The distribution and turnover of tryptamine in the brain and spinal cord

Abstract

Tryptamine levels have been determined in mouse brain regions and spinal cord and in rat spinal cord. They were; caudate nucleus 2.5 ng·g⁻¹, hypothalamus <0.5 ng·g⁻¹, hippocampus <0.7 ng·g⁻¹, olfactory bulb <0.7 ng·g⁻¹, olfactory tubercles <0.6 ng·g⁻¹, brain stem <0.4 ng·g⁻¹, cerebellum <1.0 ng·g⁻¹, and the “rest” 0.9 ng·g⁻¹. The mouse whole brain was found to have 0.5 ng·g⁻¹, the mouse spinal cord 0.3 ng·g⁻¹, and the rat spinal cord 0.3 ng·g⁻¹. These concentrations increased rapidly to 22.8 ng·g⁻¹, 14.2 ng·g⁻¹, and 6.6 ng·g⁻¹ respectively at 1 hr after 200 mg·kg⁻¹ pargyline. The turnover rates and half lives of tryptamine in the mouse brain and spinal cord and rat spinal cord were estimated to be 0.14 nmol·g⁻¹·h⁻¹ and 0.9 min; 0.054 nmol·g⁻¹·h⁻¹ and 1.5 min and 0.04 nmol·g⁻¹·h⁻¹ and 1.6 min respectively. The aromaticl-aminoacid decarboxylase inhibitors NSD 1034 and NSD 1055 reduced synthesis of tryptamine in controls and pargyline pretreated animals. Tryptophan increased the concentrations of mouse striatal tryptamine and 5-hydroxytryptamine and brain stem 5-hydroxyindole acetic acid.p-Chlorophenylalanine reduced formation of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid but did not change that of tryptamine.