DOPAMINE RELEASE FROM THE RAT SUBSTANTIA NIGRA INVITRO - EFFECT OF RAPHE LESIONS AND VERATRIDINE STIMULATION

In order to eliminate the 5-hydroxytryptaminergic input to the substantia nigra lesions were placed in the dorsal and medial raphe nuclei in a number of rats. The release of exogenously applied [3H]dopamine from the partially denervated substantia nigra was determined in vitro and found to be very similar to the release observed from slices of control substantia nigra. These results lend further support to the theory that the release of exogenously applied [3H]dopamine at the level of the substantia nigra occurs mainly from dopaminergic dendrites, rather than from terminals of 5-hydroxytryptamine-containing neurons. A veratridine-induced release of [3H]dopamine from the pars reticulata of the substantia nigra is also described. An almost complete blockade of veratridine (3.0 μM) stimulation was observed with 100 nM tetrodotoxin. Similar effects of veratridine and tetrodotoxin were also observed on [3H]dopamine release from slices of corpus striatum. These results suggest that dendrites of the dopaminergic neurones in the substantia nigra contain fast, tetrodotoxin-sensitive sodium channels. © 1979.