Sevoflurane inhibits contraction of uterine smooth muscle from pregnant rats similarly to halothane and isoflurane.
OBJECTIVE
The present study was designed to clarify the direct effects of the volatile anesthetics halothane, isoflurane and sevoflurane on oxytocin-induced uterine smooth muscle contraction from pregnant rats.


METHODS
Longitudinal smooth muscle layers were obtained from pregnant rats. Intracellular concentration of free Ca++ ([Ca++](i)) was measured, using a fluorescence technique, simultaneously with muscle tension. Inward Ba++ current (I(Ba)) through voltage-dependent Ca++ channels (VDCCs) was measured using a whole cell patch clamp technique. After incubation with 20 nM oxytocin, halothane, isoflurane or sevoflurane (1, 2, and 3%) was introduced into the tissue bath.


RESULTS
All volatile anesthetics significantly inhibited muscle contraction concomitant with a decrease in [Ca++](i). Volatile anesthetics also inhibited the peak I(Ba). When the anesthetic concentrations were expressed as multiples of minimum alveolar concentrations, there were no differences in the inhibitory potencies of the three volatile agents tested for muscle tension and VDCC.


CONCLUSIONS
Volatile anesthetics halothane, isoflurane and sevoflurane reduce the oxytocin-induced contraction of pregnant uterine smooth muscle. Inhibition of the contraction by the volatile anesthetics is due, at least in part, to the decrease in [Ca++](i), and the decrease in [Ca++](i) may be mediated by inhibition of VDCC activity.
Yamakage
Michiaki
M
Department of Anesthesiology, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan. yamakage@sapmed.ac.jp
Tsujiguchi
Naoki
N
Chen
Xiangdong
X
Kamada
Yasuhiro
Y
Namiki
Akiyoshi
A
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes; D016257:Fura-2; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D008738:Methyl Ethers / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects; D010121:Oxytocin / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077149:Sevoflurane; D014590:Uterine Contraction / Q000187:drug effects*
D018685:Anesthetics, Inhalation; D015220:Calcium Channels; D005456:Fluorescent Dyes; D008738:Methyl Ethers; D001464:Barium; D000077149:Sevoflurane; D010121:Oxytocin; D007530:Isoflurane; D002118:Calcium; D016257:Fura-2; D006221:Halothane