What is the difference between excitatory and inhibitive presynaptic neurons?

Question

IB Summer HW question... can't find it anywhere!

Answer 1

It has to do with the nature of the transmitter and transmitter-receptor interaction.  If the presynaptic neuron, e.g. contains and releases GABA, that will almost always result in inhibition of the target neuron. On the other hand, if the presynaptic neuron contains and releases glutamic acid, that will almost always result in excitation of the target neuron.  Hope this helps.