Low CSF somatostatin associated with response to nimodipine in patents with affective illness

Background: In patients with depression, treatment with nimodipine has been shown to increase cerebrospinal fluid (CSF) somatostatin (SRIF) and ameliorate baseline global cerebral hypometabolism. This study was conducted to assess whether a low baseline level of CSF SRIF was associated with response to nimodipine treatment. Methods: Twenty-one depressed patients underwent lumbar puncture for analysis of CSF somatostatin-like immunoreactivity (SRIF-LI) during a medication-free period and after at least 6 weeks of nimodipine monotherapy. Twenty-five healthy control subjects were utilized as a comparison group. Clinical improvement was assessed using the Clinical Global Impression Scale for Bipolar Illness. Results: As predicted, baseline CSF SRIF-LI was significantly lower in eventual nimodipine responders (33.1 ± 2.8 pg/mol) compared to eventual nonresponders [41.9 ± 2.6 pg/mL; t(19) = 1.98, p = .03, one-tailed]. Conclusions: Low baseline CSF somatostatin in depression may be associated with response to nimodipine, which in turn may be related to the ability of nimodipine to increase CSF somatostatin.