Fig. 3.

EMs obtained from postnatal d 10 rat visual cortex, showing β-AR immunoreactivity using HRP-DAB label and an antiserum directed against the C-terminus of the receptor. (A) A dendritic shaft receiving two synaptic inputs from unlabed axon terminals (T) one of which is immunolabeled over the postsynaptic density (curved arrow) and another that is unlabeled (open arrow points to the postsynaptic density).Arrowheads point to the unlabeled smooth saccules, indicating robust membrane turnover, that accompany the process of maturatlOn. Another profile,exhibits immunoreactivity along the plasma membrane: judging from its irregular contour (asterisks) it is most likely a glial process (LG). (B) The same antiserum β-ARs in presynaptic terminals (LT), identified by the clustering of small clear vesicles) (curved arrow) The same terminal contains a dense-cored vesicle (arrowhead). (A,C) β-AR immunoreactivity at postsynaptic sites occur not only over postsynaptic densities, but adjoining intracellular membranes and plasma membranes (small arrows). Calibration bar = 500 nm (from ref. 17, reproduced with permission from Cambridge University Press).