ABSTRACT
Differing from other subtypes of inhibitory interneuron, chandelier or axo-axonic cells form depolarizing GABAergic synapses exclusively onto the axon initial segment (AIS) of targeted pyramidal cells (PCs). However, the debate whether these AIS-GABAergic inputs produce excitation or inhibition in neuronal processing is not resolved. Using realistic NEURON modeling and electrophysiological recording of cortical layer-5 PCs, we quantitatively demonstrate that the onset-timing of AIS-GABAergic input, relative to dendritic excitatory glutamatergic inputs, determines its bi-directional regulation of the efficacy of synaptic integration and spike generation in a PC. More specifically, AIS-GABAergic inputs promote the boosting effect of voltage-activated Na+ channels on summed synaptic excitation when they precede glutamatergic inputs by >15 ms, while for nearly concurrent excitatory inputs, they primarily produce a shunting inhibition at the AIS. Thus, our findings offer an integrative mechanism by which AIS-targeting interneurons exert sophisticated regulation of the input-output function in targeted PCs.
Subject(s)
Axon Initial Segment , Axons/physiology , Neurons , Synapses/physiology , Pyramidal Cells/physiology , Interneurons/physiology , Action Potentials/physiologyABSTRACT
The axon initial segment (AIS) is a highly specialized axonal compartment where the action potential is initiated. The heterogeneity of AISs has been suggested to occur between interneurons and pyramidal neurons (PyNs), which likely contributes to their unique spiking properties. However, whether the various characteristics of AISs can be linked to specific PyN subtypes remains unknown. Here, we report that in the prelimbic cortex (PL) of the mouse, two types of PyNs with axon projections either to the contralateral PL or to the ipsilateral basal lateral amygdala, possess distinct AIS properties reflected by morphology, ion channel expression, action potential initiation, and axo-axonic synaptic inputs from chandelier cells. Furthermore, projection-specific AIS diversity is more prominent in the superficial layer than in the deep layer. Thus, our study reveals the cortical layer- and axon projection-specific heterogeneity of PyN AISs, which may endow the spiking of various PyN types with exquisite modulation.
Subject(s)
Mice , Animals , Axon Initial Segment , Synapses/physiology , Pyramidal Cells/physiology , Cerebral Cortex , Axons/physiologyABSTRACT
Intraocular foreign bodies (IOFBs) present in varied manners which in turn necessitate their removal in majority of the cases. A stone foreign body can remain inert inside the eye for years. Retinal detachment in eyes following penetrating trauma with an IOFB is common, but a combination of fresh rhegmatogenous retinal detachment in an eye with a longstanding inert stone foreign body is extremely rare. We report a case of a 50-year-old male with rhegmatogenous retinal detachment with a longstanding stone foreign body, where we managed such a scenario with a chandelier-assisted, sutureless, scleral buckle without removing the stone foreign body.
ABSTRACT
Direct perfluorocarbon liquid (PFCL)-silicone oil exchange presents its own set of challenges in the micro incision vitreous surgery era. We propose a simple bimanual technique to circumvent this problem. Thirteen eyes of patients with retinal detachment associated with giant retinal tears underwent vitrectomy followed by self-retaining endo illuminator (Chandelier) assisted direct PFCL-silicone exchange. No intra or postoperative complications related to the surgical technique were noted. All patients had attached retinas and satisfactory visual recovery at 6 months. Direct bimanual PFCL silicone oil exchange using a Chandelier seems to be a safe and effective technique.
ABSTRACT
Purpose: To describe chandelier-assisted retroillumination for phacoemulsification in patients with poor fundal glow due to posterior segment pathology during combined phacovitrectomy procedure. Methods: This was a prospective observational study. Thirty eyes underwent combined phacoemulsification and 25G sutureless pars plana vitrectomy. Sclerotomy port for chandelier tip was made in the inferotemporal or superonasal quadrant based on the incision site for phacoemulsification. Later, it was replaced with infusion cannula or endoilluminator. Cases included had posterior segment pathologies such as vitreous hemorrhage and vitritis. Results: Red reflex was markedly enhanced during phacoemulsification for all cases. In all eyes, a continuous curvilinear capsulorhexis was achieved without the use of dye. The posterior capsule remained intact in all cases. The visual acuity in all patients improved, and the median best-corrected visual acuity was 20/60 (range: 4/60�/30) at 6 months. There were no intraoperative or postoperative complications. Conclusion: Cases with poor red reflex pose a challenge for anterior segment surgeons, and chandelier-assisted retroillumination proves to be a safe and effective tool in combined phacovitrectomy surgeries. Moreover, no additional cannula port is required for this chandelier insertion.
