Estrogen modulates the spinal N-methyl-D-aspartic acid-mediated pelvic nerve-to-urethra reflex plasticity in rats

The effects of gonadal steroids on glutamate-mediated pelvic nerve-to-urethra reflex (PUR) plasticity were investigated in rats, which received a sham operation (Sham), ovariectomy (OVX), or ovariectomy with daily supplemental estrogen (50 μg/kg, OVX ± E₂). The magnitude of the repetitive stimulation (RS, 1 Hz)-induced potentiation in PUR activity decreased significantly in the OVX group when compared with the Sham groups (18.09 ± 3.91 and 7.40 ± 1.03 spikes/stimulation in Sham and OVX group; respectively, P < 0.01, n = 21). Supplemental estrogen (OVX + E ₂, 12.60 ± 1.49 spikes/stimulation) significantly reversed the decrease in RS-induced PUR potentiation caused by OVX (P < 0.01, n = 21). The magnitude of the RS-induced potentiation in PUR activity decreased significantly after intrathecal 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxaline [(20 μM, 10 μl), from 18.09 ± 3.91 to 10.40 ± 0.81, from 7.40 ± 1.03 to 3.20 ± 0.94, and from 12.60 ± 1.49 to 8.06 ± 0.32 spikes/stimulation in Sham, OVX, and OVX + E ₂, respectively, P < 0.01, n = 18] and _D-2-amino-5- phosphonoraleric acid [(100 μM, 10 μl), from 18.09 ± 3.91 to 1.04 ± 0.12, from 7.40 ± 1.03 to 1.06 ± 0.22, and from 12.60 ± 1.49 to 0.98 ± 0.25 spikes/stimulation in Sham, OVX, and OVX + E₂, respectively, P < 0.01, n = 18]. In addition, potentiation in PUR activities was induced by intrathecal L-glutamate (0.1 mM, 10 μl, from 1.04 ± 0.02 to 21.60 ± 0.93, from 1.10 ± 0.06 to 8.40 ± 1.50, and from 1.03 ± 0.03 to 18.04 ± 0.84 spikes/stimulation in Sham, OVX, and OVX + E₂, respectively, P < 0.01, n = 18) and N-methyl-D-aspartic acid (0.1 mM, 10 μl, from 1.04 ± 0.02 to 14.80 ± 0.97, from 1.10 ± 0.06 to 4.60 ± 0.48, and from 1.03 ± 0.03 to 9.09 ± 0.63 spikes/stimulation in Sham, OVX, and OVX + E₂); N-methyl-D-aspartic acid-mediated PUR plasticity in female rats and may contribute to alterations in urinary dysfunction after menopause.