LONG-TERM ENHANCEMENT OF SYNAPTIC TRANSMISSION IN THE HIPPOCAMPUS AFTER TETANIZATION OF SINGLE NEURONS BY SHORT INTRACELLULAR CURRENT PULSES

Long-term potentiation (LTP) in area CA1 of the hippocampus is thought to depend on Hebbian-like mechanisms which imply pairings of presynap tic activation with postsynaptic depolarization. Here we describe an i ncrease in amplitudes of evoked minimal excitatory postsynaptic potent ials after intracellular tetanization of CA1 neurones with short (5 ms ) 100 Hz current pulses. Similar to LTP, this ''intracellular potentia tion'' (ICP) was reproducible (7 out of 12 neurones), large (typically > 40% increase) and non-decremental for at least 40 min. The interact ion of ICP and LTP indicates common mechanisms. However, it was not ne cessary to pair current pulses with presynaptic activation to induce I CP. It is hypothesized that a sufficient number of short current pulse s either elevates the intracellular Ca2+ concentration (by influx thro ugh voltage-gated channels or/and release from intracellular stores) o r/and releases unknown intracellular messengers which activate a seque nce of metabolic processes leading to LTP.