Synaptic Specializations of Melanopsin-Retinal Ganglion Cells in Multiple Brain Regions Revealed by Genetic Label for Light and Electron Microscopy

Abstract

Graphical Abstract Highlights d Membrane-tethered miniSOG for correlated light and electron microscopy in vivo d Melanopsin RGCs show brain region-specific arborization and synaptic structures d A subset of SCN neurons network through dendrodendritic chemical synapses (DDCS) d SCN neurons in DDCS network receive a higher melanopsin RGC input SUMMARYThe form and synaptic fine structure of melanopsinexpressing retinal ganglion cells, also called intrinsically photosensitive retinal ganglion cells (ipRGCs), were determined using a new membrane-targeted version of a genetic probe for correlated light and electron microscopy (CLEM). ipRGCs project to multiple brain regions, and because the method labels the entire neuron, it was possible to analyze nerve terminals in multiple retinorecipient brain regions, including the suprachiasmatic nucleus (SCN), olivary pretectal nucleus (OPN), and subregions of the lateral geniculate. Although ipRGCs provide the only direct retinal input to the OPN and SCN, ipRGC terminal arbors and boutons were found to be remarkably different in each target region. A network of dendro-dendritic chemical synapses (DDCSs) was also revealed in the SCN, with ipRGC axon terminals preferentially synapsing on the DDCS-linked cells.The methods developed to enable this analysis should propel other CLEM studies of long-distance brain circuits at high resolution. AUTHOR CONTRIBUTIONSM.H.E. played a key role in SBEM data collection for the project, and S. Panda played a key role in the biology and data analyses of this project. Quantitative Data Analyses, K

Advances of RRAM Devices: Resistive Switching Mechanisms, Materials and Bionic Synaptic Application

“…Reversely, when the spike occurs on the postsynaptic membrane earlier than that on the presynaptic membrane, the postsynaptic current will be depressed, namely long-term depression. In addition, it is noted that with the change of relative time between two stimulations (commonly pulses), the postsynaptic current will also be influenced [154]. Due to the existence of RS characteristics, the resistance states of RRAM devices can be manipulated by applied voltages and the microscopic conductive paths through the RS medium will be acquired.…”

Current Insights into Optimal Lighting for Promoting Sleep and Circadian Health: Brighter Days and the Importance of Sunlight in the Built Environment

“…[21][22][23][24] The most prominent of the connections is a monosynaptic pathway running along the retinohypothalamic tract to the brain's circadian pacemaker, the suprachiasmatic nucleus (SCN), which enables entrainment to light-dark cycles. [25][26][27][28] NIF processes mediated by pRGCs, including entrainment [29][30][31] but also light suppression of pineal melatonin synthesis [32][33][34][35][36] and light-mediated arousal, [36][37][38] exhibit short-wavelength sensitivity consistent with the action spectrum for melanopsin. Blind humans and animals with mutations causing degeneration of classic photoreceptors retain many NIF functions.…”

“… 21–24 The most prominent of the connections is a monosynaptic pathway running along the retinohypothalamic tract to the brain’s circadian pacemaker, the suprachiasmatic nucleus (SCN), which enables entrainment to light-dark cycles. 25–28 …”

Nighttime Light Hurts Mammalian Physiology: What Diurnal Rodent Models Are Telling Us

“…These intrinsically photosensitive retinal ganglion cells (ipRGCs) have a maximum sensitivity to blue short-wavelength light (480 nm), and play a fundamental role for non-image-forming visual functions [ 20 ]. In rodents (mice), five subtypes (M1-5) of ipRGCs have been characterized [ 21 ]. Interestingly, in a recent study, the function of human ipRGCs was evaluated and at least three subtypes of ipRGCs were revealed according to their electrical activity responses to light; these responses are similar between rodents and humans [ 22 ].…”