The Amino Acid transmitters operate through receptors that are either a part of
an ion channel* or directly coupled to it.  When the transmitter receptor is
occupied, the channels open, and ions flow into or out of the neuron.

For excitatory transmitters, the opened channel allows Na, Ca and to some extent
K, to enter the neuron, depolarizing it.

For inhibitory transmitters, the opened channel allows Cl ions to flow into the
neuron, to produce a hyperpolarizing action.