Moore-Dotson, J. M., Beckman, J. J., Mazade, R. E., Hoon, M., Bernstein, A. S., Romero-Aleshire, M. J., Brooks, H. L., & Eggers, E. D. (2016). Early Retinal Neuronal Dysfunction in Diabetic Mice: Reduced Light-Evoked Inhibition Increases Rod Pathway Signaling. Investigative ophthalmology & visual science, 57(3), 1418-30.
BIO5 Collaborators
Heddwen L Brooks, Erika D Eggers
Recent studies suggest that the neural retinal response to light is compromised in diabetes. Electroretinogram studies suggest that the dim light retinal rod pathway is especially susceptible to diabetic damage. The purpose of this study was to determine whether diabetes alters rod pathway signaling.
Eggers, E. D., & Lukasiewicz, P. D. (2011). Multiple pathways of inhibition shape bipolar cell responses in the retina. Visual neuroscience, 28(1), 95-108.
Bipolar cells (BCs) are critical relay neurons in the retina that are organized into parallel signaling pathways. The three main signaling pathways in the mammalian retina are the rod, ON cone, and OFF cone BCs. Rod BCs mediate incrementing dim light signals from rods, and ON cone and OFF cone BCs mediate incrementing and decrementing brighter light signals from cones, respectively. The outputs of BCs are shaped by inhibitory inputs from GABAergic and glycinergic amacrine cells in the inner plexiform layer, mediated by three distinct types of inhibitory receptors: GABA(A), GABA(C), and glycine receptors. The three main BC pathways receive distinct forms of inhibition from these three receptors that shape their light-evoked inhibitory signals. Rod BC inhibition is dominated by slow GABA(C) receptor inhibition, while OFF cone BCs are dominated by glycinergic inhibition. The inhibitory inputs to BCs are also shaped by serial inhibitory connections between GABAergic amacrine cells that limit the spatial profile of BC inhibition. We discuss our recent studies on how inhibitory inputs to BCs are shaped by receptor expression, receptor properties, and neurotransmitter release properties and how these affect the output of BCs.
Sebe, J. Y., Eggers, E. D., & Berger, A. J. (2003). Differential effects of ethanol on GABA(A) and glycine receptor-mediated synaptic currents in brain stem motoneurons. Journal of neurophysiology, 90(2), 870-5.
Ethanol potentiates glycinergic synaptic transmission to hypoglossal motoneurons (HMs). This effect on glycinergic transmission changes with postnatal development in that juvenile HMs (P9-13) are more sensitive to ethanol than neonate HMs (P1-3). We have now extended our previous study to investigate ethanol modulation of synaptic GABA(A) receptors (GABA(A)Rs), because both GABA and glycine mediate inhibitory synaptic transmission to brain stem motoneurons. We tested the effects of ethanol on GABAergic and glycinergic miniature inhibitory postsynaptic currents (mIPSCs) recorded from neonate and juvenile rat HMs in an in vitro slice preparation. Bath application of 30 mM ethanol had no significant effect on the GABAergic mIPSC amplitude or frequency recorded at either age. At 100 mM, ethanol significantly decreased the GABAergic mIPSC amplitude recorded from neonate (6 +/- 3%, P 0.05) and juvenile (16 +/- 3%, P 0.01) HMs. The same concentration of ethanol increased the GABAergic mIPSC frequency recorded from neonate (64 +/- 17%, P 0.05) and juvenile (40 +/- 15%, n.s.) HMs. In contrast, 100 mM ethanol robustly potentiated glycinergic mIPSC amplitude in neonate (31 +/- 3%, P 0.0001) and juvenile (41 +/- 7%, P 0.001) HMs. These results suggest that glycine receptors are more sensitive to modulation by ethanol than GABA(A) receptors and that 100 mM ethanol has the opposite effect on GABA(A)R-mediated currents in juvenile HMs, that is, inhibition rather than enhancement. Further, comparing ethanol's effects on GABAergic mIPSC amplitude and frequency, ethanol modulates GABAergic synaptic transmission to HMs differentially. Presynaptically, ethanol enhances mIPSC frequency while postsynaptically it decreases mIPSC amplitude.
Eggers, E. D., & Berger, A. J. (2004). Mechanisms for the Modulation of Native Glycine Receptor Channels by Ethanol. Journal of Neurophysiology.
Eggers, E. D., & Lukasiewicz, P. D. (2006). GABAA, GABAC and glycine receptor-mediated inhibition differentially affects light-evoked signaling from mouse retinal rod bipolar cells. Journal of Physiology.
