Kainic acid (KA) is a potent agonist at non-N-methyl-D-aspartate (non-NMDA) ionotropic glutamate receptors and commonly used to induce seizures and excitotoxicity in animal models of human temporal lobe epilepsy. Among other factors, Ca 2.3 voltage-gated calcium channels have been implicated in the pathogenesis of KA-induced seizures. At physiologically relevant concentrations, endogenous trace metal ions (Cu , Zn ) occupy an allosteric binding site on the domain I gating module of these channels and interfere with voltage-dependent gating. Using whole-cell patch-clamp recordings in human embryonic kidney (HEK-293) cells stably transfected with human Ca 2.3d and β -subunits, we identified a novel, glutamate receptor-independent mechanism by which KA can potently sensitize these channels. Our findings demonstrate that KA releases these channels from the tonic inhibition exerted by low nanomolar concentrations of Cu and produces a hyperpolarizing shift in channel voltage-dependence by about 10 mV, thereby reconciling the effects of Cu chelation with tricine. When tricine was used as a surrogate to study the receptor-independent action of KA in electroretinographic recordings from the isolated bovine retina, it selectively suppressed a late b-wave component, which we have previously shown to be enhanced by genetic or pharmacological ablation of Ca 2.3 channels. Although the pathophysiological relevance remains to be firmly established, we speculate that reversal of Cu -induced allosteric suppression, presumably via formation of stable kainate-Cu complexes, could contribute to the receptor-mediated excitatory effects of KA. In addition, we discuss experimental implications for the use of KA in vitro, with particular emphasis on the seemingly high incidence of trace metal contamination in common physiological solutions.

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BackgroundImpairment of neurovascular coupling (NVC) was recently reported in the context of subarachnoid hemorrhage and may correlate with disease severity and outcome. However, previous techniques to evaluate NVC required invasive procedures. Retinal vessels may represent an alternative option for non-invasive assessment of NVC.MethodsA prototype of an adapted retinal vessel analyzer was used to assess retinal vessel diameter in mice. Dynamic vessel analysis (DVA) included an application of monochromatic flicker light impulses in predefined frequencies for evaluating NVC. All retinae were harvested after DVA and electroretinograms were performed.ResultsA total of 104 retinal scans were conducted in 21 male mice (90 scans). Quantitative arterial recordings were feasible only in a minority of animals, showing an emphasized reaction to flicker light impulses (8 mice; 14 scans). A characteristic venous response to flicker light, however, could observed in the majority of animals. Repeated measurements resulted in a significant decrease of baseline venous diameter (7 mice; 7 scans, p < 0.05). Ex-vivo electroretinograms, performed after in-vivo DVA, demonstrated a significant reduction of transretinal signaling in animals with repeated DVA (n = 6, p < 0.001).ConclusionsTo the best of our knowledge, this is the first non-invasive study assessing murine retinal vessel response to flicker light with characteristic changes in NVC. The imaging system can be used for basic research and enables the investigation of retinal vessel dimension and function in control mice and genetically modified animals.

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Ex vivo neuronal recording in the murine retina is able to detect transient impairment of transretinal signaling by UCB in WT, but not in KO. This new model may be useful to further clarify the role of calcium channels in neuronal signal alteration in the presence of BHMDPs.

