Image_5_Parvalbumin and GABA Microcircuits in the Mouse Superior Colliculus.JPEG (343.4 kB)
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Image_5_Parvalbumin and GABA Microcircuits in the Mouse Superior Colliculus.JPEG

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posted on 04.05.2018, 12:16 by Claudio A. Villalobos, Qiong Wu, Psyche H. Lee, Paul J. May, Michele A. Basso

The mammalian superior colliculus (SC) is a sensorimotor midbrain structure responsible for orienting behaviors. Although many SC features are known, details of its intrinsic microcircuits are lacking. We used transgenic mice expressing reporter genes in parvalbumin-positive (PV+) and gamma aminobutyric acid-positive (GABA+) neurons to test the hypothesis that PV+ neurons co-localize GABA and form inhibitory circuits within the SC. We found more PV+ neurons in the superficial compared to the intermediate SC, although a larger percentage of PV+ neurons co-expressed GABA in the latter. Unlike PV+ neurons, PV+/GABA+ neurons showed predominantly rapidly inactivating spiking patterns. Optogenetic activation of PV+ neurons revealed direct and feedforward GABAergic inhibitory synaptic responses, as well as excitatory glutamatergic synapses. We propose that PV+ neurons in the SC may be specialized for a variety of circuit functions within the SC rather than forming a homogeneous, GABAergic neuronal subtype as they appear to in other regions of the brain.

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