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J Pharmacol Exp Ther. 1991 Dec;259(3):1188-96.

Effect of metaphit on dopaminergic neurotransmission in rat striatal slices: involvement of the dopamine transporter and voltage-dependent sodium channel.

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Center for Neurochemistry, N.S. Kline Institute for Psychiatric Research, Ward's Island, New York.


Metaphit, an isothiocyanate analog of phencyclidine (PCP), increased the basal release of radioactivity (outflow) from perfused rat striatal slices preloaded with [3H]dopamine above levels observed with the dopamine uptake blocker nomifensin. Preperfusing the slices with metaphit, followed by its removal, attenuated the amphetamine- or dopamine-induced outflow. In slices prepared from reserpine-pretreated rats, the metaphit (100 microM)-induced outflow was reduced to that observed with 10 microM nomifensin, suggesting a vesicular releasing effect of metaphit in addition to dopamine uptake blockade. Electrically induced overflow of radioactivity from normal slices was stimulated by nomifensin and PCP, and by metaphit at 3 microM; it was unaffected by metaphit at 10 and 25 microM, and inhibited by higher concentrations of metaphit. Evidence that the latter effect is due to blockade of voltage-dependent sodium channels is as follows. First, metaphit, as did PCP, inhibited the binding of [3H]batrachotoxinin A 20-alpha benzoate to rat striatal synaptoneurosomes by increasing its dissociation rate; the effect of PCP, but not that of metaphit, was reversible by washing. Second, metaphit, as did PCP, inhibited veratridine (5 microM)-induced influx of [14C]guanidinium ion into synaptoneurosomes. Third, metaphit inhibited overflow of radioactivity from [3H]dopamine-preloaded slices induced by 2.5 microM veratridine, as did the sodium channel blocker tetrodotoxin.

[Indexed for MEDLINE]

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