Probing subicular inputs to the medial prefrontal cortex

Abstract

Summary The hippocampal formation is anatomically and functionally divided into a dorsal and a ventral part, being involved in processing cognitive tasks and emotional stimuli, respectively. The ventral subiculum as part of the hippocampal formation projects to the medial prefrontal cortex (mPFC), but only very little is known about connections arising from the dorsal SUB (dSUB). Here, we investigate the dSUB to mPFC connectivity in acute brain slices using electrophysiology and optogenetics. We show that the anterior cingulate cortex (ACC) is the main target of dorsal subicular projections to the mPFC, with no preference between excitatory or inhibitory neurons. In addition to superficial neurons in the ACC, the prelimbic and infralimbic PFC are also targeted by subicular fibers. Thus, these novel region- and layer-specific connections between the dSUB and the prefrontal cortices challenge existing anatomical data and refine the hippocampocortical wiring diagram.

Transcriptomically-guided pharmacological experiments in neocortical and hippocampal NPY-positive GABAergic interneurons

“…Brains were sliced in the horizontal plane for hippocampal recordings or the coronal plane for neocortical recordings as previously described ( Winterer et al, 2019 ; Beerens et al, 2021 ). NPY cells were recorded from superficial layers [layer 1 (L1)-L2] of the AC and SLM of the CA3 in ACSF using standard potassium gluconate solutions [for the sequencing experiments: ACSF: 126 m m NaCl, 2.5 m m KCl, 10 m m glucose, 1.25 m m NaH 2 PO 4 , 2 m m MgCl 2 , 2 m m CaCl 2 , and 26 m m NaHCO 3 ; intracellular solution: 95 m m potassium gluconate, 50 m m KCl, 10 m m HEPES, 4 m m Mg-ATP, 0.5 m m Na-GTP, and 10 m m phosphocreatine; pH 7.2, KOH-adjusted, 300 mOsm ( Winterer et al, 2019 ), and for the pharmacological experiments: ACSF: 115 m m NaCl, 25 m m NaHCO 3 , 3 m m KCl, 1.25 m m NaH 2 PO 4 , 2 m m CaCl 2 , 1 m m MgCl 2 , 3 m m sodium pyruvate, and 10 m m glucose; intracellular solution 125 m m potassium gluconate, 10 m m HEPES, 6 m m KCl, 0.2 m m EGTA, 2 m m MgCl 2 , 2 m m Na-ATP, 0.5 m m Na-GTP, and 5 m m sodium phosphocreatine ( Beerens et al, 2021 )].…”