Analysis of neurotransmitter metabolite concentrations in canine cerebrospinal fluid

The concentrations of dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindole-3-acetic acid (5-HIAA) in CSF obtained from the cisterna magna of 21 nonneurologically compromised dogs were determined by high-pressure liquid chromatography and electrochemical detection. A rapid method of sample preparation, which involved single filtration through a deproteinizing membrane, was used. Canine CSF obtained in this manner contained 5.78 +/- 0.78 ng of DOPAC/ml, 72.19 +/- 4.09 ng of HVA/ml, and 29.95 +/- 1.67 ng of 5-HIAA/ml. Linear regression analysis between HVA and 5-HIAA yielded a correlation coefficient of 0.4804. The neurotransmitter index, HVA/5-HIAA, was found to be more indicative of the dopaminergic metabolite HVA than the acid metabolite of serotonin, 5-HIAA (correlation coefficient with HVA = 0.5529 vs a correlation coefficient with 5-HIAA = -0.4462). A poor relationship (correlation coefficient = -0.1715) was found to exist between the 2 dopaminergic metabolites DOPAC and HVA in the CSF.