Knowledge Bank

The hippocampus is involved in processing a diverse array of information that is transmitted to the rest of the brain. Recent work suggests that circuits between heterogenous populations of excitatory and inhibitory neurons endows the hippocampus with the ability to process such diverse information. Somatostatin-expressing interneurons are involved in regulating the flow of information through the hippocampus, but it is unknown how they integrate into circuits with diverse populations of CA1 pyramidal cells. Here, we use four transgenic mouse lines to assay the synaptic physiology between deep and superficial pyramidal cells and somatostatin-expressing stratum oriens interneurons. We show that superficial pyramidal cells have a higher connection probability than deep pyramidal cells to somatostatin-expressing and Nkx2.1+ stratum oriens interneurons, but not to 5HT3A+ or Chrna2+ cells. Reciprocally, superficial pyramidal cells are more strongly inhibited by somatostatin-expressing stratum oriens interneurons, but not by Chrna2+ oriens-lacunosum moleculare cells. Our data highlight a novel feedback inhibitory circuit between pyramidal cells and somatostatin-expressing interneurons in CA1 hippocampus.