Decreased cerebrospinal fluid concentrations of substance P in treatment-resistant depression and lack of alteration after acute adjunct vagus nerve stimulation therapy

Lumbar punctures for cerebrospinal fluid (CSF) collection in relation to vagus nerve stimulation (VNS) D-02 study timeline. LP=lumbar puncture; B=pre-stimulation baseline; E=post-stimulation endpoint (following 10–12 weeks active VNS); EE=extended endpoint, following 22 weeks active stimulation. Analysis of effects of VNS on CSF substance P concentrations for 18 subjects in this report included specimens from B and E from all individuals, regardless of initial assignment to active or sham conditions. Assessment of depressive symptoms at B and E took place on concurrent LP procedure days, prior to CSF collection.

Basal (mean and S.D.) CSF concentrations of substance P in patients with treatment-resistant depression and matched healthy controls.

CSF substance P concentrations in 18 patients with treatment-resistant depression before and after receiving 10–12 weeks treatment with adjunctive vagus nerve stimulation (VNS). The difference between pre-VNS baseline and post-VNS endpoint is not statistically significant (mean±S.D. 27.3±22.0 versus 34.3±33.8 fmol/ml; t=0.98, P=0.34).