5-Hydroxytryptamine metabolism in nervous tissue of two acridids, Oedipoda caerulescens and Paracinema tricolor: A comparative study

The concentrations of 5-hydroxytryptamine (5-HT), N-acetyl-5-hydroxytryptamine (NAS), 5-hydroxyindoleacetic acid (5-HIAA) (HPLC-EC) and tryptophan (Trp) were determined in the cerebral ganglia and ventral nerve cord (VNC) of both sexes of two acridids. In both species, the maximum values for all compounds appeared in the brain region, the converse occurring for Trp levels. 5-HT and its metabolites followed in both acridids the same tendency, males showing higher values than females. These male-female differences were markedly significant for NAS and 5-HIAA concentrations in Paracinema tricolor, and for 5-HT concentrations in Oedipoda caerulescens. Both acridids differed for brain concentrations of such compounds. Thus, P. tricolor showed the maximum values for NAS and 5-HIAA and O. caerulescens for 5-HT levels. Furthermore, in both species NAS represented about 75–90% of both catabolic products considered as a whole. The results support the idea of a coexistence of N-acetylation and oxidative deamination in both acridids, with higher importance of the 5-HT N-acetyl derivative. A differential 5-HT turnover between sexes is also suggested.