Explanation

The kind of action potential to be developed on the membrane of postsynaptic neuron depends upon the action of neurotransmitter. It is summarized as follows (i) Neurotransmitter $\rightarrow$ Excitatory Receptor $\rightarrow$ Open channels of $Na^{+}$ ions or both for $Na^{+}$ and $K^{+}$ $\rightarrow$ Depolarising of plasma membrane of postsynaptic Neuron $\rightarrow$ Action potential (ii) Neurotransmitter $\rightarrow$ Inhibitory Receptor $\rightarrow$ Opens $K^{+}$ or $Cl^{-}$ channels $\rightarrow$ Hyperpolarisation of plasma membrane of postsynaptic neuron $\rightarrow$ No action potential so, the new potential developed may be either excitatory or inhibitory