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Effects of phasic and tonic activation on contraction dynamics in smooth muscle

Uvelius, Bengt LU and Hellstrand, Per LU (1980) In Acta Physiologica Scandinavica 109(4). p.399-406
Abstract
Responses to isotonic quick releases of rabbit urinary bladder strips and rat portal veins activated by AC-stimulation and K+-high medium were studied. The AC stimulation was adjusted to give the same tension as th K+-contractures. Releases were performed at peak of the contractions (which was attained after 1.5-4.5 s AC-stimulation or 2-3 min in K+-high solution). The length response consisted of 3 parts: (1) elastic recoil, (2) isotonic transient, (3) steady shortening. Shortening velocity was determined at 100 ms after the release, as phase (2) had subsided by then. Characteristics of the initial elastic response was virtually unaffected by the mode of stimulation for both preparations. Vmax was significantly higher for the... (More)
Responses to isotonic quick releases of rabbit urinary bladder strips and rat portal veins activated by AC-stimulation and K+-high medium were studied. The AC stimulation was adjusted to give the same tension as th K+-contractures. Releases were performed at peak of the contractions (which was attained after 1.5-4.5 s AC-stimulation or 2-3 min in K+-high solution). The length response consisted of 3 parts: (1) elastic recoil, (2) isotonic transient, (3) steady shortening. Shortening velocity was determined at 100 ms after the release, as phase (2) had subsided by then. Characteristics of the initial elastic response was virtually unaffected by the mode of stimulation for both preparations. Vmax was significantly higher for the AC-stimulations than for the K+-contractures (bladder: 0.37 l/s vs. 0.26 l/s, portal vein: 0.46 l/s vs. 0.33 l/s). By means of computer analysis a fast exponential shortening component comprising the larger part of phase (2) could be separated from the subsequent slower shortening (see further in Hellstrand & Johansson 1979). In each preparation the amplitude of this exponential was the same for both modes of activation. The time constant was, however, smaller for the AC-stimulation preparations. Our results thus indicate that in response to a sudden decrease in force the initial elastic recoil is the same whereas the rate of transition to steady shortening, and the steady shortening velocity itself, are lower for preparations activated by K+-high medium compared to AC-stimulation. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Acta Physiologica Scandinavica
volume
109
issue
4
pages
399 - 406
publisher
Wiley-Blackwell
external identifiers
  • pmid:7468260
  • scopus:0018973030
ISSN
0001-6772
language
English
LU publication?
yes
id
3e0613c7-f909-4c54-8623-346b942cc843 (old id 1102786)
date added to LUP
2008-08-14 09:20:31
date last changed
2017-06-04 04:24:40
@article{3e0613c7-f909-4c54-8623-346b942cc843,
  abstract     = {Responses to isotonic quick releases of rabbit urinary bladder strips and rat portal veins activated by AC-stimulation and K+-high medium were studied. The AC stimulation was adjusted to give the same tension as th K+-contractures. Releases were performed at peak of the contractions (which was attained after 1.5-4.5 s AC-stimulation or 2-3 min in K+-high solution). The length response consisted of 3 parts: (1) elastic recoil, (2) isotonic transient, (3) steady shortening. Shortening velocity was determined at 100 ms after the release, as phase (2) had subsided by then. Characteristics of the initial elastic response was virtually unaffected by the mode of stimulation for both preparations. Vmax was significantly higher for the AC-stimulations than for the K+-contractures (bladder: 0.37 l/s vs. 0.26 l/s, portal vein: 0.46 l/s vs. 0.33 l/s). By means of computer analysis a fast exponential shortening component comprising the larger part of phase (2) could be separated from the subsequent slower shortening (see further in Hellstrand & Johansson 1979). In each preparation the amplitude of this exponential was the same for both modes of activation. The time constant was, however, smaller for the AC-stimulation preparations. Our results thus indicate that in response to a sudden decrease in force the initial elastic recoil is the same whereas the rate of transition to steady shortening, and the steady shortening velocity itself, are lower for preparations activated by K+-high medium compared to AC-stimulation.},
  author       = {Uvelius, Bengt and Hellstrand, Per},
  issn         = {0001-6772},
  language     = {eng},
  number       = {4},
  pages        = {399--406},
  publisher    = {Wiley-Blackwell},
  series       = {Acta Physiologica Scandinavica},
  title        = {Effects of phasic and tonic activation on contraction dynamics in smooth muscle},
  volume       = {109},
  year         = {1980},
}