ENHANCEMENT OF POSTSYNAPTIC SEROTONIN-ACTIVATED CL- CURRENTS BY DEPOLARIZATION-INDUCED CA2+ ENTRY INTO LEECH NEURONS

Postsynaptic Ca2+ signals are a precondition for many types of synapse modification, including long-term potentiation.1,16,17 Here we descri be a postsynaptic mechanism that augments synaptic currents at the ser otonergic Retzius-P cell synapse of the leech. Depolarizations large e nough to elicit Ca2+ currents evoked an increase in the amplitude of s erotonin-activated Cl- currents in isolated embryonic neurons as well as at the Retzius-P cell synapse. The effect on embryonic whole cell c urrents lasted for up to one hour and was abolished in solutions conta ining Cd2+ as a Ca2+ channel blocker. Hence, Ca2+ influx into the post synaptic neuron may be a common step regulating the plasticity of vari ous vertebrate as well as invertebrate synapses.