The impact of gabapentin administration on brain GABA and glutamate concentrations: a 7T ¹H-MRS study.

Gamma-aminobutyric acid (GABA) and glutamate are implicated in numerous neuropsychiatric and substance abuse conditions, but their spectral overlap with other resonances makes them a challenge to quantify in humans. Gabapentin, marketed for the treatment of seizures and neuropathic pain, has been shown to increase in vivo GABA concentration in the brain of both rodents and humans. Gabapentin effects on glutamate are not known. We conducted a gabapentin (900 mg) challenge in healthy human subjects to confirm and explore its effects on GABA and glutamate concentrations, respectively, and to test the ability of single voxel localized proton magnetic resonance spectroscopy (¹H-MRS) to reliably measure GABA and glutamate in the visual cortex at the ultra-high magnetic field of 7 Tesla. Reproducibility of GABA and glutamate measurements was determined in a comparison group without drug twice within day and 2 weeks apart. Although GABA concentration changes were small both within day (average 5.6%) and between day (average 4.8%), gabapentin administration was associated with an average increase in GABA concentration of 55.7% (6.9-91.0%). Importantly, drug-induced change in GABA levels was inversely correlated to the individual's baseline GABA level (R²=0.72). Mean glutamate concentrations did not change significantly with or without drug administration. In conclusion, localized ¹H-MRS at 7 Tesla can be successfully applied to the measurement of GABA concentration and is sensitive to acute drug-induced changes in cortical GABA. Whether baseline GABA concentrations predict clinical efficacy of gabapentin is an area worthy of exploration.

A survey of patient acceptability of repetitive transcranial magnetic stimulation (TMS) during pregnancy.

OBJECTIVE: Given the data that depression is common during pregnancy and that pregnant women prefer non-medication treatment options, we hypothesize repetitive transcranial magnetic stimulation (TMS) may be a treatment option. Given the novelty of TMS, we sought to assess whether patient acceptability would be a barrier to enrolling pregnant women in TMS studies. METHODS: In Study 1, 500 pregnant women were surveyed in an outpatient, urban obstetrics clinic using the Edinburgh Depression Rating Scale (EPDS) and a treatment acceptability survey. In Study 2, 51 women were surveyed with the EPDS and acceptability survey using an informational video to increase participant knowledge about TMS. RESULTS: Approximately 25% of participants had an EPDS score of ≥12 in both studies. Psychotherapy was identified as the most acceptable treatment option. TMS was considered an unacceptable treatment option to virtually all women before the informational video. After the video, 15.7% considered TMS an acceptable treatment option. CONCLUSION: Psychotherapy is the most acceptable treatment option for depression to pregnant women. Increasing participant knowledge about TMS increased its acceptability significantly. Large-scale multi-center trials are needed for confirmation of these results.