Spinal cord stimulation (SCS) modulates activity of lumbosacral spinal neurons receiving inputs from urinary bladder in rats

Abstract

SCS decreases the visceromotor and spinal neuronal responses to mechanical stimuli in sensitized rat colon and reduces the symptoms of irritable bowel syndrome (IBS) in patients. The aim of this study was to determine if SCS modulates activity of lumbosacral spinal neurons receiving noxious input from urinary bladder, another pelvic visceral organ that is dysfunctional in patents with IBS. Extracellular potentials of lumbosacral (L6-S2) spinal neurons were recorded in pentobarbital anesthetized, paralyzed and ventilated male rats. SCS (50 Hz, 0.2 ms, 3–5 min) at low intensity (90% motor threshold) was applied on the dorsal column of upper cervical (C1-C2) and lumbar (L2-L3) ipsilateral spinal segments, respectively. Urinary bladder distension (UBD, 0.5–2.0 ml, 20s) was produced by warm saline inflation through a catheter inserted into the fundus. SCS on L2-L3 spinal segments significantly reduced excitatory responses of 17/25 (68%) spinal neurons to noxious UBD (≥1.0 ml) and did not affect UBD-response in 8 neurons. SCS on the C1-C2 segments suppressed excitatory responses of 12/19 (63%) neurons to noxious UBD, enhanced UBD-responses in 2 neurons, and did not affect UBD-responses in 5 neurons. SCS affected spinal neurons with either high or low threshold response to UBD. These results indicated that upper cervical or lumbar SCS modulated responses of lumbosacral spinal neurons to noxious mechanical stimulation of urinary bladder. It suggested that a potential therapeutic effect of SCS is on visceral hypersensitivity of urinary bladder in patients with cystitis or IBS. (Supported by NS-35471; HL-075524)