ELECTRICAL POLYSPERMY BLOCK IN SEA URCHINS: NICOTINE AND LOW SODIUM EXPERIMENTS1.

Nicotine reduces the amplitude of the fertilization potential in sea urchin eggs, at least in part because it decreases the slope of the current voltage relation of the unfertilized egg membrane. The reduced fertilization potential amplitude provides an electrophysiological explanation for previous observations that nicotine impairs the fast block to polyspermy. The block to polyspermy is also impaired by fertilization in low sodium sea water, a medium which has been reported to reduce fertilization potential amplitude.