Receptor sites for neurotransmitters are present on

In a chemical synapse, receptors for neurotransmitters are present on the plasma membrane of the postsynaptic neuron. When neurotransmitters bind to their receptors, it triggers the activation of ligand-gated ion channels, which allows ions to move across the postsynaptic membrane. This flow of ions leads to the generation of postsynaptic potentials.

(1) Presynaptic neuron releases neurotransmitters. The presynaptic membrane lacks receptors for neurotransmitters.

(2) Tips of axons (axon terminals) lack receptors for neurotransmitters. 

(4) Synaptic vesicles store neurotransmitters. Their membranes lack receptors for neurotransmitters.