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The Journal of Physiology Mar 19871. The electrophysiological and pharmacological properties of the excitatory post-synaptic potentials (e.p.s.p.) evoked by electrical stimulation of the optic tract were... (Review)
Review
1. The electrophysiological and pharmacological properties of the excitatory post-synaptic potentials (e.p.s.p.) evoked by electrical stimulation of the optic tract were studied in projection neurones of the ventral and dorsal lateral geniculate nucleus (l.g.n.) of the rat in vitro. 2. No difference was found in the rise time of e.p.s.p.s. recorded in the dorsal and ventral l.g.n. and in their threshold for action potentials. At membrane potentials more negative than -60 mV, e.p.s.p.s. in the dorsal l.g.n. were always followed by a Ca2+-dependent potential. Its amplitude could easily reach threshold for generating an action potential and thus evoke firing from an e.p.s.p. that was subthreshold at resting potential. No Ca2+ potential was observed to follow e.p.s.p.s. recorded in the ventral l.g.n. 3. At resting potential the excitability of dorsal and ventral cells was unaffected following an initial shock to the optic tract. However, in dorsal neurones, at potentials more negative than -60 mV, the presence of Ca2+ potentials evoked by the e.p.s.p.s. resulted in a period of decreased excitability. 4. Using intrasomatic injection of Cs+ the reversal potential (E) of the e.p.s.p. and of the depolarization produced by glutamate could be measured in the same l.g.n. neurone. They were: Eepsp, -0.9 mV; and Eglut, -3.9 mV. 5. gamma-D-glutamylglycine (DGG), an excitatory amino acid antagonist, reversibly inhibited the e.p.s.p. and depolarization produced by quisqualate and glutamate by a competitive action. The concentration of DGG that produced 50% inhibition (IC50) was 2.7 mM. 6. D-2-amino-5-phosphonovalerate (APV), the potent and selective N-methyl-D-aspartate (NMDA) antagonist, had no effect on the e.p.s.p. both in the presence and absence of Mg2+. The isomers of 2-amino-4-phosphonobutyrate (APB) were inactive or had a non-specific action on the e.p.s.p. 7. No difference could be detected in either the reversal potential or the action of the antagonists between neurones of the dorsal and the ventral l.g.n. 8. These results suggest that Ca2+-dependent potentials play an important role in modulating synaptic efficacy in principal neurones of the dorsal l.g.n. The quisqualate/kainate nature of the optic nerve receptors and the similarity of Eepsp and Eglut constitute strong support in favour of a glutamate-like substance as the transmitter of the optic nerve.
Topics: 2-Amino-5-phosphonovalerate; Action Potentials; Aminobutyrates; Animals; Aspartic Acid; Calcium; Dipeptides; Glutamates; Glutamic Acid; In Vitro Techniques; Male; N-Methylaspartate; Neurons; Optic Nerve; Rats; Rats, Inbred Strains; Synapses; Thalamic Nuclei; Valine
PubMed: 2888880
DOI: 10.1113/jphysiol.1987.sp016472 -
NeuroImage. Clinical 2019In patients with retinal ganglion cell diseases, recent diffusion tensor imaging (DTI) studies have revealed structural abnormalities in visual white matter tracts such...
In patients with retinal ganglion cell diseases, recent diffusion tensor imaging (DTI) studies have revealed structural abnormalities in visual white matter tracts such as the optic tract, and optic radiation. However, the microstructural origin of these diffusivity changes is unknown as DTI metrics involve multiple biological factors and do not correlate directly with specific microstructural properties. In contrast, recent quantitative T1 (qT1) mapping methods provide tissue property measurements relatively specific to myelin volume fractions in white matter. This study aims to improve our understanding of microstructural changes in visual white matter tracts following retinal ganglion cell damage in Leber's hereditary optic neuropathy (LHON) patients by combining DTI and qT1 measurements. We collected these measurements from seven LHON patients and twenty age-matched control subjects. For all individuals, we identified the optic tract and the optic radiation using probabilistic tractography, and evaluated diffusivity and qT1 profiles along them. Both diffusivity and qT1 measurements in the optic tract differed significantly between LHON patients and controls. In the optic radiation, these changes were observed in diffusivity but were not evident in qT1 measurements. This suggests that myelin loss may not explain trans-synaptic diffusivity changes in the optic radiation as a consequence of retinal ganglion cell disease.
Topics: Adult; Diffusion Magnetic Resonance Imaging; Diffusion Tensor Imaging; Humans; Male; Optic Atrophy, Hereditary, Leber; Retinal Ganglion Cells; Visual Pathways; White Matter; Young Adult
PubMed: 31026624
DOI: 10.1016/j.nicl.2019.101826 -
Journal of Alzheimer's Disease : JAD 2015Synaptic deficits and neuronal loss are the major pathological manifestations of Alzheimer's disease. However, the link between the early synaptic loss and subsequent...