Objective: Metabolic demand increases with neuronal activity and adequate energy supply is ensured by neurovascular coupling (NVC). Impairments of NVC have been reported in the context of several diseases and may correlate with disease severity and outcome. Voltage-gated Ca2+-channels (VGCCs) are involved in the regulation of vasomotor tone. In the present study, we compared arterial and venous responses to flicker stimulation in Cav2.3-competent (Cav2.3[+/+]) and -deficient (Cav2.3[−/−]) mice using retinal vessel analysis.Methods: The mice were anesthetized and the pupil of one eye was dilated by application of a mydriaticum. An adapted prototype of retinal vessel analyzer was used to perform dynamic retinal vessel analysis. Arterial and venous responses were quantified in terms of the area under the curve (AUCart/AUCven) during flicker application, mean maximum dilation (mMDart/mMDven) and time to maximum dilation (tMDart/tMDven) during the flicker, dilation at flicker cessation (DFCart/DFCven), mean maximum constriction (mMCart/mMCven), time to maximum constriction (tMCart/tMCven) after the flicker and reactive magnitude (RMart/RMven).Results: A total of 33 retinal scans were conducted in 22 Cav2.3[+/+] and 11 Cav2.3[−/−] mice. Cav2.3[−/−] mice were characterized by attenuated and partially reversed arterial and venous responses, as reflected in significantly lower AUCart (p = 0.031) and AUCven (p = 0.047), a trend toward reduced DFCart (p = 0.100), DFCven (p = 0.100), mMDven (p = 0.075), and RMart (p = 0.090) and a trend toward increased tMDart (p = 0.096).Conclusion: To our knowledge, this is the first study using a novel, non-invasive analysis technique to document impairment of retinal vessel responses in VGCC-deficient mice. We propose that Cav2.3 channels could be involved in NVC and may contribute to the impairment of vasomotor responses under pathophysiological conditions.

Purpose The aim of the present study was to evaluate changes of best corrected visual acuity (BCVA), retinal nerve fiber layer thickness (RNFL), total macular volume (TMV), intraocular pressure (IOP) and central retinal thickness (CRT) after intravitreal injection of ranibizumab, bevacizumab and aflibercept in patients with neovascular age-related macular degeneration (nAMD) in a clinical real world setting. Methods In a retrospective clinical study design, 120 patients (80 women and 40 men) were analyzed after being diagnosed with nAMD within 8 years (2010–2018). Every patient received at least 6 anti-VEGF injections in a Pro-Re-Nata or Treat-and-Extend regimen. OCT parameters (RNFL, TMV, CRT) and visual acuity (BCVA) were assessed at first diagnosis, at treatment day and during the course. Results Intraretinal fluid was reduced significantly in a magnitude of 88–64 µm (CRT) and 0.75–0.55 mm3 (TMV). Apart from a significant reduction immediately after the therapy start (post-3 injections) with ranibizumab (− 1.4 µm, p = 0.03), RNFL thickness remained constant. A slight improvement in visual acuity of 0.06 logMAR could initially be observed. If further injections were required, only stabilization was achieved compared to baseline visual acuity. Conclusion The changes of OCT parameters CRT, TMV, and RNFL as well as the stabilization of functional results (BCVA) as illustrated in this study comparing effects of different anti-VEGF-agents provide evidence for the transferability of former results to a clinical real-world setting.

Purpose The aim of the underlying study was to present a new surgical method in PreserFlo MicroShunt surgery for glaucoma. A removable polyamide suture was placed into the lumen of the MicroShunt during implantation to prevent early postoperative hypotony. Methods Thirty-one patients undergoing stand-alone glaucoma surgery with implantation of a PreserFlo MicroShunt and an intraluminal occlusion were retrospectively reviewed and compared to a control group without occlusion. Inclusion criteria were diagnosis of primary open-angle glaucoma or secondary open-angle glaucoma due to pseudoexfoliation or pigment dispersion. Patients with a history of filtrating glaucoma surgery were excluded. Results IOP decreased from 26.9 ± 6.6 to 18.0 ± 9.5 mmHg at the first postoperative day after PreserFlo MicroShunt implantation. Postoperative removal of the occluding suture resulted in a mean IOP reduction in 11.1 ± 7.6 mmHg. Mean visual acuity was 0.43 ± 0.24 logMAR during the first postoperative examination. The interval with the occluding intraluminal suture in place varied from days to 2–3 weeks. Patients were followed up to 1 year. Conclusion Implantation of a PreserFlo MicroShunt combined with an intraluminal suture prevented postoperative hypotony in all patients. Mean postoperative pressure was reduced despite the occluding suture in place.