The role of cAMP-dependent protein kinase A in the formation of long-term memory in Bactrocera dorsalis

The cAMP-dependent protein kinase A(PKA) signaling pathway has long been considered critical for long-term memory(LTM) formation. Previous studies have mostly focused on the role of PKA signaling in LTM induction by multiple spaced conditioning with less attention to LTM induction by a single conditioning. Here, we conducted behavioral-pharmacology, enzyme immunoassay and RNA interference experiments to study the role of the PKA signaling pathway in LTM formation in the agricultural pest Bactrocera dorsalis, which has a strong memory capacity allowing it to form a two-day memory even from a single conditioning trial. We found that either blocking or activating PKA prior to conditioning pretreatment affected multiple spaced LTM, and conversely, they did not affect LTM formed by single conditioning. This was further confirmed by enzyme-linked immunosorbent assay(ELISA) and silencing of the protein kinase regulatory subunit 2 and catalytic subunit 1. Taken together, these results suggest that activating PKA during memory acquisition helps to induce the LTM formed by multiple spaced conditioning but not by a single conditioning. Our findings challenge the conserved role of PKA signaling in LTM, which provides a basis for the greater diversity of molecular mechanisms underlying LTM formation across species, as well as possible functional and evolutionary implications.