Immune Challenge Alters Reactivity of Hippocampal Noradrenergic System in Prenatally Stressed Aged Mice

Figure 2

LPS treatment in juvenility (at one month of age) induces long-lasting changes of long-term hippocampal plasticity in both control (Ct) and prenatally stressed (PS) mice, including alterations in the reactivity to the activation of the adrenergic system. (a) Input-output curves of excitatory postsynaptic potential (EPSP) slopes for dorsal hippocampal slices of control (Ct) and prenatally stressed (PS) mice showed no significant difference between saline and LPS treatments. (b) Examination of paired-pulse facilitation (PPF) of the EPSP slopes expressed as a response to the 2nd stimulation over the 1st at different interpulse intervals (IPIs; 10, 20, 40, 60, 80, and 100 ms) in Ct and PS slices. No difference in PPF was found between saline and immune challenged slices, except for a significant decrease of PPF in the Ct-LPS group at 60 ms interval. (c–f) Effect of isoproterenol (Iso, 1 μM), a nonselective β-adrenergic agonist, application on long-term potentiation (LTP) of CA3-CA1 synapse activity recorded from the stratum radiatum of dorsal hippocampal slices. LTP was induced by application of theta burst stimulation (TBS, 10 trains of 4 pulses at 100 Hz with an interburst interval of 200 ms, applied 3 times in 10 s intervals). The first TBS was delivered to pathway 1 after 20 minutes of baseline recording. The second TBS was applied to the previously unpotentiated pathway 2 after 15 minutes of washing in Iso (the bar shown above the record). The arrows denote the points at which TBS was delivered. Insets in (c–f) are sample illustrations of the EPSPs recorded at the times indicated in the averaged traces (a–d) before and after the TBS application. Hippocampal slices from PS mice showed an impaired ability to undergo LTP in response to TBS. LPS injections significantly affected LTP magnitude in aged animals of both Ct-LPS and PS-LPS groups. The facilitating effect of Iso on LTP was observed in the PS-LPS group only. (g) Summary bar graph of the results shown in (c–f). Significant differences at .

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