Stimulation of the cAMP system by the nitric oxide-cGMP system underlying the formation of long-term memory in an insect

[摘要] The nitric oxide (NO)-cGMP signaling system and CAMP system play critical roles in the formation of multiple-trial induced, protein synthesis-dependent long-term memory (LTM) in many vertebrates and invertebrates. The relationship between the NO-cGMP system and CAMP system, however, remains controversial. In honey bees, the two systems have been suggested to converge on protein kinase A (PICA), based on the finding in vitro that cGMP activates PICA when sub-optimal dose of CAMP is present. In crickets, however, we have suggested that NO-cGMP pathway operates on PICA via activation of adenylyl cyclase and production of CAMP for LTM formation. To resolve this issue, we compared the effect of multiple-trial conditioning against the effect of an externally applied cGMP analog for LTM formation in crickets, in the presence of sub-optimal dose of CAMP analog and in condition in which adenylyl cyclase was inhibited. The obtained results suggest that an externally applied cGMP analog activates PICA when sub-optimal dose of CAMP analog is present, as is suggested in honey bees, but cGMP produced by multiple-trial conditioning cannot activate PICA even when sub-optimal dose of CAMP analog is present, thus indicating that cGMP produced by multiple-trial conditioning is not accessible to PICA. We conclude that the NO-cGMP system stimulates the CAMP system for LTM formation. We propose that LTM is formed by an interplay of two classes of neurons, namely, NO-producing neurons regulating LTM formation and NO-receptive neurons that are more directly involved in the formation of long-term synaptic plasticity underlying LTM formation. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

[发布日期] 2009-12-25

[关键词] Olfactory learning;Memory;Nitric oxide synthase;Antagonist;Cricket