The distribution of immunoreactivity for intracellular androgen receptors in the cerebral cortex of hormonally intact adult male and female rats: localization in pyramidal neurons making corticocortical connections.

Gonadal hormones are known to broadly influence cortical information processing. Findings from this study in rats suggest that for androgens, this influence may include stimulation of underlying corticocortical connections. First, immunoreactivity for intracellular androgen receptors, while present in all regions and layers examined, was found to be particularly abundant in sensory and motor regions, and within these, within their major pyramidal cell layers, i.e. layers II/III and V/VI. Double labeling immunocytochemical studies for androgen receptors and for neuron-specific markers then confirmed that the majority of receptor-bearing cortical cells were pyramidal neurons. Finally, combined analyses of cortical receptor immunoreactivity and retrograde labeling produced by tracer injections made in specific subcortical (caudate, nucleus accumbens, superior colliculus, thalamus) areas yielded only isolated examples of receptor/tracer overlap. However, injections made within the cortex itself (sensory, motor, associational areas) retrogradely labeled cortical cells some 50% or more - especially within injected hemispheres, were receptor-immunoreactive. Thus, the regional, laminar, and cellular distributions of immunoreactivity in the rat cerebrum largely identify pyramidal neurons with connectional signatures aligning intracellular androgen receptors with the local, associational, and to a lesser degree, callosal circuits that interlink territories of the cortical mantle and play key roles in cortical information processing.