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.

The current study investigates whether the spinal pelvic nerve-to-external urethra sphincter (EUS) reflex potentiation can be induced by a mechanical stimulation and whether the glutamatergic mechanism is involved in yielding such a reflex potentiation. The external urethra sphincter electromyogram (EUSE) activity, evoked by a single or by repetitive pelvic nerve stimulation, in 30 anesthetized rats was recorded with/without bladder saline distension. Without saline distension (0 cmH(2)O), a single pulse nerve stimulation evoked a single action potential in the reflex activity, whereas repetitive pelvic stimulation and saline distension (6 approximately 20 cmH(2)O) both elicited a long-lasting reflex potentiation (20.05 +/- 3.21 and 75.01 +/- 9.87 spikes/stimulation, respectively). The saline distension-induced pelvic nerve-to-EUS reflex potentiation was abolished by D-2-amino-5-phosphonovalerate [APV; a glutamatergic N -methyl-D-aspartic acid (NMDA) receptor antagonist; 100 microM, 10 microl, 1.72 +/- 0.31 spikes/stimulation] and attenuated by 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxaline [NBQX; a glutamatergic alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA) receptor antagonist; 100 microM, 10 microl, 26.16 +/- 7.27 spikes/stimulation], but was not affected by bicuculline (a GABAergic antagonist; 100 microM, 10 microl, 53.62 +/- 15.54 spikes/stimulation). Intrathecal administration of glutamate (31.12 +/- 8.25 spikes/stimulation, 100 microM, 10 microl) and NMDA (26.25 +/- 4.12 spikes/stimulation, 100 microM, 10 microl) both induced a long-lasting pelvic nerve-to-EUS reflex potentiation without saline distension, which was similar to the findings observed from saline distension only. The duration of the contraction wave of the urethra was elongated by the saline distension-induced pelvic nerve-to-EUS reflex potentiation, whereas the peak pressure of the contraction wave was not affected. Our findings suggest that saline distension in the bladder elicits a pelvic nerve-to-EUS reflex potentiation and the glutamatergic mechanism contributes to the presence of such a reflex potentiation.

The purposes of this study were to investigate whether the pelvic nerve-to-external urethra sphincter (EUS) reflex potentiation can be induced under physiological conditions and to determine whether glutamatergic neurotransmission is involved in the reflex potentiation. Stimulation-evoked reflex activities, during rhythmic bladder contractions caused by a continuous saline infusion, in 21 anesthetized rats were recorded with/without the intrathecal administration of 10 microl of CNQX (a glutamatergic AMPA receptor antagonist; 100 microM) and APV( a glutamatergic NMDA receptor antagonist; 100 microM). Reflex activities became potentiated following the increment of intravesical pressure (IVP) during the storage phase (2.39 +/- 0.28 spikes/mmHg, n = 21) and the ascending period of the voiding phase (1.46 +/- 0.35 spikes/mmHg, n = 21) and decreased following the decrement of IVP during the descending period of the voiding phase (1.50 +/- 0.33 spikes/mmHg, n = 21). Although it is characterized by a low IVP, a postvoiding reflex potentiation in stimulation-evoked activities was elicited at the critical period after a voiding contraction had just finished (23.95 +/- 8.96 spikes/mmHg, n = 21). The slope of the regression line of evoked activities vs. the IVP during the storage phase was significantly (P < 0.01) higher than that of the ascending and descending periods of the voiding phase, but there was no statistical difference between the ascending and the descending periods (P > 0.05). In addition, the slope of the regression line of posttetanic reflex potentiation was significantly higher than that of the storage phase (P < 0.01). All the slopes of the regression lines decreased after intrathecal CNQX administration (from 3.15 +/- 0.44, 2.10 +/- 0.57, 2.13 +/- 0.53, and 21.30 +/- 3.41 to 0.83 +/- 0.31, 0.74 +/- 0.12, 0.76 +/- 0.12, and 4.31 +/- 3.71 spikes/mmHg in storage, ascending and descending period of the voiding phase, and postvoiding potentiation, respectively; all P < 0.01, n = 10). The slopes of the regression lines became almost horizontal after intrathecal APV administration (from 3.15 +/- 0.44, 2.10 +/- 0.57, 2.13 +/- 0.53, and 21.30 +/- 3.41 to 0.16 +/- 0.12, 0.21 +/- 0.07, 0.18 +/- 0.05, and 0.23 +/- 0.76 spikes/mmHg in storage, ascending and descending period of voiding phase, and postvoiding potentiation, respectively; all P < 0.01, n = 10). Our results suggest that a potentiation in the pelvic nerve-to-EUS reflex can be induced under physiological conditions and the glutamatergic mechanism appears to be involved in this reflex potentiation.

