Reduced ionic conductance in turtle brain.

Whole cell recording techniques were employed to measure whole cell (Gw) and specific membrane (Gm) conductance in turtle and rat pyramidal neurons in slices. Results indicate that rat neurons are 4.2 times more conductive compared with turtle neurons at 25 degrees C, which is accentuated by temperature, so that rat neurons at 37 degrees C are 22 times more conductive than turtle neurons at 15 degrees C. A conductance Q10 of 1.9 was measured for both turtle (15-25 degrees C) and rat (25-35 degrees C) pyramidal neurons. Conductance measurements of turtle pyramidal neurons over 6-9 h of anoxia indicate no statistical difference between Gm or Gw from normoxic control measures. These results indirectly support the concept of low ATP-dependent ion pump activity in the turtle brain as one mechanism for reduced energy expenditure in the normoxic state.