In vivo assessment of dopamine and norepinephrine release in rat neocortex: gas chromatography-mass spectrometry measurement of 3-methoxytyramine and normetanephrine.
A new method with the sensitivity and specificity required to measure regional levels of 3-methoxytyramine (3-MT) and normetanephrine (NMN) in the rat cortex is described. The method utilizes a liquid ion exchanger to isolate the parent amines, dopamine (DA) and norepinephrine (NE), along with their methylated metabolites. These samples are derivatized and analyzed by negative ion gas chromatography-mass spectrometry. Using this method, we examined a number of drug actions on steady-state levels as well as pargyline-induced increases in 3-MT and NMN. In the prefrontal cortex, cingulate cortex, striatum, and olfactory tubercle, nomifensine was found to increase 3-MT steady-state levels and accumulation rates. Similar actions of this drug were observed in the cingulate and prefrontal cortices with NMN. In contrast, clonidine decreased cortical NMN levels and accumulation. A unique action was observed with haloperidol, in that both 3-MT levels and accumulation after pargyline were increased in the nigrostriatal and mesolimbic dopaminergic projections, whereas only the accumulation rates were accelerated in the mesocortical projections. In summary, our data indicate that this new assay is a useful approach for the in vivo evaluation of DA and NE release in cortical regions of the rat. This approach is unique in that no surgery, restraint, or anesthetic is required, thereby permitting more complicated experimental paradigms to be utilized.
D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D003000:Clonidine / Q000494:pharmacology; D004298:Dopamine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D009627:Nomifensine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D009647:Normetanephrine / Q000032:analysis*; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D009647:Normetanephrine; D009627:Nomifensine; D010293:Pargyline; D006220:Haloperidol; C001746:3-methoxytyramine; D003000:Clonidine; D004298:Dopamine; D009638:Norepinephrine