Modulation of Spontaneous Electrical Activity in Urethral Smooth Muscle

2003 ◽  
Vol 35 (3/4) ◽  
pp. 217-223
Author(s):  
N. G. McHale ◽  
K. D. Thornbury ◽  
M. A. Hollywood ◽  
G. P. Sergeant
Keyword(s):  
Smooth Muscle ◽  
Electrical Activity ◽  
Spontaneous Electrical Activity ◽  
Urethral Smooth Muscle

Long-term observations of spontaneous electrical activity of the uterine smooth muscle

1959 ◽  
Vol 196 (2) ◽  
pp. 343-350 ◽  
Author(s):  
C. Y. Kao
Keyword(s):  
Smooth Muscle ◽  
Electrical Activity ◽  
Action Potentials ◽  
Local Conditions ◽  
Pregnant Uterus ◽  
Implanted Electrodes ◽  
Spontaneous Electrical Activity ◽  
Myometrial Cells ◽  
Uterine Smooth Muscle

The spontaneous electrical activity of uterine smooth muscle was rather variable when acute observations were made. Therefore, a series of chronic experiments was performed with implanted electrodes to monitor a group of myometrial cells under different physiological conditions for periods up to eight weeks. The results showed that consistent behavior of myometrial cells could be observed provided similar hormonal status was maintained. Action potentials were rare or absent in myometrium of oophorectomized animals but were caused to appear by estrogen. In the pregnant uterus, action potentials increased both in amplitude and frequency of discharge as parturition approached, reached a peak at that time, and then declined in the postpartum days. The results indicated that in estrogen treatment and in parturition activities of myometrial cells were more synchronous. There was suggestive evidence that there were central impulses initiating activity in the pregnant uterus, and that the responses of the myometrium were affected by the local conditions.

scholarly journals Characterization of T-type calcium current and its contribution to electrical activity in rabbit urethra

2004 ◽  
Vol 286 (5) ◽  
pp. C1078-C1088 ◽  
Author(s):  
J. E. Bradley ◽  
U. A. Anderson ◽  
S. M. Woolsey ◽  
K. D. Thornbury ◽  
N. G. McHale ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Electrical Activity ◽  
Calcium Current ◽  
Pharmacological Properties ◽  
Patch Clamp Technique ◽  
Steady State Inactivation ◽  
Rabbit Urethra ◽  
Patch Configuration ◽  
Urethral Smooth Muscle

Rabbit urethral smooth muscle cells were studied at 37°C by using the amphotericin B perforated-patch configuration of the patch-clamp technique, using Cs+-rich pipette solutions. Two components of current, with electrophysiological and pharmacological properties typical of T- and L-type Ca2+ currents, were recorded. Fitting steady-state inactivation curves for the L current with a Boltzmann equation yielded a V1/2 of -41 ± 3 mV. In contrast, the T current inactivated with a V1/2 of -76 ± 2 mV. The L currents were reduced by nifedipine (IC50 = 225 ± 84 nM), Ni2+ (IC50 = 324 ± 74 μM), and mibefradil (IC50 = 2.6 ± 1.1 μM) but were enhanced when external Ca2+ was substituted with Ba2+. The T current was little affected by nifedipine at concentrations <300 nM but was increased in amplitude when external Ca2+ was substituted with Ba2+. Both Ni2+ and mibefradil reduced the T current with an IC50 = 7 ± 1 μM and ∼40 nM, respectively. Spontaneous electrical activity recorded with intracellular electrodes from strips of rabbit urethra consisted of complexes comprising a series of spikes superimposed on a slow spontaneous depolarization (SD). Inhibition of T current reduced the frequency of these SDs but had no effect on either the number of spikes per complex or the amplitude of the spikes. In contrast, application of nifedipine failed to significantly alter the frequency of the SD but reduced the number and amplitude of the spikes in each complex.

Electrical Activity in Chick Amnion

1956 ◽  
Vol 187 (3) ◽  
pp. 546-548 ◽  
Author(s):  
C. Ladd Prosser ◽  
Nancy S. Rafferty
Keyword(s):  
Smooth Muscle ◽  
Electrical Activity ◽  
Muscle Fibers ◽  
Chick Embryos ◽  
Spontaneous Electrical Activity

Isolated amnions from chick embryos showed spontaneous electrical activity, both local and conducted. Responses to barium and to shocks were conducted at an average of 2.9 cm/sec. (38–40°C). Conducted responses were observed in amnions at 5–10 days of incubation. Failure of conduction in older amnions appears related to the shortening and increased randomness of the muscle fibers. This preparation gives conclusive proof of conduction in nerve-free smooth muscle.

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