H(+)-ATPase and transport of DOPAC, HVA, and 5-HIAA in monoamine neurons.
The effects of N-methylmaleimide (N-MtM), a vacuolar H(+)-ATPase inhibitor, were evaluated in the putamen of the cat to study the in vivo transport mechanisms of dopamine (DA), 5-hydroxytryptamine (5-HT), and their metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindolacetic acid (5-HIAA), using the brain focal microdialysis technique combined with HPLC. The addition of N-MtM to the perfusate altered invariably the flux of the DOPAC, HVA, and 5-HIAA in a similar pattern, resulting in a decrease of the extracellular levels of such metabolites, its extent being N-MtM concentration dependent, thus indicating that the mechanism(s) of such a decrease is (are) related most likely to decreased transport from the intracellular to the extracellular space as the consequence of the inhibition of the vacuolar H(+)-ATPase of DA and 5-HT neurons by the N-MtM. Furthermore, N-MtM masked the release of DA and 5-HT produced by KCl 120 mmol/l. Indeed, N-MtM increased the extracellular levels of such transmitters to values exceeding 4 to 6 times of those produced by KCl 120 mmol/l alone, which suggests that vacuolar H(+)-ATPase is probably involved also in the retention and/or reuptake process of DA and 5-HT.
Miyamoto
J K
JK
Second Department of Physiology, University of the Ryukyus, School of Medicine, Okinawa, Japan.
Uezu
E
E
Jiang
P J
PJ
Miyamoto
A T
AT
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002415:Cats; D006719:Homovanillic Acid / Q000378:metabolism*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology; D017494:Proton Pumps / Q000502:physiology; D006180:Proton-Translocating ATPases / Q000502:physiology*; D011699:Putamen / Q000502:physiology*; D013572:Synaptic Vesicles / Q000502:physiology
D017494:Proton Pumps; D015102:3,4-Dihydroxyphenylacetic Acid; D006897:Hydroxyindoleacetic Acid; D006180:Proton-Translocating ATPases; D006719:Homovanillic Acid