Table 1.
Comparison of responses at term and during established labour
| PGF (10−5 M) | |||||||
|---|---|---|---|---|---|---|---|
| Plateau | Tension | Hyperpolarization | |||||
| Vrest(mV) | Level(mV) | Duration(min) | Amplitude(%) | Decline(to %) | Level(mV) | Amplitude(mV) | |
| Term (n= 22) | −59 ± 1 | −19 ± 1 | 2.3 ± 0.2 | 134 ± 7 | 69 ± 4 | −85 ± 2 | 22 ± 1 |
| Labour (n= 10) | −61 ± 2 | −22 ± 1 | 1.4 ± 0.2* | 190 ± 13* | 85 ± 5* | −70 ± 2* | 9 ± 1* |
Vrest: resting membrane potential. Plateau: the level of membrane potential attained during the plateau component of the action potential and the duration from spike upstroke to the initial repolarization. Tension: the peak amplitude of the increase in tension (as a percentage of spontaneous tension), and the level attained during the decline in tension (immediately prior to commencement of relaxation, as a percentage of the initial peak). Hyperpolarization: the level of membrane potential attained during the hyperpolarization and its amplitude (level minus Vrest). Observations at term (weeks 37–40 of pregnancy) and in established labour.
Significantly different from observations at term.