PDF《Adult Rats》

1 ml/kg unless otherwise stated. Lipopolysaccharide injections. To determine whether a single inflam- matory event during development can influence seizure susceptibility in later life, male rats were injected intraperitoneally on P14 with LPS (Esch- erichia coli, serotype O26:B6;

25, 100, or

250 ?g/kg) or pyrogen-free saline. We previously established that

100 ?g/kg LPS generates a mild inflammatory response in the host that lasts for ?6C8 h (Heida et al., 2004;

Ellis et al., 2006). Additional groups of rats were also injected on P14 with saline or LPS (100 ?g/kg) to evaluate both the acute and chronic effects of LPS on cytokine and glial cell activity in the hippocampus (a seizure-vulnerable region). P14 is considered by some to be developmen- tally equivalent to a human infant of ?1C2 years of age (Gottlieb et al., 1977;

Avishai-Eliner et al., 2002). To determine whether there was a critical age at which LPS could cause long-term changes to seizure sus- ceptibility, rats were also treated with saline or LPS (100 ?g/kg) at P1, P7, or P20. In vitro hippocampal electrophysiology. Hippocampal slices (n ? 43) were prepared from ?5-week-old male rats that had been treated with either saline or LPS (100 ?g/kg) on P14. Under halothane anesthesia, brains were removed and placed in cold (0C4°C) slicing solution (in mM):

87 NaCl, 2.5 KCl,

25 NaHCO3,

7 MgCl2, 1.25 NaH2PO4,

25 D-glucose,

20 sucrose, and 0.48 CaCl2 that was bubbled with 5% CO2/ 95% O2. Horizontal hippocampal slices (400 ?m) were cut using a vi- bratome and maintained for

45 min in a warm (32°C) recovery solution composed of artificial CSF (aCSF) (in mM):

126 NaCl, 2.5 KCl, 1.2 NaH2PO4, 1.2 MgCl2, 2.4 CaCl2,

18 NaHCO3,

11 D-glucose, and 1.5 kynurenic acid, and continuously bubbled with 5% CO2/95% O2 to maintain a pH of 7.4. After

45 min, slices were transferred into a second chamber that contained aCSF (but without kynurenic acid) for 3C4 h at room temperature. Slices were then transferred to a recording chamber that was continuously perfused with aCSF at 32°C. Extracellular field potentials were recorded with glass micropipettes filled with aCSF (2C3 M?) and signals were acquired using an Axopatch 200B amplifier (Mo- lecular Devices;

low-pass filter,

5 kHz;

high-pass filter,

1 Hz;

acquisition frequency,

10 kHz;

gain, 500?). Evoked field EPSPs (fEPSPs) were elic- ited in the CA1 stratum radiatum region of the hippocampus by electri- cally stimulating the Schaffer collaterals (CA3) with a concentric bipolar electrode at 0, 25, 50, 75, and 100% maximal stimulation. The point at which the fEPSP slope did not increase further with increasing stimula- tion was taken as 100% maximal stimulation. To record spontaneous field activity, recording electrodes were placed in the CA1 stratum pyra- midale. Spontaneous epileptiform activity (burst-firing) was induced by bath perfusion with aCSF containing

75 ?M 4-AP, a potassium channel blocker (Perreault and Avoli, 1991;

Yonekawa et al., 1995;

Motamedi et al., 2006), for

30 min. The epileptiform activity was quantified b........