In rats with vitamin D deficiency, the effect of MK-801, an NMDA (N-methyl-D-aspartate) receptor antagonist which indirectly activates dopaminergic activity and also induces hyperlocomotion in animals, was found to be attenuated with the use of haloperidol, a DRD2 (Dopamine Receptor D2) anatgonist88. Here, DRD2 is linked to vitamin D deficiency.