THE GENERAL ANESTHETIC PROPOFOL INHIBITS TRANSMEMBRANE CALCIUM CURRENT IN CHICK SENSORY NEURONS

The action of propofol on voltage-gated calcium channels was investiga ted in cultured dorsal root ganglion neurons from chick embryos. The C a2+ current was measured by using the patch-clamp technique in whole c ell configuration. Low-voltage-activated (LVA) and high-voltage-activa ted (HVA) Ca2+ currents were selected by means of appropriate stimulat ion protocols. Propofol (0.3 mM) inhibited the LVA T-type current by 8 0% (P < 0.001). The same concentration of propofol reduced the HVA Ga2 + current with a high variability (10%-75%). The inactivation time con stant of the HVA current was also shortened to 50% by propofol. omega- Conotoxin and nifedipine were used to discriminate between the HVA N- and L-type current components. Only the L-type component was strongly depressed (75%) by propofol (P < 0.001); different effects on the HVA current might, therefore, reflect different percentages of L- and N-ty pe channels in neurons. We conclude that propofol inhibits the T-type and L-type components of the Ca2+ current. This inhibition may play a role in the cardiovascular side effects clinically observed.