Thus, the reduction in the level of SNAP-25 in the hippocampus observed in the model of coexistence of depression and hypothyroidism may be an essential cause of the weakening of short-term synaptic plasticity, which we demonstrated previously with electrophysiological methods in this model, and which depends on the presynaptic mechanisms of neurotransmitter release [14]. Here, SNAP25 is linked to major depressive disorder.