Dopamine output upon death reflects intraneuronal aspects while alive: accumulation of releasable dopamine during tetrodotoxin perfusion

Abstract

Intraneuronal and extracellular dopamine (DA) metabolism in rat striatum during inhibition of neurotransmission processes by tetrodotoxin (TTX) perfusion was examined by analysis of the striatal DA content and the amount of initial post-mortem DA output. In spite of there being an excess amount of DA already present in the striatum, the contents of DA and its metabolites were increased time-dependently by TTX perfusion through a microdialysis membrane. A massive increase in extracellular level of DA occurred immediately after death. The amount of the post-mortem DA output was further increased in proportion to the preceding TTX perfusion time. The ratio of the amount of post-mortem DA output to the striatal DA content was also increased by previous perfusion with TTX. Verapamil, a Ca 2+ channel blocker, delayed the appearance of the peak of the DA output. These results suggest that releasable DA accumulates in neurons during TTX perfusion, and that the early part of the DA output upon death reflects intraneuronal aspects of DA metabolism while the animal is alive.