Ultrastructural examination of the corticocollicular pathway in the guinea pig: a study using electron microscopy, neural tracers, and GABA immunocytochemistry.

Ultrastructural examination of the corticocollicular pathway in the guinea pig: a study using electron microscopy, neural tracers, and GABA immunocytochemistry.

Nakamoto Kyle T; Mellott Jeffrey G; Killius Jeanette; Storey-Workley Megan E; Sowick Colleen S; Schofield Brett R

Frontiers in neuroanatomy

2013

2013

Projections from auditory cortex (AC) can alter the responses of cells in the inferior colliculus (IC) to sounds. Most IC cells show excitation and inhibition after stimulation of the AC. AC axons release glutamate and excite their targets, so inhibition is presumed to result from cortical activation of GABAergic IC cells that inhibit other IC cells via local projections. However, it is not known whether cortical axons contact GABAergic IC cells directly. We labeled corticocollicular axons by injecting fluorescent dextrans into the AC in guinea pigs. We visualized the tracer with diaminobenzidine and processed the tissue for electron microscopy. We identified presumptive GABAergic profiles with post-embedding anti-GABA immunogold histochemistry on ultrathin sections. We identified dextran-labeled cortical boutons in the IC and identified their postsynaptic targets according to morphology (e.g., spine, dendrite) and

auditory cortex; bouton classification; corticofugal pathways; inferior colliculi; synaptic targets; ultrastructural variations

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