Involvement of beta-adrenergic receptors in protein synthesis-dependent late long-term potentiation (LTP) in the dentate gyrus of freely moving rats: the critical role of the LTP induction strength.
We have investigated the requirement of beta-adrenergic receptor activation and protein synthesis for the induction and specifically for the maintenance of long-term potentiation (LTP) in the dentate gyrus of freely moving rats in dependency on different LTP-induction procedures. Three tetanization paradigms were used: a relatively weak protocol A (10 bursts of 15 biphasic pulses at 200 Hz; 10-s interburst interval; 0.2-ms pulse width per phase), a stronger protocol B (as protocol A but 20 bursts and 0.25-ms pulse width) and, as the strongest condition, protocol C (2 times protocol B; inter-tetanus interval: 5 min). All protocols led to robust late-LTP in control animals. Late- but not early-LTP was protein synthesis-dependent under all tetanization conditions as indicated by the absence of long-lasting LTP when the protein synthesis inhibitor anisomycin was applied before tetanization. Application of the beta-adrenergic receptor antagonist propranolol before LTP induction prevented late-LTP when either protocol A or B but not when protocol C was used. Thus, repeated strong tetanization can compensate for the loss of beta-adrenergic receptor activation. We suggest that the results could provide a link to cellular mechanisms of memory consolidation in respect to the strength and relevance of the incoming sensory information during learning.
Straube
T
T
Leibniz-Institute for Neurobiology, Department of Neurophysiology, Brenneckestrasse 6, D-39118, Magdeburg, Germany. straube@ifn-magdeburg.de
Frey
J U
JU
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D018891:Dentate Gyrus / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D011433:Propranolol / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D000319:Adrenergic beta-Antagonists; D011500:Protein Synthesis Inhibitors; D011943:Receptors, Adrenergic, beta; D000841:Anisomycin; D011433:Propranolol