Postnatal Expression Patterns of Estrogen Receptor Subtypes and Choline Acetyltransferase in Different Regions of the Papez Circuit.

The Papez circuit is crucial for several brain functions, including long-term memory and emotion. Estradiol modulates cognitive functions based on the expression pattern of its receptor subtypes including estrogen receptor (ER) α, β, and G protein-coupled receptor 30 (GPR30). Similarly, the activity in the cholinergic system correlates with several brain functions, such as learning and memory. In this study, we used immunofluorescence to examine the expression patterns of ERβ and Western blotting to analyze GPR30 and choline acetyltransferase (ChAT) expression, in different regions of the Papez circuit, including the prefrontal cortex, hippocampus, hypothalamus, anterior nucleus of the thalamus, and cingulum in female rats at postnatal days (PND) 1, 10, and 56. Our main finding was that the highest expression of ERβ and GPR30 was noted in each brain area of the Papez circuit in the PND1 rats, whereas the expression of ChAT was the highest in PND10 rats. These results provide vital information on the postnatal expression patterns of ER subtypes and ChAT in different regions of the Papez circuit.