists in other mammals.
Subject(s)
Inferior Colliculi/physiology , Retina/physiology , Animals , Brain Mapping , Horseradish Peroxidase , Macaca fascicularis , Macaca mulatta , Neural Pathways/physiology , Rats , Rats, Inbred StrainsABSTRACT
Retinal projections in rats were studied using anterograde horseradish peroxidase (HRP) tracing and electron microscopic (EM) degeneration. HRP-labeled axons were observed to leave the optic tract in the vicinity of the lateral geniculate nucleus and enter the stria terminalis where they coursed anteriorly to the bed nucleus of the stria terminalis (BNST), and the anterodorsal (TAD) and anteroventral (TAV) thalamic nuclei. After enucleation, selected areas studied with EM confirmed that retinal presynaptic terminals are located in the BNST and TAV. These results support the finding of Conrad and Stumpf that the retina has a direct link to the limbic system.
Subject(s)
Limbic System/anatomy & histology , Retina/anatomy & histology , Animals , Dominance, Cerebral/physiology , Horseradish Peroxidase , Microscopy, Electron , Nerve Degeneration , Neurons/ultrastructure , Rats , Rats, Inbred Strains , Thalamic Nuclei/anatomy & histology , Visual Pathways/anatomy & histologyABSTRACT
Horseradish peroxidase (HRP) labeled neuronal somas were consistently found in the medial pretectal area after intraocular injection of HRP. The labeled cells represent the source of centrifugal fibers to the rat retina.
Subject(s)
Retina/anatomy & histology , Superior Colliculi/anatomy & histology , Animals , Dominance, Cerebral/physiology , Efferent Pathways/anatomy & histology , Female , Horseradish Peroxidase , Male , Neurons/ultrastructure , RatsSubject(s)
Hyaluronoglucosaminidase/pharmacology , Nerve Regeneration/drug effects , Pancreatic Elastase/pharmacology , Spinal Cord/drug effects , Trypsin/pharmacology , Animals , Cholinergic Fibers/drug effects , Connective Tissue/drug effects , Female , Microscopy, Fluorescence , Rats , Time FactorsSubject(s)
Axonal Transport/drug effects , Horseradish Peroxidase/metabolism , Ornithine/pharmacology , Peroxidases/metabolism , Animals , Geniculate Bodies/enzymology , Optic Nerve/enzymology , Optic Nerve/ultrastructure , Rats , Retina/enzymology , Retina/ultrastructure , Superior Colliculi/enzymology , Supraoptic Nucleus/enzymology , Supraoptic Nucleus/ultrastructure , Synapses/enzymology , Synapses/ultrastructure , Visual Pathways/enzymologyABSTRACT
The fine structure of the principal compound eye of the shrimp, Palaemonetes, was studied under conditions of light and dark adaptation. Ommatidium the situation in other decapod crustaceans. Light and dark adapted eyes differ in that the rhabdom changes its shape; morphological evidence suggests a possible sequence of events involving production, utilization, and degradation of photoreceptor membrane, a discontinuous process occurring only during changes from light to dark and dark to light. A hypothesis of membrane turnover is proposed.