ABSTRACT
Fine-needle aspiration biopsy (FNAB) of intraocular mass lesions is an important intervention in the presence of diagnostic difficulty. FNAB of intraocular mass lesions is also likely to become more commonly recommended for prognostication of tumors such as choroidal melanoma. The most commonly described approach for tumor localization and visualization during FNAB is transillumination and indirect ophthalmoscopic viewing. Herein, we report endoillumination (chandelier) and wide-angle viewing assisted, microscope-based approach for FNAB in two patients using two port minimally invasive vitreoretinal surgical approach. The submission is supported by a video demonstration. The entire procedure was completed under the microscope. Adequate sample was obtained. In the first patient, the inflammatory nature of the lesion was confirmed though magnetic resonance imaging had been reported as melanoma. In the second patient, a clinical diagnosis of amelanotic melanoma was confirmed. Endoillumination-assisted FNAB of intraocular mass lesions is easier to learn and more precise and hence carries lesser risks.
ABSTRACT
@#AIM: To evaluate advantages of chandelier illumination system during scleral buckling(SB)procedures for rhegmatogenous retinal detachment(RRD)surgery. <p>METHODS: In this comparative, retrospective study, data of 72 eyes of 72 patients undergoing SB for RRD at Minerva Hospital(Santa Maria Capua Vetere, Italy), divided in 2 groups of 36 eyes each were collected. In one group(group A)eyes underwent SB with chandelier, in the other one(group B)eyes underwent SB without using chandelier illumination system. Every eye of both groups was checked before surgery and at 1, 3, 7, 14, 30, 90 and 180d follow up. Parameters such as additional procedures, best spectacles visual acuity(BSVA)(measured with Snellen Lines as decimal fraction), surgical time and retinal breaks recurrences had been analyzed before and after surgery and statistical comparison have been run between two groups.<p>RESULTS: A significant(<i>P</i><0.01)improvement in BSVA was observed at 6mo follow up in both groups; comparing groups A and B, no significant clinical differences was found in recurrences rate whereas mean surgical time in group A was statistically lower than the group B ones. <p>CONCLUSION: According to results observed, even if they need to be confirmed in further studies with larger population, chandelier illumination system could be considered a valuable tool for SB surgery in eyes affected by RRD.
ABSTRACT
PURPOSE: To report the outcome of scleral buckling using a non-contact wide-angle viewing system with a 25-gauge chandelier endoilluminator. METHODS: Retrospective analyses of medical records were performed for 17 eyes of 16 patients with primary rhegmatogenous retinal detachment (RRD) without proliferative vitreoretinopathy who had undergone conventional scleral buckling with cryoretinopexy using the combination of a non-contact wide-angle viewing system and chandelier endoillumination. RESULTS: The patients were eight males and five females with a mean age of 26.8 ± 10.2 (range, 11 to 47) years. The mean follow-up period was 7.3 ± 3.1 months. Baseline best-corrected visual acuity was 0.23 ± 0.28 logarithm of the minimum angle of resolution units. Best-corrected visual acuity at the final visit showed improvement (0.20 ± 0.25 logarithm of the minimum angle of resolution units), but the improvement was not statistically significant (p = 0.722). As a surgery-related complication, there was vitreous loss at the end of surgery in one eye. As a postoperative complication, increased intraocular pressure (four cases) and herpes simplex epithelial keratitis (one case) were controlled postoperatively with eye drops. One case of persistent RRD after primary surgery needed additional vitrectomy, and the retina was postoperatively attached. CONCLUSIONS: Scleral buckling with chandelier illumination as a surgical technique for RRD has the advantages of relieving the surgeon's neck pain from prolonged use of the indirect ophthalmoscope and sharing the surgical procedure with another surgical team member. In addition, fine retinal breaks that are hard to identify using an indirect ophthalmoscope can be easily found under the microscope by direct endoillumination.