Pre- and postsynaptic changes mediated by two second messengers contribute to expression of Aplysia long-term heterosynaptic inhibition.
FMRFamide evokes long-term inhibition of the sensorimotor connection of Aplysia that includes structural alterations in the presynaptic sensory cell. FMRFamide also evokes a down-regulation of the adhesion molecule apCAM from the surface of the postsynaptic motor cell L7. We examined the second messenger pathways mediating the long-term actions of FMRFamide on both the pre- and postsynaptic cells and determined whether the activation of each pathway is required for the expression of long-term functional and structural plasticity. Inhibition of the lipoxygenase pathway of arachidonic acid metabolism, but not the cyclooxygenase pathway, blocks the long-term changes in the presynaptic sensory cell evoked by FMRFamide. The down-regulation of apCAM in L7 appears to be mediated by cAMP-dependent activation of protein kinase A. Blocking the cAMP-dependent changes also blocks FMRFamide-induced long-term functional and structural changes. These results suggest that the expression of long-term heterosynaptic inhibition in Aplysia may require concomitant presynaptic and postsynaptic changes, each transduced by specific second messenger systems.
Wu
F
F
Center for Neurobiology and Behavior, Columbia University, College of Physicians and Surgeons, New York, New York.
Schacher
S
S
D000818:Animals; D001048:Aplysia; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology; D019835:FMRFamide; D008084:Lipoxygenase / Q000378:metabolism; D009433:Neural Inhibition / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology; D015290:Second Messenger Systems; D013569:Synapses / Q000502:physiology*; D013997:Time Factors
D015816:Cell Adhesion Molecules, Neuronal; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D019835:FMRFamide; D000242:Cyclic AMP; D008084:Lipoxygenase