Changes in the 5-hydroxytryptamine content of rat, rabbit and human brain after death.

The fall in 5-hydroxytryptamine concentration which occurs in brain tissues in the first 48 hr after death varies in different areas of the brain and is of the same order of magnitude in those areas of the rat and rabbit in which it was estimated, namely, hypothalamus, hippocampal gyrus and frontal cortex, and also in human frontal cortex. The loss of 5-hydroxytryptamine is greater in the hypothalamus than in the cerebral cortex. The extent of this change depends on the temperature and conditions of storage of tissues. It is least in tissues which remain within the skull after death before chemical extraction and in tissues stored at -17 degrees C. Comparison of cerebral 5-hydroxytryptamine content in control animals and animals pretreated with iproniazid suggests that the differences are for the greater part due to the action of mono-amine oxidase.