BACKGROUND
Synaptic deficits and neuronal loss are the major pathological manifestations of Alzheimer's disease. However, the link between the early synaptic loss and subsequent neurodegeneration is not entirely clear. Cell culture studies have shown that amyloid-β (Aβ) applied to axonal terminals can cause retrograde degeneration leading to the neuronal loss, but this process has not been demonstrated in live animals.
OBJECTIVE
To test if Aβ applied to retinal ganglion cell axonal terminals can induce axonal damage in the optic nerve and optic tract in mice.
METHODS
Aβ was injected into the terminal field of the optic tract, in the left lateral geniculate nucleus of wildtype C57BL/6 mice. Following the injection, monthly diffusion tensor imaging was performed. Three months after the injection, mice underwent visual evoked potential recordings, and then sacrificed for immunohistochemical examination.
RESULTS
There were no significant changes seen with diffusion tensor imaging in the optic nerve and optic tract 3 months after the Aβ injection. The myelin and axons in these regions remained intact according to immunohistochemistry. The only significant changes observed in this study were delayed transduction and reduced amplitude of visual evoked potentials, although both Aβ and its reversed form caused similar changes.
CONCLUSION
Despite the published in vitro studies, there was no significant axonal damage in the optic nerve and optic tract after injecting Aβ onto retinal ganglion cell axonal terminals of wildtype C57BL/6 mice.
Topics: Amyloid beta-Peptides; Animals; Axons; Diffusion Tensor Imaging; Evoked Potentials, Visual; Female; Geniculate Bodies; Humans; Immunohistochemistry; Mice, Inbred C57BL; Microelectrodes; Myelin Sheath; Optic Nerve; Optic Tract; Peptide Fragments; Retrograde Degeneration; Visual Cortex; Visual Perception
PubMed: 25697704
DOI: 10.3233/JAD-142154 -
Medicine Oct 2022We report the case of a patient who developed asymptomatic bilateral papillitis after coronavirus disease 2019 (COVID-19) vaccination.
RATIONALE
We report the case of a patient who developed asymptomatic bilateral papillitis after coronavirus disease 2019 (COVID-19) vaccination.
PATIENT CONCERNS
A 61-year-old man presented to our tertiary clinic with bilateral optic disc edema, which was incidentally detected during his visit to a primary ophthalmology clinic. He had received an adenovirus-vectored COVID-19 vaccine 2 weeks before the optic disc edema was detected and had experienced no ocular discomfort, except for a floater in his right eye. Although his visual acuity was normal and he had no color vision deficiencies or marked visual field defects, the optic disc edema worsened over several days. Orbital magnetic resonance imaging showed no optic tract enhancement, and lumbar puncture revealed normal cerebrospinal fluid pressure. The patient tested negative for aquaporin-4 and myelin oligodendrocyte glycoprotein antibodies and Leber hereditary optic neuropathy-associated gene mutations.
DIAGNOSIS
The patient was diagnosed with bilateral papillitis, possibly induced by the COVID-19 vaccination.
INTERVENTIONS
The patient received steroid pulse therapy with methylprednisolone (500 mg/day) for 3 days followed by an oral prednisolone taper for 3 weeks.
OUTCOMES
The patient's papillitis started to subside 3 weeks after he received systemic steroid therapy and completely resolved without any sequelae 2 months later. A year after the diagnosis, the fundus remained stable without disease recurrence or optic disc atrophy.
LESSONS
Healthy individuals receiving COVID-19 vaccines may present with various manifestations of optic neuritis. In the present case, the patient presented with asymptomatic progressive bilateral optic disc edema and had a favorable long-term course after receiving steroid therapy.
Topics: Humans; Male; COVID-19; COVID-19 Vaccines; Methylprednisolone; Papilledema; Vaccination; Middle Aged
PubMed: 36254071
DOI: 10.1097/MD.0000000000031112 -
Neuroscience Letters Jan 2017For humans and non-human primates, the alteration of the visual pathway's white matter fibers after visual deprivation has been partially explored. However, the changes...
