Serotonin and its N-Acetylated and Acidic Derivatives in Insect Brain as Determined by High-Performance Liquid Chromatography with Electrochemical Detection

Abstract

The determination of serotonin (5-HT), N-acetylserotonin (NAS) and 5-hydroxy-3-indoleacetic acid (5-HIAA) in single brains of two acridids (Paracinema tricolor and Oedipoda caerulescens) was accomplished using a HPLC method combined with amperometric detection. A hydrodynamic voltammetry approach was used to assess the identity of each peak by comparing the voltammograms of standards and those of samples. The analytical method gave satisfactory reproducibility and sensitivity, and detected levels of 5-HT, NAS and 5-HIAA as low as 29, 55 and 10 fmol, respectively. This high sensitivity together with the simplicity of sample processing make the present analytical method suitable for a wide range of studies concerning indoleamine analyses in the insect nervous system. In both acridids, 5-HT showed the largest quantities, while its derivatives occurred in extremely low amounts. The results suggest that N-acetylation of 5-HT is quantitatively preferred to oxidative deamination in both species (NAS levels were 4-fold those of 5-HIAA). The relative importance of each catabolic pathway is discussed as related to physiological and genetic aspects.