OXT and autism: Therefore, dynamic changes in neurotransmitter concentration, release, and receptor density may directly affect neural circuit function and thus behavioural performance.396 Increasing evidence shows that disturbances in neurotransmitter systems, including the glutamate, GABA, serotonin (5-hydroxytryptamine, 5-HT),397,398 melatonin,397,399 dopamine (DA),396,400,401 OT and arginine vasopressin (AVP) systems, are associated with autism (Fig. 7).