The neural and non-neural mechanisms involved in urethral activity in XXXX .

@entity2997 @entity1169 @entity3858 @entity1494 @entity1421 @entity5521 @entity95 @entity3009 @entity8765 @entity3897 @entity3352 @entity2899 @entity121 @entity1339
The effects of electrical and chemical stimulation on the mechanical or electrical properties of the circular smooth muscle cells of the @entity1494 , and proximal urethra of the male @entity95 were investigated by means of micro-electrode, double-sucrose-gap and tension-recording methods. In the @entity1494 , application of short current pulses (50 microseconds) produced an initial excitatory junction potential (e.j.p.) with a superimposed spike, followed by a late depolarization, and these electrical events evoked contraction. The initial e.j.p. was unaffected by @entity2997 , @entity5521 , @entity3858 or @entity8765 , indicating the initial e.j.p. is not mediated by activation of adrenergic, tryptaminergic or histaminergic receptors. The late depolarization was enhanced by pre-treatment with @entity1339 (10(-7) M) and abolished by @entity3897 (10(-6) M). In the proximal urethra, electrical-field stimulation evoked phasic contraction which was followed by relaxation, associated with initial e.j.p.s, late depolarization and inhibitory junction potentials (i.j.p.s). @entity2997 (10(-5) M) or @entity5521 (10(-6) M) reduced the size of the initial e.j.p. to 40-50% of the control value and combined application of @entity2997 and @entity3897 further reduced the amplitude of the e.j.p. to 20-30%. There was a parallel reduction in the mechanical response. The late depolarization was enhanced by @entity1339 and abolished by @entity3897 . The i.j.p. and @entity121 were not affected by @entity1169 , @entity5521 , @entity2997 or @entity3897 . These results indicate that the proximal urethral smooth muscle cells are innervated by adrenergic and cholinergic excitatory, and by non-cholinergic non-adrenergic inhibitory nerve fibres. In the prostatic urethra, field stimulations also evoked twitch contractions with or without following phasic contraction and relaxation. The twitch contractions were abolished by @entity2899 (10(-6) M), suggesting that they arise from striated muscle. Exogenously applied @entity3009 (PG) E1, @entity1421 or PGF2 alpha (greater than 10(-10) M) evoked sustained increase in the muscle tone in the presence or absence of @entity3352 , and enhanced the amplitude of @entity121 evoked by the field stimulation without affecting the resting membrane potential. @entity3352 (10(-6)-10(-5) M) gradually reduced the muscle tone of the proximal urethra with no change in the resting membrane potential. At the reduced muscle tone, electrical-field stimulation did not evoke @entity121 . Thus, the amplitude of @entity121 evoked by field stimulation was dependent on the level of muscle tone of the circular muscle strips.(ABSTRACT TRUNCATED AT 400 WORDS)
