Regulation of the Synaptosomal Tyrosine Hydroxylase Activity via Presynaptic Receptors in the Nucleus Accumbens of Rats

There is increasing evidence for the existence of presynaptic dopamine (DA)-autoreceptors as well as serotonin (5HT)-heteroreceptors modulating the DA release in the striatum (Ennis et al., 1981) and the nc. accumbens of rats (Hetey et al., 1982). On the other hand, there exist contradictory experimental data about the control of tyrosine hydroxylase (TH) activity via autoreceptors. Especially the role of DA is questionable because of its direct inhibition of the enzyme. Furthermore, a direct comparison of receptors modulating TH as well as DA release is not possible, since the methodic approaches are too different. Therefore we investigated the modulation of the synaptosomal TH activity under the same conditions as we used for DA release studies in the nc. accumbens (in 30 mM K+-buffer, at inhibition of the amine uptake; see Hetey et al., 1983).