Fig. 1.

Cranial irradiation inhibits long-term potentiation at the hippocampal–prefrontal cortex pathway. Cranial irradiation to a dose of 10 Gy inhibits long-term potentiation (LTP) at the hippocampal–PFC pathway. A baseline was obtained and confirmed to be stable for 20 minutes before high-frequency stimulation (HFS) was applied. The postsynaptic potential amplitudes indicate potentiation of synaptic transmission relative to the baseline. LTP amplitude was 153.5% ± 1.6% (relative to baseline) in sham radiation controls (n = 6), dropping to 104.9% ± 1.2% in irradiated rats (n = 6) at 3 days after irradiation. Two-way analysis of variance with repeated measures showed significant differences between treatment groups [F_(3,76) = 103.8, P < 0.001].