Gender difference in BK channel expression in amygdala complex of rat brain

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Abstract

The expression of large-conductance Ca2+-activated K+ (BK) channel protein in amygdala complex was higher in adult (8–10 weeks old) male rats than in female. Castration at 4–6 weeks old significantly reduced BK channel expression in amygdala to the level similar to that in female. Immunocytochemical analyses of pyramidal-like neurons isolated from amygdala revealed that somas with relatively large size were highly immunoreactive to both anti-androgen receptor (AR) and anti-BK channel antibodies, while those with smaller size were not. The double-immunopositive neurons were dominant (60%) among pyramidal-like neurons isolated from amygdala of male rats but rare among those from female. The membrane current sensitive to penitrem A, a BK channel blocker, was the major K+ current component in large neurons and showed higher current-density than that in smaller ones. These results suggest the gender-dependent cell population expressing BK channels in amygdala complex and its up-regulation by AR stimulation.

Section snippets

Materials and methods

Animal and tissue preparation. Intact and castrated male and female adult rats (8–10 weeks old, Wistar-ST) were decapitated. Castration, when applicable, was performed 4 weeks prior to use. The brain were removed rapidly from the skull and placed in ice-cold oxygenated saline containing (in mM) KCl 2.4, MgSO4 10, CaCl2 0.5, piperazine-N,N′-bis(ethanesulfonic acid) (PIPES) 20, glucose 10, and sucrose 195, pH 7.35. Coronal slices (500 μm in thickness) were cut from a block of tissue containing the

Regional expression of AR and BK channel in rat brain

The mRNA expression of AR and BKα in amygdala complex, pituitary, and hippocampus in male rat brain was examined by quantitative real-time PCR analyses (Fig. 1A). The expression of AR and BKα mRNAs was detected in these regions and BKα mRNA expression was apparently higher than that of AR. The mRNA expression analyses of BK channel β subunit isoforms (BKβ1, β2, β3, and β4) revealed that BKβ4 was predominant isoform in amygdala complex of male rats (Fig. 1B and C).

The expression of BKα and AR

Discussion

We report here that the expression of BK channel in amygdala complex is gender-dependent, much higher in male rats than in female, and may possibly be consistently up-regulated by the stimulation of ARs in male rats.

Acknowledgments

This work was supported by a Grant-in-Aid for Scientific Research on Priority Areas (20056027) from the Ministry of Education, Culture, Sports, Science and Technology and by a Grant-in-Aid for Scientific Research (B) (20390027) from the Japan Society for the Promotion of Sciences to Y.I. This work was also supported by a Grant-in-Aid for Young Scientists (B) from Japan Society for the Promotion of Science (18790058) to S.O.

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