A comparison of the effects of methylphenidate and amphetamine on the simultaneous release of radiolabelled dopamine and p- or m-tyramine from rat striatal slices.
The release of [14C]dopamine (DA) from slices of rat caudate nucleus was studied simultaneously with the release of either [3H]para-tyramine (pTA) or [3H]meta-tyramine (mTA). Amphetamine (10(-5) M) caused a large concurrent release of [14C]DA and [3H]pTA; similar results were obtained when [14C]DA and [3H]mTA release were studied. The release of all three amines by amphetamine was quantitatively similar. In contrast, methylphenidate caused a release of [3H]pTA similar to that seen with amphetamine, but only a very small simultaneous release of [14C]DA. [3H]mTA was also strongly released by methylphenidate concurrent with a minimal release of [14C]DA. The inclusion of reserpine in the incubation medium had no detectable effect on the release of any of the three amines by amphetamine. Methylphenidate-induced release of tritiated mTA and pTA was also unaffected by reserpine. However, the release of [14C]DA by methylphenidate was potentiated in the presence of reserpine. The uptake of radiolabelled pTA, mTA and DA was inhibited by both amphetamine and methylphenidate, although amphetamine was a stronger inhibitor of the uptake of all three amines. It is suggested that release of endogenous tyramines may be involved in mediating some actions of psychomotor stimulant drugs.
D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D002421:Caudate Nucleus / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D014439:Tyramine / Q000378:metabolism*
D008774:Methylphenidate; D012110:Reserpine; D000661:Amphetamine; C028169:3-tyramine; D004298:Dopamine; D014439:Tyramine