Quantitative immunogold evidence that glutamate is a neurotransmitter in afferent synaptic terminals within the isthmo-optic nucleus of the pigeon centrifugal visual system (original) (raw)
Visual Neuroscience, 1995
The present study examined GABA immunoreactivity within the retinopetal nucleus isthmo-opticus (NIO) of the pigeon centrifugal visual system (CVS) using light- (immunohistofluorescence, peroxidase anti-peroxidase: PAP) and electron- (postembedding GABA immunogold) microscopic techniques. In some double-labeling experiments, the retrograde transport of the fluorescent dye rhodamine β−isothiocyanate (RITC) after its intraocular injection was combined with GABA immunohistofluorescence. GABA-immunoreactive (-ir) somata were demonstrated within the neuropilar zone of the NIO adjacent to the centrifugal cell laminae whereas the centrifugal neurons were always immunonegative. A quantitative ultrastructural analysis was performed which distinguished five categories of axon terminal profiles (P1–5) on the basis of various cytological criteria: type of synaptic contact (symmetrical or asymmetrical); shape, size, and density of synaptic vesicles as well as the immunolabeling (positive or negat...
The Journal of Comparative Neurology, 2008
The ultrastructure of the lateroventral subcomponent of the visual dorsolateral anterior thalamic nucleus of the pigeon (DLLv) was analyzed using hodological techniques and GABA-immunocytochemistry. Two types of GABA-immunonegative hyperpalliopetal neurons and a single type of strongly GABA-immunoreactive (-ir) interneuron were identified, the latter displaying long dendrites with some containing synaptic vesicles (DCSV). Ten types of axon terminal were identified and divided into two categories. The first, GABAimmunonegative and making asymmetrical synaptic contact, contain round (RT1, RT2, RT3) or pleiomorphic synaptic and many dense-core vesicles (DCT). RT1 terminals are retinothalamic and RT2 terminals hyperpalliothalamic; both mainly contact dendrites of projection neurons (72% and 78% respectively), less frequently dendrites of interneurons and sometimes DCSV; RT1 terminals are rarely involved in synaptic triads. The second category are consistently GABA-immunopositive. Four types (PT1-4), distinguished by their pleiomorphic synaptic vesicles, make symmetrical synaptic contact essentially with dendrites of projection neurons, more rarely on dendrites of interneurons (PT2). PT1 terminals are very probably those of interneurons, whereas the rare PT4 terminals are of retinal origin. A fifth type (RgT) contains round synaptic vesicles and makes asymmetrical synaptic contact with dendrites of projection neurons and interneurons. PT2 and RgT terminals occasionally contact DCSV of interneurons, which are sometimes involved in synaptic triads. Two final subcategories (DCgT1-2) contain many dense-core vesicles. Our findings are compared with those of previous studies concerning the fine structure and neurochemical properties of the GLd of reptiles and mammals, with special reference to the origin of the extraretinal and extracortical projections to this structure.
Journal of Comparative Neurology, 2014
The nucleus geniculatus lateralis pars ventralis (GLv) is a prominent retinal target in all amniotes. In birds, it is in receipt of a dense and topographically organized retinal projection. The GLv is also the target of substantial and topographically organized projections from the optic tectum and the visual wulst (hyperpallium). Tectal and retinal afferents terminate homotopically within the external GLvneuropil. Efferents from the GLv follow a descending course through the tegmentum and can be traced into the medial pontine nucleus. At present, the cells of origin of the Tecto-GLv projection are only partially described. Here we characterized the laminar location, morphology, projection pattern, and neurochemical identity of these cells by means of neural tracer injections and intracellular fillings in slice preparations and extracellular tracer injections in vivo. The Tecto-GLv projection arises from a distinct subset of layer 10 bipolar neurons, whose apical dendrites show a complex transverse arborization at the level of layer 7. Axons of these bipolar cells arise from the apical dendrites and follow a course through the optic tract to finally form very fine and restricted terminal endings inside the GLv-neuropil. Double-label experiments showed that these bipolar cells were choline acetyltransferase (ChAT)immunoreactive. Our results strongly suggest that Tecto-GLv neurons form a pathway by which integrated tectal activity rapidly feeds back to the GLv and exerts a focal cholinergic modulation of incoming retinal inputs.
