Heterologous expression of the XXXX @entity972 channel eliminates spike broadening and the induction of a depolarizing afterpotential in the peptidergic bag cell neurons.

@entity18650 @entity9399 @entity460 @entity972
The bag cell neurons of Aplysia are a cluster of cells that control egg laying behavior. After brief synaptic stimulation, they depolarize and fire spontaneously for up to 30 min. During the first few seconds of this afterdischarge, the action potentials of the bag cell neurons undergo pronounced broadening. Single bag cell neurons in culture also show spike broadening in response to repeated depolarizations. This broadening is frequency-dependent and associated with the induction of a depolarizing afterpotential lasting minutes. In some neurons the depolarizing afterpotential is sufficient to trigger spontaneous firing. To test the possibility that spike broadening during stimulation is required to trigger the depolarizing afterpotential, we eliminated frequency-dependent broadening by heterologous expression of the @entity9399 @entity972 channel. This channel has rapid activation and deactivation kinetics and no use-dependent inactivation. Expression of @entity9399 prevented spike broadening and also eliminated the depolarizing afterpotential. Measurements of the integral of @entity460 current during voltage commands, which simulated the action potentials of the control neurons and those expressing @entity9399 , indicate that spike broadening produces up to a fivefold increase in @entity460 entry. Manipulations that limit @entity460 entry during action potentials or chelation of intracellular @entity460 using @entity18650 AM prevented the induction of the depolarizing afterpotential. We conclude that spike broadening is essential for the induction of the depolarizing afterpotential probably by regulating @entity460 influx and suggest that one of the physiological roles of spike broadening may be to regulate long-term changes in neuronal excitability.
