title: Long-term potentiation in the dentate gyrus in freely moving rats is reinforced by intraventricular application of norepinephrine, but not oxotremorine.
abstract: Growing evidence suggests that processes of synaptic plasticity, such as long-term potentiation (LTP) occurring in one synaptic population, can be modulated by consolidating afferents from other brain structures. We have previously shown that an early-LTP lasting less than 4 h (E-LTP) in the dentate gyrus can be prolonged by stimulating the basolateral amygdala, the septum or the locus coeruleus within a specific time window. Pharmacological experiments have suggested that noradregeneric (NE) and/or cholinergic systems might be involved in these effects. We have therefore investigated whether the direct intraventricular application of agonists for NE- or muscarinic receptors is able to modulate synaptic plasticity. E-LTP was induced at the dentate gyrus of freely moving rats using a mild tetanization protocol that induces only an E-LTP. NE or oxotremorine (OXO) were applied icv 10 min after the tetanus. Results show that low doses of NE (1.5 and 5 nM) effectively prolong LTP. A higher dose (50 nM) was not effective. None of the OXO doses employed (5, 25, and 50 nM) showed similar effects. These results stress the importance of transmitter-specific modulatory influences on the time course of synaptic plasticity, in particular NE whose application mimics the reinforcing effect of directly stimulating limbic structures on LTP.
authors.affiliation: Department of Experimental Neurophysiology, International Center for Neurological Restoration (CIREN), Havana, Cuba.
authors.forename: William
authors.initials: W
authors.lastname: Almaguer-Melian
authors.forename: Yeneissy
authors.initials: Y
authors.lastname: Rojas-Reyes
authors.forename: Armando
authors.initials: A
authors.lastname: Alvare
authors.forename: Juan C
authors.initials: JC
authors.lastname: Rosillo
authors.forename: Julietta U
authors.initials: JU
authors.lastname: Frey
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Bergado
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D018891:Dentate Gyrus / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D007276:Injections, Intraventricular; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018721:Muscarinic Agonists / Q000008:administration & dosage; D009638:Norepinephrine / Q000008:administration & dosage* / Q000502:physiology; D010095:Oxotremorine / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D018709:Statistics, Nonparametric
chemical_list: D018721:Muscarinic Agonists; D010095:Oxotremorine; D009638:Norepinephrine