Inhibition of the electrically induced release of [3H]dopamine by serotonin from superfused rat striatal slices

The effect of opioid drugs on the release of dopamine and 5-hydroxytryptamine from rat striatum following activation of nicotinic-cholinergic receptors

The effect of (Met5)enkephalin, (D-Ala2,D-Met5)enkephalin, (Leu5)enkephalin, (D-Ala2,D-Met5)enkephalin and morphine on the release of [3H]dopamine, endogenous dopamine and [3H]5-hydroxytryptamine produced by the nicotinic-cholinergic agonist, dimethylphenyl piperazinium iodide (DMPP), was examined in rat striatal slices. The DMPP-induced release of [3H]dopamine and endogenous dopamine was reduced by the presence of (Met5)enkephalin, (D-Ala2,D-Met5)enkephalin (1-10 microM) or morphine (10 microM) but not by (Leu5)enkephalin or (D-Ala2,D-Leu5)enkephalin. The DMPP-induced release of [3H]5-hydroxytryptamine was reduced by (Leu5)enkephalin, (D-Ala2,D-Leu5)enkephalin, (Met5)enkephalin, (D-Ala2,D-Leu5)enkephalin (1-10 microM), and morphine (10 microM). All three opioids failed to alter the release of [3H]dopamine induced by field stimulation or potassium depolarization (30 microM). The inhibitory effects of opioid peptides and morphine demonstrated in the present study appear to be due to an initial interaction with nicotinic-cholinergic receptors in the striatum.

Release of dopamine and 5-hydroxytryptamine from rat striatal slices following activation of nicotinic cholinergic receptors

1. The administration of the nicotinic cholinergic agonists dimethylphenylpiperazinium iodide (DMPP) or nicotine caused a concentration dependent release of [3H] dopamine, [3H]5-hydroxytryptamine as well as endogenous dopamine and 5-hydroxytryptamine from superfused slices of rat striatum. 2. Release of both labelled and non-labelled transmitter was antagonized by the nicotinic antagonist, hexamethonium but not the muscarinic antagonist, atropine. 3. The present study provides additional evidence that nicotinic-cholinergic receptors are present in the mammalian central nervous system. 4. Activation of these nicotinic-cholinergic receptors in the striatum results in the release of both dopamine and 5-hydroxytryptamine.