Peptide containing vesicles within neuro-neuronal synapses.

In the descending part of the classical neurosecretory system, the axon terminals are not differentiated or they take the form of presynaptic elements which then form synaptoids or synapses with pituicytes or adenohypophyseal glandular cells respectively. In contrast, the axon terminals of the ascending part fulfil the criteria of true presynaptic elements which form synapses with other neurones. The presence of neurophysin vesicles in the presynaptic element is a particular morphologic feature of these neuro-neuronal synapses.