Orexin A (ORX-A) is implicated in the regulation of various
physiological processes, including sleep/wake cycles and
reward/motivation. The hypothalamic ORX-A neurons project throughout the
brain and spinal cord. In the present study we established and compared
ORX-A levels in lumbar and ventricular cerebrospinal fluid (CSF)
samples, drawn from idiopathic normal pressure hydrocephalus (INPH)
patients, during respectively, lumbar puncture and shunt placement.
Ventricular and lumbar CSF levels of total protein and of the dopamine,
serotonin and norepinephrine metabolites HVA, 5-HIAA and MHPG
respectively, were also estimated. ORX-A was quantified using a
commercially available radioimmunoassay kit. Neurotransmitter
metabolites were quantified by high performance liquid chromatography.
Expectedly, HVA and 5-HIAA levels were significantly higher and total
protein levels lower in ventricular compared to lumbar CSF while there
were no differences in MHPG levels. However, in contrast to HVA and
5-HIAA and similar to total protein, lumbar ORX-A levels were
significantly higher than ventricular levels. The higher lumbar compared
to ventricular ORX-A levels may reflect elevated contributions from the
spinal cord. The finding of a ventriculo-lumbar difference for ORX-A
should be considered in studies utilizing its CSF levels in assessing
Orexin system status. (C) 2013 Elsevier Inc. All rights reserved
