Publications by authors named "Lauw J Klaassen"

Article Synopsis
  • The study focused on how different types of horizontal cells (HCs) in zebrafish retinas connect to photoreceptors, emphasizing the role of gap junctions and connexin (Cx) hemichannels in this process.
  • Researchers characterized various Cx types in Xenopus oocytes, finding differences in their properties that impact HC coupling and feedback signals to cones.
  • Morphological analysis using fluorescent proteins revealed specific Cx promoter activities in HCs, and functional tests showed different response types based on which photoreceptors the HCs connected to, suggesting a mechanism for processing spectral information under different lighting conditions.
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Neuronal computations strongly depend on inhibitory interactions. One such example occurs at the first retinal synapse, where horizontal cells inhibit photoreceptors. This interaction generates the center/surround organization of bipolar cell receptive fields and is crucial for contrast enhancement.

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In the vertebrate retina, cones project to the horizontal cells (HCs) and bipolar cells (BCs). The communication between cones and HCs uses both chemical and ephaptic mechanisms. Cones release glutamate in a Ca(2+)-dependent manner, while HCs feed back to cones via an ephaptic mechanism.

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Zebrafish is becoming an increasingly popular model in the field of visual neuroscience. Although the absorption spectra of its cone photopigments have been described, the cone action spectra were still unknown. In this study we report the action spectra of the four types of zebrafish cone photoreceptors, determined by measuring voltage responses upon light stimulation using whole cell patch clamp recordings.

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Connexins are the building blocks of gap-junctions; sign conserving electrical synapses. Recently it has been shown that connexins can also function as hemichannels and can mediate a sign inverting inhibitory synaptic signal from horizontal cells to cones via an ephaptic mechanism. In this review we will discuss the critical requirements for such an ephaptic interaction and relate these to the available experimental evidence.

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In the vertebrate retina, horizontal cells generate the inhibitory surround of bipolar cells, an essential step in contrast enhancement. For the last decades, the mechanism involved in this inhibitory synaptic pathway has been a major controversy in retinal research. One hypothesis suggests that connexin hemichannels mediate this negative feedback signal; another suggests that feedback is mediated by protons.

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