Cerebrovascular reactivity following administration of mirtazapine in healthy probands--a randomized, placebo controlled double-blind clinical study.

INTRODUCTION: Cerebrovascular reactivity (CVR) reflects the compensatory dilatory capacity of cerebral arterioles to a dilatory stimulus and is important for maintaining constant cerebral blood flow. A reduced CVR increases the risk of stroke. We recently found that CVR was reduced in patients with depression. This might contribute to the higher risk of stroke that has been found in subjects suffering from depression. The characterization of pathophysiological conditions in the cerebral circulation requires the knowledge of influencing factors on CVR. We therefore investigated the influence that antidepressant administration might have on CVR in humans. METHODS: We investigated CVR in 48 healthy men before and after a 10-day application of either mirtazapine or placebo. CVR was determined by calculating the increase in cerebral blood flow velocity after stimulation with acetazolamide. Blood flow velocities were measured by transcranial Doppler ultrasound. RESULTS: There was no significant group-difference of CVR after the treatment trial compared to baseline. DISCUSSION: Mirtazapine does not seem to have an influence on CVR, or any impact on CVR might have been quickly limited by a cerebral autoregulatory response.

Determinants of lumbar CSF protein concentration.

OBJECTIVE: To determine factors influencing the wide variation of protein concentration in lumbar cerebrospinal fluid (CSF). METHODS: Patient variables with potential influence on spinal CSF flow and resorption were measured in different patient settings and compared with albumin and IgG CSF/serum quotients. RESULTS: In patients whose diagnostic lumbar puncture produces normal CSF the albumin quotient increased with body mass index (r = 0.408), abdominal circumference (r = 0.399), and body weight (r = 0.317), age-corrected with partial correlation. Body motion before lumbar puncture showed only marginal influence on albumin quotient. In patients with radiculography the albumin quotient decreased with iodine contrast medium elimination from spinal subarachnoid space (r = -0.598) and increased with narrowing of lumbosacral spinal canal (r = 0.515). CONCLUSION: Correlation of albumin quotient with body mass index and related variables may be mediated by spinal CSF resorption, which should be impaired in overweight patients with elevated venous pressure. Negative correlation of albumin quotient with iodine resorption from spinal CSF supports this assumption. Correlation of albumin quotient with narrowing of lumbosacral canal should be due to slowed spinal CSF flow which does increase protein concentration. Tested variables explain part of variation of CSF protein concentration. Other variables like blood-CSF barrier permeability and pulsatile spinal CSF flow should have additional influence.