Conscious voiding during bladder obstruction in guinea pigs correlates with contractile activity of isolated bladders.
OBJECTIVE
There are many hypotheses accounting for detrusor overactivity; however, the exact mechanisms are still incompletely understood. We used a model of bladder outlet obstruction in male guinea pigs as a way to produce detrusor overactivity. The objective was to determine whether changes in voiding of obstructed guinea pigs correlates with specific changes in contractile activity of their isolated bladders in vitro.


METHODS
Conscious voiding activity of sham-operated and obstructed animals was measured in metabolic cages. Contractile activity (spontaneous or evoked by distension, electrical field stimulation or cholinergic agonists) was recorded via a pressure transducer in the isolated bladders in vitro.


RESULTS
The frequency of conscious voiding increased (while voiding volume decreased) in the obstructed group, compared with the sham-operated group, 4 weeks after surgical intervention. In comparison to the sham-operated animals, the bladders from the obstructed guinea pigs were enlarged and inflamed, their frequency of spontaneous contractions was higher, while the amplitudes of electrical field stimulation (EFS)-induced contractions and bladder compliance were lower. Changes in conscious voiding during obstruction were significantly associated with alterations in structural parameters (bladder weight, thickness and histological damage score) and functional contractile parameters (frequency of spontaneous contractions, amplitude of EFS-induced contractions and bladder compliance) of their isolated bladders.


CONCLUSIONS
Our findings revealed significant association between conscious voiding and structural and contractile activity changes of the isolated bladders in obstruction. The data suggest that change in contractile activity of the bladder itself is a major contributor to obstruction-induced bladder overactivity.
Discipline of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University, Adelaide, Australia.
Sarah
S
Nicholas
Discipline of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University, Adelaide, Australia.
Lauren
L
Keightley
Discipline of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University, Adelaide, Australia.
Simon
S
Brookes
Discipline of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University, Adelaide, Australia.
Marcello
M
Costa
Discipline of Anatomy and Histology, Flinders Medical Science and Technology Cluster, Flinders University, Adelaide, Australia.
Ian
I
Gibbins
Discipline of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University, Adelaide, Australia. Electronic address: vladimir.zagorodnyuk@flinders.edu.au.
Vladimir
V
Zagorodnyuk
D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003243:Consciousness; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D009929:Organ Size; D010830:Physostigmine / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D001748:Urinary Bladder Neck Obstruction / Q000473:pathology / Q000503:physiopathology*; D014554:Urination / Q000187:drug effects / Q000502:physiology*
D002800:Cholinesterase Inhibitors; D018721:Muscarinic Agonists; D018723:Bethanechol; D010830:Physostigmine
Bladder; Contraction; Obstruction; Overactivity; Smooth muscle