D2 Receptors Modulating Dopamine Synthesis in Striatal Synaptosomes

Abstract

This chapter discusses the D 2 receptors modulating dopamine synthesis in striatal synaptosomes. On the basis of in vivo evidence, it is assumed that dopamine (DA) synthesis in nigrostriata1 DA neurons is regulated not only by postsynaptic DA receptors and striatonigral neuronal loop, but also by DA autoreceptors located in DA nerve terminals. Thus, neither elimination of postsynaptic DA receptor function by kainic acid-induced striatal lesion nor elimination of impulse activity in DA neurons by axotomy or gammabuty-rolactone (GBL) administration diminishes the inhibitory effect on DA synthesis by DA agonists. The inhibition of DA synthesis by DA agonists is enhanced after chronic treatment with neuroleptics and this enhancement persists after intrastriatal kainic acid or systemic GBL administration and is considered to be because of the supersensitivity of DA autoreceptors. A direct method to study the properties and function of terminal DA autoreceptors regulating DA synthesis should be the use of synaptosomal preparations which are known to have been a highly successful tool in the study of other presynaptic functions of different neurons.