title: Functional brain interactions during reflexive micturition are absent from spinal cord injured rats with neurogenic bladder.
abstract: OBJECTIVE
  The micturition reflex is initiated by urinary bladder distension triggering afferent pathways and activation of specific brain centers for controlling urine storage and release. We evaluated brain activation patterns using blood oxygenation level dependent functional magnetic resonance imaging (fMRI) during reflexive micturition in normal and spinal cord injury (SCI) rats.
  
  
  METHODS
  Sprague-Dawley female rats, either intact or with complete spinal cord transection, were anesthetized with urethane for simultaneous isovolumetric cystometry (CMG) and fMRI evaluations. A 9.4-Tesla MRI system with a 4-elements receiver array and a quadrature volume transmit coil was used to maximize the sensitivity detection. Gradient echo-planar imaging (EPI) was used to evaluate brain activation during CMG compared to the empty bladder condition. Group analysis was conducted with a cluster threshold of Z > 2.5 and significance threshold of P = 0.05.
  
  
  RESULTS
  The amplitude of bladder contractions was 10-fold higher in control rats and inter-contractile intervals were significantly shorter in SCI rats, indicative of neurogenic overactivity. Group analysis in intact rats showed both known and novel activation patterns in hippocampus, dentate gyrus, ectorhinal cortex, thalamic nucleus, septal nucleus, primary and secondary motor cortex, primary somatosensory cortex, and the periaqueductal gray matter. SCI rats did not exceed the Z-threshold during CMG.
  
  
  CONCLUSIONS
  We standardized a suitable urodynamic protocol to study supraspinal activation during reflexive micturition using simultaneous CMG/fMRI with high spatial resolution. Small contractions in SCI rats may be caused by increased excitability of afferent pathways without brain activation. Our results represent the first fMRI study in SCI rats.
authors.affiliation: Department of Systems Medicine and Bioengineering, TT & WF Chao Center for BRAIN, Houston Methodist Research Institute, Houston, Texas.|Department of Radiology, Houston Methodist Hospital, Weill Cornell Medical College, Houston, Texas.
authors.forename: Kelvin
authors.initials: K
authors.lastname: Wong
authors.affiliation: Department of Urology, Houston Methodist Hospital, Weill Cornell Medical College, Houston, Texas.|Department of Urology, Houston Methodist Research Institute, Houston, Texas.|Michael E. DeBakey Veterans Affairs-Medical Center, Houston, Texas.
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Boone
authors.affiliation: Department of Systems Medicine and Bioengineering, TT & WF Chao Center for BRAIN, Houston Methodist Research Institute, Houston, Texas.|Department of Radiology, Houston Methodist Hospital, Weill Cornell Medical College, Houston, Texas.|Department of Neurology, Methodist Neurological Institute, Houston Methodist Hospital, Weill Cornell Medical College, Houston, Texas.|Department of Pathology and Laboratory Medicine, Houston Methodist Hospital, Weill Cornell Medical College, Houston, Texas.
authors.forename: Stephen T C
authors.initials: ST
authors.lastname: Wong
authors.affiliation: Department of Urology, Houston Methodist Research Institute, Houston, Texas.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Munoz
mesh_terms: D000818:Animals; D001921:Brain / Q000503:physiopathology*; D005260:Female; D059907:Functional Neuroimaging; D008279:Magnetic Resonance Imaging; D009119:Muscle Contraction; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology*; D001750:Urinary Bladder, Neurogenic / Q000209:etiology / Q000503:physiopathology*; D014554:Urination / Q000502:physiology*; D014563:Urodynamics
keywords: functional-magnetic resonance imaging; micturition; reflex; spinal cord injury; urinary bladder