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Examination of potential sources of smooth muscle for use as a transplantable, innervated sphincter.
Author(s) -
BRAMICH N.J.,
O'CONNELL H.E.,
HIRST G.D.S.
Publication year - 2006
Publication title -
bju international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.773
H-Index - 148
eISSN - 1464-410X
pISSN - 1464-4096
DOI - 10.1111/j.1464-410x.2006.06085_79.x
Subject(s) - depolarization , stimulation , contraction (grammar) , membrane potential , anatomy , sphincter , chemistry , electrophysiology , stimulus (psychology) , medicine , biophysics , biology , psychology , psychotherapist
Aim: To examine the electrical and mechanical properties of different smooth muscle tissues for their suitability to assist the malfunctioning urethral sphincter in the treatment of stress urinary incontinence. Methods: Changes in contractile state and membrane potential, in response to nerve stimulation, were measured from guinea‐pig mesenteric veins, detrusor smooth muscle and rat dartos. Results: Intracellular recordings made from mesenteric veins (diameter 100–250 ??m) displayed stable resting membrane potentials (RMPs) of –65.2 ± 2.7 mV (10 cells, five animals). Stimulation with long trains at low frequencies (80s, 0.5–2 Hz), evoked slow sustained membrane depolarizations and constrictions which reached a peak within 50s. Stimulation at 2Hz evoked a membrane depolarization of 16.3 ± 4mV and a 17 ± 7% reduction in vessel diameter. Upon cessation of stimulation, the membrane potential and blood vessel diameter rapidly returned to baseline levels. Detrusor smooth muscle cells had RMPs of –40 ± 4 mV ( n = 3). Stimulation at frequencies of 1 to 5 Hz evoked muscle action potentials and contractions. Contractions evoked by long trains of nerve stimulation were not sustained for the duration of stimulus. For example, a stimulus train of 80 s at 1 Hz, evoked a contraction of 20 ± 9 mN which reduced to 3 ± 1 mN ( n = 3). Hyoscine reduced the secondary phase of the contraction from 3 ± 0.4 mN to 0.7 ± 0.4 mN ( P < 0.01, n = 3). Rat dartos smooth muscle had a RMP of –64 ± 1 mV ( n = 38). Long trains of low frequency nerve stimulation (1 Hz for 80s), evoked a slow membrane depolarization of 15 ± 4 mV and sustained contraction of 12 ± 2 mN. Increasing the frequency of stimulation caused a graded increase in the amplitude of both the membrane depolarization and contraction. Following the cessation of stimulus, the membrane potential and force generated by the smooth muscle immediately returned to baseline. All responses were blocked by the α‐adrenoceptor antagonists phentolamine (1 μM) and prazosin (0.1 μM). Conclusion: Smooth muscles of the mesenteric vein and dartos display contractile properties which make them suitable for use as transplantable sphincters. In addition, dartos smooth muscle possesses similar pharmacological properties to the proximal urethral sphincter.