Modulation of hippocampal primed burst potentiation by anesthesia.

This study demonstrates that the anesthetics urethane and pentobarbital differentially affect a low threshold form of long-lasting synaptic plasticity, termed primed burst (PB) potentiation, in the CA1 area of rat hippocampus. PB potentiation was generated by the delivery of a 5-pulse patterned stimulus train, consisting of one priming pulse followed 170 ms later by a burst of 4 pulses at 200 Hz. PB potentiation could not be reliably generated in urethane-anesthetized rats unless stimulus currents were raised to 150% of baseline levels during the stimulus train. In pentobarbital-anesthetized rats, PB potentiation could always be evoked at baseline stimulus intensities. Differences between the anesthetics which could contribute to their varying effects upon PB potentiation are discussed.