Electrophysiological studies on the effects of the neurotoxin apamin on cultured neurons

Primary cultures of rat embryonic central nervous system were grown for 3 to 4 weeks in vitro. Impalement of neurons by means of high-resistance glass pipettes revealed that firing of action potentials could either be elicited by application of short square pulses or occurred spontaneously. The presence of the neurotoxin apamin caused a hyperpolarization of the membrane potential accompanied by an increase of the spike amplitude as well as an increase of membrane resistance. The significance of this effect is discussed in terms of a postsynaptic effect of this toxin.