THE EFFECTS OF NITROUS-OXIDE ON A GLUTAMATE-GATED ION-CHANNEL AND THEIR REVERSAL BY HIGH-PRESSURE - A SINGLE-CHANNEL ANALYSIS

Nitrous oxide reversibly affects the kinetics, but not the conductance , of the qGluR channel of locust muscle. 0.5 atm N2O at 20.5 degrees C was without effect but both 1.5 and 2.7 atm significantly reduced the probability of the channel opening, the frequency of opening and the mean open time, and prolonged the mean closed time. 100 atm helium was without effect on these parameters, but when 98.5 atm He was combined with 1.5 arm N2O they, and the associated dwell time distributions, w ere restored to normal. 100 atm similarly combined with 2.7 atm N2O ex erted a comparable trend which fell short of significance. The results are consistent with nitrous oxide binding to the channel with a signi ficant molar volume increase, which pressure opposes. This suggests th at nitrous oxide may cause conformational changes in the channel, and that the pressure reversal of nitrous oxide anaesthesia in animals cou ld be caused by molecular antagonism.