Reflex pathways controlling urethral striated and smooth muscle function in the male rat.


Journal Article

The organization of vesicourethral reflex mechanisms in the male rat was studied by monitoring intraurethral pressure and the external urethral sphincter (EUS) electromyogram. EUS striated and urethral smooth muscle activities were elicited by reflex isovolumetric bladder contractions evoked by bladder filling or electrical stimulation of nerves in the bladder wall. Evoked EUS bursting activity in normal rats was eliminated in chronic spinal rats and replaced by tonic activity. Reflex urethral smooth muscle activity mediated by an increase in urethral pressure after paralysis of the EUS with alpha-bungarotoxin occurred in normal and chronic spinal rats. The response was significantly larger in chronic spinal (21.3 +/- 3.0 cmH2O) than in normal rats (4.2 +/- 0.7 cmH2O). NG-nitro-L-arginine methyl ester (a nitric oxide synthase inhibitor, 20 mg/kg i.v.) increased the smooth muscle response in normal (5.9 +/- 1.3 cmH2O) and chronic spinal rats (6.9 +/- 1.8 cmH2O). This increase in urethral pressure was not changed by sympathetic nerve transection or prazosin (0.2-0.3 mg/kg i.v.) but was abolished by hexamethonium and reduced 74-89% by atropine. These results indicate that coordinated EUS function (bursting activity) in the male rat is dependent on supraspinal pathways and that the urethral smooth muscle response during voiding is composed of a predominant cholinergic, atropine-sensitive contraction as well as a nitric oxide-mediated relaxation. Both are mediated by activation of parasympathetic pathways and are maintained or significantly larger after spinal cord injury, indicating that they are dependent on spinal reflex pathways.

Full Text

Duke Authors

Cited Authors

  • Kakizaki, H; Fraser, MO; De Groat, WC

Published Date

  • May 1997

Published In

Volume / Issue

  • 272 / 5 Pt 2

Start / End Page

  • R1647 - R1656

PubMed ID

  • 9176360

Pubmed Central ID

  • 9176360

International Standard Serial Number (ISSN)

  • 0002-9513

Digital Object Identifier (DOI)

  • 10.1152/ajpregu.1997.272.5.R1647


  • eng

Conference Location

  • United States