For humans and non-human primates, the alteration of the visual pathway's white matter fibers after visual deprivation has been partially explored. However, the changes in the optic tracts after the transection of the optic nerve have not been well characterized. In the current study, we attempted to investigate the differences in optic tracts between normal and unilateral optic nerve transected macaque monkeys using diffusion tensor imaging (DTI). Four healthy neonatal macaque monkeys were randomly divided into 2 groups, with 2 in each group. Group A served as a control group, and Group B underwent unilateral (right eye) optic nerve transection to produce monocular blindness. Sixteen months (Group B and thirty-two months (Group B) after optic nerve transection, diffusion tensor imaging was performed on all monkeys. Then, we compared fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) in bilateral optic tracts between Group A and Group B and between Group B and Group B. In both Group B and Group B, when compared with normal monkeys in Group A, FA was decreased and MD, AD and RD were increased in the bilateral optic tracts of monkeys with monocular blindness. Furthermore, compared with Group B, FA was reduced and MD, AD, RD were more obviously increased in the bilateral optic tracts of Group B, and noticeable differences in MD, AD and RD were found between the left and right optic tracts in group B. We believe that the results of this study would be helpful in investigation of the histological abnormalities of the integrity damage, axonal degeneration and demyelination of optic tracts in macaque monkeys with monocular blindness by DTI parameters in noninvasively and quantitatively.
Topics: Animals; Anisotropy; Blindness; Diffusion Tensor Imaging; Macaca; Optic Nerve Injuries; Optic Tract; Visual Pathways; White Matter
PubMed: 27864005
DOI: 10.1016/j.neulet.2016.11.030 -
Fa Yi Xue Za Zhi Aug 2023To investigate the characteristics and objective assessment method of visual field defects caused by optic chiasm and its posterior visual pathway injury.
OBJECTIVES
To investigate the characteristics and objective assessment method of visual field defects caused by optic chiasm and its posterior visual pathway injury.
METHODS
Typical cases of visual field defects caused by injuries to the optic chiasm, optic tracts, optic radiations, and visual cortex were selected. Visual field examinations, visual evoked potential (VEP) and multifocal visual evolved potential (mfVEP) measurements, craniocerebral CT/MRI, and retinal optical coherence tomography (OCT) were performed, respectively, and the aforementioned visual electrophysiological and neuroimaging indicators were analyzed comprehensively.
RESULTS
The electrophysiological manifestations of visual field defects caused by optic chiasm injuries were bitemporal hemianopsia mfVEP abnormalities. The visual field defects caused by optic tract, optic radiation, and visual cortex injuries were all manifested homonymous hemianopsia mfVEP abnormalities contralateral to the lesion. Mild relative afferent pupil disorder (RAPD) and characteristic optic nerve atrophy were observed in hemianopsia patients with optic tract injuries, but not in patients with optic radiation or visual cortex injuries. Neuroimaging could provide morphological evidence of damages to the optic chiasm and its posterior visual pathway.
CONCLUSIONS
Visual field defects caused by optic chiasm, optic tract, optic radiation, and visual cortex injuries have their respective characteristics. The combined application of mfVEP and static visual field measurements, in combination with neuroimaging, can maximize the assessment of the location and degree of visual pathway damage, providing an effective scheme for the identification of such injuries.
Topics: Humans; Optic Chiasm; Visual Pathways; Visual Fields; Evoked Potentials, Visual; Random Amplified Polymorphic DNA Technique; Hemianopsia; Vision Disorders; Optic Nerve Injuries; Brain Injuries, Traumatic
PubMed: 37859473
DOI: 10.12116/j.issn.1004-5619.2023.230309 -
Developmental Dynamics : An Official... Oct 2014Heparan sulfate proteoglycans (HSPG) are important for embryonic development by means of the regulation of gradient formation and signaling of multiple growth factors...
BACKGROUND
Heparan sulfate proteoglycans (HSPG) are important for embryonic development by means of the regulation of gradient formation and signaling of multiple growth factors and morphogens. Previous studies have shown that Bmp/Shh/Fgf signaling are required for the regionalization of the optic vesicle (OV) and for the closure of the optic fissure (OF), the disturbance of which underlie ocular anomalies such as microphthalmia, coloboma, and optic nerve hypoplasia.
RESULTS
To study HSPG-dependent coordination of these signaling pathways during mammalian visual system development, we have generated a series of OV-specific mutations in the heparan sulfate (HS) N-sulfotransferase genes (Ndst1 and Ndst2) and HS O-sulfotransferase genes (Hs2st, Hs6st1, and Hs6st2) in mice. Of interest, the resulting HS undersulfation still allowed for normal retinal neurogenesis and optic fissure closure, but led to defective optic disc and stalk development. The adult mutant animals further developed optic nerve aplasia/hypoplasia and displayed retinal degeneration. We observed that MAPK/ERK signaling was down-regulated in Ndst mutants, and consistent with this, HS-related optic nerve morphogenesis defects in mutant mice could partially be rescued by constitutive Kras activation.
