Do nerve terminals and cell bodies of nigrostriatal dopaminergic neurons of the rat contain similar receptors?

Abstract

The question was investigated whether dopamine release-controlling receptors are evenly distributed over somatodendritic sites and nerve terminals of nigrostriatal dopaminergic neurons of the rat. Prototypical drugs of 5 different (sub)types of receptors (D 2, cholinergic, GABA B, NMDA and non-NMDA) were infused via a microdialysis probe into the striatum, and effects on dopamine released from nerve terminals were determined by microdialysis. In separate experiments the same drugs were infused into the substantia nigra and effects on dendritic release of dopamine were recorded. In addition, the effect of calcium depletion and tetrodotoxin infusion (1 μmol/l) was studied in both areas. Infusion of (-)-N0437 (1 μmol/l). (-)-sulpiride (1 μmol/l), NMDA (300 μmol/l), AMPA (100 μmol/l), kainic acid (30 μmol), tetrodotoxin and depletion of calcium induced comparable changes in the release of dopamine when applied into the striatum as well as into the nigra. Carbachol (100 μmol/l) and baclofen (5 μmol/l) inhibited dendritic dopamine release when administered into the nigra; however, the latter drugs were not effective when infused into the striatum. It is concluded that the release-controlling receptors are not evenly distributed over somata and nerve terminals of dopaminergic neurons.