AUTHOR=Villalobos Claudio A. , Wu Qiong , Lee Psyche H. , May Paul J. , Basso Michele A. TITLE=Parvalbumin and GABA Microcircuits in the Mouse Superior Colliculus JOURNAL=Frontiers in Neural Circuits VOLUME=12 YEAR=2018 URL=https://www.frontiersin.org/journals/neural-circuits/articles/10.3389/fncir.2018.00035 DOI=10.3389/fncir.2018.00035 ISSN=1662-5110 ABSTRACT=

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.