CONCLUSIONS
These results suggest that HSPGs, depending on their HS sulfation pattern, regulate multiple signaling pathways in optic disc and stalk morphogenesis.
Topics: Amidohydrolases; Animals; Embryo, Mammalian; Heparan Sulfate Proteoglycans; Mice; Mice, Transgenic; Morphogenesis; Optic Disk; Optic Nerve Diseases; Optic Tract; Retinal Degeneration; Signal Transduction; Sulfotransferases
PubMed: 24753163
DOI: 10.1002/dvdy.24142 -
Journal of Glaucoma Feb 2017The purpose of the study was to evaluate neurodegeneration along brain visual pathways in primary open angle glaucoma (POAG) using improved analysis methods of...
PURPOSE OF THE STUDY
The purpose of the study was to evaluate neurodegeneration along brain visual pathways in primary open angle glaucoma (POAG) using improved analysis methods of volumetric and diffusion tensor magnetic resonance imaging (MRI) data.
METHODS
Eleven POAG patients (60.0±9.2 y) with primarily mild to moderate POAG and 11 age-matched controls (55.9±7.5 y) were studied using structural and diffusion tensor MRI. Surface-based segmentation was applied to structural MRI to obtain visual cortical area and volume. Fiber tracking was applied to diffusion tensor data to obtain diffusion parameters along the optic tract and optic radiation. MRI parameters in glaucoma patients were compared with the corresponding left and right visual fields and retinal nerve fiber layer thicknesses, instead of with the left and right eye.
RESULTS
Area and volume of the primary visual cortex were significantly reduced in POAG patients compared with controls (P<0.05) but did not correlate with visual field loss. Fractional anisotropy was reduced at multiple locations along the optic tracts and optic radiations in POAG patients compared with controls. Axial and radial diffusivity along the fiber tracts showed trends but were not significantly different between POAG patients and controls when averaged over the whole structures. Only fractional anisotropy (P<0.05) of the optic radiations was significantly correlated with visual field loss. No MRI parameters were correlated with retinal nerve fiber layer thickness.
CONCLUSIONS
Improved analysis techniques of MRI data improves delineation of degeneration in the brain visual pathways and further supports the notion that neurodegeneration is involved with glaucoma pathogenesis.
Topics: Adult; Aged; Brain; Diffusion Tensor Imaging; Female; Glaucoma, Open-Angle; Humans; Intraocular Pressure; Magnetic Resonance Imaging; Male; Middle Aged; Nerve Fibers; Visual Fields; Visual Pathways
PubMed: 27661989
DOI: 10.1097/IJG.0000000000000558 -
Journal of Neurological Surgery. Part... Feb 2018Endoscopic transsphenoidal extended endoscopic approach (EEA) represents a valid alternative to microsurgery for craniopharyngiomas removal, especially for...
Endoscopic transsphenoidal extended endoscopic approach (EEA) represents a valid alternative to microsurgery for craniopharyngiomas removal, especially for retrochiasmatic lesions without large parasellar extension. The present video illustrates the salient surgical steps of the EEA for craniopahryngioma removal. A 52-year-old man presented with a bitemporal hemianopia and a bilateral decreased visual acuity. MRI showed a Kassam type III cystic craniopharyngioma with a solid component ( Fig. 1 , panels A and B). The head is rotated 10 degrees toward the surgeons. The nasal step is started through the left nostril with a middle turbinectomy. A nasoseptal flap is harvested and positioned in the left choana. The binostril approach allows a large sphenoidotomy to expose the key anatomic landmarks. The craniotomy boundaries are the planum sphenoidale superiorly, the median opticocarotid recesses, the internal carotid artery laterally and the clival recess inferiorly. After dural opening and superior intercavernous sinus coagulation, the tumor is entirely removed ( Fig. 2 , panels A and B). Skull base reconstruction is ensured by fascia lata grafting and nasoseptal flap positioning. Postoperative MRI showed the complete tumor resection ( Fig. 1 , panels C and D). At 3 months postoperatively, the bitemporal hemianopia regressed and the visual acuity improved. A novel left homonymous hemianopia developed secondary to optic tract manipulation. The extended EEA is a valid surgical approach for craniopharyngioma resection. A comprehensive knowledge of the sellar and parasellar anatomy is mandatory for safe tumor removal with decreased morbidity and satisfactory oncologic results. The link to the video can be found at: https://youtu.be/NrCPPnVK2qA .
PubMed: 29404250
DOI: 10.1055/s-0038-1623527 -
Annals of Indian Academy of Neurology 2022
PubMed: 35936637
DOI: 10.4103/aian.aian_937_21