Certified by...........................

It has been assumed that Ca2+ influx of different duration and amplitude would generate different level of potentiation. The conventional protocols of generat-ing LTP have been 1. tetanic stimulation of presynaptic cell, 2. theta burst stimulation of presynaptic cell, and 3. correlated stimulation of pre- and post-synaptic cells. However, the effects of different Ca2+ influx can not be precisely dissected with the conventional protocols for the following defects: 1. the pro-tocols do not discriminate between pre- and postsynaptic side plasticity, 2. the protocols observe synaptic plasticity between two cells which involve multiple synapses with heterogenous properties, 3. precise control and measurement of the amount of Ca2+ influx are not possible in the protocols. In the present experiment, we perfused glutamate directly on to a single postsynaptic site, de-polarized the postsynaptic intracellular potential to a controlled voltage for a controlled duration of time, thus controlling the opening of postsynaptic NMDA receptors and Ca2+ influx. By using this method, we found 1. that modifica