Deep brain stimulation electrode insertion and depression: Patterns of activity and modulation by analgesics

An initial antidepressant effect when using deep brain stimulation (DBS) of the subcallosal area of the cingulate cortex (Cg25) to treat resistant depression that could be the result of electrode insertion has been described. We previously showed that electrode insertion into the infralimbic cortex (ILC; the Cg25 rodent correlate) provokes a temporally limited antidepressant-like effect that is counteracted by non-steroidal anti-inflammatory drugs, such as those routinely used for pain relief.

We characterized the effect of electrode insertion using functional neuroimaging and evaluated the impact of different analgesics on this effect.

The effect of electrode insertion into the ILC was evaluated by positron emission tomography. The effect of analgesics (ibuprofen, tramadol and morphine) on the behavioral effect induced by electrode insertion were evaluated through the forced swimming test and the novelty suppressed feeding test. Furthermore, glial fibrillary acidic protein (GFAP) and p11 expression were measured.

Electrode implantation produces an antidepressant- and anxiolytic-like effect, a local decrease in glucose metabolism, and changes in several brain regions commonly related to depression and the antidepressant response. Ibuprofen counteracted the behavioral and molecular changes produced by electrode insertion (changes in GFAP and p11 protein expression). However, analgesics with no anti-inflammatory properties (e.g., tramadol) neither counteract the behavioral effects of electrode implantation nor the molecular mechanisms triggered.

Analgesics without anti-inflammatory properties may not limit the transient benefit produced by electrode insertion reducing the time required to achieve remission in depressive DBS patients.