NeuropharmacologyInvolvement of β-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
Section snippets
Subjects and surgery
The experiments including the minimal required number of animals conformed with the Institutional, Federal German and International guidelines on the ethical use of animals approved by the Land Saxony Anhalt to JUF. Under Nembutal anesthesia (40 mg/kg, i.p.), 100 male Wistar rats (8–9 weeks old, 200–300 g) were stereotaxically fixed to place bregma 1 mm higher than lambda after incising and retracting the scalp. Small holes were drilled in the skull, and the rats were implanted with a bipolar
Results
The three different strong tetanization protocols resulted in comparable and robust late-LTP in saline-treated animals as indicated by the PSA values after 24 h (protocol A: 164.4±14.64%; protocol B: 192.3±14.72%; protocol C: 201.5±9.17%; all P<0.05 compared with baseline, see Fig. 1 and control group in Fig. 2, Fig. 3).
In the first set of experiments, we examined whether late-LTP was protein synthesis-dependent under each LTP-induction condition. Application of the protein synthesis
Discussion
We showed that β-adrenergic receptors are partially involved in the induction of protein synthesis-dependent late- but not early-LTP in the DG of freely moving rats. The requirement of β-adrenergic receptor activation for the occurrence of late-LTP was, in contrast to the necessity of protein synthesis, coupled on the tetanization strength. Thus, late-LTP was blocked by propranolol when the most moderate protocol A was used. Late-LTP was also significantly suppressed by propranolol when using
Acknowledgements
We thank Jill Leutgeb for her help to improve the English of the manuscript. This work was supported by funds of the LSA 3121A/0029H and by the EU Framework V “NAPPY” to JUF.
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