Cellular and biophysical mechanisms contributing to regulation of reflex excitability of inking behavior in Aplysia.

Inking behavior in Aplysia offers a simple test system whereby it is possible to examine the cellular and biophysical determinants of a simple behavior and its ability to undergo a short-term behavioral modification. The features of the behavior and its underlying neural circuit, as well as the intrinsic biophysical properties of the effector motor neurons, have been analyzed. Inking behavior shows a selective sensitivity to long-duration stimuli, which appears due to presence of a voltage-dependent fast K+ current and a slow buildup of synaptic input in the ink gland motor neurons. The ability of the behavior to undergo a short-term modification of reflex-excitability appears due to the activation of a prolonged synaptic current in the ink motor neurons.