title: Transmitter-like release of endogenous 3,4-dihydroxyphenylalanine from rat striatal slices.
abstract: Biphasic electrical field stimulation (0.5-5 Hz, 2 ms, 25 V, 3 min) and high K+ (10-30 mM, 5 min) released endogenous 3,4-dihydroxyphenylalanine (DOPA) from superfused rat striatal slices. Characteristics of the DOPA release were compared with those of 3,4-dihydroxyphenylethylamine (dopamine, DA). Electrical stimulation at 2 Hz evoked DOPA and DA over similar time courses. alpha-Methyl-p-tyrosine (0.2 mM) markedly reduced release of DOPA but not of DA. Maximal release (0.3 pmol) of DOPA was obtained at 2 Hz and at 15 mM K+. The impulse-evoked release of DOPA and DA was completely tetrodotoxin (0.3 microM) sensitive and Ca2+ dependent and the 15 mM K+-evoked release was also Ca2+ dependent. On L-[3,5-3H]tyrosine (1 microM) superfusion, high K+ (15 and 60 mM) released DOPA and DA together with concentration-dependent decreases in tyrosine 3-monooxygenase (EC 1.14.16.2) activity as indicated by [3H]H2O formation, followed by concentration-dependent increases after DOPA and DA release ended. These findings suggest that striatal DOPA is released by a Ca2+-dependent excitation-secretion coupling process similar to that involved in transmitter release.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004295:Dihydroxyphenylalanine / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D004558:Electric Stimulation; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013779:Tetrodotoxin / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D019805:alpha-Methyltyrosine
chemical_list: D008781:Methyltyrosines; D018377:Neurotransmitter Agents; D013779:Tetrodotoxin; D004295:Dihydroxyphenylalanine; D019805:alpha-Methyltyrosine; D014446:Tyrosine 3-Monooxygenase; D011188:Potassium; D002118:Calcium; D004298:Dopamine