title: Intrinsic differences in sensitivity to 5-HT between high- and low-output terminals innervating the same target.
abstract: The differential action of neuromodulators on synapses of various efficacy provides additional fine tuning of synaptic regulation beyond frequency induced plasticity. We used the well-characterized high- and low-output motor nerve terminals, of the tonic and phasic neuromuscular junctions (NMJs) in the walking leg extensor muscle of the crayfish, to investigate differential actions of serotonin (5-HT) since both terminals innervate the same target. The excitatory postsynaptic potentials of the tonic NMJ are enhanced to a greater extent than for the phasic NMJs during exposure to 5-HT (100 nM). Macropatch current recordings at identified sites along the motor nerve terminals and quantal analysis indicate that mean quantal content is substantially increased by 5-HT. The overall probability of vesicular release increases to a greater extent at tonic terminals than at phasic terminals when exposed to 100 nM 5-HT. Measures in the area (i.e. charge) of spontaneous quantal currents indicate no difference in postsynaptic receptivity to the glutamatergic synaptic transmission upon exposure to 5-HT. The results provide new details concerning differential modulation of low- and high-output synapses present on the same target tissue.
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA. rlcoop1@pop.uky.edu
authors.forename: Robin L
authors.initials: RL
authors.lastname: Cooper
authors.forename: Ahmet
authors.initials: A
authors.lastname: Dönmezer
authors.forename: Joseph
authors.initials: J
authors.lastname: Shearer
mesh_terms: D000818:Animals; D003400:Astacoidea; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000502:physiology; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*
chemical_list: D012701:Serotonin