title: Multiple serotonergic mechanisms contributing to sensitization in aplysia: evidence of diverse serotonin receptor subtypes.
abstract: The neurotransmitter serotonin (5-HT) plays an important role in memory encoding in Aplysia. Early evidence showed that during sensitization, 5-HT activates a cyclic AMP-protein kinase A (cAMP-PKA)-dependent pathway within specific sensory neurons (SNs), which increases their excitability and facilitates synaptic transmission onto their follower motor neurons (MNs). However, recent data suggest that serotonergic modulation during sensitization is more complex and diverse. The neuronal circuits mediating defensive reflexes contain a number of interneurons that respond to 5-HT in ways opposite to those of the SNs, showing a decrease in excitability and/or synaptic depression. Moreover, in addition to acting through a cAMP-PKA pathway within SNs, 5-HT is also capable of activating a variety of other protein kinases such as protein kinase C, extracellular signal-regulated kinases, and tyrosine kinases. This diversity of 5-HT responses during sensitization suggests the presence of multiple 5-HT receptor subtypes within the Aplysia central nervous system. Four 5-HT receptors have been cloned and characterized to date. Although several others probably remain to be characterized in molecular terms, especially the Gs-coupled 5-HT receptor capable of activating cAMP-PKA pathways, the multiplicity of serotonergic mechanisms recruited into action during learning in Aplysia can now be addressed from a molecular point of view.
authors.affiliation: Département de biochimie, Université de Montréal, Québec H3C 3J7, Canada.
authors.forename: Demian
authors.initials: D
authors.lastname: Barbas
authors.forename: Luc
authors.initials: L
authors.lastname: DesGroseillers
authors.forename: Vincent F
authors.initials: VF
authors.lastname: Castellucci
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Carew
authors.forename: Stéphane
authors.initials: S
authors.lastname: Marinesco
mesh_terms: D000818:Animals; D001048:Aplysia; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D007395:Interneurons / Q000502:physiology*; D007858:Learning / Q000502:physiology; D008568:Memory / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009046:Motor Neurons / Q000502:physiology; D009473:Neuronal Plasticity; D009475:Neurons, Afferent / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011985:Receptors, Serotonin / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D012018:Reflex / Q000502:physiology; D012701:Serotonin / Q000502:physiology*; D015398:Signal Transduction; D009435:Synaptic Transmission
chemical_list: D011985:Receptors, Serotonin; D012701:Serotonin; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases