Comparison of regional brain 5-HT and 5-HIAA content in flexor and extensor rats

Hindlimb extension (HLE) induced by maximal electroshock seizures (MES) can be markedly affected by drugs which affect CNS 5-hydroxytryptamine (5-HT). Consequently, it has been proposed that the natural resistance of certain rats (flexor rats) to HLE is due to elevated levels of 5-HT. We have tested the hypothesis that the increased resistance of flexor rats to MES-induced HLE is due to elevated serotonergic levels in some region(s) of the CNS by examining 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels in 8 regions of the CNS in rats classified by MES as either flexors or extensors. Furthermore, we compared the in vivo synthesis rate of 5-HT between flexor and extensor rats in 6 regions of the brain by measuring the accumulation of 5-HTP following aromatic amino acid decarboxylase inhibition with NSD-1015. All neurochemical analyses were carried out on rats sacrificed one week after their last seizure test. No differences in 5-HT, 5-HIAA or 5-HTP synthesis rate were detected between flexor and extensor rats for any of the regions examined, suggesting that enhanced serotonergic levels are not responsible for the unusual resistance of flexor rats to HLE.