title: Presynaptic NMDARs in the hippocampus facilitate transmitter release at theta frequency.
abstract: A rise in [Ca(2+)](i) provides the trigger for neurotransmitter release at neuronal boutons. We have used confocal microscopy and Ca(2+) sensitive dyes to directly measure the action potential-evoked [Ca(2+)](i) in the boutons of Schaffer collaterals. This reveals that the trial-by-trial amplitude of the evoked Ca(2+) transient is bimodally distributed. We demonstrate that "large" Ca(2+) transients occur when presynaptic NMDA receptors are activated following transmitter release. Presynaptic NMDA receptor activation proves critical in producing facilitation of transmission at theta frequencies. Because large Ca(2+) transients "report" transmitter release, their frequency on a trial-by-trial basis can be used to estimate the probability of release, p(r). We use this novel estimator to show that p(r) increases following the induction of long-term potentiation.
authors.affiliation: Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
authors.forename: Lindsay
authors.initials: L
authors.lastname: McGuinness
authors.forename: Chanel
authors.initials: C
authors.lastname: Taylor
authors.forename: Ruth D T
authors.initials: RD
authors.lastname: Taylor
authors.forename: Christopher
authors.initials: C
authors.lastname: Yau
authors.forename: Tobias
authors.initials: T
authors.lastname: Langenhan
authors.forename: Michael L
authors.initials: ML
authors.lastname: Hart
authors.forename: Helen
authors.initials: H
authors.lastname: Christian
authors.forename: Patricia W
authors.initials: PW
authors.lastname: Tynan
authors.forename: Peter
authors.initials: P
authors.lastname: Donnelly
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Emptage
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009924:Organ Culture Techniques; D017729:Presynaptic Terminals / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology*
chemical_list: D018377:Neurotransmitter Agents; D016194:Receptors, N-Methyl-D-Aspartate