Excitable properties of insect neurones in culture: A developmental study

The passive and excitable electrical properties of cockroach neurones growing in vitro have been investigated using intracellular recording techniques. The resting membrane potentials of the neurones are similar to those of their in vivo counterparts but the input resistances and membrane capacitive properties are more typical of embryonic insect neurones. During the first 12 days of growth in vitro the neurones exhibit delayed rectification in response to the injection of depolarising current steps. After this period “all or none” action potentials can be evoked by depolarising pulses in approximately half of the neurones tested. These spikes are abolised by 1 μM tetrodotoxin but are unaffected by 5 mM Co²⁺. Spontaneous excitatory activity develops in approx 25% of the neurones after 3 weeks in culture.