Effects of selective unilateral dorsal root(s) rhizotomy on micturition reflex in anesthetized rats

Purpose: To clarify the contributions of sensory inputs and glutamate transmissions to the spinal micturition reflex. Materials and Methods: Cystometrogram and external urethral sphincter electromyogram activities evaluated the L6 and/or S1 levels. Results: Changes in intravesicular pressure (IVP) in response to saline infusion (0.1 ml/min) were found after unilateral dorsal root rhizotomy at the L6 level, which showed significant increases in threshold pressure (rhizotomized vs. control: 14.25 ± 0.82 vs. 8.40 ± 0.69 cmH₂O, P <0.01, n = 28), post-voiding pressure (7.66 ± 0.56 vs. 5.42 ± 0.52 cmH₂O, P <0.01, n = 28), holding duration (135.06 ± 23.6 vs. 77.73 ± 13.56 sec, P <0.05, n = 28), and inter-contraction interval (140.62 ± 23.29 vs. 82.40 ± 13.57 sec, P <0.05, n = 28). Several (mean = 2.32 ± 1.31 vs. 0.12 ± 0.21, P <0.01, n = 28, P <0.01, n = 28) non-voiding contractions with gradual increase in IVP were found ahead of voiding contraction after rhizotomy. An additional dorsal root rhizotomy at the ipsilateral S1 level caused further increases in urodynamic parameters (threshold pressure, 18.18 ± 1.67 cmH₂O, P <0.01; post-voiding pressure 8.07 ± 0.96 cmH₂O, P <0.01; holding duration, 211.44 ± 42.54 sec, P <0.01; inter-contraction interval, 264.2 ± 59.99 sec, P <0.05; non-voiding contractions, 4.41 ± 2.12, P <0.01, n = 7). Intrathecal glutamate (100 μM, 10 μl) ameliorated all the pathological conditions induced by unilateral dorsal root rhizotomy at the L6 level in a dose dependent manner (ED₅₀ = 1.25 ± 10^-5). Intrathecal CNQX (6-cyano-7-nitroquinoxaline-2,3- dione; 100 μM, 10 μl) and APV (D-2-amino-5-phosphonovaleric acid; 100 μM, 10 μl) injections after rhizotomy at the L6 level induced disturbances similar to that caused by an additional rhizotomy at ipsilateral S1 level. Wherease, glutamate (100 μM, 10 μl) reversed the disturbances caused by CNQX but showed no effect on that by APV. Conclusions: Acute partial sensory deprivation caused acute impaired micturition reflex in rat models. In addition, glutamatergic NMDA and AMPA receptors are important for mediating these impairments in micturition reflex.