17Beta-estradiol suppresses AMPA-induced increases in regional cerebral O2 consumption

Abstract

We tested the hypothesis that 17beta-estradiol would reduce the cerebral O₂ consumption response resulting from glutamate receptor stimulation by alpha amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA). Fourteen ovariectomized rats were separated into 17beta-estradiol (0.5 mg 21 day release pellet) and control (placebo pellet) groups to determine cerebral blood flow (¹⁴C-iodoantipyrine) and O₂ consumption (microspectrophotometry). After topical cortical stimulation with 10^-3 M and 10-4 M AMPA, cerebral blood flow increased significantly in both groups in a concentration-dependent manner. Cerebral O₂ extraction was not significantly different in any region of the 17beta-estradiol treated group. In the placebo treated group, the O₂ extraction in the saline treated cortex and in the 10^-3 M AMPA treated cortex was significanly higher when compared to the 10^-4 M AMPA treated cortex. Cerebral O₂ consumption in the control group increased by 20%, from 5.2 ± 0.6 to 6.1 ± 0.7, with 10^-4 M AMPA and significantly increased by 64% to 8.5 ± 0.8 ml O₂ min^-1 100 g^-1 with 10^-3 M AMPA. The 17beta-estradiol group demonstrated no statistically significant difference in O₂ consumption between the saline treated and AMPA treated cortex. Thus, 17beta-estradiol reduced the effects of AMPA in increasing cerebral O₂ consumption.