Contractile activity of mouse small intestinal longitudinal smooth muscle.
BACKGROUND
Interest in genomic modulation experimentally often necessitates use of mouse models.


METHODS



OBJECTIVE
To characterize and quantitate smooth muscle contractile activity of the mouse small intestine using in vitro techniques. Full-thickness jejunal and ileal muscle strips from mice were cut in the direction of longitudinal muscle, suspended in tissue baths (37 degrees C), and connected to force transducers. Spontaneous contractility and two dose-response curves to the cholinergic agonist bethanechol and adrenergic agonist norepinephrine were quantitated for 6 h.


RESULTS
Total contractile activity increased over 4 to 5 h in jejunum (P < 0.01) but not in ileum. Frequency of contractions (counts/min) in jejunum increased from 16 to 33 (P < 0.01) in the first 4 h, then remained stable; ileal frequency did not change. One hour of cold preservation had no major effect on contractile activity and frequency. Bethanechol increased and norepinephrine decreased contractile activity in dose-dependent fashion. The dose of bethanechol producing 50% increase in maximal response did not differ between the first and second dose-response; in contrast, the concentration of norepinephrine producing 50% decrease in activity for the second dose-response in jejunum was decreased compared to the first dose-response (P < 0.01). Cold preservation had no substantive effect on agonist responses.


CONCLUSIONS
Experiments in murine jejunal but not ileal longitudinal muscle in vitro must consider early changes in contractile activity after tissue harvest. These experiments serve as a baseline for comparison of stimuli or genetic modifications on murine contractile activity of longitudinal muscle in vivo.
Ueno
Tatsuya
T
Department of Surgery and the Gastroenterology Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA.
Duenes
Judith A
JA
Kost
Louis J
LJ
Sarr
Michael G
MG
D000322:Adrenergic Agonists / Q000494:pharmacology; D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D007082:Ileum / Q000502:physiology*; D007583:Jejunum / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology
D000322:Adrenergic Agonists; D018679:Cholinergic Agonists; D018723:Bethanechol; D009638:Norepinephrine