Calcium/calmodulin protein kinase (CaMK)-dependent nitric oxide (NO) and the downstream intracellular messenger cGMP, which is activated by soluble guanylate cyclase (sGC), are believed to induce long-term changes in efficacy of synapses through the activation of protein kinase G (PKG). The aim of this study was to examine the involvement of the CaMKII-dependent NO/sGC/PKG pathway in a novel form of repetitive stimulation-induced spinal reflex potentiation (SRP). A single-pulse test stimulation (TS; 1/30 Hz) on the afferent nerve evoked a single action potential, while repetitive stimulation (RS; 1 Hz) induced a long-lasting SRP that was abolished by a selective Ca 2ϩ /CaMKII inhibitor, autocamtide 2-related inhibitory peptide (AIP). Such an inhibitory effect was reversed by a relative excess of nitric oxide synthase (NOS) substrate, L-arginine. In addition, the RS-induced SRP was abolished by pretreatment with the NOS inhibitor, N G -nitro-L-arginine-methyl ester (L-NAME). The sGC activator, protoporphyrin IX (PPIX), reversed the blocking effect caused by L-NAME. On the other hand, a sGC blocker, 1H-[1, 2, 4]oxadiazolo[4, 3-␣]quinoxalin-1-one (ODQ), abolished the RS-induced SRP. Intrathecal applications of the membrane-permeable cGMP analog, 8-bromoguanosine 3Ј,5Ј-cyclic monophosphate sodium salt monohydrate (8-Br-cGMP), reversed the blocking effect on the RS-induced SRP elicited by the ODQ. Our findings suggest that a CaMKII-dependent NO/sGC/PKG pathway is involved in the RSinduced SRP, which has pathological relevance to hyperalgesia and allodynia.spinal reflex potentiation; soluble guanylate cyclase; cyclic monophosphate sodium salt monohydrate; spinal cord; windup ACTIVITY-DEPENDENT REFLEX plasticity, the dynamic regulation of reflex strength by ongoing neural activities, is a fundamental component of normal CNS functions. Long-term potentiation (LTP), a form of well-known activity-dependent reflex potentiation in synaptic responses that occurs in the CA1 area of the hippocampus, is considered the base for some forms of learning and memory (45). In the hippocampal CA1 region, LTP is induced by brief tetanic stimulation of afferent glutamatergic fibers and is typically dependent on activation of postsynaptic N-methyl-D-aspartate (NMDA) receptors (3).A key-initiating event in LTP induction is the activation of Ca 2ϩ /calmodulin protein kinase II (CaMKII) (14, 44, 30; 54). An increase in the intracellular Ca 2ϩ concentration, partly by the influx through NMDA receptor channels, activates calmodulin, which in turn triggers the activation of CaMKII, causing it to bind to the postsynaptic density. It is a well-known fact that nitric oxide (NO) stimulates soluble guanylyl cyclase, and, in turn, produces intracellular cGMP and subsequently activates the protein kinase G (PKG) to induced activity-dependent reflex potentiation (53). Brenman and Bredt (6) reported that NO can be activated by CaMKII. Several investigators revealed that NO plays a role in LTP as indicated by experiments showing that LTP is eliminated or...

This study was conducted to investigate whether dorsolateral pontine tegmentum stimulation modulates spinal reflex potentiation (SRP) and whether serotonergic neurotransmission is involved in such a modulation. Reflex activities of the external urethra sphincter (EUS) electromyogram in response to a test stimulation (TS; 1/30 Hz) or repetitive stimulation (RS; 1 Hz) on the pelvic afferent nerve in 35 anesthetized rats were recorded with/without synchronized train pontine stimulation (PS; 300 Hz, 30 ms) and/or intrathecal administrations of 10 l of 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxaline (NBQX;cyclohexanecarboxamide trihydrochloride (WAY 100635; 100 M), and 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT; 100 M). The TS evoked a single action potential (1.00 Ϯ 0.00 spikes/stimulation), while the RS produced a long-lasting SRP (16.12 Ϯ 1.59 spikes/stimulation) that was abolished by APV (1.57 Ϯ 0.29 spikes/stimulation) and was attenuated by NBQX (7.42 Ϯ 0.57 spikes/stimulation). Synchronized train PS with RS (PSϩRS) produced facilitation in RS-induced SRP (25.17 Ϯ 2.21 spikes/stimulation). Intrathecal WAY 100635 abolished the facilitation in SRP as a result of the synchronized PS (14.66 Ϯ 1.58 spikes/stimulation). On the other hand, intrathecal 8-OH-DPAT elicited facilitation in the RS-induced SRP (25.16 Ϯ 1.05 spikes/ stimulation) without synchronized PS. Our findings suggest that dorsolateral pontine tegmentum may modulate N-methyl-D-aspartic acid-dependent SRP via descending serotonergic neurotransmission. This descending modulation may have physiological/pharmacological relevance in the neural controls of urethral closure. long term potentiation; SRP; pontine tegmentum; serotonin; WAY 100635; 8-OH-DPAT ACTIVITY-DEPENDENT REFLEX plasticity, known as long-term potentiation (4, 5, 42) and windup phenomenon (37,50,51,58), has been widely studied in the central neural system, including the hippocampus and the spinal cord, for exploring the mechanisms of memory (3, 41) and hypergesia (46, 57), respectively. Forms of activity-dependent reflex plasticity can be elicited by applying electric shocks (6, 13) and by reagent injections/perfusions to specific sites (24). On the other hand, an established/establishing reflex plasticity may be modified by genetic (50), pharmacological (23, 46), surgical (27, 48, 54), or behavioral manipulations (2, 47). To the best of our knowledge, few studies have explored the possibility of modulating activity-dependent reflex plasticity by activating the higher nucleus of a specific neural projection to the site, where the reflex plasticity occurs. However, modulating activity-dependent reflex plasticity from a neural nucleus may mimic the physiological conditions of neural functions and offer gateways to elucidate the physiological/pharmacological relevancies in such activity-dependent reflex plasticity (1).Kuru (29) emphasized the importance of understanding the descending innervations from the brain stem to modulate the spinal reflexes involved in pelvic viscera, incl...