Analysis of glutamatergic innervation of the mouse dorsal raphe nucleus using array tomography

MARIANO SOIZA REILLY

Janelia Farm, Ashbourn, VA, USA

Conferencia; Janelia Farm Conference: "Light-based approaches to neural circuit reconstruction"; 2010

Howard Hughes Medical Institute, Janelia Farm Research Campus

@font-face { font-family: "Arial"; }@font-face { font-family: "Cambria"; }@font-face { font-family: "AdvPSHN-H"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0in 0in 10pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; } Serotonin (5-HT) neurons located in the dorsal raphe nucleus (DR) represent the main source of forebrain 5-HT and regulate emotional states. Although DR dysfunction has been implicated in pathophysiology of affective disorders including anxiety and depression, the fine architecture of its neural circuits remains poorly understood. DR neurons are subjected to an excitatory regulation driven by glutamate axons arising from different brain anatomical areas that selectively express three different types of vesicular glutamate transporters (vGluts). In this study we used a new high-resolution imaging technique called array tomography to analyze quantitatively the glutamatergic innervation of the mouse DR. We identified populations of axonal boutons by immunolabeling for vGlut1, vGlut2 and vGlut3, and examined their associations with postsynaptic elements at glutamatergic synapses (e.g. PSD-95) as well as with 5-HT cells, identified by immunostaining for tryptophan hydroxylase. We found that all three populations of axonal boutons are represented in the DR, however those containing vGlut2 remarkably established more often close appositions with PSD-95. Additionally, vGlut2-containing appositions were also more markedly associated with 5-HT cells. Our data support a prominent contribution of glutamate axons expressing vGlut2, and likely arising from subcortical areas, to the excitatory regulation of DR activity.