Interneurons are the local targets of hippocampal inhibitory cells which project to the medial septum

摘要: A subset of GABAergic neurons projecting to the medial septum has long been described in hippocampus. However, lack information about their local connectivity pattern or correspondence with any well-established hippocampal interneuron types hampered understanding functional role. Retrograde tracing combined immunostaining for neurochemical markers adult rat hippocampus showed that nearly all hippocampo-septal (HS) express somatostatin (>95%) and, hilus and CA3 stratum lucidum, many contain calretinin (>45%). In contrast, oriens CA1 subfields, majority HS (>86%) calbindin (>73%), but not calretinin. Because somatostatin-positive interneurons have most extensively characterized CA1, we focused our further analysis on cells found this region. 18-20-day-old rats, intracellularly filled CA1-HS had extensive axon collaterals crossing subfield boundaries innervating region dentate gyrus. Electron microscopic provided evidence terminals form symmetrical synapses selectively interneurons, both locally addition, double retrograde labelling experiments revealed dorsal also collateral projections ventral Thus, innervate inhibitory remote regions, addition targeting mostly septum. This dual projection striking target selectivity may be ideally suited synchronize neuronal activity along septo-hippocampal axis.