Which of the following statements is true about presynaptic inhibition?

presynaptic inhibition into two categories: (1) inhibition mediated by axo-axonic or dendro-axonic projections (i.e., a third pay interferes with the transmission of synaptic responses between a synaptically coupled pair of two neurons), which we may describe as heterosynaptic inhibition; and (2) inhibition mediated by the release of neurotransmitter from the active presynaptic terminal itself, or autoreceptive inhibition Ref: guyton and hall textbook of medical physiology 12 edition page number:546,547,548