Modulation of the perforant path-evoked potential in dentate gyrus as a function of intrahippocampal β-adrenoceptor agonist concentration in urethane-anesthetized rat

Lethbridge, Rebecca and Walling, Susan G. and Harley, Carolyn W. (2014) Modulation of the perforant path-evoked potential in dentate gyrus as a function of intrahippocampal β-adrenoceptor agonist concentration in urethane-anesthetized rat. Brain and Behavior, 4 (1). pp. 95-103. ISSN 2157-9032

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Abstract

Background β-adrenoceptor activation in the hippocampus is sufficient to induce heterosynaptic long-term potentiation of perforant path input to the dentate gyrus. However, in vitro and in vivo studies suggest the plasticity effects of β-adrenoceptor activation may vary depending on the level of receptor activation. Methods The present experiments use an in vivo model concurrently infusing differing concentrations of the β-adrenoceptor agonist, isoproterenol (ISO; 0, 0.1, 1, 10, and 100 μmol/L in aCSF; 1 μL over 12.5 min) in the dentate gyrus, while monitoring changes in the perforant path-evoked potential at the same site. Results Long-term depression (LTD) of fEPSP slope was elicited by 0.1 μmol/L ISO. Higher doses did not alter fEPSP slope. Maximal long-term potentiation of the perforant path-evoked population spike (183% >3 h) occurred at 10 μmol/L ISO. Transient depression of spike amplitude occurred at 0.1 μmol/L ISO. Conclusions These data demonstrate concentration-dependent effects of β-adrenoceptor activation on the perforant path-evoked potential. Long-term depression and long-term potentiation of perforant path-evoked responses are variably elicited as a function of the degree of receptor activation.

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