Figure 7.

Blocking endogenous estrogen production in NCM suppresses neuronal selectivity for BOS in HVC, and the rapid actions of estrogens in NCM appear to depend on acute membrane-mediated actions. A, Schematic of dual NCM–HVC electrophysiology recordings (identical to Fig. 1A) used for retrodialysis delivery of the aromatase inhibitor FAD and the cell-membrane-impermeable biotin-conjugated estradiol (E6biotin). B, Chemical structure of E6biotin, showing the biotin conjugate in the carbon-6 position of E2, which retains receptor binding capacity of E2 but restricts diffusion through cell membranes. Adapted with permission from Steraloids. C, Acute suppression of local estrogen production within NCM (via FAD-mediated aromatase inhibition) does not alter Z-score values in HVC (top) but significantly suppresses the selectivity index d′ for BOS in HVC (bottom). In contrast, the d′ values for REV and CON remain unchanged. Insets show individual data for all five birds showing rapid changes in d′ values in HVC for the neuronal responses to BOS during aCSF (left), FAD (middle), and wash (right) treatment periods and no consistent changes for Z-score values (axes are unlabeled but are identical to bar graphs). Each time period is 30 min in duration. *p < 0.05 for the Wilcoxon's signed-rank post hoc test comparing FAD versus aCSF conditions on a within-stimulus basis. D, Retrodialysis of the cell-membrane-impermeable compound E6biotin into NCM fully mimics the acute actions of unconjugated E2 on Z-score values for BOS (top) and selectivity index d′ for BOS (bottom) in HVC. Insets show individual data, respectively, for all five birds showing rapid changes for BOS during aCSF (left), E6biotin (middle), and wash (right) treatment periods (axes are unlabeled but are identical to bar graphs). Each time period is 30 min in duration. *p < 0.05 for Wilcoxon's signed-rank post hoc tests comparing E6biotin versus aCSF conditions on a within-stimulus basis. Other abbreviations are as defined in the legend to Figure 1.