Grant Glatfelter Ph.D., received his B.S. in Psychology with a minor in Biology from York College of Pennsylvania in 2013. From 2012 – 2014, Grant worked prior to graduate school as a research assistant primarily under Matthew W. Johnson Ph.D. at the Johns Hopkins Behavioral Pharmacology Research Unit, where he assisted various studies administering alcohol, methamphetamine, cocaine, and psilocybin to human volunteers to examine effects on delay discounting measures as well as therapeutic efficacy. 
Grant next obtained his Ph.D. in Pharmacology & Toxicology working in the lab of Margarita L. Dubocovich Ph.D. at the University of Buffalo Jacobs School of Medicine and Biomedical Sciences (July 2014 – 2019), where he studied the neuropharmacology and chronobiological effects of environmental chemicals and novel pharmacological tools acting at melatonin receptors.
Currently, Dr. Glatfelter is a staff research fellow in the Designer Drug Research Unit (DDRU) of the National Institute on Drug Abuse Intramural Research Program in Baltimore, MD. Dr. Glatfelter joined the DDRU in the Fall of 2019 and primarily studies the neuropharmacology of emerging new psychoactive substances (NPS) and novel medications of the opioid, cannabinoid, stimulant, and psychedelic classes under expert mentorship of Michael H. Baumann Ph.D. In the Fall of 2023, Dr. Glatfelter was promoted to a full-time scientist position in the DDRU where he continues research efforts in medication development and to study emerging NPS.

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Serotonin transporter activity modulates the psychedelic-like effects of 4-methoxy-N-methyl-N-isopropyltryptamine and related analogs in mice

Tryptamine psychedelics induce effects via actions at serotonin 2A receptors (5-HT 2A ), but are generally non-selective. Previous studies show that 4-hydroxy, 4-acetoxy- and 4-methoxy analogs of N-methyl-N-sopropyltryptamine (4-HO-MiPT, 4-AcO-MiPT, and 4-MeO-MiPT, respectively) are uptake blockers at 5-HT transporters (SERT), in addition to acting as agonists at 5-HT 2A . Here we studied the receptor target profiles,  monoamine transporter activities, and in vivo pharmacological effects of 4-HO-MiPT, 4-AcO-MiPT, and 4-MeO-MiPT.
Receptor target profiles were determined in vitro across 40+ potential sites of action. Next, the ability of the compounds to inhibit [ 3 H]neurotransmitter uptake at SERT and related monoamine transporters was examined in rat brain synaptosomes. Lastly, we compared the dose-related effects of acute subcutaneous 4-HO-MiPT, 4-AcO-MiPT, and 4-MeO-MiPT (0.03 - 30 mg/kg) on 5-HT 2A -mediated head twitch responses (HTRs) in C57BL/6J mice.
Target screening revealed that MiPT analogs primarily interacted with 5-HT receptors but also had notable affinities for alpha-adrenergic receptors, sigma receptors, and SERT. Functional assays showed the compounds are fully efficacious 5-HT 2A  agonists (EC 50  range = 6–120 nM; E max  range = 90–102%), with reduced activities at other 5-HT 2  subtypes. 4-MeO-MiPT also displayed potent and selective uptake inhibition at SERT (IC 50  = 57 nM) relative to the other compounds (IC 50 s = 423–1,398 nM) and cocaine (IC 50  = 326 nM). In mice, the compounds had similar potencies for inducing HTRs (ED 50  range = 0.75–0.97 mg/kg) but variable efficacies. In particular, 4-MeO-MiPT had reduced efficacy for inducing HTRs relative to 4-HO-MiPT and 4-AcO-MiPT (E max  = 34 vs 77–80 HTRs/30 min). Interestingly, combined treatment with 4-HO-MiPT and the SERT inhibitor fluoxetine (10 mg/kg) reduced the number of HTRs when compared to 4-HO-MiPT alone (E max  = 48 vs 77 HTRs/30 min).
Overall, our data indicate that 4-position ring-substituted MiPT analogs interact mainly with 5-HT 2A  and other 5-HT receptors, but they have relevant effects as SERT uptake blockers. The relative potency of 4-MeO-MiPT as a SERT inhibitor may underly its reduced psychedelic-like effects. Ongoing studies are evaluating the effects of altering the 4-alkoxy chain and/or N-alkyl group of 4-MeO-MiPT to better understand the basic pharmacology of hybrid 5- HT2A/SERT inhibitor tryptamines