[Effects of nitrous oxide and isoflurane on the L-type calcium current of rabbit ventricular myocytes and their modulation by beta-adrenoceptor stimulation].
BACKGROUND
We compared the effects of nitrous oxide (N2O) plus isoflurane with equianesthetic isoflurane alone on the L-type calcium current (I(Ca,L)), and also investigated their modulation of beta-adrenoceptor stimulation.


METHODS
I(Ca,L) was recorded from enzymatically isolated rabbit ventricular myocytes using the whole-cell patch clamp technique. Ventricular myocytes were exposed to prepluses of -40 mV from a holding potential of -80 mV and then to +50 mV in 10 mV increments and thereafter the depolarization pulses that acquire peak currents were applied every 10 seconds. The changes in I(Ca,L) were measured in exposure to experimental gases of 1 MAC:1) 0.5% isoflurane and N2O:O2 (2:1) (I-N20) and 2) 1.15% isoflurane and N2:O2,(2:1) (I-N2).


RESULTS
I-N2O and I-N2 depressed the peak I(Ca,L) by 15.6 +/- 9.2 and 14.6 +/- 8.1%, respectively. In the presence of 1 microM isoproterenol or 10 microM forskolin, the depression by I-N20 was significantly suppressed, but not by I-N2.


CONCLUSIONS
The results show that I-N2O and I-N2 depressed I(Ca,L) to a similar degree without beta-adrenoceptor stimulation. The depression by I-N2O, however, was modulated by beta-adrenoceptor stimulation. Beta-adrenoceptor stimulation was thus found to modulate the effect of N2O combined with isoflurane rather than equianesthetic isoflurane alone.
Fan
Liu
L
Department of Anesthesiology, Juntendo University School of Medicine, Tokyo.
Sonoda
Seijiro
S
Watanabe
Makino
M
Tsujikawa
Hiroto
H
Okada
Takao
T
Nishimura
Kinya
K
Takamori
Kenji
K
Ogawa
Hideoki
H
Inada
Eiichi
E
Kugimiya
Toyoki
T
D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D004338:Drug Combinations; D006352:Heart Ventricles / Q000166:cytology; D007530:Isoflurane / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000187:drug effects*; D009609:Nitrous Oxide / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
D000777:Anesthetics; D020746:Calcium Channels, L-Type; D004338:Drug Combinations; D011943:Receptors, Adrenergic, beta; D005576:Colforsin; D007530:Isoflurane; D009609:Nitrous Oxide; D007545:Isoproterenol