When the axon terminal of a modulatory neuron (cell m) terminates close to the axon terminal of a presynaptic cell (cell p) and decrease the amount of neurotransmitter released by cell p. the resulting type of modulation is called

Presynaptic Inhibition

Explanation:

Presynaptic inhibition refers to mechanisms that suppress release of neurotransmitters from axon terminals or varicosities. It involves binding of chemical messengers to inhibitory receptors at transmitter release sites on the axon. Presynaptic inhibition is a significant synaptic event within the enteric microcircuits of the gastric corpus and antrum, as well as the small and large intestine and rectum of the guinea pig. It is a mechanism that prevents runaway excitation in feed-forward synaptic circuits.  Presynaptic inhibitory receptors are found at fast and slow excitatory synapses, at inhibitory synapses, and at neuromuscular junctions.

if you're asking what comes out, it's steam.