The in vivo modulation of dopamine synthesis by calcium ions: influences on the calcium independent release.
To investigate the contribution of the dopamine (DA) synthesis to both the calcium-dependent and the carrier-mediated, mechanisms of DA release in the striatum, anaesthetized rats were locally superfused in the striatum with a push pull cannula supplied with an artificial CSF containing tritiated tyrosine. DA, dihydroxyphenylacetic acid (DOPAC) and their respective specific activity were measured in effluent and used to evaluate changes in the DA synthesizing rate. Excluding calcium ions from the CSF only partially reduced spontaneous DA release (70%) still leaving a possible carrier-mediated DA release. This effect was not additive with a local superfusion with 0.1 mM a-methyl-p-tyrosine, a blocker of DA synthesis, suggesting that synthesis could already be reduced by calcium-free superfusion. Local superfusion with 100 microM cadmium in the presence or not of calcium ions, increased the DA release (220 and 350%, respectively), simultaneously reducing DA synthesis. Local application of 1 microM calcium ionophore (A23187) was without effect on the basal release of DA but enhanced DA synthesis and increased the amphetamine-evoked and carrier-mediated amine release. We conclude that DA synthesis can be a modulatory process of the firing-independent and carrier-mediated amine release while it weakly affects the classical calcium-dependent release.
Olivier
V
V
Institut Alfred Fessard, CNRS, Gif sur Yvette, France.
Gobert
A
A
Guibert
B
B
Leviel
V
V
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D020013:Calcium Signaling / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000096:biosynthesis* / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D051381:Rats; D017208:Rats, Wistar; D014443:Tyrosine / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D019805:alpha-Methyltyrosine / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002352:Carrier Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D007476:Ionophores; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D002104:Cadmium; D015102:3,4-Dihydroxyphenylacetic Acid; D000001:Calcimycin; D014443:Tyrosine; D019805:alpha-Methyltyrosine; D000661:Amphetamine; D014446:Tyrosine 3-Monooxygenase; D002118:Calcium; D004298:Dopamine