Journal of Chemical Neuroanatomy, 1998
The aim of the present study was to analyze the neurochemical properties of the centrifugal visual system (CVS) of the quail using an immunohistochemical approach by testing 16 neuropeptides (angiotensin: ANG, bradykinin: BK, cholecystokinin, dynorphin, L and M-enkephalin, i-endorphin: i-END, galanin, h-neoendorphin, neurokinin A, neuropeptide Y (NPY), ocytocin, somatostatin, substance P, vasopressin, vasoactive intestinal polypeptide) and three neurotransmitters or their synthetic enzymes (choline acetyltransferase: ChAT, tyrosine hydroxylase: TH, serotonin: 5-HT and nitric oxide synthase: NOS, including the histochemical nicotinamide adenine dinucleotide phosphate diaphorase technique). For each substance, the somatic and afferent fiber and terminal labeling was analyzed within the nucleus isthmo-opticus (NIO) and the ectopic area (EA) and compared with that of retinopetal cell bodies labeled retrogradely with RITC following its intraocular injection (double-labeling procedure). The results showed that none of the centrifugal neurons were reactive to any of the substances tested. In contrast, all with the exception of ANG, BK and i-END, labeled fibers and terminals within the EA and only four (ChAT, 5-HT, NPY and NOS) within the NIO. Possible sources of these immunoreactive fibers terminating in the NIO and EA were investigated by mapping the somatic immunolabeling of the different substances within brainstem regions previously shown by Miceli and other authors to project upon the centrifugal neurons. The data suggests that, besides the rapid retino-tecto-NIO-retinal loop, which facilitates the transfer of meaningful or more relevant information within particular portions of the visual field, the multiple afferent input which stems from various brainstem regions utilizes a wide range of neuroactive substances. Some of these afferent projections upon the centrifugal neurons appear to belong to nonspecific systems which might play a role in modulating the Abbre6iations: AL, ansa lenticularis; AVT, area ventralis of TSAI; Cb, cerebellum; Ce, externel laminae of the nucleus isthmo-opticus; Ci, internel laminae of the nucleus isthmo-opticus; Cp, commissura posterior; EA, ectopic area; EC, centrifugal ectopic neurons; EW, nucleus of Edinger-Westphal; FLM, fasciculus longitudinalis medialis; FRL, formatio reticularis lateralis mesencephali; FRM, formatio reticularis lateralis mesencephali; ICo, nucleus intercollicularis; Imc, nucleus isthmi magnocellularis; Ipc, nucleus isthmi parvocellularis; L7, 9 -10, layers 7, 9 -10 of the optic tectum; LC, nucleus linearis caudalis; Li, lingula; LoC, nucleus ceruleus; MLd, nucleus mesencephalicus pars dorsalis; N, neuropilar zone of the nucleus isthmo-opticus; N III, nervus oculomotorius; N IV, nucleus nervis trochlearis; NV, nervus trigeminus; N VII, nucleus nervi facialis; N VIII, nervus octatus; N IX, nucleus nervi glossopharyngei; nBOR, nucleus of the basal optic root; NIO, nucleus isthmo- 00034-9 M. Médina et al. / Journal of Chemical Neuroanatomy 72 (1998) 75-95 76 excitability of centrifugal neurons as a function of arousal.
The Journal of Comparative Neurology, 2006
The cholinergic division of the avian nucleus isthmi, the homolog of the mammalian nucleus parabigeminalis, is composed of the pars parvocellularis (Ipc) and pars semilunaris (SLu). Ipc and SLu were studied with in vivo and in vitro tracing and intracellular filling methods. 1) Both nuclei have reciprocal homotopic connections with the ipsilateral optic tectum. The SLu connection is more diffuse than that of Ipc. 2) Tectal inputs to Ipc and SLu are Brn3a-immunoreactive neurons in the inner sublayer of layer 10. Tectal neurons projecting on Ipc possess "shepherd's crook" axons and radial dendritic fields in layers 2-13. 3) Neurons in the mid-portion of Ipc possess a columnar spiny dendritic field. SLu neurons have a large, nonoriented spiny dendritic field. 4) Ipc terminals form a cylindrical brush-like arborization (35-50 m wide) in layers 2-10, with extremely dense boutons in layers 3-6, and a diffuse arborization in layers 11-13. SLu neurons terminate in a wider column (120 -180 m wide) lacking the dust-like boutonal features of Ipc and extend in layers 4c-13 with dense arborizations in layers 4c, 6, and 9 -13. 5) Ipc and SLu contain specialized fast potassium ion channels. We propose that dense arborizations of Ipc axons may be directed to the distal dendritic bottlebrushes of motion detecting tectal ganglion cells (TGCs). They may provide synchronous activation of a group of adjacent bottlebrushes of different TGCs of the same type via their intralaminar processes, and cross channel activation of different types of TGCs within the same column of visual space.
