Influence of temperature on urethra to bladder micturition reflex in the awake ewe.
OBJECTIVE
The flow of fluid along the urethra is known to facilitate detrusor contraction during micturition. This reflex, previously described in awake ewes, helps to achieve complete bladder emptying. In anesthetized cats, another urethra to bladder reflex involving urethral cold receptors has been described. The aim of this study was to investigate whether the urethral reflex first described in awake ewes could also be temperature-dependent.


METHODS
Experiments were performed on 10 healthy ewes. Urethral flows were performed by injecting 10 ml saline (ranging from 17 to 43 degrees C) at the level of the proximal urethra. Catheterization of the bladder was performed so that detrusor pressure was continually recorded during the experiments.


RESULTS
Urethral flows using body temperature saline (37-39 degrees C) consistently evoked detrusor contraction. Urethral flows using saline at temperatures between 40 and 43 degrees C induced detrusor contractions that were not significantly different from those observed at 37-39 degrees C. Urethral flows using saline at temperatures below 37-39 degrees C (17-36 degrees C) resulted in a weaker or absent detrusor contraction.


CONCLUSIONS
In ewes, we have shown that urethral to bladder micturition reflex involving mechanoreceptors is decreased at temperatures below the physiological range. It is suggested that transient receptor potential vanilloid cation channels (e.g., TRPV4 which is activated by sheer/stress flows at near-body temperature) could be involved in this urethra to bladder reflex. In humans, this reflex has hardly been described and is still a matter of debate. Our results reinforce that its full investigation may require systematic use of a range of saline flows at different temperatures.
Combrisson
Helene
H
Department of Physiology and Therapeutics, Ecole Nationale Vétérinaire d'Alfort, 7 Avenue Général de Gaulle, 94704 Maisons-Alfort, France. hcombrisson@vet-alfort.fr
Allix
Sebastien
S
Robain
Gilberte
G
D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D002415:Cats; D003627:Data Interpretation, Statistical; D004576:Electromyography; D005260:Female; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D012756:Sheep; D050051:Transient Receptor Potential Channels / Q000187:drug effects / Q000502:physiology; D014521:Urethra / Q000502:physiology*; D001743:Urinary Bladder / Q000502:physiology*; D014554:Urination / Q000502:physiology*; D014563:Urodynamics
D050051:Transient Receptor Potential Channels