This paper investigates the mutual information of synaptic molecular communications using a realistic end-to-end synaptic model. In particular, we have considered the influence of astrocytes on neural signaling within the synaptic molecular communication. We have evaluated the average mutual information of the resultant tripartite synapse while considering realistic synaptic geometry that accounts for neurotransmitter reflections from the pre-synaptic and post-synaptic boundaries. The clearance of neurotransmitters from the synapse through diffusion and re-absorption by pre-synaptic terminal is also considered in the simulated model. Moreover, we have used a generic three-state model for postsynaptic receptors to include desensitization state of the receptors. The presented simulation results depict the effects of different pre-synaptic and post-synaptic parameters on the information transfer for a tripartite synaptic channel with three-state receptor model, which is more realistic than the commonly-used bipartite synaptic channel with the two-state receptor model.