Continence and some properties of the urethral striated muscle of male greyhounds.

OBJECTIVE

To determine the properties of the striated muscle of the greyhound (dog) urethra and to consider its role in maintaining continence. Materials and methods The thickness of the muscle layers and the muscle types were determined by examining sections stained with haematoxylin and eosin or Masson's trichrome. These factors were correlated with the mechanical and electrical responses of muscle strips to nerve stimulation, and compared with muscle from other breeds of dog and other parts of the animal.

RESULTS

The striated muscle formed approximately 70% of the membranous urethra and was predominantly (68%) type IIa muscle (i.e. fast but fatigue-resistant). The mean resting membrane potential was -74 mV; nerve stimulation produced an action potential with a mean amplitude of 97 mV and contraction lasting about 200 ms. All responses were abolished by D-tubocurarine. The contractions were well maintained with continuous or intermittent stimulation. The properties were intermediate between those of the anconeus (slow) and the extensor carpi radialis (fast) muscles.

CONCLUSIONS

The distribution, fibre type and contractile characteristics would enable the striated urethral muscle to maintain tension for continence at rest and provide additional continence during sprints.