PET Imaging of mGLuR5 With Drug Challenge

Aim 1: To determine the acute effect of medication-induced glutamate release on mGluR5 availability in human subjects. Hypothesis 1: We hypothesize administration of ketamine or n-acetylcysteine (NAC) will lead to a decrease in mGluR5 availability. Aim 2: To determine if glutamate release via administration of ketamine or NAC has pro cognitive benefits. Hypothesis 2: We hypothesize an improvement in memory and attentional skills after drug challenge. Aim 3: To determine if there is synaptogenesis detectable by PET and MRI post ketamine or NAC within a week of drug challenge (at the time of greatest antidepressant response). Hypothesis 3: We hypothesize an increase in mGluR5 availability and change in MRI measures, post drug challenge as compared to baseline, signifying synaptogenesis. Aim 4: To determine if there is a difference in reduction of mGluR5 availability after ketamine administration when radiotracer is administered bolus as compared to bolus to constant infusion in the same subjects (ABP688 radiotracer only). Hypothesis 4: We expect there should not be a significant difference in reduction in mGluR5 availability due to differences in ABP688 radiotracer infusion.