Fig. 2.

PSA immunoreactivity in the HNS under stimulated conditions of neurosecretion. As shown in this example from a lactating rat, the light microscopic distribution (A) in the SON is basically similar to that in unstimulated animals (compare with Fig. 1A). There is, nonetheless, some diminution of labeling associated with clusters of magnocellular somata (arrows). As seen with electron microscopy (B, C), such clusters contain dendritic (d₁, d₂) (B) and somatic (S₁, S₂) (C) profiles whose surfaces are directly juxtaposed, with no glial interposition (betweenarrows). Note that PSA immunoreactivity is not associated with juxtaposed neuronal membranes, although it continues to be visible in adjacent astrocytic profiles (astro.,arrowheads). A, Immunofluorescence;B, C, immunoperoxidase reaction.