Analysis of the afferent limb of the vesicovascular reflex using neurotoxins, resiniferatoxin and capsaicin

Abstract

The afferent limb of the vesicovascular reflex (VV-R) evoked by distension or contraction of the urinary bladder (UB) was studied in urethane-anesthetized female rats by examining the changes in VV-R after administration of C-fiber afferent neurotoxins [capsaicin and resiniferatoxin (RTX)]. Systemic arterial blood pressure increased parallel (5.1 to 53.7 mmHg) with graded increases in UB pressure (20 to 80 cm H(2)O) or during UB contractions. The arterial pressor response to UB distension was significantly reduced (60-85%) by acute or chronic (4 days earlier) intravesical administration of RTX (100-1,000 nM) or by capsaicin (125 mg/kg sc) pretreatment (4 days earlier). Chronic neurotoxin treatments also increased the volume threshold (>100%) for eliciting micturition in anesthetized rats but did not change voiding pressure. Acute RTX treatment (10-50 nM) did not alter the arterial pressor response during reflex UB contractions, whereas higher concentrations of RTX (100-1,000 nM) blocked reflex bladder contractions. It is concluded that VV-R is triggered primarily by distension- and contraction-sensitive C-fiber afferents located, respectively, near the luminal surface and deeper in the muscle layers of the bladder.

Efficacy of a Novel Device for Assessment of Autonomic Sensory Function in the Rat Bladder

“…Normal voiding has been shown to be dependent on Aδ-fiber bladder afferents, whereas Cfiber afferents are responsible for bladder nociceptive responses 16,17 . The previous and successful use of Neurometer® and measurement of current perception threshold (CPT) in cutaneous afferent sites [13][14][15] makes this technique an attractive modality to assess the status of the specific afferent nerve fibers in the bladder or other visceral organs.…”

Herpes simplex virus vector-mediated delivery of glial cell line-derived neurotrophic factor rescues erectile dysfunction following cavernous nerve injury

“…The best ICP value was divided by simultaneous mean arterial pressure (ICP/AP) that was measured during the period of electrostimulation of pelvic nerve, because pelvic nerve stimulation possibly increased AP due to activation of pelvic nerve afferents to induce pressor responses such as that known as the vesico-vascular reflex. 62 ICP/AP was measured at 2 or 4 weeks after the nerve injury. After the ICP measurement, the bilateral MPG was dissected out and histological studies were performed.…”

Mechanisms inducing autonomic dysreflexia during urinary bladder distention in rats with spinal cord injury

“…3 These earlier results indicated that the bladder-to-vascular reflex is induced by the activation of C-fiber bladder afferent pathways during bladder distention of normal rats. The current study extends the earlier findings to rats with SCI induced by complete Th4-5 spinal cord transection.…”

“…3 In brief, PE-50 tubing (Clay-Adams, Parsippany, NJ, USA) was inserted into the bladder through the urethra and tied in place by a ligature around the urethral orifice. Then the PE-50 tubing in the urethra was connected via a three-way stopcock to a pressure transducer and to a syringe pump for recording intravesical pressure and for infusing saline into the bladder, respectively.…”

“…1 It has been shown that vascular responses (that is, hypertension) induced by bladder distention are mediated by the activation of TRPV1 (capsaicin receptor)-expressing C-fiber bladder afferent pathways in spinal-intact (SI) rats. 3 In addition, the expression of TRP channels such as TRPV1 and TRPA1 are involved in the sensitization of C-fiber afferent pathways. 4 Previous studies have also indicated that increased levels of nerve growth factor (NGF) in the bladder is one of the key mediators to induce hyperexcitability of C-fiber bladder afferent pathways after SCI, resulting in detrusor overactivity (DO), [5][6][7][8] and that intrathecal application of NGF antibodies, which reduces NGF levels in bladder afferent pathways, is effective for DO as well as AD in SCI rats.…”