title: Glutamate is the fast excitatory neurotransmitter of small cardioactive peptide-containing Aplysia radula mechanoafferent neuron B21.
abstract: B21 is a radula mechanoafferent neuron in the mollusc Aplysia which likely plays a crucial role in integrating environmental cues into the feeding motor program. To facilitate understanding B21's interactions with its postsynaptic followers, we sought to identify its neurotransmitter. We find that B21 makes a chemical synapse onto the follower neuron B8. Although B21-induced excitatory postsynaptic potentials (EPSPs) in B8 paradoxically diminish in amplitude with B8 hyperpolarization, we show that an inwardly rectifying current is responsible. We conclude that these B21-induced EPSPs are likely glutamatergic as they are blocked by the glutamate antagonist DNQX. Furthermore, B8 exhibits a depolarizing response to exogenous glutamate, which is antagonized by DNQX. Finally, exogenous glutamate occludes B21-evoked EPSPs in B8.
authors.affiliation: Department of Physiology and Biophysics, Box 1218, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, New York, NY 10029, USA. ak1@doc.mssm.edu
authors.forename: A N
authors.initials: AN
authors.lastname: Klein
authors.forename: K R
authors.initials: KR
authors.lastname: Weiss
authors.forename: E C
authors.initials: EC
authors.lastname: Cropper
mesh_terms: D000818:Animals; D001048:Aplysia / Q000502:physiology*; D018698:Glutamic Acid / Q000502:physiology*; D007447:Invertebrate Hormones / Q000502:physiology; D009043:Motor Activity / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D009479:Neuropeptides / Q000502:physiology*
chemical_list: D007447:Invertebrate Hormones; D009479:Neuropeptides; D018698:Glutamic Acid; C041307:small cardioactive peptide B; C045659:small cardioactive peptide A