Dear Hans,
Thank you for the explanation! If tsodyks_synapse transmits the effective synaptic weight u(t)*x(t)*w to the postsynaptic neuron where it is converted to postsynaptic current or conductance, depending on the type of the model, then the present *_exp models should work with it just fine, as I understand. And taking into account approximate nature of synaptic models, the tsodyks_synapse, for practical purposes, can also be combined with *_alpha or *_beta type neuron models, I think. Although in this case synaptic parameters will have to be adjusted to fit the original behavior.
Thank you for your explanation and sorry for my confusion, I am not a native NEST user.
Best regards, Alex.