title: Effects of taurine, homotaurine and GABA on hypothalamic and striatal dopamine metabolism.
abstract: To elucidate the effects of taurine on hypothalamic and striatal dopaminergic neurotransmission we compared its effects to those of gamma-aminobutyric acid (GABA) and homotaurine (a GABAA-receptor agonist) on hypothalamic and striatal concentrations of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and, in the case of striatum, 3-methoxytyramine (3-MT) in rats. In addition, hypothalamic and striatal 5-hydroxytryptamine (5-HT) und 5-hydroxyindoleacetic acid, hypothalamic noradrenaline (NA) and 3-methoxy-4-hydroxyphenylglycol sulfate, and pituitary DA concentrations were also measured. The amino acids were injected into the lateral brain ventricles of conscious male rats in doses of 10 and 36 mumol/rat, and rat were sacrificed 15 and 60 min later, respectively. Homotaurine (by 11%) but not the other two amino acids elevated striatal DA, whereas hypothalamic DA was increased by both taurine (36%) and homotaurine (31%). All three amino acids at 36 mumol elevated striatal DOPAC, homotaurine (51%) more than taurine (31%) or GABA (30%), and hypothalamic DOPAC, both taurine (102%) and homotaurine (82%) clearly more than GABA (34%). Neither striatal nor hypothalamic HVA was altered by any of the amino acids. At 10 mumol the amino acids decreased striatal 3-MT by about 40%. At 36 mumol taurine and homotaurine reduced 3-MT by about 70%, whereas increasing the dose of GABA did not further reduce 3-MT. Both taurine and homotaurine at 36 mumol decreased hypothalamic NA content. Neither hypothalamic nor striatal 5-HT metabolism was altered. In the neurointermediate lobe of the pituitary gland taurine at 10 mumol but not at 36 mumol slightly (20%) increased DA.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacy, University of Helsinki, Finland.
authors.forename: E
authors.initials: E
authors.lastname: Panula-Lehto
authors.forename: M
authors.initials: M
authors.lastname: Mäkinen
authors.forename: L
authors.initials: L
authors.lastname: Ahtee
mesh_terms: D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007276:Injections, Intraventricular; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism; D013654:Taurine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D013654:Taurine; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; C001355:tramiprosate; D004298:Dopamine; D009638:Norepinephrine