Habituation: regulation through presynaptic inhibition.

During tail-flip escape responses of crayfish, synaptic transmission at the habituation-prone synapses of the lateral giant reflex pathway is presynaptically inhibited. This prevents transmitter release and all subsequent postsynaptic actions and spares the reflex from becoming habituated to stimuli produced by an animal's own escape movements. These observations demonstrate the existence of a control circuit whose adaptive function is to regulate the malleability of inherently plastic synapses. They also suggest that regulation of plasticity could be a common use of presynaptic inhibition.