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. 2022 Mar 17;16:858617. doi: 10.3389/fncel.2022.858617

FIGURE 2.

FIGURE 2

Electron micrographs of immunogold staining for glutamate in adjacent thin sections through anterogradely labeled Glut+ terminals (#1–#4) in the parabrachial nucleus (PBN, A–D) and medullary reticular formation (RF, E–H) after tracer injection in the rNST. Postsynaptic targets of Glut+ labeled terminals (boutons) are different in the PBN and RF. Glut+ labeled terminals are presynaptic to the dendritic spine more frequently in the PBN than in the RF, while they are presynaptic to soma or proximal dendrite more frequently in the RF than in the PBN. (A–D) The labeled terminals (#1, #2) in the PBN establish synaptic contacts (arrowheads) with a dendritic shaft (d; A,B) and a dendritic spine (ds; C,D). (E–H) The labeled terminals in the RF (#3, #4) establish synaptic contacts (arrowheads) with a small dendritic shaft (d; E,F) and a cell body (soma; G,H). The labeled terminals can be identified by the presence of the HRP reaction product (arrows) within the axoplasm. Labeled terminals that are Glut+ were analyzed in this study: note the high density of gold particles coding for glutamate over the areas of the axoplasm containing synaptic vesicles. Glut immunoreactivity is consistent in the pairs of serial sections of the labeled terminal, confirming their glutamatergic nature. The labeled terminals and the postsynaptic dendritic spine are outlined with a dashed line for clarity. Scale bar, 500 nm.