Experimental neurology
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Experimental neurology · Nov 2004
Bladder and urethral sphincter responses evoked by microstimulation of S2 sacral spinal cord in spinal cord intact and chronic spinal cord injured cats.
Urinary bladder and urethral sphincter responses evoked by bladder distention, ventral root stimulation, or microstimulation of S2 segment of the sacral spinal cord were investigated under alpha-chloralose anesthesia in cats with an intact spinal cord and in chronic spinal cord injured (SCI) cats 6-8 weeks after spinal cord transection at T9-T10 spinal segment. Both SCI and normal cats exhibited large amplitude reflex bladder contractions when the bladder was fully distended. SCI cats also exhibited hyperreflexic bladder contractions during filling and detrusor-sphincter dyssynergia during voiding, neither was observed in normal cats. ⋯ However, this stimulation evoked incomplete voiding due to either co-activation of the urethral sphincter or detrusor-sphincter dyssynergia. Stimulation in the S2 dorsal horn evoked large amplitude sphincter responses. The effectiveness of spinal cord microstimulation with a single electrode to induce prominent bladder and urethral sphincter responses in SCI animals demonstrates the potential for using microstimulation techniques to modulate lower urinary tract function in patients with neurogenic voiding dysfunctions.
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Experimental neurology · Nov 2004
Impaired axonal transport and altered axolemmal permeability occur in distinct populations of damaged axons following traumatic brain injury.
Traumatic axonal injury (TAI) evolves within minutes to hours following traumatic brain injury (TBI). Previous studies have identified axolemmal disruption and impaired axonal transport (AxT) as key mechanisms in the evolution of TAI. While initially hypothesized that axolemmal disruption culminates in impaired AxT, previous studies employed single-label methodologies that did not allow for a full determination of the spatial-temporal relationships of these two events. ⋯ These studies confirm that axolemmal disruption and impaired AxT occur as distinct non-related events early in the pathogenesis of TAI. Further, these studies provide evidence that the process of impaired axonal transport and subsequent axonal disconnection leads to delayed axolemmal instability, rather than proceeding as a consequence of initial axolemmal failure. This finding underscores the need of multiple approaches to fully assess the axonal response to TBI.