Serotonin turnover rate in raphe and cortex of mice infected with Venezuelan equine encephalomyelitis virus.

The turnover of serotonin (5HT) was determined in the raphe area and cortex of mice infected with Pixuna, a strain of intermediate virulence of Venezuelan equine encephalomyelitis virus (VEEV). NMRI-mice, 24 days old, were inoculated intracerebrally (ic) with 300 LD50 of the virus. The animals were sacrificed 4, 7, 15, 21, 30, and 60 days postinoculation. 5HT and 5-hydroxyindoleacetic acid (5HIAA) in raphe and cortex were determined by high performance liquid chromatography (HPLC) with electrochemical detection. Turnover rate of 5HT was determined by the administration of pargyline, p-chlorophenylalanine, and probenecid. The content of 5HT or 5HIAA and 5HT/5HIAA ratios were not significantly different in infected compared with control mice. However, a decrease of 5HT turnover rate, determined after pargyline treatment, was observed in the raphe and not in the cortex of infected mice at 4 and 7 days after the inoculation. The turnover rate/(5HT)0 in raphe is decreased in infected mice with signs of illness, suggesting a lower density of 5HT innervation in this brain area. The administration of p-chlorophenylalanine and probenecid showed that the cortex is also affected, but the synthesis is less modified than metabolism or elimination. Cell bodies of 5HT neurons seem to be more susceptible than projections to infection by Pixuna strain of VEEV.