211 EFFECTS OF GLYCINE TRANSPORTER INHIBITORS ON BLADDER OVERACTIVITY IN RATS WITH CYCLOPHOSPHAMIDE-INDUCED CYSTITIS

Abstract

cation of ATP. The intravesical infusion of ATP and systemic application of AF-353, a P2X2/3 receptor-specific antagonist, allowed us to evaluate the contribution of P2X2/3 purinergic receptors to the activity of spinal neurons. METHODS: Following anesthesia with isoflurane, suprapubic, venous and tracheal catheters were implanted in female rats. After L1–L2 laminectomy, the cervical spinal cord was transected, rats were mechanically pithed, ventilated, and paralyzed. Urinary bladder pressure was monitored and the neural activity was acquired at a rate of 10 KHz via a computerized data acquisition system. Field potentials in the dorsal horn of the spinal cord were measured via tungsten microelectrodes in response to intravesical pressure steps ranging from 0–60 cm/H2O in A) control (saline in the bladder), B) after stimulation of urothelial purinergic receptors (1mM vesical ATP), C) after i.v. application of AF-353 (10 mg/kg), D) following a second i.v. injection of AF-353 (20 mg/kg), and E) after i.v. suramin (100 mg/kg). Pressure steps were maintained for one minute followed by three minutes of recovery. RESULTS: Only neurons that showed an increased activity during bladder distention were evaluated. Under control conditions, field potentials increased concomitantly with bladder pressure steps. Intravesical application of 1mM ATP produced an increase (27%) in the baseline electrical activity and a greater response (25%) to pressure changes than the saline controls. The first systemic application of AF-353 generated a marked decrease (52%) in electrical activity during isobaric stimulation; further additive inhibition (75%) was achieved after a second application of AF-353 30 minutes later. The application of suramin, following AF-353 treatments, maximally inhibited (87%) the response in neural activity to pressure changes. CONCLUSIONS: Our results suggest that purinergic receptors in the urothelium are important modulators of C-fiber mediated noxious bladder activation of lumbosacral dorsal spinal neurons. Moreover, the marked inhibition evoked by systemic application of AF-353 implicates P2X2/3 sensory purinergic receptors as significant drivers of bladder C-fiber mediated spinal neuronal activity.