Retinal afferents to the tectum opticum and the nucleus opticus principalis thalami in the pigeon
Journal of Comparative Neurology, 1991
The retinal afferents of the tectum opticum and the n. opticus principalis thalami (OPT) were studied with fluorescent tracers in pigeons. Injections into the tectum opticum revealed topographically related areas of high density labelling in the contralateral retina. In these areas up to 15,000 cells/mm2 were labelled. After tectal injections the soma sizes of labelled retinal ganglion cells in the area centralis ranged from 5 to 23 μm with a mean of 7.5 μm. Afferents from the ipsilateral retina could not be demonstrated. Injections into the OPT labelled neurons throughout the retina without a clear topographical relation to the locus of injection. The density never exceeded 150 cells per mm2. The soma size range was 8 to 35 μm with a mean of 14.6 μm. Independently of the injection area within the OPT, the red field in the dorsotemporal retina was always extremely sparsely labelled. The number of labelled ganglion cells in this area never exceeded 25 neurons/mm2. After OPT injection...
Visual neuroscience, 1996
The isthmo-optic nucleus (ION) is the main source of efferents to the retina in birds. Isthmo-optic neurons project in topographical order on amacrine cells in the ventral parts of the retina, and a subclass of these known as proprioretinal neurons project onto the dorsal retina. We propose that, through the intermediary of the amacrine target cells, activity in the isthmo-optic pathway excites ganglion cells locally in the ventral retina but inhibits those in dorsal regions. This circuit would thereby mediate centrifugally controlled switches in attention between the dorsal retina, involved in feeding, and the more ventral parts, involved in scanning for predators. This hypothesis accounts for a wide range of disparate data from behavior, comparative anatomy, endocrinology, hodology, and neurophysiology.
Journal of Neurochemistry, 1976
The distribution of choline acetyltransferase (ChAT) and glutamate decarboxylase (GAD) in different layers of the pigeon optic tectum and in some nuclei of the optic lobe have been investigated. About 40y, of GAD and 2 % : , of ChAT were found in the superficial part of tectum. but negligible activity was found in the stratum opticum. The highest GAD activity was found in layers 3-7 (according to the nomenclature of CAJAL, 1911) with a peak in layer 4. ChAT activity peaked in layers 3. 5. 8 and l O / l l. Its distribution correlated well with the staining pattern of AChE, particularly in the superficial part of the tectum. The distribution of ChAT and GAD did not change significantly 4 weeks after enucleation. ChAT and GAD activities were high in the nucleus isthmi, pars parvocellularis (Ipc). The activity of GAD was also high in the nucleus intercollicularis (KO), the other nuclei showed less activity of both enzymes. THE PIGEON optic tectum is a highly laminated and anatomically well described structure (for review see: REPERANT, 1973) and therefore an attractive model for the study of topographical distributions of neurotransmitters. Recent electrophysiological (BARTH & FELIX, 1974; FErrx rr al., 1975) and biochemical (HENKE rt al., 1976) studies have suggested a number of putative neurotransmitters in the tectum. Among these are ACh and GABA, both reasonably well established neurotransmitters in the CNS of vertebrata (HOSKIN, 1972; FONNUM, 19750). The enzymes ChAT (acetyl CoA-choline 0-acetyl transferase, EC 2.3.1.6) and G A D (L-glutamate I-carboxylyase, EC 4.1.1.15) which govern the levels of ACh and GABA in brain are excellent markers for cholinergic and GABA-ergic structures respectively. The enzymes are better measuring parameters than the transmitters per sr which may redistribute during the preparation of the tissue or be metabolised post mortem (BAXTER. 1970; SILVER. 1974; FONNUM, 1973; FONNUM. 1975~). Furthermore, several groups of investigators have shown that there is a good correlation between GABA level and G A D activity in the nervous system of vertebrata (KURIYAMA rt a/., 1968; KURIYAMA et a/.. 1966; BAXTER. 1970). We have studied the topographical and subcellular distribution of ChAT and G A D in the optic tectum and in some of the nuclei of the optic lobe in an attempt to describe the localization of cholinergic and GABA-ergic structures in this region. The topogra-'Present address: Brain Research Institute, August Forel Ahhrcriations used: ChAT. choline acetyltransferase; Strasse I. 8029 Zurich. Switzerland. GAD. glutamate decarboxylase phical distribution of ChAT activity has been compared with the distribution of AChE visualized with histochemical techniques. MATERIALS AND METHODS Nomenclarurr. The tectal layers are named according to CAJAL (1911). For the tectal nuclei the nomenclature of KARTEN & Horns (1967) was used. Auimuls. Sixteen pigeons (Columha liuia