Table 3.
Summary of studies that investigated the effects of transcranial direct current stimulation (tDCS) with [11C]carfentanil and [11C]raclopride PET.
| Study | Design | Subjects | Intervention | Main Findings |
|---|---|---|---|---|
| Dos Santos et al. 2012 [53] |
Acute effects (single session), sham-controlled, single-blind, case study | 62-year-old woman with trigeminal neuropathic pain from post-herpetic neuralgia | Anode: primary M1, Cathode: supraorbital region, 2 mA, 20 min [11C]carfentanil PET |
No changes in clinical pain improvements. Significantly decreased MOR BPND levels in key pain-matrix structures, including the nucleus accumbens, anterior cingulate cortex, insula, and posterior thalamus. |
| Dos Santos et al. 2014 [52] |
Acute effects (single session), sham-controlled, single-blind | Healthy subjects N = 9 |
Anode: right M1, Cathode: left supraorbital region, 2 mA, 20 min [11C]carfentanil PET |
Sham tDCS resulted in a decrease in MOR BPND in the periaqueductal gray matter (PAG), precuneus, and thalamus, which indicates activation of the endogenous µ-opioid system. Active tDCS (2 mA for 20 min) also prompted MOR activation in the PAG and precuneus, but additionally increased MOR activation in the left prefrontal cortex. |
| Fonteneau et al. 2018 [57] |
Acute effects (single session), sham-controlled, double-blind | Healthy subjects N = 32, Sham = 18, tDCS = 14 |
Anode: left DLPFC, Cathode: right DLFPC, 2 mA, 20 min [11C]raclopride PET |
A single session of bilateral DLFPC tDCS induced dopamine release in cognitive and affective striatal areas. |
| Fukai et al. 2019 [58] |
Acute effects, sham-controlled, double-blind, crossover design | Healthy subjects N = 20 |
Anode: left DLPFC, Cathode: right DLPFC, 2 mA, 13 min × 2 [11C]raclopride PET |
tDCS over the DLPFC resulted in increased accuracy on a neuropsychological attentiveness test, which was significantly correlated with dopamine release in the right ventral striatum. |