title: Modulation of the perforant path-evoked potential in dentate gyrus as a function of intrahippocampal β-adrenoceptor agonist concentration in urethane-anesthetized rat.
abstract: BACKGROUND
  β-adrenoceptor activation in the hippocampus is sufficient to induce heterosynaptic long-term potentiation of perforant path input to the dentate gyrus. However, in vitro and in vivo studies suggest the plasticity effects of β-adrenoceptor activation may vary depending on the level of receptor activation.
  
  
  METHODS
  The present experiments use an in vivo model concurrently infusing differing concentrations of the β-adrenoceptor agonist, isoproterenol (ISO; 0, 0.1, 1, 10, and 100 μmol/L in aCSF; 1 μL over 12.5 min) in the dentate gyrus, while monitoring changes in the perforant path-evoked potential at the same site.
  
  
  RESULTS
  Long-term depression (LTD) of fEPSP slope was elicited by 0.1 μmol/L ISO. Higher doses did not alter fEPSP slope. Maximal long-term potentiation of the perforant path-evoked population spike (183% >3 h) occurred at 10 μmol/L ISO. Transient depression of spike amplitude occurred at 0.1 μmol/L ISO.
  
  
  CONCLUSIONS
  These data demonstrate concentration-dependent effects of β-adrenoceptor activation on the perforant path-evoked potential. Long-term depression and long-term potentiation of perforant path-evoked responses are variably elicited as a function of the degree of receptor activation.
authors.affiliation: Behavioral Neuroscience, Psychology Department, Memorial University of Newfoundland St. John's, NL, A1B 3X9, Canada.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Lethbridge
authors.affiliation: Behavioral Neuroscience, Psychology Department, Memorial University of Newfoundland St. John's, NL, A1B 3X9, Canada.
authors.forename: Susan G
authors.initials: SG
authors.lastname: Walling
authors.affiliation: Behavioral Neuroscience, Psychology Department, Memorial University of Newfoundland St. John's, NL, A1B 3X9, Canada.
authors.forename: Carolyn W
authors.initials: CW
authors.lastname: Harley
mesh_terms: D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D018891:Dentate Gyrus / Q000187:drug effects*; D005071:Evoked Potentials / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects*; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000187:drug effects*; D036881:Long-Term Synaptic Depression / Q000187:drug effects*; D008297:Male; D009638:Norepinephrine / Q000031:analogs & derivatives; D019580:Perforant Pathway / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014520:Urethane / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D018686:Anesthetics, Intravenous; D014520:Urethane; D007545:Isoproterenol; D009638:Norepinephrine
keywords: LTP; Long-term depression; NE-LTP; noradrenaline; norepinephrine