Involvement of cholinergic presynaptic receptors of nicotinic and muscarinic types in the control of the spontaneous release of dopamine from striatal dopaminergic terminals in the rat.

Rat striatal slices (two) were superfused continuously with L-3,5-3H tyrosine and 3H-dopamine (3H-DA) release was estimated in serial fractions of superfusates. The spontaneous release of 3H-DA was reduced by about 50% when slices were superfused with a calcium-free medium containing ethylene glycol bis (beta-aminoethyl ether)- N,N'-tetraacetic acid (EGTA) (10(-4) M) or with a medium containg tetrodotoxin (5 x 10(-7) M). These effects were not related to a change in 3H-DA synthesis since the rate of L-3,5-3H tyrosine hydroxylation, as measured by 3H-H2O formation was not significantly reduced.

Nicotinic effect of acetylcholine on the release of newly synthesized (3H)dopamine in rat striatal slices and cat caudate nucleus.

The effect of acetylcholine (ACh), carbachol and nicotinic blocking agents on the release of newly synthesized [3H]dopamine ([3H]DA) was studied in vitro on rat striatal slices and in vivo on the cat caudate nucleus. In the latter case, the animals were anaesthetized with halothane; in some experimetns an 'encéphale isolé' preparation was used to eliminate anaesthesia. Rat striatal slices placed in a superfusion chamber were continuously superfused with L-[3,5-3H]tyrosine.

The role of presynaptic receptors in the release and synthesis of 3H-dopamine by slices of rat striatum.

Striatal slices were continuously superfused with L-3,5-(3)H-tyrosine (50 muCi/ml) and 4H-H2O [index of 3H-dopamine (3H-DA) synthesis] and 3H-DA estimated in 0.5 ml (2.5 min) superfusate fractions.