Frequency-dependent associative long-term potentiation at the hippocampal mossy fiber-CA3 synapse.
The mossy fiber-CA3 synapse displays an N-methyl-D-aspartate-receptor-independent mu-opioid-receptor-dependent form of long-term potentiation (LTP) that is thought not to display cooperativity or associativity with coactive afferents. However, because mossy fiber LTP requires repetitive synaptic activity for its induction, we reevaluated cooperativity and associativity at this synapse by using trains of mossy fiber stimulation. Moderate-, but not low-, intensity trains induced mossy fiber LTP, indicating cooperativity. Low-intensity mossy fiber trains that were normally ineffective in inducing LTP could induce mossy fiber LTP when delivered in conjunction with trains delivered to commissural-CA3 afferents. Associative mossy fiber LTP also could be induced with single mossy fiber pulses when delivered with commissural trains in the presence of a mu-opioid-receptor agonist. Our findings suggest a frequency-dependent variation of Hebbian associative LTP induction that is regulated by the release of endogenous opioid peptides.
Derrick
B E
BE
Department of Psychology, University of California, Berkeley 94720.
Martinez
J L
JL
D000344:Afferent Pathways; D000818:Animals; D004558:Electric Stimulation; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D017774:Long-Term Potentiation / Q000187:drug effects; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D011712:Pyramidal Tracts / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000037:antagonists & inhibitors; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission; D013997:Time Factors
D004745:Enkephalins; D010879:Piperazines; D016194:Receptors, N-Methyl-D-Aspartate; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C049352:phenylalanyl-cyclo(cysteinyltyrosyl-tryptophyl-ornithyl-threonyl-penicillamine)threoninamide; D013004:Somatostatin; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid