PRESYNAPTIC CALCIUM CALMODULIN-DEPENDENT PROTEIN-KINASE-II REGULATES HABITUATION OF A SIMPLE REFLEX IN ADULT DROSOPHILA/

On repetitive stimulation, the strength of a reflex controlling leg po sition in Drosophila decreased, and this response decrement conformed to the parametric features of habituation. To study the presynaptic fu nction of CaMKII in this nonassociative form of learning, we used a P[ Gal4] insertion line to target the expression of mutant forms of CaMKI I to the sensory neurons controlling the reflex. Targeted expression o f a calcium-independent CaMKII construct (T287D) in the sensory neuron s eliminated habituation. Targeted expression of a mutant CaMKII incap able of achieving calcium independence (T287A) reduced the initial ref lex response, but a strong facilitation then occurred, and this elimin ated most of the habituation. Finally, when a CaMKII inhibitory peptid e (ala) was expressed in sensory neurons, the initial response was red uced, followed by facilitation. These results suggest that basal CaMKI I levels in the presynaptic neurons set the response level and dynamic s of the entire neural circuit.