Changes in blood neurotransmitter and steroid levels during evoked vertigo.

HYPOTHESIS AND BACKGROUND: Experimental evidence suggests that steroids as well as various neurotransmitters are critically involved in the functioning of the vestibular system in health and disease. Yet there are no pertinent human data. We hypothesized that changes in the serum levels of cortisol and plasma levels of excitatory and inhibitory neurotransmitters may occur during evoked vertigo. SUBJECTS AND METHODS: Ten healthy volunteers (median age 37, range 21-57) entered the study. Subjects were investigated at rest and at the time of maximal nystagmic reaction during caloric irrigation. The determination of glutamate, aspartate, and gamma-aminobutyric acid (GABA) was performed by reverse phase high-performance liquid chromatography, whereas cortisol measurements were performed with an immunoenzymatic assay with fluorescence polarization. RESULTS: During evoked vertigo, cortisol levels increased from a baseline value of 11.86 (+/-1.272) microg/dl to 14.375 (+/-2.183) microg/dl (p < 0.01), whereas all neurotransmitter levels decreased significantly. Glutamate levels, for instance, fell from a resting value of 25.99 (+/-6.30) ng/ml to 17.40 (+/-5.50) ng/ml (p < 0.001), and aspartate and GABA decreased as well. CONCLUSION: Evoked vertigo is consistently associated with an increase in steroid serum levels and accompanying decreases in the plasma levels of glutamate, aspartate, and GABA. The possible underlying mechanisms and the functional significance of these findings are discussed.

Ascorbate in healthy subjects, amyotrophic lateral sclerosis and Alzheimer's disease.

The aim of the present study was to report the levels of ascorbic acid in amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) and the effectiveness of ascorbic acid homeostasis in the central nervous system. Plasma and CSF ascorbic acid levels were measured by high performance liquid chromatography in 19 ALS patients, 17 AD patients and 15 controls. No statistically significant difference was found between patients and controls. However, wide fluctuations of plasma concentrations were found to result in relatively stable CSF levels, by appropriate adjustments of CSF/plasma ratio. It appears that in normal subjects and in the disease under study, this ratio reflects the activity of the choroid plexus ascorbate transporter.