Morphology and function of three VIP-expressing amacrine cell types in the mouse retina

Abstract

Amacrine cells (ACs) are the most diverse class of neurons in the retina. The variety of signals provided by ACs allows the retina to encode a wide range of visual features. Of the 30-50 AC types in mammalian species, few have been studied in detail. Here, we combine genetic and viral strategies to identify and to characterize morphologically three vasoactive intestinal polypeptide-expressing GABAergic AC types (VIP1-, VIP2-, and VIP3-ACs) in mice. Somata of VIP1- and VIP2-ACs reside in the inner nuclear layer and somata of VIP3-ACs in the ganglion cell layer, and they show asymmetric distributions along the dorsoventral axis of the retina. Neurite arbors of VIP-ACs differ in size (VIP1-ACs ≈ VIP3-ACs > VIP2-ACs) and stratify in distinct sublaminae of the inner plexiform layer. To analyze light responses and underlying synaptic inputs, we target VIP-ACs under 2-photon guidance for patch-clamp recordings. VIP1-ACs depolarize strongly to light increments (ON) over a wide range of stimulus sizes but show size-selective responses to light decrements (OFF), depolarizing to small and hyperpolarizing to large stimuli. The switch in polarity of OFF responses is caused by pre- and postsynaptic surround inhibition. VIP2- and VIP3-ACs both show small depolarizations to ON stimuli and large hyperpolarizations to OFF stimuli but differ in their spatial response profiles. Depolarizations are caused by ON excitation outweighing ON inhibition, whereas hyperpolarizations result from pre- and postsynaptic OFF-ON crossover inhibition. VIP1-, VIP2-, and VIP3-ACs thus differ in response polarity and spatial tuning and contribute to the diversity of inhibitory and neuromodulatory signals in the retina.

Multiple cell types form the VIP amacrine cell population

“…A fourth medium‐field amacrine cell type was in the GCL. These findings show that the VIP‐ires‐Cre and VIP‐immunoreactive amacrine cells in the mouse retina (Tornqvist, Uddman, Sundler, & Ehinger, ; Cellerino, Arango‐Gonzalez, Pinzon‐Duarte, & Kohler, ; Zhu et al, ; Akrouh & Kerschensteiner, ; Park et al, ) consist of multiple amacrine cell types. The VIP‐ires‐Cre amacrine cells have distinct synaptic and receptive field properties (Akrouh & Kerschensteiner, ; Park et al, ) suggesting distinct functional roles in visual processing.…”

“…One cell type is a wide‐field bistratified amacrine cell that ramifies in both the OFF and ON sublayers of the IPL and three cell types are medium‐field amacrine cells that ramify in the ON sublayer of the IPL. VIP amacrine cell types are reported to have distinct synaptic and receptive field properties (Akrouh & Kerschensteiner, ; Park et al, ) suggesting each cell type has a distinct functional role or roles in visual processing.…”

“…They are members of the “VIP‐2” amacrine cells (see fig. C in Akrouh & Kerschensteiner, ) and the “narrow‐field INL” cell group in the VIP‐ires‐Cre line (Park et al, ). These amacrine cells were designated as a “narrow‐field” amacrine cell in an earlier study (Park et al, ), although they do not meet the classical definition of a narrow‐field cell (MacNeil & Masland, ; Menger & Wässle, ; Pang et al, ) based on the size of their fields, and their expression of GABA‐ and not glycine‐immunoreactivity (Vaney, ).…”

“…This approach has become a valuable tool for untangling the diversity of amacrine cells and defining their synaptic relationships and connectivity, and their intrinsic and receptive field properties. For instance, recent studies have labeled Cre‐expressing amacrine cells using either Cre‐dependent reporter mouse lines or AAVs for anatomical characterization and electrophysiological studies of both the vGluT3‐Cre and VIP‐ires‐Cre amacrine cells (Grimes, Seal, Oesch, Edwards, & Diamond, ; Lee et al, ; Zhu, Xu, Hauswirth, & DeVries, ; Akrouh & Kerschensteiner, ; Park et al, ). Cre‐expressing amacrine cells can also be manipulated using optogenetic molecules to selectively stimulate or inhibit retinal cells and chemogenetic approaches (PSAM or DREADDs) to reversibly manipulate Cre‐expressing retinal cell populations (Magnus et al, ; Madisen et al, ; Huang & Zeng, ; Sternson & Roth, ; Vlasits et al, ).…”

Patch Clamp Recording of Starburst Amacrine Cells in a Flat-mount Preparation of Deafferentated Mouse Retina

“…Our technique is more efficient when compared to several published procedures, where the vitreous is removed manually in solution 17,19 or by enzymatic actions 18,20 . Another frequently used method is to tear the inner limiting membrane off using an empty patch pipette for each cell to be recorded 21,22 . We did not pursue the tearing method for fear of dismounting the retina.…”