Transient and sustained types of long-term potentiation in the CA1 area of the rat hippocampus.
Synaptic potentiation induced by high frequency stimulation was investigated by recording field excitatory postsynaptic potentials (f-EPSPs) in rat hippocampal slices. Potentiation consisted of a transient period of decaying f-EPSPs (short-term potentiation, STP) that led to a plateau of continuously potentiated f-EPSPs (long-term potentiation, LTP). Here we show that a previously unknown type of transient, use-dependent, long-lasting potentiation (t-LTP) can account for STP. t-LTP could be stored for more than 6 h and its decay was caused by synaptic activation. Both the expression and the decay of t-LTP were input specific. t-LTP was induced differently from conventional LTP in that the amplitude of t-LTP was dependent upon the stimulation frequency, whereas the magnitude of LTP was dependent on the number of stimuli in the induction train. The decay of t-LTP could not be prevented by the blockage of glutamate receptors, but was prevented by the blockage of stimulus-evoked neurotransmitter release, suggesting that t-LTP is expressed presynaptically. Paired-pulse stimulation experiments showed that the decay of t-LTP was mediated by a decrease in the probability of neurotransmitter release. The decline of t-LTP could be prolonged by the activation of NMDA receptors. Hence, both single and paired-pulse stimuli prolonged the decline of the t-LTP. This decline could be prevented by high frequency burst stimulation (200 Hz). We conclude that t-LTP allows dynamic modulation of synaptic transmission by providing not only spatial association but also temporal convergence between synaptic inputs. Therefore, t-LTP might be a substrate for the encoding of synaptic memory.
Volianskis
Arturas
A
Department of Neurobiology, Institute of Anatomy, University of Aarhus, Wilhelm Meyers Allé, Building 233/234, DK-8000 Aarhus C, Denmark. av@neuro.au.dk
Jensen
Morten S
MS
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000502:physiology; D013569:Synapses / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D018377:Neurotransmitter Agents; D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate; D008274:Magnesium; D002118:Calcium