Intrathecal veratridine administration increases minimum alveolar concentration in rats.
BACKGROUND
Results from several studies point to sodium channels as potential mediators of the immobility produced by inhaled anesthetics. We hypothesized that the intrathecal administration of veratridine, a drug that enhances the activity or effect of sodium channels, should increase MAC.


METHODS
We measured the change in isoflurane MAC caused by intrathecal infusion of various concentrations of veratridine into the lumbothoracic subarachnoid space of rats. We compared these result with those obtained from intracerebroventricular infusion.


RESULTS
As predicted, intrathecal infusion of veratridine increased MAC. The greatest infused concentration (25 microM) also produced neuronal injury in the hindlimbs of two rats and decreased the peak effect on MAC. A concentration of 1.6 microM produced the largest (21%) increase in MAC. Intraventricular infusion of 1.6 and 6.4 microM veratridine did not alter MAC. Rats given 25 microM died.


CONCLUSIONS
Intrathecal administration of veratradine increases MAC of isoflurane, a finding consistent with a role for sodium channels as potential mediators of the immobility produced by inhaled anesthetics.
Zhang
Yi
Y
Department of Anesthesiology, Fuwai Hospital and Cardiovascular Institute, Beijing, China.
Sharma
Manohar
M
Eger
Edmond I
EI
Laster
Michael J
MJ
Hemmings
Hugh C
HC
Harris
R Adron
RA
D000758:Anesthesia / Q000379:methods; D000777:Anesthetics / Q000008:administration & dosage; D000818:Animals; D004305:Dose-Response Relationship, Drug; D007103:Immobilization; D020128:Inhibitory Concentration 50; D007278:Injections, Spinal / Q000379:methods*; D007530:Isoflurane / Q000494:pharmacology; D008297:Male; D011650:Pulmonary Alveoli / Q000187:drug effects*; D051381:Rats; D020318:Rats, Long-Evans; D015222:Sodium Channels / Q000737:chemistry; D013346:Subarachnoid Space / Q000378:metabolism; D014701:Veratridine / Q000008:administration & dosage*
D000777:Anesthetics; D015222:Sodium Channels; D014701:Veratridine; D007530:Isoflurane