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

Figure 4

LPS treatment of eight-month-old mice had a profound effect on LTP in prenatally stressed mice. (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 treatment groups. Note that LPS treatment led to some increase in basal synaptic transmission in Ct, but not in the PS group. (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. LPS treatment led to a significant decrease in paired-pulse facilitation at 10 ms and 20 ms of IPIs in the Ct-LPS group as well as at IPIs of 20 ms, 40 ms, and 60 ms in the PS-LPS group. (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 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. Immune challenge at eight months of age led to a significant impairment of LTP magnitude in both Ct and PS groups. Activation of the adrenergic system by application of Iso did not alter LTP expression in Ct-Saline and Ct-LPS groups but was instrumental in facilitating LTP in both PS-Saline and PS-LPS groups. (g) Summary bar graph of the results shown in (c–f). Significant differences at .

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