Tyrosine hydroxylase-positive GABAergic juxtaglomerular neurons are the main source of the interglomerular connections in the mouse main olfactory bulb

The interglomerular connections in the mouse olfactory bulb were examined with the retrograde-tracer experiments using Fluorogold. When the injections were restricted to the glomerular layer, we encountered tracer-labeled cells in the glomerular layer and the superficial part of the external plexiform layer, not only near the injection sites but also more than 500 μm distant from the injection sites. Almost of those tracer-labeled neurons distant from the injection sites were large tyrosine hydroxylase-positive juxtaglomerular neurons, some of which were confirmed to have intraglomerular dendrites. Thus, the long interglomerular connections were mainly made by a particular type of dopaminergic-GABAergic juxtaglomerular neurons.