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 microg/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 + E2, 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 microm, 10 microl), 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 + E2, respectively, P < 0.01, n = 18] and D-2-amino-5-phosphonoraleric acid [(100 microm, 10 microl), 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 microl, 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 microl, 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.