In this paper on Aplysia operant conditioning, Fred Lorenzetti and colleagues find that PKC activity is upstream of an Adenylyl cyklase making cAMP (with other hypotheses dimmed). In Drosophila, we have a different PKC (aPKC) than in Aplysia, but this may be due to aPKC having evolved after the split (needs to be tested). Dopamine, in Drosophila may be used for regulation, not convergence. This would entail some hypotheses worth testing.

According to the RNAseq database, the adenylyl cyklase rutabaga is also expressed in the motor neurons where we think the plasticity for operant self-learning takes place. We know that mutations in the rut gene improve self-learning, excluding the hypotheiss that rut may be downstream of aPKC. However, Lorenzetti et al. found that their Aplysia AC in question was a type II AC, while rut is a type I AC. It is conceivable that removal of rut could free its cAMP pool for the type II AC and improve learning.

At the same time, it may be that this type II AC is downstream of a D2 receptor receiving input from the MBs inhibiting this AC, leading to inhibited self-learning while predictive colors are present. Imaging cAMP in these neurons would help us test this hypothesis.

Alternatively, hypothetically, aPKC may be downstream of an inhibitory cAMP pathway, perhaps via rut, such that rut mutation would lead to improved self-learning and rut activation via D1 receptors would inhibit self-learning. This is not impossible, as rut mutant flies show premature habit formation (N=30):