Background and purpose
We investigated the effects of centrally administered stress-related neuropeptide, angiotensin II, on the micturition reflex and the downstream signalling pathways in rats. Experimental approach: Male Wistar rats were anaesthetized with urethane for cystometry before and after i.c.v. administration of vehicle or angiotensin II (30 pmol). Muscimol (a GABAA receptor agonist) or baclofen (a GABAB receptor agonist) was i.c.v. administered 30 min before or 15 min after central angiotensin II administration. Telmisartan [an angiotensin II type 1 (AT1 ) receptor antagonist], valsartan (an AT1 receptor antagonist), PD123319 (an AT2 receptor antagonist), U-73122 (a PLC inhibitor), chelerythrine chloride (a PKC inhibitor), apocynin (a NADPH oxidase inhibitor) or tempol (an antioxidant) was centrally administered 30 min before central angiotensin II administration. Key
Purpose
We investigated the effects of centrally administered stress-related neuropeptide, angiotensin II, on the micturition reflex and the downstream signalling pathways in rats. Experimental approach: Male Wistar rats were anaesthetized with urethane for cystometry before and after i.c.v. administration of vehicle or angiotensin II (30 pmol). Muscimol (a GABAA receptor agonist) or baclofen (a GABAB receptor agonist) was i.c.v. administered 30 min before or 15 min after central angiotensin II administration. Telmisartan [an angiotensin II type 1 (AT1 ) receptor antagonist], valsartan (an AT1 receptor antagonist), PD123319 (an AT2 receptor antagonist), U-73122 (a PLC inhibitor), chelerythrine chloride (a PKC inhibitor), apocynin (a NADPH oxidase inhibitor) or tempol (an antioxidant) was centrally administered 30 min before central angiotensin II administration. Key
Results
Centrally administered angiotensin II significantly shortened the intercontraction interval and decreased the voided volume and bladder capacity without altering the maximum voiding pressure, post-voiding residual urine volume or voiding efficacy. Muscimol, baclofen, telmisartan, valsartan, U-73122, chelerythrine chloride, apocynin or tempol pretreatment significantly suppressed the reduction in intercontraction interval induced by central angiotensin II. Post-treatment with muscimol or baclofen also ameliorated the decrease in intercontraction interval induced by central angiotensin II. Conclusions and implications: Angiotensin II in the CNS facilitates micturition reflex by inhibiting central GABAergic activity and activating the AT1 receptor/PLC/PKC/NADPH oxidase/superoxide anion pathway.