The effects of 1-ethyl-4-phenyl-1,2,3,6-tetrahydropyridine (EPTP) on striatal dopamine, cortical norepinephrine and cardiac norepinephrine concentrations in mice were compared to the effects of the 1-methyl analog (MPTP). One week after the last of four daily injections of MPTP into mice, persistent depletion of dopamine and its metabolites in the striatum and of norepinephrine in the frontal cortex was found. EPTP did not produce these effects even at doses up to 4 times those of MPTP. A single dose of MPTP depleted cardiac norepinephrine 24 hrs later in mice. EPTP and the corresponding pyridinium compound (EPP+) depleted cardiac norepinephrine to a similar extent as did MPTP. These results and earlier observations show differences between the characteristics of MPTP-induced depletion of brain catecholamines and those of MPTP-induced depletion of cardiac norepinephrine.
The effects of L-5-hydroxytryptophan (L-5HTP) and L-5HTP inosinate injection on brain 5-hydroxyindoles in rats were compared. L-5HTP and L-5HTP inosinate caused indistinguishable dose-dependent increases in 5HTP and 5HIAA (5-hydroxyindoleacetic acid) but not serotonin concentrations in whole brain at 1 hr in rats. Our results do not substantiate a previous claim that L-5HTP inosinate is superior to L-5HTP itself in increasing brain serotonin formation.
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