Oxytocin enhances action potentials in pregnant human myometrium--a study with microelectrodes.
OBJECTIVE
Our purpose was to quantitatively assess the effects of oxytocin on membrane properties in the pregnant human myometrium.


METHODS
Specimens were obtained from the lower uterine segment during cesarean section at term. Electrical activity was recorded from individual cells by a conventional microelectrode method and the membrane functions were analyzed.


RESULTS
Two types of spontaneous action potentials were seen: a long plateau potential and a spike-like action potential. With no change in the resting membrane potential, low concentrations of oxytocin either evoked an action potential with a plateau phase, increased the amplitude and duration of the plateau potential, or increased the frequency of generation of action potentials. Oxytocin also lowered the threshold for evoking an action potential. Higher concentrations depolarized the membrane with an associated reduction in membrane resistance.


CONCLUSIONS
Oxytocin augments the excitability of pregnant human myometrial cells by multiple actions on the membrane, affecting both frequency and amplitude of action potentials.
Nakao
K
K
Department of Pharmacology, Faculty of Medicine, Kyushu University, Japan.
Inoue
Y
Y
Okabe
K
K
Kawarabayashi
T
T
Kitamura
K
K
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000328:Adult; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes; D009215:Myometrium / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D010121:Oxytocin / Q000494:pharmacology*; D011247:Pregnancy / Q000502:physiology*
D010121:Oxytocin