Figure 5.

SDS-FRL images show the localization of μ-opioid (μOR) receptor and GABA_A receptor subunits α1, α2, and β3 on the P-face of Imp dendrites. (A) Double labeling for μOR (10 nm) and α1 subunit (5 nm gold particle, indicated by red arrows) shows strong expression of μOR in extrasynaptic areas of Imp dendrites. Only background labeling levels were observed for the α1 subunit. Insert shows an enlarged view of a single 5 nm immunogold particle. (B) Triple-labeling for μOR (5 nm), α1 (15 nm), and β3 (10 nm) shows the lack of detectable α1 labeling both in a GABAergic synapse identified by concentrated immunogold particles for the β3 subunit (indicated by red arrows) on a distinct cluster of intramembrane particles, and in the extrasynaptic area consistent with the lack or very low density of the α1 subunit at Imp dendrites. Black arrows show immunogold particles for μOR located in extrasynaptic areas. (C) Double labeling for α2 (5 nm) and β3 (10 nm) subunits showing their colocalization in a single GABAergic synapse of an Imp dendrite. (D) Double-labeling for α1 (10 nm) and α2 (5 nm) showing the colocalization of these two subunits in a GABAergic synapse of a pyramidal cell dendrite of the basal nucleus of the amygdala. Scale bars: A, 500 nm; Insert, 250 nm; B, −500 nm; C and D, 200 nm.