title: Effects of K+-stimulation and precursor loading on the in vivo release of dopamine, serotonin and their metabolites in the nucleus accumbens of the rat.
abstract: The in vivo efflux of endogenous 3,4-dihydroxyphenylethylamine (DA 5-hydroxytryptamine (5-HT), 3,4-dihydroxyphenyl-acetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxy-indoleacetic acid (5-HIAA) in the nucleus accumbens of the anesthetized rat was studied using a push-pull cannula. Local perfusion for 10 minutes with 35 mM K+ significantly (P less than 0.01) increased the release of DA and 5-HT, but not their metabolites, from their respective control levels of 0.95 and 0.04 pmol/15 min to 2.5 and 0.23 pmol/15 min. Exposure to 35 mM K+ a second and third time resulted in a decrement in the amount of stimulated release for both DA and 5-HT. This decrease was prevented by local perfusion for 10 minutes with 50 uM L-tyrosine and -tryptophan starting 30 minutes before each episode of depolarization. The baseline amounts of DOPAC, HVA and 5-HIAA observed in the perfusates were several fold higher than the basal levels found for 5-HT and DA. In the absence of precursors, the efflux of DOPAC, HVA and 5-HIAA decreased approximately 60, 40 and 25%, respectively, from the first to the last baseline fraction collected. Addition of precursors prevented the decrease for DOPAC and 5-HIAA but not for HVA. The data indicated that (a) the in vivo release of DA and 5-HT, along with their metabolites, could be simultaneously measured with the present procedure, and (b) when using the push-pull cannula, local perfusion with precursors may be necessary following periods of sustained and/or repeated stimulation in order to replenish the monoamine transmitter pools.
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D006719:Homovanillic Acid / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D009714:Nucleus Accumbens / Q000378:metabolism*; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D012686:Septal Nuclei / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D014443:Tyrosine; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D011188:Potassium; D004298:Dopamine; D006719:Homovanillic Acid